Thesis for the degree of Doctor of Philosophy, Sundsvall 2015

WINTER BROWSING BY MOOSE AND HARES IN SUBARCTIC BIRCH FOREST – SCALE DEPENDENCY AND RESPONSES TO

FOOD ADDITION

Sara M. Öhmark

Supervisors:

Professor R. Thomas Palo

Professor Glenn R. Iason

Professor Bengt-Gunnar Jonsson

Faculty of Science, Technology, and Media

Mid Sweden University, SE-851 70 Sundsvall, Sweden

ISSN 1652-893X

Mid Sweden University Doctoral Thesis 229

ISBN 978-91-88025-38-8

Akademisk avhandling som med tillstånd av Mittuniversitetet i Sundsvall

framläggs till offentlig granskning för avläggande av filosofie doktorsexamen i

biologi, fredagen den 2 oktober 2015, klockan 10.15 i sal O102, Mittuniversitetet

Sundsvall.

Seminariet kommer att hållas på engelska.

WINTER BROWSING BY MOOSE AND HARES IN SUBARCTIC BIRCH FOREST – SCALE DEPENDENCY AND RESPONSES TO FOOD ADDITION

Sara M. Öhmark

© Sara M. Öhmark, 2015

Department of Natural Sciences, Faculty of Science, Technology, and Media

Mid Sweden University, SE-851 70 Sundsvall

Sweden

Telephone: +46 (0)10-142 80 00

Printed by Mid Sweden University, Sundsvall, Sweden, 2015

“…whilst this planet has gone cycling on according to the fixed law of gravity, from

so simple a beginning endless forms most beautiful and most wonderful have been,

and are being, evolved.”

-Charles Darwin, The Origin of Species

Till min familj

Lyckan, i alla dess oändliga former,

finner jag varje dag i er.

i

WINTER BROWSING BY MOOSE AND HARES IN SUBARCTIC BIRCH FOREST – SCALE DEPENDENCY AND RESPONSES TO FOOD ADDITION

Sara M. Öhmark

Department of Natural Sciences

Mid Sweden University, SE-851 70 Sundsvall, Sweden

ISSN 1652-893X, Mid Sweden University Doctoral Thesis 229;

ISBN 978-91-88025-38-8

ABSTRACT

Despite their difference in body size and morphology, the moose (Alces alces) and

the mountain hare (Lepus timidus) sustain themselves during winter on similar plant

species and plant parts in in subarctic environments, namely apical twigs of

mountain birch (Betula pubescens ssp. czerepanovii). Herbivores must select areas and

items of food that provide sufficient intake rates and food nutritional quality while

balancing this against their intake of dietary fiber and potentially detrimental plant

secondary metabolites. This selection takes place simultaneously at multiple spatial

scales, from individual plants and plant parts to patches of food and parts of the

wider landscape. While the herbivores must consider their need for food to sustain

daily activities, for body growth and reproduction it is also necessary to avoid

predators and harsh environmental conditions. For managers, an understanding of

key factors for animal foraging distributions is pivotal to reach intended goals of

management and conservation plans. Knowledge in this area is also important for

models to make accurate predictions of foraging responses of herbivores to resource

distributions. The mountain birch forest displays a naturally heterogeneous

distribution of trees and shrubs which presents herbivores with a challenge to find

good feeding areas. In an investigation of the spatial distribution of moose browsing

on birch and willows (Salix spp.) in two winter seasons separated in time by 14 years,

it was found that moose browsing patterns in 1996 were correlated to those observed

in 2010. It was also found that moose browsing was spatially clustered within the

same distances (1000-2500 m) as densities of willow and birch, but at other spatial

ii

scales, browsing was mostly randomly distributed. It was concluded that forage

density is a cue for moose but only at certain spatial scales. Similarly, a comparison

of foraging distribution by hare and moose showed that high birch density was a

key factor for both species. In spite of this, hares and moose used different parts of

the same environment because they respond to food resource distribution at

different spatial scales. Hares fed from smaller plants, and focused their foraging

activity on smaller spatial scales than moose. These results emphasize the

importance of taking into account the distribution of food resources at spatial scales

relevant for each species in plans for conservation and management. In an

experimental study it was found that intensified browsing on natural forage by

mountain hares can be induced locally through placement of food. The induced

browsing varied with the amount and quality of the added food, but also with the

density of natural food plants and natural foraging distribution by hares. Finally, in

a last experiment habitat preference of mountain hares across edges between open

and forested areas was studied. The results were not consistent; hares utilized bait

to a greater extent within forested areas than bait placed on a nearby lake ice, but

bait on mires and heaths was either preferred over bait in nearby forest, or utilized

to a similar extent. A possible explanation is that hares have knowledge of their

environment such that both forested areas and subarctic mires and heaths are part

of its natural home range, whilst the extreme environment on the lake ice is not.

During recent decades arctic areas have had an increase in vegetation density and

will be affected by future climate warming and therefore, factors that determine

foraging ecology of key herbivores need to be identified. This thesis sheds some light

on these factors in relation to spatial scale and forage distribution for two high

profile herbivores in the subarctic.

Keywords: foraging distribution, moose (Alces alces), mountain birch (Betula

pubescens sp. czerepanovii), willow (Salix spp.), spatial scale, niche separation,

supplementary feeding, edge effects

iii

SAMMANDRAG

Skogshare (Lepus timidus) och älg (Alces alces) lever under vintertid i huvudsak

av kvist från träd och buskar i subarktisk fjällbjörkskog (Betula pubescens ssp.

czerepanovii) och delar alltså samma födokälla trots skillnader i storlek och

morfologi. För att tillgodose sina näringsbehov måste växtätare välja de områden

och de plantor som ger tillräckliga mängder mat av tillräckligt god näringsmässig

kvalitet. Samtidigt måste de balansera detta mot intaget av fibrer och potentiellt

skadliga sekundära metabiloter i växterna. Dessa val sker på flera rumsliga

skalnivåer samtidigt; från valet av individuell växt och växtdelar, till grupper av

växter och delar av landskap. Växtätaren behöver även balansera sitt behov av mat

med andra prioriteter, som att undvika rovdjur och söka möjlighet att föröka sig.

För att uppnå avsedda mål för skötsel- och bevarandeåtgärder, är det nödvändigt

att förstå växtätares respons på fördelning av resurser. Kunskap inom detta område

är även viktigt för att i modeller kunna göra tillförlitliga prediktioner av växtätares

födosöksmönster. Fjällbjörkskogen uppvisar naturligt en fläckvis utbredning, vilket

innebär en utmaning för växtätare som söker områden med god tillgång till föda.

Den rumsliga fördelningen av älgbete på fjällbjörk och viden undersöktes under två

vintersäsonger med 14 års mellanrum (Salix spp.) och det visades att älgens

betesmönster under 1996 var positivt korrelerat till det som observerades under

2010. Älgbetet var koncentrerat inom samma distanser (1000-2500 m) som densiteten

av vide och björk, medan älgbetet sett över andra rumsliga skalor var slumpvis

fördelat. En slutsats av dessa resultat är att densiteten av födoväxter styr älgens

födosöksmönster, men bara inom vissa rumsliga skalnivåer. En jämförelse av

betesfördelning mellan hare och älg visade på ett liknande sätt att hög densitet av

björk var avgörande för födosöksmönstren hos båda arterna. Trots detta var det

uppenbart att hare och älg utnyttjar olika delar av samma områden eftersom de

reagerar på fördelningen av resurser på olika rumsliga skalnivåer. Harar betade från

mindre björkar och fokuserade sitt bete inom mindre rumsliga skalor jämfört med

älg. Dessa resultat belyser vikten av att se till fördelningen av födoresurser på de

skalnivåer som är relevanta för respektive art vid planering och utförande av

skötsel- och bevarandeåtgärder. I en experimentell studie befanns det att ökat

harbete på naturlig vegetation kan framkallas lokalt genom utplacering av foder.

Det ökade betet varierade med mängd och kvalitet av det utplacerade fodret, men

det berodde även på tätheten hos björkskogen på foderplatser samt på den naturliga

distributionen av harbete på björk. Slutligen, i en sista studie undersöktes harens

preferens för olika miljöer där fjällbjörkskog angränsar till öppna ytor. Hararnas

iv

respons till utplacerat foder i öppen terräng jämfört med i fjällbjörkskog var inte

konsekvent. Hararna undvek sjöis men visade antingen en positiv eller en neutral

respons till foder placerat på subarktiska myrar eller hedar, jämfört med foder

placerat i fjällbjörkskog. En möjlig förklaring till detta är att hararna känner till

miljön inom sina hemområden som innefattar både fjällbjörkskog och subarktiska

hedar och myrar medan sjöisen inte utgör ett habitat för haren. Under senare

decennier har en ökad tillväxt av träd och buskar observerats i arktiska områden,

och dessa områden förväntas påverkas särskilt starkt av ett allt varmare klimat även

i framtiden. Därför är det relevant att identifiera de faktorer som är avgörande för

födosök och födointag hos växtätare. Denna avhandling belyser dessa faktorer i

relation till rumsliga skalor och fördelningen av bete för två växtätare som har stor

påverkan på subarktisk miljö.

v

TABLE OF CONTENTS

ABSTRACT ......................................................................................................................... I

SAMMANDRAG ............................................................................................................ III

TABLE OF CONTENTS .................................................................................................. V

LIST OF PAPERS ............................................................................................................ VI

1. INTRODUCTION ...................................................................................................... 1

1.1. THESIS BACKGROUND ............................................................................................. 1

1.2. PLANTS AS A FOOD RESOURCE ................................................................................ 1

1.3. STUDY SPECIES ....................................................................................................... 4

1.3.1. Mountain hare (Lepus timidus) ...................................................................... 5

1.3.2. Moose (Alces alces) ........................................................................................ 6

1.4. HARE AND MOOSE IN MOUNTAIN BIRCH FOREST ...................................................... 7

1.5. CONSEQUENCES OF CONTRASTING BODY SIZES ....................................................... 9

1.6. FORAGING MODELS/OPTIMALITY MODELS ............................................................. 10

1.7. SCALE DEPENDENCE .............................................................................................. 11

1.8. EDGE EFFECTS ....................................................................................................... 13

1.9. BAITING AND SUPPLEMENTARY FEEDING OF WILD HERBIVORES ........................... 14

2. OBJECTIVES ............................................................................................................. 15

3. METHODS ................................................................................................................ 16

3.1. STUDY AREA ........................................................................................................ 16

3.2. DATA COLLECTION ................................................................................................ 19

3.3. RESPONSE VARIABLES ........................................................................................... 20

3.4. DESIGN OF SAMPLE PLOTS ..................................................................................... 21

4. RESULTS AND DISCUSSION ............................................................................. 23

4.1. PAPER I ................................................................................................................. 23

4.2. PAPER II ................................................................................................................ 24

4.3. PAPER III ............................................................................................................... 25

4.4. PAPER IV .............................................................................................................. 26

5. CONCLUSIONS ....................................................................................................... 27

6. ACKNOWLEDGEMENTS ..................................................................................... 28

7. REFERENCES ........................................................................................................... 30

vi

LIST OF PAPERS

This thesis is mainly based on the following four papers, herein referred to by their

Roman numerals:

Paper I Distribution of winter browsing by moose: evidence of long-term

stability in northern Sweden

R. Thomas Palo, Sara M. Öhmark, and Glenn R. Iason, 2015, Alces 51,

35-43

Paper II Spatially segregated foraging patterns of moose (Alces alces) and

mountain hare (Lepus timidus) in a subarctic landscape: different

tables in the same restaurant?

Sara M. Öhmark, Glenn R. Iason, and R. Thomas Palo, 2015, Canadian

Journal of Zoology 93, 391-396

Paper III Artificially added forage for wild mountain hares (Lepus timidus)

increases browsing on surrounding mountain birch (Betula

pubescens ssp. czerepanovii)

Sara M. Öhmark, R. Thomas Palo, and Glenn R. Iason, manuscript,

submitted to Journal of Wildlife Management

Paper IV The influence of mountain birch (Betula pubescens ssp.

czerepanovii) forest cover and distance from forest edges on

utilization of added food by mountain hares (Lepus timidus) in a

natural forest mosaic

Sara M. Öhmark, Glenn R. Iason, and R. Thomas Palo, manuscript

Paper I and II were reprinted with kind permission from the journal Alces and NRC

Research Press.

1

1. INTRODUCTION

1.1. Thesis background

For foraging herbivores, food quantity and quality determine the choice of foraging

area, the time the animal stays within the area and the rate of forage intake (Brown

1988; Searle et al. 2005; Ungar & Noy-Meir 1988). During winter, browsers in boreal

environments are mainly restricted to a diet of woody plant parts, which are low in

nutrients and high in fibers and secondary metabolites (Rousi et al. 1991; Palo et al.

1992; Nordengren et al. 2003). By altering e.g., movement rates, bite size and site

selection, animals can improve their chances to maintain sufficient intake of energy

and nutrients as they move through heterogeneous environments (Demment &

Greenwood 1988). There is a broad range of physiological and morphological

adaptations to herbivory among animals, such as the complex digestive system

among ruminants (Hofmann 1989). Behavioral adaptations might not be as readily

identified and interpreted as morphological or physiological ones since free living

animals are often difficult to observe in nature, but behavior and physiological

function are closely related (Van Soest 1996; Laca et al. 2010). Spatial distribution

and habitat use by animals is often well described (Cederlund & Sand 1994; Hulbert

et al. 1996; Kauhala et al. 2005; Dussault et al. 2005). However, the multitude of

factors that influence animal utilization of resources means that it is a challenge to

define and understand the underlying causes of their spatial distribution and

foraging patterns (Owen-Smith et al. 2010; Stolter et al. 2005). This thesis addresses

the response of herbivores to natural and artificial distribution of forage in a

subarctic mountain birch (Betula pubescens ssp. czerepanovii) forest environment in

northern Sweden. The hypothesis that herbivores seek the best habitats as measured

in the quality and amount of food was tested in a series of experiments and

observations on moose (Alces alces) and mountain hare (Lepus timidus), to reveal

factors that affect the distribution of these animals.

1.2. Plants as a food resource

While a carnivore’s diet fulfills basic dietary needs with nutritional components

that are easily extracted, herbivores face a food source that is relatively poor in

nutrient content and partly indigestible (Iason & Van Wieren 1999; Steuer et al.

2013). With respect to qualitative issues, plant material can be divided into two

functional fractions, namely cell contents and cell walls. Cell contents are mainly

2

soluble carbohydrates and proteins that are easily digested in vertebrate stomachs

(Demment & Van Soest 1985). In contrast, cell walls mainly consist of indigestible

(lignin) and potentially digestible (cellulose, hemicelluloses) compounds (Iason &

Van Wieren 1999; Van Soest 1994). Although cell walls cannot be degraded by

vertebrate enzymes, it can be hydrolysed by microbial fermentation within

herbivore gut systems (Flint & Bayer 2008). High rates of lignified cell wall material

in the forage decrease the rate of digestion, thereby depressing nutrient value (Van

Soest 1967; Hjeljord et al. 1982). However, several classes of fibres, both digestible

and indigestible, are essential for the digestive health and function of animals

(Gidenne 2003; Van Soest 1994). The consequence of fibre content on food quality is

thus a sum of contrasting factors, and it is dependent on proportion of cell wall

material to plant content, as well as on the rate of lignification (Van Soest 1994).

Plants produce a vast array of substances that are commonly referred to as

“secondary” compounds, so called because they were earlier mostly not known to

be involved in primary processes of plant metabolism, such as protein synthesis

(Fraenkel 1959). These compounds are widely recognized as key players in

interactions between plants and animals (Palo 1984; Dearing et al. 2005; Iason 2005).

Some secondary compounds can reduce the ability of herbivores to digest food or

assimilate nutrients, while other act as toxins (Belovsky & Schmitz 1994). Defensive

compounds are generally not allocated evenly within a plant, but are concentrated

in plant parts that contribute most to plant fitness (Ballaré 2014; Zangerl & Bazzaz

1992).

As the food source of herbivores is often low in nutritional value, a high intake

rate is necessary for meeting dietary needs (Owen-Smith & Novellie 1982). However,

making up for low nutrient content in the food by high rates of ingestion is not a

solution that comes without restrictions. The digestive capacity among herbivorous

mammals for any forage depends on gut volume, intake rate and passage rate of

food (Clauss et al. 2007). The design of the digestive system is also a major

determinant for its function apart from the size of the gut. A categorization of

herbivores can be made based on the placement of the fermentation chamber. The

fermentation chamber within digestive systems of mammalian herbivores is either

situated in the rumen (foregut), or in the cecum/colon (hindgut) (Janis 1976). The

ruminant digestive system is characterized by foregut fermentation, as the rumen is

the site of microbial digestion of plant material (Van Soest 1994). Particle size

reduction in ruminants is performed by regurgitation and chewing of food that

enhances the exposure of particle surface to rumen microbes (Welch 1982; Pond et

al. 1984). The passage between the ruminoreticulum and third forestomach acts as a

bottleneck, controlling the outflow of digesta from the rumen. This function

3

prolongs the time of microbial digestion of the rumen content, but limits the rate at

which new food can be ingested (Hofmann 1989). In hindgut fermenters, particle

separation and fermentation takes place after the passage through the small

intestine, which is the primary site for absorption of nutrients (Hintz et al. 1978). To

minimize the loss of microbial protein and vitamins while managing food with high

fibre content, many hindgut fermenters, especially of small size and including

mountain hare, re-ingest the cecum content, a function called caecotrophy

(Hirakawa 2001; Pehrson 1983a). In this way, microbial nutrients are utilized rather

than lost through defecation, and this is especially important for herbivores living

on low-nutrient forages in harsh environments, such as hares (Björnhag & Snipes

1999).

A heterogenic plant dispersion is common in natural environments, whereas

homogenous distributions are often only found in managed grazing pastures, or

rarely in natural monocultures. A common way of illustrating the distribution of

forage for animals is as patches of food embedded in a matrix that is devoid of food

resources (Charnov 1976). Patches of vegetation are seldom discrete items, but

display a variable degree of contrast to the surrounding landscape matrix (Kotliar &

Wiens 1990). Such patches can be viewed as assemblies of food that are utilized by

herbivores to various extents rather than being simply emptied or killed (MacArthur

& Pianka 1966). One way to define a patch is that food items belong to the same

patch if the time to chew and swallow the food exceeds the time it takes to travel to

another patch (Spalinger & Hobbs, 1992). The spatial distribution of plants in

relation to other available forage is essential for the food selection of herbivores

(Milligan & Koricheva 2013; Bergman et al. 2005). A highly preferred plant can either

receive protection from herbivory by the association with a less preferred plant

(repellent plant-hypothesis) or by growing near an even more palatable plant

(attractant-decoy hypothesis) (Atsatt & O’Dowd 1976).

Depending on their dietary niche mammalian herbivores are categorized either as

browsers, which preferably eat from forbs, shrubs and trees or as grazers, which

preferably consume grasses (Shipley 1999; Hofmann 1989). There is also a

differentiation between generalists, which include many plant species in their diets,

and specialists, which only feed from a few plant species (Freeland & Janzen 1974;

Shipley et al. 2009). Dietary specialization of herbivores is rare, and this has been

proposed to either be due to that few plant species can satisfy all dietary demands,

or due to satiation of plant secondary compounds in a narrow diet (Dearing et al.

2000). Shipley et al. (2009) suggested that mammalian herbivores should be assigned

as either “obligate” or “facultative” specialists or generalists, to indicate the causes

for the dietary niche. The term obligate specialist or generalist should be used if

4

specialization or generalization occurs due to behavioral and/or morphological

adaptation, and for facultative specialist or generalist, the local availability of forage

forces a narrow or a broad diet. In the latter case the specialization depends on

spatial and temporal scale.

In summary, herbivores face a food source that is unevenly distributed in terms

of availability and quality and their ability to respond to this variation depends on

species- specific contraints. This forms an important part of the background of this

thesis, which focuses on the distribution of moose and hare foraging activity in

relation to food quantity and quality. The mountain hare practises caecotrophy and

particle separation in the hindgut which preferentially accelerates excretion rather

than retention of larger poorly digestible food fragments, whereas the moose

physically degrades ingested food by chewing and rumination and is likely to be

unable to respond to lower quality diets by increasing food intake due to passage

constraints in its foregut. The utilisation of food resources by these two herbivores

(paper II) is likely to be underpinned by these contrasting methods of digestive

processing.

1.3. Study species

Figure 3. Mountain hare (Lepus timidus) in white winter pelage. Photo by Sara Öhmark.

5

1.3.1. Mountain hare (Lepus timidus)

The mountain hare (Figure 1) is a generalist herbivore with a capacity to rely on

food sources that are very low in nutrient content (Pehrson 1983b). It is a hindgut

fermenter that displays an intermediate feeding strategy between grazing and

browsing and it is highly flexible in diet intake (Hulbert & Andersen 2001). In winter

in Fennoscandia, the hares predominantly browse on species of birch and willow,

whereas the summer diet mainly consists of herbs (Johannessen & Samset 1994;

Pulliainen & Tunkkari 1987). If high quality food such as grass is available it is

preferred also during winter as browse material is eaten when the availability of

better-quality food is restricted (Hulbert et al. 2001). The choice of food source

among mountain hares has been suggested to depend on the digestibility, fibre

content and concentration of plant secondary compounds, rather than on nutrient

concentration in plants (Hjältén & Palo 1992).

Hares cannot rely on fat reserves during harsh periods as is common for larger

animals like the moose (Alces alces), but will instead maintain their body weight

throughout winter (Cederlund et al. 1991; Lindlöf 1980; Thomas 1987). Since hares

also have a high metabolic rate relative to larger herbivores (see section 1.5), the daily

food intake is of utmost importance. To maintain itself on a diet of twigs, a mountain

hare weighing 3.5 kg needs an intake of at least 500 g fresh twigs per day (Pehrson

1979). Caged mountain hares maintain their body weight in outdoor winter

conditions when fed on twigs from deciduous plants, including birch and willows,

with the exception for birch twigs of less than 1.5 mm in diameter (Pehrson 1983b).

Even in habitats were a single plant species is dominant, hares are able to survive

(Angerbjörn & Pehrson 1987; Hewson 1976). Under such conditions, choosing

individual plants and plant parts with high nutrient content is important for the

hares to meet their nutritional demands. In habitats with mixed vegetation, the scope

to obtain sufficient nutrient intake from a mixed diet may diminish the significance

of the nutritional quality of a single species (Angerbjörn & Pehrson 1987).

Hares are not competitive for territory, although they show high site-fidelity both

between years and between seasons (Dahl 2005). The establishment of a home range

occurs within 90 days of age for a mountain hare in northern Sweden (Dahl &

Willebrand 2005). In harsh environments with uneven distribution food, it is

essential that a home range includes sheltered resting sites and a sufficient amount

of forage (Hewson & Hinge 1990). As hares track food resources that change over

seasons, their home ranges will be focused to areas with comparatively high quality

and availability of food (Dahl 2005). Relocation of snowshoe hares has been found

to cause an increased mortality due to predation, which suggests that local

6

knowledge is important for the survival of hares (Sievert & Keith 1985). A study in

northern boreal parts of Sweden (Dahl & Willebrand 2005) and a study in boreal

Finland (Kauhala et al. 2005) gave median annual home ranges of 271 hectares, and

of 206 hectares, respectively. Results from these studies showed annual fluctuations

in home range sizes, with smaller median values during summer and autumn and

larger during winter and spring. The combination of a restricted home range size, a

high metabolism and a high food intake rate, makes the mountain hare a suitable

species for studying foraging mechanisms in response to food availability and

quality.

Figure 2. Moose (Alces alces). Photo by Sara Öhmark.

1.3.2. Moose (Alces alces)

The moose (Figure 2) is a large ruminant weighing 250-600 kg that typically feeds

from browse material (Cederlund et al. 1986; Wam & Hjeljord 2010). It is considered

a model species for ecological studies of a browsing ruminant (Shipley 2010) because

it occupies a wide global range, is of high recreational interest, and has high

economic and ecological impacts on its surroundings (Milligan & Koricheva 2013;

Muiruri et al. 2015; Condon & Adamowicz 1995). The moose can behave as a

generalist forager, or as a specialist depending on season and location, which has

made it difficult to define its dietary niche. Shipley et al. (2009) suggested that it

should be termed a facultative specialist, i.e., an animal that has the potential of

keeping a varied diet but that eats a narrow range of food plants of comparatively

poor nutrient value during certain times or at certain locations. Moose have a low

passage rate of fluids and small particles through their forestomach compared with

7

other large ruminants. This has been suggested to limit food choice for moose to

browse material (Lechner et al. 2010). Moose also have a long cropping time relative

to other herbivores which restricts intake rates (Shipley et al. 1994).

During summer, moose predominantly eat deciduous leaves and forbs, while its

winter food mostly consist of deciduous and coniferous twigs (Shipley et al. 1998;

Wam & Hjeljord 2010). Summer intake rates are higher than during winter, while

the rate of selectivity is higher during summer as more diverse food items are

available (Renecker & Hudson 1986). However, selectivity of food items during

winter can to some extent make up for low availability of forage (Shipley et al. 1998).

As the possibility to make selections of food types is limited in winter the animals

are confined to a restricted diet which may not support a positive energy balance

(Sæther & Gravem 1988; Moen et al. 1997). Moose are most active during sunset and

sunrise and alternate bouts of active food search with inactive bouts when the food

is processed by rumination (Cederlund & Sand 1994). During winter more time is

needed for rumination as the food contains higher amounts of fiber, while less time

is put on actively searching and ingesting food (Renecker & Hudson 1989). Daily

intake of dry matter per kilo body weight varies with age and gender of the moose,

and with forage availability (Vivås & Sæther 1987; Nyström 1980; Renecker &

Hudson 1986). Daily winter dry matter intake for moose calves in Grimsö, central

Sweden, has been estimated to 22 grams per kilo body weight (Nyström 1980).

Home range sizes for moose vary with age and male moose in central Sweden

have increasing home range sizes with age, but this does not apply for females. Male

moose (25,9 km2) tend to have larger home ranges than females 13,7 km2) (Cederlund

& Sand 1994). Differences in home range sizes may be more correlated to different

needs for nutrients and for social activity, rather than to just body size (Dussault et

al. 2005). Several studies of moose foraging patterns suggest that moose choose their

diet according to an optimization of net energy intake and not as a response to the

frequency of forage occurrence (Danell & Ericson 1986; Lundberg et al. 1990;

Belovsky 1978). Månsson et al. (2007) on the other hand determined food availability

as the most important variable steering moose intake rate, regardless of spatial scale.

1.4. Hare and moose in mountain birch forest

Food shortage during winters is a limiting factor for several mammalian

herbivores in boreal zones (Skogland 1985; Krebs et al. 1995; Huitu et al. 2003). When

the ground is covered by snow, the accessibility to low plants becomes limited and

for animals that feed above the snow cover, twigs and bark of woody plants is the

8

main available forage (Hodder et al. 2013; Nordengren et al. 2003). When preferred

food items occur at low densities the animal cannot fulfil its food requirements by

selecting the best plants only, but must also eat less preferred plants (Pulliainen &

Tunkkari 1987). Mountain birch is an important food source for several herbivores

in alpine and subalpine areas of Fennoscandia, although not always favoured if

other deciduous species are available in large amounts (Pulliainen & Tunkkari 1987).

In mountain birch forest the low diversity of food plants during winter forces

herbivores above snow cover to keep a narrow diet (i.e., facultative specialization)

(Shipley et al. 2009).

For moose and hare, the quality of woody plants is an important factor determining

foraging patterns (Pehrson 1983b; Ball et al. 2000). These animals are able to

discriminate between and within plants and they feed selectively from plants high

in nutrient content and low in fiber and secondary plant compounds (Rousi et al.

1991; Stolter et al. 2005). Despite the low plant species diversity in mountain birch

forest, herbivores will find variation in forage quantity and digestibility over

multiple scales. Concentrations of nitrogen and secondary compounds in mountain

birch twigs vary within and between individual trees and between sites in the

landscape (Hodar & Palo 1997). Within individual birches, twig diameter, height

level and tissue type are important for physical and chemical characteristics that

determine nutritional quality for mammalian herbivores (Palo et al. 1992; Hodar &

Palo 1997; Nordengren et al. 2003). With increasing diameter the fiber content

increases while the level of plant secondary compounds and nutrients decrease (Palo

et al. 1992; Hodar & Palo 1997).

Herbivory can induce morphological and chemical responses of plants that can

subsequently alter plant selection of herbivores. It has been suggested that such

induced plant responses provide plants with protection from herbivory, as when

insect herbivory on leaves of mountain birch cause subsequent growth of leaves

with reduced nutritional value (Hanhimäki 1989). However, moose winter browsing

and simulated browsing of mountain birch buds prior to leaf development has

induced development of leaves with higher nutritional values (Senn & Haukioja

1994; Stark et al. 2007). Further, clipping of buds yields higher production of new

shoots, as well as leaves with increased sizes (Lehtilä et al. 2000). Danell and Huss-

Danell (1985) showed that hares do not browse differently on slightly or moderately

moose browsed birches, whereas moose preferred previously browsed silver birch

B. pendula and downy birch B. pubescens to unbrowsed birches.

9

1.5. Consequences of contrasting body sizes

Animals require energy for physical functions such as metabolism,

thermoregulation and locomotion. The basal metabolic rate (BMR) is a summary of

the minimum energy expenditure for an endothermic animal at rest (Elgar & Harvey

1987). Among herbivorous mammals, the basic metabolic rate (W/kg/day) decreases

nonlinearly with body weight (Kleiber 1932). Kleiber (1932) suggested that the

metabolic rate scales with body mass to the power of ¾, but this has been the subject

of some debate and other exponents for this relationship have been proposed, the

scaling exponent of ²/3 being one competing hypothesis (Dodds et al. 2001).

Although the energy expenditure of animals is generally dependent on body mass,

other features among the animals such as taxonomic affiliation, habitat, diet and

foraging mode are possible determinants of the FMR (Nagy 2005). A nonlinear

decrease of basal metabolic rate to body weight has implications for the energetic

requirements of animals. Although the total energy requirement is higher for a large

animal, such as the moose, compared to a small animal, such as the mountain hare

(L. timidus), the required amount of food per kg body weight is larger for the hare

than for the moose.

While metabolic rate dictates the energy demand for an animal, the intake of food

is limited by the animal`s gut capacity. There is a linear increase of gut capacity with

body weight resulting in a diminishing metabolic requirement/gut capacity for

larger animals (Demment & Van Soest 1985). This results in the larger animals being

able to tolerate a gut fill of lower quality than smaller ones. In other words, food

quality demands are more relaxed for moose than for hares as moose can make up

for low diet quality by ingesting larger quantities of food. Larger gut size in relation

to body size would allow for a longer retention time of food and hence a more

effective microbial fermentation of food. However, large animals must also

compensate for disadvantages that are related to increased body size. For examples,

the ratio of gut surface: gut volume is negatively correlated with the volume of the

gut, and large animals ingest larger particle sizes, compared to small animals (Clauss

& Hummel 2005). In summary, although mountain hare and moose in mountain

birch forest rely on the same food source whilst enduring severe winter conditions,

they face different digestive and metabolic constraints. These body size

considerations act in concert with the digestive strategy differences described in

section 1.2 to determine the overall nutritional strategy of these contrasting

mammals.

10

1.6. Foraging models/optimality models

In 1966, two simultaneously published studies aimed to explain animal diet

choice through quantification of time or energy expenditures during foraging

(Emlen 1966; MacArthur & Pianka 1966). Both studies suggest that natural selection

should favor an optimized exploitation of available food sources among animals.

Following these publications, a number of studies have explored and suggested

potential mechanisms that might result in an optimized foraging behavior. These

include animal diet choice, patch choice, time allocation choice among patches, and

speed and movement patterns (Reynolds 2012; Wilson et al. 2013; Farnsworth &

Illius 1998; Courant & Fortin 2012). Two basic problems of animal foraging have

been addressed by foraging models, i.e., what food to eat and when to leave each

patch of food. The first problem includes the event of encountering food patches, as

well as the possible capability of the animal to recognize and categorize the food.

The second problem can be measured as the amount of time spent at each patch of

food or as the density of food left in in a patch by a foraging animal (Stephens &

Krebs 1986; Bedoya-Perez et al. 2013).

A model termed the “marginal value theorem” (MVT) predicts that since

environmental characters often differ within the habitat of animals, the optimized

use of the habitat must vary with different patches of the habitat (Charnov 1976;

Parker & Stuart 1976). In order to optimize the habitat exploitation, an animal should

only forage in a patch as long as the rate of energy gain within the patch does not

sink below an average energy gain rate for the whole habitat. A similar way of

reasoning around the optimal utilization of patches is evident in the concept of

“giving up time“(GUT) (Krebs et al. 1974). This is a measurement of a threshold time

each animal reach at a patch while searching for food, before leaving the patch in

search for a new food source. Determining factors for GUT is the quality of each

patch as well as the distance to adjacent patches much in similarity to the MVT

(McNair 1982; Bailey & Provenza 2008). Yet further cost associated with foraging are

to be considered, than those accounted for within the MVT. Costs of risk may be

associated to foraging in a certain patch, and of missed opportunities as other

options for the time spent at the moment of foraging will be lost (Jacob & Brown

2000; Brown 1988). Optimization and MVT seems to work reasonably well for

herbivores when operating at scales where patch depletion occurs but will not

always explain foraging patterns when forage is plentiful (Bailey & Provenza 2008).

However, selection for high plant quality is predicted to increase with high forage

availability, as has been shown for moose (Lundberg & Palo 1993). An optimal

foraging model designed to predict animal distribution between resource patches is

the “ideal free distribution” (IFD) model. This model predicts that the density of

11

animals in a habitat will reflect the density of available resources within the habitat

(Fretwell & Lucas 1970; Stewart & Komers 2012). The idea that herbivores should

strive to optimize their food intake and that the distribution of food resources will

explain the distribution of foraging animals is fundamental for the studies presented

in this thesis. The IFD is tested through hypotheses stated in papers I and II. The

MVT and GUT are focal considerations in the study of patch manipulation presented

in paper III, as well as in paper IV where the focus is on herbivores´ assessment of

costs and benefits associated with different habitats.

Many foraging optimality models assume that animals should be able to estimate

the cost of transit between different patches of feeding areas, as well as the expected

gain of food intake at the different feeding patches. However, the assumption that

animals would have complete knowledge of their surroundings has been questioned

(Carmel & Ben-Haim 2005; Bergman et al. 2005). It has been suggested that animals

have an imperfect knowledge of their surroundings and that they will use recent

experience to evaluate each patch and update their knowledge (Marshall et al. 2013),

or alternatively, use sensory capability such as vision or olfaction (Valone & Brown

1989).

1.7. Scale dependence

Within the field of ecology, the concept of scale became rapidly recognized during

the 1980s (Schneider 2001). In essence, all patterns within an ecological system are

dependent upon the level of scale at which they occur (Wiens 1989). Problems of

scale within the science of ecology are related to both time and space. Some

ecological phenomena that occur over large temporal or spatial scales may be

difficult to monitor or detect while patterns detected at small scales may not

represent patterns occurring at wider scales (Johnson et al. 2001; Schneider 2001;

Månsson et al. 2007). The variability in time and space of ecosystems can be

expressed in numerous fashions such as landscape patchiness, (Wang et al. 2014;

Johnson et al. 2001) species composition (Freestone & Inouye 2006; Mathisen &

Skarpe 2011; Olsson et al. 2012) or process rates (Rastetter et al. 2003; Bardgett &

Wardle 2003; Ohashi & Hoshino 2014). From this follows that all species will be

affected by several different ecological factors simultaneously operating across

multiple scales (Searle et al. 2005; Gross et al. 1995; Owen-Smith 2014). To what

extent different scale-dependent phenomena can affect an animal will depend upon

characters intrinsic to the species (Borthagaray et al. 2012; Eby et al. 2014). Ecological

phenomena operating on small geographical scales are likely to be of importance to

animals that have a restricted mobility, due to size or other physical constraint

12

(Gehring & Swihart 2003). Animals with ability to move over extensive areas are

impacted by and in turn impact ecological phenomena occurring across small as well

as large patches and landscapes (Veen et al. 2012; Edenius et al. 2002; Månsson et al.

2007). As an example, Bergman et al. (2005) showed a difference in feeding strategy

between roe deer (Capreolus capreolus) and rabbits (Oryctolagus cuniculus). An

important result from that study was that rabbits and deer have different

perceptions of available forage, due to their different height. The roe deer make

selection of plants at a patch level as well as choosing plant parts, while rabbits focus

forage selections to a more spatially narrow scale level within plants. Differences in

habitat use over several spatial scales is also expected between hare and moose

(paper II), at least partly due to the perception-based differences presented by

Bergman et al. (2005).

To understand and predict patterns of movement, distribution and resource

utilization of animals it is necessary for researchers to adapt a multi-scale view

(Harvey & Fortin 2013; Van Beest et al. 2011). With increasing scale of observation

the spatial complexity and number of potential interactions between species and

structures grows. Therefore, drivers of foraging decisions by herbivores at small

scales are fairly well understood and predictable, while landscape scale interactions

are more difficult to interpret (Bellu et al. 2012; Van Beest et al. 2011; Månsson et al.

2012). The daily food intake of an animal can be summarized as an aggregate of

many small-scale processes (Laca et al. 2001). Bites are commonly regarded as the

finest unit within the foraging behaviour of animals (Kotliar & Wiens 1990;

WallisDeVries et al. 1999). Short-term intake rates will be influenced by bite size, and

this in turn is decisive for the time it takes to chew each bite. Large bites allows for

the gut to be filled, and for the nutritional requirements to be met more quickly. That

leaves more time for competing activities such as avoiding predators or reproducing

(Shipley 2007). Physical constraints is suggested to be of primary importance for

food intake at small scales such as bites. At the larger scales, such as larger patches

and home ranges, and at larger time scales, spatial memory may be used for foraging

decisions (Bailey et al. 1996). Animals can increase their energy gain by using their

memory of past resource distribution and hence, decrease environmental

uncertainty (Merkle et al. 2014).

Objects that are closely related in space are often more similar than distant objects

and this phenomenon, termed “spatial autocorrelation” is found for most

environmental data (Legendre & Fortin 1989). An example is that food items for

herbivores are likely to be found in patches rather than being evenly distributed in

space due to restricted spread of seeds, or because local conditions for the

establishment and growth of plants vary (Dirnböck & Dullinger 2004). An example

13

of how spatial and temporal autocorrelations operate is how leaf development and

winter dormancy of birch occurs in synchrony within species and at local geographic

sites (Li et al. 2003). This has implications for standard statistical analysis methods

like regressions since assumptions of a random spatial distribution of data becomes

violated (Miller 2012). If the spatial structure of data added into models is not

accounted for, the risk of type I errors increases (Legendre et al. 2002). However,

spatial dependence between observations is not just a nuisance during statistical

analysis; it is one of the most important issues in the analysis of spatial data

(Legendre & Fortin 1989). For an ecologist it is relevant to determine the spatial scale

at which food resources for herbivores are clustered, as it provides an explanation

for the spatial distribution of herbivory (Saracco et al. 2004). To identify the scales of

significant positive (clustered) or negative (regularly spaced) patterns, a statistic

termed local Moran’s I can be used (Anselin 1995), as was used in paper I and II. If

a foraging herbivore closely tracks a certain resource the patterns of spatial

autocorrelation of food intake over increasing spatial scale is assumed to resemble

that of the tracked resource (Saracco et al. 2004). However, a precondition is that the

animal is able to collect information or to respond to environmental variation at the

scales over which the resource is clustered.

1.8. Edge effects

Edges between adjacent patches are central features in landscape ecology as they

control fluxes of energy and material, act as barriers or as specific habitats

(Cadenasso & Pickett 2000; Vidus-Rosin et al. 2012). The abiotic and biotic conditions

along edges will be characterized by conditions prevailing in each of the adjacent

habitats, which makes the perimeter of an ecosystem different from its interior

(Harper et al. 2005; Magura 2002). As an example, forest edges generally exhibit

lighter and dryer conditions than the forest interior (Williams-Linera 1990). Apart

from such abiotic edge effects there are also direct biological effects from the

physiological conditions along edges, such as an increase in light-demanding plant

species near edges due to improved light conditions (Guirado et al. 2006). Indirect

biological effects also depend on the presence of edges, such as rates of predation

and parasitism (Ludwig et al. 2012; Hahn & Hatfield 1995). It was early recognized

that edges would impact the dispersal abilities of game species (Leopold 1987) and

later it has been recognized that species responses to edges can either be positive,

negative or neutral depending on species and context studied (Debinski & Holt

2000). Species that are adapted to conditions intrinsic to interior areas of a certain

habitat will be less abundant near edges and such species are expected to experience

negative effects from habitat fragmentation (Herkert 1994). The importance of

14

negative edge effects to species distributions and abundances have been

investigated in fragmented landscapes such as forests with clear-cuts (Harper et al.

2005; Borchtchevski et al. 2003). The distribution of vegetation and the presence of

forest edges are landscape features that impact the distribution and foraging

activities of herbivores (Ewacha et al. 2014; Brazaitis et al. 2014). Following global

climate change, altered landscape composition is to be expected especially in arctic

and alpine habitats due to ongoing alterations in the location of tree lines (Kullman

& Öberg 2009). To evaluate the consequences of this, it is essential to investigate the

present impact from forest distribution on habitat use of herbivores in arctic and

subarctic environment (paper IV).

1.9. Baiting and supplementary feeding of wild herbivores

As herbivores distribute themselves in response to resource distribution, artificial

placement of food is expected to alter herbivore distribution and forage selection.

This provides the opportunity to steer wildlife away from e.g. areas of heavy road

traffic to decrease the risk of accidents, or from sensitive or economically important

vegetation (Sahlsten et al. 2010; Garrido et al. 2014). Using food to attract animals for

these purposes, or for facilitating research, or tourism that requires observation, or

for trapping, culling or for distribution of vaccines, is referred to as baiting (Dunkley

& Cattet 2003). Supplementary feeding is used for the purpose of increasing or

maintaining population sizes where food availability is a limiting factor, such as

during winter in boreal forests (Putman & Staines 2004). The lack of effect from

artificial feeding on foraging pressure on natural vegetation at the landscape scale

implies that added food mainly impacts feeding patterns at local scales (Van Beest

et al. 2010).

The practice of adding food for wild populations is controversial, as it can

increase the risk of intra- and interspecific disease transmission (Sorensen et al.

2014). Artificial placement of food (which in this thesis refers to food addition for

the purposes of baiting or supplementary feeding) can also impact non-target

species (Pedersen et al. 2014). Placement of food can also cause problems such as

encounters between animals and people, and nuisance behavior among animals that

are drawn to human facilities. Steyaert et al. (2014) suggested that individual

variation in responses to additional food will dilute the population responses to

added food. Studies of mountain hares have revealed that individuals will be more

or less prone to use supplementary food or bait depending on their condition and

that only a subset of a target population would use it (Newey et al. 2010; Bisi et al.

2011). The response of herbivores, like moose, to additional food also depends on

15

the composition of the surrounding landscape and on the prior distribution of the

target population (Gundersen et al. 2004). In subarctic birch forest, the low diversity

of food plants that are available above the snow cover during winter limits herbivore

food choices. The daily food intake and hence the daily selection of foraging sites is

imperative for hares to maintain their energy balance during winter in northern

environments (Thomas 1987). Mountain hares in subarctic birch forest therefore

provide a suitable system for studies of herbivore responses to food patch

manipulation, (paper III in this thesis).

2. OBJECTIVES

As summarized in the review above, mountain hare and moose ought to respond to

variation in plant quality and quantity. It is expected that their winter browsing will

be located in areas that contain high availability of good-quality forage relative to

the average availability in the surrounding landscape. As the distribution of good

patches for foraging is steered by e.g., topography, elevation and soil nutrients,

herbivores would show predictable foraging patterns over time and over the

landscape. Given the physiological constraints of these species, hare and moose are

expected to respond to resource allocation at contrasting spatial scales, which in turn

would lead to separate location of their foraging activity. As herbivores

continuously track good areas to feed in, manipulation of forage distribution should

result in altered foraging distribution. Forests provides shelter form severe weather

and high availability of winter browse relative to un-forested areas. Food resources

situated in forest should therefore be preferred by herbivores over resources situated

in un-forested areas. These predictions were tested in the four studies that are

presented in this thesis.

In paper I, it was tested if browsing patterns by moose in a mountain birch forest

were consistent and, hence, predictable between two periods separated by 14 years.

It was ascertained whether density of food plants could explain the distribution of

moose browsing and if the spatial scale where moose browsing was clustered was

similar between the two periods.

Paper II investigated whether the foraging distribution of hare and moose would

be separated spatially as predicted by their contrasting body size, even in a situation

when the two species share the same principal food source. This was tested on

several spatial scales, from the level of individual plants to the landscape scale. It

was predicted that hares would target areas with high densities of small birches

while moose would prefer areas with larger trees.

16

The aim of paper III was to test if the addition of fodder to local patches would

enhance patch quality perceived by hares, so that the utilization of natural food

would increase. It was assessed how the quality and quantity of the added food

would steer the local use of vegetation. It was predicted that browsing on birch

induced by the addition of food would increase with increasing birch density and

with previous patch utilization.

In paper IV, it was investigated whether mountain birch forest cover would impact

habitat use of mountain hares. It was tested if the intake of added food would

depend on distance from forest edges, and if microclimate characters and the

presence of red fox would differ between forested and treeless areas.

3. METHODS

3.1. Study area

The field studies were conducted in a subarctic tundra landscape near the village

of Abisko (68°21N, 18°49 E) (Figure 3 a-b). The forest in this area is part of the

northern boundary of tree growth in Scandinavia and is exposed to severe weather

conditions at all times of the year. The latitude, along with a mountainous

topography and the close proximity to the Atlantic coast, characterizes the climate

and weather (Holmgren & Tjus 1996). The Abisko Valley has lower amounts of

precipitation compared to the surrounding mountain region, with a yearly

precipitation of 300 mm per year. The snow cover amounts on average to 50 cm at

its peak in March (Kohler et al. 2006).

The mountain birch forest landscape is characterized by a patchy tree growth

intersected by open heathland (Figure 4). Mountain birches are generally 4-6 meters

high and commonly polycormic (multi-stemmed) on dry and nutrient-poor sites

while monocormic trees (single-stemmed) grow on more moist and rich sites

(Bylund & Nordell 2001). The most common ground-layer vegetation consists of

dwarf shrubs such as bilberry (Vaccinium myrtillus), crowberry (Empetrum nigrum)

and dwarf-birch (B. nana), along with some species of grass, mosses and lichens

(Tømmervik et al. 2009). In addition to mountain birch, tree species present in the

area are willows, grey alder (Alnus incana), pine (Pinus sylvestris) and aspen (Populus

tremula) (Berglund et al. 1996).

17

Figure 3 a-b. Location (a) of the study area in northwest Sweden, marked with a black

square. Orthophoto (b) of the northern part of the Abisko Valley with Mt. Njulla

seen in the upper left corner of the image. The Abisko Scientific Research

Station is marked with a white arrow.

Figure 4. Part of the study area viewed from Mt. Njulla with the lake Torneträsk seen on

the left in the image and the tree line on the far right. The mires, heaths and

a. b.

Abisko

Torneträsk

18

lakes that intersect the forest are seen as white patches. Photo by Sara

Öhmark.

The cover of shrub and trees has increased in the Abisko Valley from the 1970s

to 2010 (Rundqvist et al. 2011). This vegetation increase is mostly observed for

mountain birch and dwarf birch, while willows show inconsistent patterns of

growth with time. The vegetation change is possibly due to past and present human

activities in the area, due to recovery from insect outbreaks and/or due to an ongoing

climate warming (Emanuelsson 1987; Tenow 1996; Callaghan et al. 2010; Kullman &

Öberg 2015). The mountain birch forest is unmanaged but it is affected by defoliation

during repetitive events of large-scale insect outbreaks (Tenow 1996). An outbreak

of the autumnal moth (Epirrita autumnata) defoliated and to large parts killed the

birch forest in the Abisko Valley in 1955/56. Much of the present forest is therefore

derived from basal sprouts from stems killed by the moth larvae (Tenow 1996).

Another factor behind killings and damage of tree stands in the area is the

occurrence of severe frost during growing seasons and during dormant stages of the

trees. Mountain birch grows near its altitudinal limit in the Abisko Valley and is

affected by aboveground and belowground temperature. Growth rate and nitrogen

uptake are both limited by low temperatures (Weih & Karlsson 2002). The woody

vegetation in the area is also subjected to herbivory during winter and summer by

vertebrate herbivores; these are apart from moose and hare ptarmigan (Lagopus

mutus), willow grouse (L. lagopus) and several species of voles (Microtinae). Moose

browsing has a notable impact on the vegetation in the area. Young pines (Pinus

silvestris) in the Abisko Valley show signs of continuous browsing by moose and this

herbivory in combination with fungal infection is suggested to be a primary cause

of suppressed pine recruitment in the area (Stöcklin & Körner 1999). The Abisko

Valley is used for reindeer grazing during summer and autumn (information from

the Sametinget webpage: www.sametinget.se/9392).

Research on climate, geology and ecology in the Abisko Valley and the

surrounding area is intense since the establishment of the Abisko Scientific Research

Station in 1913. Environmental conditions such as snow depth and daily

temperatures and wind speeds are monitored, and some of these recordings have

been ongoing for over a century (Jonasson et al. 2012). The Abisko national park

covering a 77 km2 area was formed in 1909. Within the protected area lies the Abisko

tourist station built in 1902, a ski lift, and the northern end of the Kungsleden trail,

a path that apart from serving as a ski trail during winter is used by snow mobiles

and dog sleds. During summer, the path is mainly utilized by hikers. At present the

19

Abisko national park is the most visited national park in the Norrbotten county with

some 40 000 visitors per year.

3.2. Data collection

For paper I and II we made observations of un-manipulated winter browsing by

hare and moose on mountain birch and willows. It is possible to distinguish hare

browsing from moose browsing by the appearance of the browsed twig. Hares clip

twigs with their sharp incisors, leaving a smooth cut surface (Figure 5 a). Moose use

their molars to rip off twigs and this gives a rugged surface at the cut (Figure 5 b).

Further, the age of the cut is revealed by the color of the twig at the cut, as the wood

turns grey with time. Twigs cut during the current winter season has a light color

that is easily distinguishable from twigs cut during previous winter seasons (Figure

5 a-b).

a. b.

Figure 5 a-b. Birch twig cut by winter browsing hare (a) and moose (b). The twig cut by hare

was browsed prior to the winter season when the photo was taken, which is

apparent from the dark color of the wood at the cut, while the moose browsing

was recent, as is apparent from the light color of the wood at the cut. Photos by

Sara Öhmark.

Occasionally it was difficult to discern if browsing on very fine birch and willow

twigs was done by hare or willow grouse. If there was any doubt, the browse was

noted as caused by an unknown browser. Although heavy reindeer summer

browsing can reduce shoot length of willows, this occurs through growth responses

20

following leaf-stripping, not through clipping of twigs, and therefore this is highly

unlikely to be confounded with the effects of moose browsing (Olofsson &

Strengbom 2000). Lichens are the principal winter food for reindeer in Fennoscandia,

while utilization of vascular plants increase with high reindeer population density

and low availability of lichens (Danell et al. 1994; Heggberget et al. 2002; Kumpula

2001; Skogland 1984).

During the data collection in 2010, there was no reindeer tracks within the sample

plots. Reindeer tracks were observed on a few occasions in 2010 in the study area,

but no browsing on birch or willow twigs was found near reindeer tracks. It is

therefore unlikely that effects of reindeer winter browsing would compromise the

results of the browsing survey of moose presented in papers I and II. Moose tracks

were commonly found below birches and willows with fresh browsing.

3.3. Response variables

In the studies presented in this thesis, foraging activity of free-ranging mountain

hare and moose on winter browse was measured and set in relation to natural

environmental conditions such as vegetation density, snow depth and elevation.

Foraging intensity by hares on added food under varied natural conditions was

measured. Finally, foraging intensity by hares on natural browse in response to

addition of forage was assessed. For papers I, II and III, the relative browsing

intensity between different sites in the study area was measured, but not the

absolute intake by hare or by moose. For the purpose of studying relative offtake of

browse per site, it was sufficient to count the number of apical birch and willow

twigs cut by moose or by hare per unit area.

For paper I, the accumulated moose browsing on birch and willow deriving from

the winter seasons of 1998-1996 and 2009-2010 was measured. Thus, only

observations of fresh moose browsing were used. The distance between sites with

different browsing intensities was measured to assess the occurrence of spatial

autocorrelation (clumped distribution) of foraging activity at different spatial scales.

The relative moose density for the two winter seasons was estimated by counting

numbers of moose tracks crossing transects.

For paper II, hare and moose browsing deriving from both the winter season of

2009-2010 and from previous winters was measured (Figures 4a-b). It was noted if

both fresh/old browsing and hare/moose browsing occurred within the same sample

sites and at the same birch or willow stems. Distance between sample plots to test

21

for the occurrence of spatial autocorrelation at different spatial scales was assessed

also in this study.

For paper III, numbers of hare-browsed birch twigs were measured at sites

manipulated through addition of food and these observations were compared to

numbers of browsed twigs at un-manipulated sites. Numbers of visits by hares after

the termination of the experiment at ex-manipulated sites and at control sites were

measured as the number of hare tracks crossing these sites. Daily observations of

browsing activity was measured at some manipulated sites both while added food

was available for hares and after the food had been depleted by hares.

For paper IV, hare responses to forest cover was measured as the amount of

consumed added forage in areas with and without mountain birch forest. In this

study, the effect of forest cover on microclimate (local air temperature and wind

speed) was also measured.

3.4. Design of sample plots

For paper III and IV, the field studies included artificial placement of food for

hares. This was either hay or straw, tied in 30-gram bunches that were tied to trees

or shrubs, or alternatively, where no vegetation was present, to sticks that were

inserted into the snow or into lake ice using a drill. Visual cues of hare activity was

also used (fresh browsing on twigs, tracks, urine or faeces) to determine if visits from

hares had occurred at the artificially placed food (Figure 6). Such cues were often

quite evident but after heavy snowfall or during windy conditions, tracks and faeces

would be concealed. Surveillance of the sites with added food using film cameras

provided a complement to the visual cues of hare visits, and also revealed if other

species than hares had visited the sites and/or utilized the added food. The film

material also revealed the diurnal activity patterns of hares in the study area.

22

Figure 6. Hare tracks and faeces at a site with added food; bunches of hay attached to a

mountain birch.

We measured vegetation density and hare browsing intensity within sample

plots in all four studies presented in this thesis, but the size and shape of the plots

differed between studies. Plots used for paper III (5*5 m with addition of two

transects placed adjacent to each plot of 2*20 m=105 m2) was smaller compared to

the plots presented in papers I and II (25*25 m=625 m2). The design of sample plots

was intended to represent local vegetation characteristics and browsing patterns.

Where mountain birches were polycormic (as seen in Figure 6), an individual birch

could cover several square meters. The sample plots used in papers I and II were of

sufficient size to include several polycormic birches. They would generally also

include both willow and birch vegetation where willow shrubs of large sizes

occurred, which provided information of browsing pressure on birch adjacent to

willows. The inventory of these plots was more time consuming compared with the

plots used for paper III. The large number of sample plots necessary to provide

replication of all combinations of treatments in addition to controls called for a

design that allowed for a rapid inventory of vegetation and hare browsing. The

23

transects in paper III provided measurements of variation in vegetation and

browsing pressure while reducing the surface assessed, and hence the time spent

per site. Another reason for restricting the size of the sample plots for paper III was

that we aimed at comparing responses from hares to different site treatments in

nearby and, hence, according to the principle of spatial autocorrelation, similar sites.

The size of the sample plots partially determined the size of the blocks that contained

groups of plots. The chance of observing browsing within a plot will increase with

the size of the sample plot, but browsing intensity measured as cut twigs per unit

area or percentage of trees with browsing is not impacted by this.

4. RESULTS AND DISCUSSION

4.1. Paper I

The measurements of vegetation density in 1996 and in 2010 follows the general

trend with increasing cover and density of trees and shrubs described by Olofsson

et al. (2009) and Rundqvist et al. (2011). Both the number of sample plots with

occurrence of willows and the mean density of willows per plot increased from 1996-

2010, but Rundqvist et al. (2011) did not find a consistent trend in the cover of

willows in the Abisko Valley from 1976-1977 to 2009-2010. Results from paper I

shows that birch densities in 1996 were positively correlated to birch densities in

2010 but for willows there was no such consistency over time.

Microsite conditions exhibit sharp contrast over short distances in tree line

ecotones in Fennoscandia due to the varied local topography and this gives a

consistent spatial pattern of growth, morphology and reproduction patterns of

mountain birch (Anschlag et al. 2008). Mountain birch reproduces with root suckers

as well as sexually. After major disturbances like insect attacks, the regrowth of root

shoots is therefore a major part of the recovery of the birch forest (Tenow & Bylund

2000). Root shoots are less sensitive to herbivory than the growth of seedlings, which

adds to the importance of asexual regrowth after disturbances and this promotes

consistent spatial distribution of mountain birch over time (Lehtonen & Heikkinen

1995). In paper I it was predicted that moose foraging patterns in mountain birch

forest should be consistent over time and results showed that the spatial scale where

foraging decisions takes place remained the same after 14 years. Further, moose

browsing was concentrated to the same sites in 2010 that were most intensely

browsed in 1996.

24

These findings demonstrate that moose browsing patterns can be predicted over

time. Defining factors and processes that remains stable over time are important for

the success of management and conservation actions as these rely on accurate

predictions of future conditions (Sutherland 2006; Seiler 2005; Gordon et al. 2004).

There was less snow in 1996 than in 2010. If snow depth is positively related to

vegetation density, deep snow could hinder moose from utilizing sites with good

availability of forage. However, snow depth was not a significant parameter in a

model predicting moose browsing intensity. There was no positive correlation

between birch density and snow depth and a plausible explanation for this is that

local topography is a strong determinant of snow accumulation (Grünewald et al.

2013). The total density of willow and birch was not a determinant of browsing on

birch at multiple spatial scales. However, both willow and birch densities clustered

at the same spatial scale as moose browsing showing that vegetation is a

determinant for moose foraging at certain spatial scales.

There was no significant effect from snow depth on moose foraging distribution.

Moose are well adapted to cope with high snow depth compared to other ungulates

(Telfer & Kelsall 1984). Even if the local variation in snow depth may hinder moose

from accessing forage at certain sites, it would not explain foraging patterns of

moose in the study area.

4.2. Paper II

Hare and moose targeted different areas during foraging and moose utilized

higher and thicker birches than the hares did. Hares are able to walk on the surface

of the snow while moose sinks through the snow, which will allow the hare to reach

high-growing browse at sites with high snow accumulation. However, the mean

snow depth of 50 cm at the peak in March would not be enough for the hares to

reach to the same heights as moose and this restricts the possibility for hare to

respond to the variation with height in forage quality and quantity that birches

display (Nordengren et al. 2003). There was a positive correlation between fine-

stemmed and thick-stemmed birches, which is expected from the occurrence of root

suckers and basal sprouts. Hares tracked areas with high densities of birches

regardless of stem diameters. Moose foraging distribution was positively correlated

to birch density only when birches of >3 cm basal diameter was considered. This can

explain the results in paper I, which shows that the density of birches of any

diameter was not an explanatory factor for moose foraging distribution. As small

and large birches would cluster in the same areas, the selection for different tree sizes

25

would not alone explain a spatial separation of feeding sites. Hares showed a

clumped distribution of their foraging at smaller spatial scales (<500 m) than moose

(1500 m). A greater selectivity of hares at small scales compared to moose is to be

expected from their body size, and this has also been demonstrated, e.g., for cattle

(Bos Taurus) and brown hares (L. europaeus) and for rabbits and roe deer (Bergman

et al. 2005; Veen et al. 2012).

Moose browsing on birch occurred in more sites and was more intense than hare

browsing but the total browsing pressure was low on birch. Neither moose nor hares

would therefore experience a depletion of birch browse in the study area and

intraspecific competition for birch would not explain the separated browsing

patterns. The browsing pressure from moose on willows was high wherever willow

occurred, while only a few observations of hare browsing on willow was made. It is

therefore likely that hares are prevented from utilizing willows due to intense moose

browsing. Patterns of spatial autocorrelation of moose browsing on birch was

positively correlated to that of willow. Both hare and moose preferably browsed the

same sites from year to year, as was evident from the positive correlation between

old and new browsing. This makes the foraging patterns of hare and moose

predictable and this behavior has been demonstrated previously albeit at larger

(home-range) spatial scales (Dahl & Willebrand 2005; Sweanor & Sandegren 1989).

4.3. Paper III

Results from this paper demonstrated that it is possible to manipulate overall

patch quality perceived by hares by adding food. The added food that was least

consumed by hares was oat straw and this food could not increase browsing

pressure on nearby birch to the same extent as the more preferred foods: hay and

hay treated with NaCl. The amount of added food also influenced the browsing

pressure on nearby birches so that birch browsing was greatest where the highest

amount of food was added. Our results underline the importance of forage

distribution for hare foraging patterns and they conform to the prediction of the

marginal value theorem that utilization of a patch should increase with patch quality

(Charnov 1976). Natural patch characteristics influenced the response to patch

manipulation so that more birch was browsed where vegetation was dense and

where previous browsing pressure was high. The annual browsing pressure was

low (26% of plots were browsed) but browsing derived from previous winter

seasons showed that over a period of several years a majority of the sampled sites

were used. A few sites had only fresh browsing, showing that hares would browse

also in sites that had not been used during previous years. This may seem

26

contradictory to previously demonstrated site-fidelity among hares, including our

own results in paper II (Öhmark et al. 2015; Dahl & Willebrand 2005). One plausible

explanation is that habitat use by hares depends on population density and hares

will utilize a greater portion of their environment during population highs

(Pulliainen & Tunkkari 1987).

The frequency of visiting hares at plots with previous addition of food remained

higher than in control plots after three weeks but the browsing intensity decreased

immediately after depletion of the added food. This indicates that mountain hares

remembers spatial distribution of resources. After one year after the experiment,

there was no increased browsing pressure in ex-feeding sites. Damage to mountain

birch can alter chemical composition and growth during subsequent growth seasons

and this can in turn increase herbivory of invertebrate herbivores on winter-browsed

trees (Lehtilä et al. 2000; Danell et al. 1997). However, our results are in line with a

previous study where hares showed indifferent response to simulated moose winter

browsing on birch (Danell & Huss-Danell 1985).

4.4. Paper IV

Forest cover was not a determinant of utilization of the added food for hares in

the mixed landscape of mountain birch forest and subarctic mires and heaths. This

demonstrates a plasticity in hare foraging behavior that enables them to use

resources across varying environments. Camera trapping showed the strict

nocturnal activity pattern that has been previously described for mountain hares

(Rehnus 2014).

Earlier studies have either found preference for forested habitat over open areas

(Pulliainen & Tunkkari 1987) or indifferent response to forested vs. open areas (Dahl

2005). The lake ice was an un-preferred habitat and an edge effect was evident as

utilization of added food decreased gradually from the interior of forest onto the

lake ice. While the lake ice offered no natural shelter or food, low shrubs were

available for the hares at the mires and heaths as the snow cover was thinner in these

areas than in adjacent forest. Mountain birch forest was warmer than adjacent open

habitats, but only when average temperatures dropped below -15°C. It is unclear if

this difference in temperature is of ecological importance for the hares. Behavioral

adaptation to wind (orientation, posture, shelter seeking) has been observed for

mountain hares (Thirgood & Hewson 1987; Flux 1970) while observations of a Finish

hare population showed little or no effect from temperatures down to -30 on habitat

selection (Pulliainen 1982). Wind speed was lower in forested than in open areas.

27

During recent decades an increase in the cover and density of trees and shrubs has

been observed in arctic areas (Rundqvist et al. 2011; Kullman & Öberg 2015). This

will provide more food for hares both in areas with forest cover and where low

shrubs constitute the only vegetation, and it will also provide more shelter from

wind and warmer microclimatic conditions.

5. CONCLUSIONS

Arctic areas are undergoing an increase in vegetation density and will be

affected by future climate warming. Herbivores influence vegetation dynamics in

subarctic areas and these influences interact with effects from global climate change

on vegetation distribution and density. In this perspective, key factors that are

important for subarctic herbivores need to be determined. This thesis sheds some

light on factors related to scale and forage distribution for two high profile, high

impact herbivores in the subarctic. The species show high fidelity to foraging sites

over time and seek habitats with high density of forage. This predictability of

feeding patterns is of essence for conservation and management practices as the

chance of reaching intended goals will increase when accurate predictions of future

conditions are made.

Forage density will only be a determinant of feeding patterns of hare and moose

at certain spatial scales, and this underlines the importance of taking spatial scales

and landscape context into consideration during ecological studies and in

conservation and management planning. Different species will respond to resource

heterogeneity at different spatial scales, and one reason is that body size restricts the

ability to perceive and respond to resource heterogeneity at different scales. By

adding forage, it is possible to increase local habitat quality and, thereby, making an

area more attractive for hares but this effect is not sustained after the added food is

removed. Apparently, hares are sensitive to changes in its environment and are able

to track changes in habitat quality over time.

The response of hares to mountain birch forest cover was inconsistent: hares

avoided lake ice and preferred nearby forest, while there was either an indifferent

or a positive response to subarctic mires and heaths compared to nearby forest. This

shows that hares will avoid extreme environments like lake ice, but they can assess

forage availability on subarctic mires and heaths as well as in mountain birch forest.

Wind speeds were lower, and temperatures higher near ground in mountain birch

forest than on nearby open areas. With increasing cover of forest and shrubs in

28

subarctic and arctic areas, the access to forage will increase for both hare and moose

and they will find forage at higher elevations. This will also provide more sheltered

habitat during winter, which may be especially important in subarctic areas where

winter conditions are severe.

6. ACKNOWLEDGEMENTS

I would like to thank my supervisors Thomas, Glenn and Bege for all the support

you gave throughout my time as a PhD student. Thank you for believing in me and

for lending me your experience and your patience! I would also like to thank Göran

Ericsson and Kerstin Sunnerheim who were my mentors and Clare McArthur for

showing me the benefits of camera traps and for giving comments to several

manuscripts. Thank you, Julia Hjalmarsson, for your comments to the thesis. I thank

the staff at the Abisko Scientific Research Station for all the practical help you gave

during field work and for making me feel welcome during every visit in Abisko.

Jennie, Johan, Sofia, Alireza, Zimon, Jossan and Julia, thank you for enduring those

subarctic storms (real ones as well as perceived) during field work, and thank you

for all your help and for the good company!

Jennie, Jenny Z, Joel, Mattias, Anna-Maria, Freddan, Julia, Saba, Rizan, Hugo,

Ghadir, Nazlin, Majid, Erika W, Anna P, Torborg, Håkan N, Lisbeth, Viktoria,

Veronica, Ingrid, Stefan B, Peter G, Svante, Nils, Annelie, Thomas N, Natalia, Amelie

and all the other great people that have been in the O- and the S-building during the

past years; how happy I am to have met you! With you I have found close friendship,

great roommates, and good company for both happy and sincere discussions during

lunches and fikas, moral support and good advice in times of need. I will miss you!

Let’s meet for a fika a.s.a.p!

Mamma och PeO, pappa och Eivor, kära syster Lina med familj, tack för att ni

alltid finns här och för att ni stöttar mig, det betyder allt för mig. Tjejkompisarna Ida,

Maria, Viktoria, Frida, Erika och Katarina, fastän vi ses alltför sällan så känns ni nära!

Fredrik, Astrid och lillskrutten i magen, ni är världens finaste familj och jag är så

glad över att få dela tillvaron med er. Tack Fredrik, för ditt stöd och ditt tålamod

som gjorde slutförandet av avhandlingen möjlig för mig.

29

30

7. REFERENCES

Angerbjörn, A. & Pehrson, Å., 1987. Factors influencing winter food choice

by mountain hares (Lepus timidus L.) on Swedish coastal islands.

Canadian Journal of Zoology, 65, pp.2163–2167.

Anschlag, K., Broll, G. & Holtmeier, F.-K., 2008. Mountain Birch

Seedlings in the Treeline Ecotone, Subarctic Finland: Variation in

Above- and Below-Ground Growth Depending on Microtopography.

Arctic, Antarctic, and Alpine Research, 40(4), pp.609–616.

Anselin, L., 1995. Local indicators of spatial association-LISA.

Geographical Analysis, 27, pp.93–115.

Atsatt, P.R. & O’Dowd, D.J., 1976. Plant defense guilds. Science (New

York, N.Y.), 193(4247), pp.24–29.

Bailey, D.W. et al., 1996. Mechanisms that result in large herbivore grazing

distribution patterns. Journal Of Range Management, 49, pp.386–400.

Bailey, D.W. & Provenza, F.D., 2008. Mechanisms determining large-

herbivore distribution. In Resource Ecology Spatial and Temporal

Dynamics of Foraging. pp. 7–28.

Ball, J.P., Danell, K. & Sunesson, P., 2000. Response of a herbivore

community to increased food quality and quantity: an experiment with

nitrogen fertilizer in a boreal forest. Journal of Applied Ecology, 37,

pp.247–255.

Ballaré, C.L., 2014. Light regulation of plant defense. Annual review of

plant biology, 65, pp.335–63.

Bardgett, R.D. & Wardle, D.A., 2003. Herbivore-mediated linkages

between aboveground and belowground communities. Ecology, 84(9),

pp.2258–2268.

Bedoya-Perez, M.A. et al., 2013. A practical guide to avoid giving up on

giving-up densities. Behavioral Ecology and Sociobiology, 67(10),

pp.1541–1553.

31

Van Beest, F.M. et al., 2010. Long-term browsing impact around

diversionary feeding stations for moose in Southern Norway. Forest

Ecology and Management, 259, pp.1900–1911.

Van Beest, F.M. et al., 2011. What determines variation in home range size

across spatiotemporal scales in a large browsing herbivore? Journal of

Animal Ecology, 80, pp.771–785.

Bellu, A. et al., 2012. Habitat use at fine spatial scale: How does patch

clustering criteria explain the use of meadows by red deer? European

Journal of Wildlife Research, 58, pp.645–654.

Belovsky, G.E., 1978. Diet optimization in a generalist herbivore: the

moose. Theoretical population biology, 14(1), pp.105–134.

Belovsky, G.E. & Schmitz, O.J., 1994. Plant defenses and optimal foraging

by mammalian herbivores. Journal of Mammalogy, 75, pp.816–832.

Berglund, B.E. et al., 1996. Holocene forest dynamics and climate changes

in the Abisko area, northern Sweden - the Sonesson model of

vegetation history reconsidered and confirmed. Ecological Bulletin, 45,

pp.15–30.

Bergman, M., Iason, G.R. & Hester, A.J., 2005. Feeding patterns by roe

deer and rabbits on pine, willow and birch in relation to spatial

arrangement. Oikos, 109(3), pp.513–520.

Bisi, F. et al., 2011. The strong and the hungry: bias in capture methods for

mountain hares Lepus timidus. Wildlife Biology, 17(3), pp.311–316.

Björnhag, G. & Snipes, R.L., 1999. Colonic separation mechanism in

lagomorph and rodent species - a comparison. Zoosystematics and

Evolution, 75(2), pp.275–281.

Borchtchevski, V.G. et al., 2003. Does fragmentation by logging reduce

grouse reproductive success in boreal forests? Wildlife Biology, 9,

pp.275–282.

Borthagaray, A.I., Arim, M. & Marquet, P.A., 2012. Connecting landscape

structure and patterns in body size distributions. Oikos, 121(5), pp.697–

710.

32

Brazaitis, G. et al., 2014. Landscape effect for the Cervidaes Cervidae in

human-dominated fragmented forests. European Journal of Forest

Research, 133, pp.857–869.

Brown, J.S., 1988. Patch use as an indicator of habitat preference, predation

risk, and competition. Behavioral Ecology and Sociobiology, 22,

pp.37–47.

Bylund, H. & Nordell, K.O., 2001. Biomass proportion, production and leaf

nitrogen distribution in a polycormic mountain birch stand (Betula

pubescens ssp. czerepanovii) in northern Sweden. In F. E. Wielgolaski,

ed. Nordic mountain birch ecosystems. Parthenon Publishing Group

Inc., New York, pp. 115–126.

Cadenasso, M.L. & Pickett, S.T.A., 2000. Linking forest edge structure to

edge function: mediation of herbivore damage. Journal of Ecology,

88(1), pp.31–44.

Callaghan, T. V et al., 2010. A new climate era in the sub-Arctic:

accelerating climate changes and multiple impacts. Geophysical

Research Letters, 37, pp.1–6.

Carmel, Y. & Ben-Haim, Y., 2005. Info-gap robust-satisficing model of

foraging behavior: do foragers optimize or satisfice? The American

naturalist, 166(5), pp.633–641.

Cederlund, G. & Sand, H., 1994. Home-Range Size in Relation to Age and

Sex in Moose. Journal of Mammalogy, 75, pp.1005–1012.

Cederlund, G.N. et al., 1986. Seasonal variation in mandible marrow fat in

moose. Journal of Wildlife Management, 50(4), pp.719–726.

Cederlund, G.N., Sand, H.K.G. & Pehrson, Å., 1991. Body mass dynamics

of moose calves in relation to winter severity. Journal of Wildlife

Management, 55(4), pp.675–681.

Charnov, E.L., 1976. Optimal foraging, the marginal value theorem.

Theoretical Population Biology, 9(2), pp.129–136.

Clauss, M. et al., 2007. A case of non-scaling in mammalian physiology?

Body size, digestive capacity, food intake, and ingesta passage in

33

mammalian herbivores. Comparative Biochemistry and Physiology - A

Molecular and Integrative Physiology, 148(2), pp.249–265.

Clauss, M. & Hummel, J., 2005. The digestive performance of mammalian

herbivores: why big may not be that much better. Mammal Review,

35(2), pp.174–187.

Condon, B. & Adamowicz, W., 1995. The economic value of moose

hunting in Newfoundland. Canadian Journal of Forest Research,

25(2), pp.319–328.

Courant, S. & Fortin, D., 2012. Time allocation of bison in meadow patches

driven by potential energy gains and group size dynamics. Oikos,

121(7), pp.1163–1173.

Dahl, F., 2005. Distinct seasonal habitat selection by annually sedentary

mountain hares (Lepus timidus) in the boreal forest of Sweden.

European Journal of Wildlife Research, 51, pp.163–169.

Dahl, F. & Willebrand, T., 2005. Natal dispersal, adult home ranges and site

fidelity of mountain hares Lepus timidus in the boreal forest of

Sweden. Wildlife Biology, 11, pp.309–317.

Danell, K. et al., 1994. Food plant selection by reindeer during winter in

relation to plant quality. Ecography, 17, pp.153–158.

Danell, K. & Ericson, L., 1986. Foraging by moose on two species of birch

when these occur in different proportions. Holarctic Ecology, 9, pp.79–

83.

Danell, K., Haukioja, E. & Huss-Danell, K., 1997. Morphological and

chemical responses of mountain birch leaves and shoots to winter

browsing along a gradient of plant productivity. Ecoscience, pp.296–

303.

Danell, K. & Huss-Danell, K., 1985. Feeding by insects and hares on

birches earlier affected by moose browsing. Oikos, 44, pp.75–81.

Dearing, M.D., Foley, W.J. & McLean, S., 2005. The influence of plant

secondary metabolites in the nutritional ecology of herbivorous

34

terrestrial vertebrates. Annual Review of Ecology, Evolution, and

Systematics, 36(1), pp.169–189.

Dearing, M.D., Mangione, A.M. & Karasov, W.H., 2000. Diet breadth of

mammalian herbivores: nutrient versus detoxification constraints.

Oecologia, 123(3), pp.397–405.

Debinski, D.M. & Holt, R.D., 2000. A survey and overview of habitat

fragmentation experiments. Conservation Biology, 14(2), pp.342–355.

Demment, M.W. & Greenwood, G.B., 1988. Forage ingestion: effects of

sward characteristics and body size. Journal of animal science, 66(9),

pp.2380–2392.

Demment, M.W. & Van Soest, P.J., 1985. A nutritional explanation for

body-size patterns of ruminant and nonruminant herbivores. The

American Naturalist, 125, p.641.

Dirnböck, T. & Dullinger, S., 2004. Habitat distribution models, spatial

autocorrelation, functional traits and dispersal capacity of alpine plant

species. Journal of Vegetation Science, 15, pp.77–84.

Dodds, P.S., Rothman, D.H. & Weitz, J.S., 2001. Re-examination of the 3/4

law of metabolism. Journal of Theoretical Biology, 209(1), pp.9–27.

Dunkley, L. & Cattet, M.R.L., 2003. A comprehensive review of the

ecological and human social effects of artificial feeding and baiting of

wildlife. Canadian Cooperative Wildlife Health Centre: Newsletters &

Publications, p.21.

Dussault, C. et al., 2005. Space use of moose in relation to food availability.

Canadian Journal of Zoology, 83(11), pp.1431–1437.

Eby, S.L. et al., 2014. The effect of fire on habitat selection of mammalian

herbivores: the role of body size and vegetation characteristics. The

Journal of animal ecology, 83(5), pp.1196–1205.

Edenius, L. et al., 2002. The role of moose as a disturbance factor in

managed boreal forests. Silva Fennica, 36, pp.57–67.

35

Elgar, M.A. & Harvey, P.H., 1987. Basal Metabolic Rates in Mammals:

Allometry, Phylogeny and Ecology. Functional Ecology, 1(1), pp.25–

36.

Emanuelsson, U., 1987. Human influence on vegetation in the Torneträsk

area during the last three centuries. Ecological Bulletins, 38, pp.95–

111.

Emlen, J.M., 1966. The role of time and energy in food preference. The

American Naturalist, 100, pp.611 – 617.

Ewacha, M.V.A., Roth, J.D. & Brook, R.K., 2014. Vegetation structure and

composition determine snowshoe hare (Lepus americanus) activity at

arctic tree line. Canadian Journal of Zoology, 92, pp.789–794.

Farnsworth, K.D. & Illius, A.W., 1998. Optimal diet choice for large

herbivores: An extended contingency model. Functional Ecology,

12(1), pp.74–81.

Flint, H.J. & Bayer, E.A., 2008. Plant cell wall breakdown by anaerobic

microorganisms from the mammalian digestive tract. Annals of the

New York Academy of Sciences, 1125, pp.280–288.

Flux, J.E.C., 1970. Life history of the mountain hare (Lepus timidus

scoticus) in north-east Scotland. Journal of Zoology, 161(1), pp.75–

123.

Fraenkel, G.S., 1959. The raison d ’ etre of secondary plant substances.

Science, 129, pp.1466–1470.

Freeland, W.J. & Janzen, D.H., 1974. Strategies in herbivory by mammals:

the role of plant secondary compounds. The American Naturalist,

108(961), pp.269–289.

Freestone, A.L. & Inouye, B.D., 2006. Dispersal limitation and

environmental heterogeneity shape scale-dependent diversity patterns

in plant communities. Ecology, 87(10), pp.2425–2432.

Fretwell, S.D. & Lucas, H.L.J., 1970. On territorial behavior and other

factors influencing habitat distribuion in birds. I. Theoretical

development. Acta Biotheoretica, 14, pp.16–36.

36

Garrido, P., Lindqvist, S. & Kjellander, P., 2014. Natural forage

composition decreases deer browsing on Picea abies around

supplemental feeding sites. Scandinavian Journal of Forest Research,

29(3), pp.234–242.

Gehring, T.M. & Swihart, R.K., 2003. Body size, niche breadth, and

ecologically scaled responses to habitat fragmentation: Mammalian

predators in an agricultural landscape. Biological Conservation,

109(2), pp.283–295.

Gidenne, T., 2003. Fibres in rabbit feeding for digestive troubles prevention:

Respective role of low-digested and digestible fibre. Livestock

Production Science, 81(2-3), pp.105–117.

Gordon, I.J., Hester, A.J. & Festa-Bianchet, M., 2004. The management of

wild large herbivores to meet economic, conservation and

environmental objectives. Journal of Applied Ecology, 41(6), pp.1021–

1031.

Gross, J.E. et al., 1995. Movement rules for herbivores in spatially

heterogeneous environments: responses to small scale pattern.

Landscape Ecology, 10(4), pp.209–217.

Grünewald, T. et al., 2013. Statistical modelling of the snow depth

distribution in open alpine terrain. Hydrology and Earth System

Sciences, 17, pp.3005–3021.

Guirado, M., Pino, J. & Rodà, F., 2006. Understorey plant species richness

and composition in metropolitan forest archipelagos: effects of forest

size, adjacent land use and distance to the edge. Global Ecology and

Biogeography, 15(1), pp.50–62.

Gundersen, H., Andreassen, H.P. & Storaas, T., 2004. Supplemental feeding

of migratory moose Alces alces: forest damage at two spatial scales.

Wildlife Biology, 10, pp.213–223.

Hahn, D.C. & Hatfield, J.S., 1995. Parasitism at the landscape scale:

Cowbirds prefer forests. Conservation Biology, 9(6), pp.1415–1424.

37

Hanhimäki, S., 1989. Induced resistance in mountain birch: defence against

leaf-chewing insect guild and herbivore competition. Oecologia, 81(2),

pp.242–248.

Harper, K.A. et al., 2005. Edge influence on forest structure and

composition in fragmented landscapes. Conservation Biology, 19(3),

pp.768–782.

Harvey, L. & Fortin, D., 2013. Spatial heterogeneity in the strength of plant-

herbivore interactions under predation risk: the tale of bison foraging in

wolf country. PloS one, 8(9), p.e73324.

Heggberget, T.M., Gaare, E. & Ball, J.P., 2002. Reindeer (Rangifer

tarandus) and climate change: Importance of winter forage. Rangifer,

22(1), pp.13–31.

Herkert, J.R., 1994. The effects of habitat fragmentation on midwestern

grassland bird communities. Ecological Applications, 4(3), pp.461–

471.

Hewson, R., 1976. Grazing by mountain hares Lepus timidus L., red deer

Cervus elaphus L. and red grouse Lagopus L. scoticus on heather

moorland in north-east Scotland. Journal of Applied Ecology, 13(3),

pp.657–666.

Hewson, R. & Hinge, M.D.C., 1990. Characteristics of the home range of

mountain hares Lepus timidus. Journal of Applied Ecology, 27,

pp.195–195.

Hintz, H.F., Schryver, H.F. & Stevens, C.E., 1978. Digestion and absorption

in the hindgut of nonruminant herbivores. Journal of Animal Science,

46, pp.1803–1807.

Hirakawa, H., 2001. Coprophagy in leporids and other mammalian

herbivores. Mammal Review, 31, pp.61–80.

Hjeljord, O., Sundstøl, F. & Haagenrud, H., 1982. The nutritional value of

browse to moose. The Journal of Wildlife Management, 2, pp.333–343.

Hjältén, J. & Palo, R.T., 1992. Selection of deciduous trees by free ranging

voles and hares in relation to plant chemistry. Oikos, 63, pp.477–484.

38

Hodar, J.A. & Palo, R.T., 1997. Feeding by vertebrate herbivores in a

chemically heterogeneous environment. Ecoscience, 4, pp.304–310.

Hodder, D.P., Rea, R. V. & Crowley, S.M., 2013. Diet content and overlap

of sympatric mule deer (Odocoileus hemionus), moose (Alces alces),

and elk (Cervus elaphus) during a deep snow winter in Northcentral

British Columbia, Canada. Canadian Wildlife Biology and

Management, 2, pp.43–50.

Hofmann, R.R., 1989. Evolutionary steps of ecophysiological adaptation

and diversification of ruminants: a comparative view of their digestive

system. Oecologia, 78(4), pp.443–457.

Holmgren, B. & Tjus, M., 1996. Summer air temperatures and tree line

dynamics at Abisko. Ecological Bulletins, 45, pp.159–169.

Huitu, O. et al., 2003. Winter food supply limits growth of northern vole

populations in the absence of predation. Ecology, 84(8), pp.2108–2118.

Hulbert, I.A., Iason, G.R. & Mayes, R.W., 2001. The flexibility of an

intermediate feeder: Dietary selection by mountain hares measured

using faecal n-alkanes. Oecologia, 129(2), pp.197–205.

Hulbert, I.A.R. et al., 1996. Home-range sizes in a stratified upland

landscape of two lagomorphs with different feeding strategies. Journal

of Applied Ecology, 33, pp.1479–1488.

Hulbert, I.A.R. & Andersen, R., 2001. Food competition between a large

ruminant and a small hindgut fermentor: the case of the roe deer and

mountain hare. Oecologia, 128, pp.499–508.

Iason, G., 2005. The role of plant secondary metabolites in mammalian

herbivory: ecological perspectives. Proceedings of the Nutrition

Society, 64(01), pp.123–131.

Iason, G.R. & Van Wieren, S.E., 1999. Digestive and ingestive adaptations

of mammalian herbivores to low-quality forage. In H. Olff, V. K.

Brown, & R. H. Drent, eds. Herbivores: between plants and predators.

Oxford: Blackwell, pp. 337–369.

39

Jacob, J. & Brown, J.S., 2000. Microhabitat use, giving-up densities and

temporal activity as short- and long-term anti-predator behaviors in

common voles. Oikos, 91, pp.131–138.

Janis, C.M., 1976. The evolutionary strategy of the Equidae and the origins

of rumen and cecal digestion. Evolution, 30(4), pp.757–774.

Johannessen, V. & Samset, E., 1994. Summer diet of the mountain hare

(lepus timidus L) in a low-alpine area in southern Norway. Canadian

Journal of Zoology, 72(4), pp.652–657.

Johnson, C.J., Parker, K.L. & Heard, D.C., 2001. Foraging across a variable

landscape: Behavioral decisions made by woodland caribou at multiple

spatial scales. Oecologia, 127(4), pp.590–602.

Jonasson, C. et al., 2012. Environmental monitoring and research in the

Abisko area-an overview. Ambio, 41(SUPPL.3), pp.178–186.

Kauhala, K., Hiltunen, M. & Salonen, T., 2005. Home ranges of mountain

hares Lepus timidus in boreal forests of Finland. Wildlife Biology,

11(3), pp.193–200.

Kleiber, M., 1932. Body size and metabolism. Hilgardia, 6, pp.315–351.

Kohler, J. et al., 2006. A long-term Arctic snow depth record from Abisko,

northern Sweden, 1913–2004. Polar Research, 25, pp.91–113.

Kotliar, N.B. & Wiens, J.A., 1990. Multiple Scales of Patchiness and Patch

Structure: A Hierarchical Framework for the Study of Heterogeneity.

Oikos, 59(2), pp.253–260.

Krebs, C.J. et al., 1995. Impact of food and predation on the snowshoe hare

cycle. Science (New York, N.Y.), 269(5227), pp.1112–1115.

Krebs, J.R., Ryan, J.C. & Charnov, E.L., 1974. Hunting by expectation or

optimal foraging? A study of patch use by chickadees. Animal

Behaviour, 22, pp.953–964.

Kullman, L. & Öberg, L., 2009. Post-Little Ice Age tree line rise and climate

warming in the Swedish Scandes: A landscape ecological perspective.

Journal of Ecology, 97(3), pp.415–429.

40

Kullman, L. & Öberg, L., 2015. Post-Little Ice Age tree line rise and climate

warming in the Swedish Scandes: a landscape ecological perspective.

Journal of Ecology, 97(3), pp.415–429.

Kumpula, J., 2001. Winter grazing of reindeer in woodland lichen pasture:

effect of lichen availability on the condition of reindeer. Small

Ruminant Research, 39(2), pp.121–130.

Laca, E., Shipley, L. & Reid, E., 2001. Structural anti-quality characteristics

of range and pasture plants. Journal of Range Management, 54(July),

pp.413–419.

Laca, E.A. et al., 2010. Allometry and spatial scales of foraging in

mammalian herbivores. Ecology Letters, 13, pp.311–320.

Lechner, I. et al., 2010. Differential passage of fluids and different-sized

particles in fistulated oxen (Bos primigenius f. taurus), muskoxen

(Ovibos moschatus), reindeer (Rangifer tarandus) and moose (Alces

alces): Rumen particle size discrimination is independent from

contents. Comparative Biochemistry and Physiology. Part A-

Molecular and Integrative Physiology, 155, pp.211–222.

Legendre, P. et al., 2002. The consequences of spatial structure for the

design and analysis of ecological field surveys. Ecography, 25,

pp.601–615.

Legendre, P. & Fortin, M., 1989. Spatial pattern and ecological analysis.

Vegetatio, 80, pp.107–138.

Lehtilä, K. et al., 2000. Allocation of resources within mountain birch

canopy after simulated winter browsing. Oikos, 90(1), pp.160–170.

Lehtonen, J. & Heikkinen, R.K., 1995. On the recovery of mountain birch

after Epirrita damage in Finnish Lapland, with a particular emphasis on

reindeer grazing. Ecoscience, 2(4), pp.349–356.

Leopold, A., 1987. Game Management, University of Wisconsin Press.

Li, C.Y. et al., 2003. Photoperiodic control of growth, cold acclimation and

dormancy development in silver birch (Betula pendula) ecotypes.

Physiologia Plantarum, 117(2), pp.206–212.

41

Lindlöf, B., 1980. Some aspects of ecology in hares, Thesis, Dept. of Zool,

University of Stockholm.

Ludwig, M. et al., 2012. Landscape-moderated bird nest predation in hedges

and forest edges. Acta Oecologica, 45, pp.50–56.

Lundberg, P. & Palo, R.T., 1993. Resource use, plant defenses, and optimal

digestion in ruminants. Oikos, 68(2), pp.224–228.

Lundberg, P., Åström, M. & Danell, K., 1990. An experimental test of

frequency-dependent food selection: Winter browsing by moose.

Holarctic Ecology, 13, pp.177–182.

MacArthur, R.H. & Pianka, E.R., 1966. On optimal use of a patchy

environment. The American Naturalist, 100(916), pp.603–609.

Magura, T., 2002. Carabids and forest edge: Spatial pattern and edge effect.

Forest Ecology and Management, 157(1-3), pp.23–37.

Marshall, H.H. et al., 2013. How do foragers decide when to leave a patch?

A test of alternative models under natural and experimental conditions.

The Journal of animal ecology, 82(4), pp.894–902.

Mathisen, K.M. & Skarpe, C., 2011. Cascading effects of moose (Alces

alces) management on birds. Ecological Research, 26(3), pp.563–574.

McNair, J.N., 1982. Optimal giving-up times and the marginal value

theorem. The American Naturalist, 119(4), pp.511–529.

Merkle, J.A., Fortin, D. & Morales, J.M., 2014. A memory-based foraging

tactic reveals an adaptive mechanism for restricted space use. Ecology

Letters, 17(8), pp.924–931.

Miller, J.A., 2012. Species distribution models: spatial autocorrelation and

non-stationarity. Progress in Physical Geography, 36(5), pp.681–692.

Milligan, H.T. & Koricheva, J., 2013. Effects of tree species richness and

composition on moose winter browsing damage and foraging

selectivity: an experimental study. The Journal of Animal Ecology, 82,

pp.739–748.

42

Moen, R., Pastor, J. & Cohen, Y., 1997. A spatially explicit model of moose

foraging and energetics. Ecology, 78(2), pp.505–521.

Muiruri, E.W. et al., 2015. Moose browsing alters tree diversity effects on

birch growth and insect herbivory. Functional Ecology, 29(5), pp.724–

735.

Månsson, J. et al., 2007. Moose browsing and forage availability: a scale-

dependent relationship? Canadian Journal of Zoology, 85, pp.372–380.

Månsson, J. et al., 2012. Spatial and temporal predictions of moose winter

distribution. Oecologia, 170(2), pp.411–419.

Nagy, K.A., 2005. Field metabolic rate and body size. Journal of

Experimental Biology, 208, pp.1621–1625.

Newey, S. et al., 2010. Population and individual level effects of over-

winter supplementary feeding mountain hares. Journal of Zoology,

282, pp.214–220.

Nordengren, C., Hofgaard, A. & Ball, J.P., 2003. Availability and quality of

herbivore winter browse in relation to tree height and snow depth.

Annales Zoologici Fennici, 40, pp.305–314.

Nyström, A., 1980. Selection and consumption of winter browse by moose

calves. Journal of Wildlife Management, 44(2), pp.463–468.

Ohashi, H. & Hoshino, Y., 2014. Disturbance by large herbivores alters the

relative importance of the ecological processes that influence the

assembly pattern in heterogeneous meta-communities. Ecology and

Evolution, 4(6), pp.766–775.

Olofsson, J. et al., 2009. Herbivores inhibit climate-driven shrub expansion

on the tundra. Global Change Biology, 15(11), pp.2681–2693.

Olofsson, J. & Strengbom, J., 2000. Response of galling invertebrates on

Salix lanata to reindeer herbivory. Oikos, 91(3), pp.493–498.

Olsson, J. et al., 2012. Landscape and substrate properties affect species

richness and community composition of saproxylic beetles. Forest

Ecology and Management, 286, pp.108–120.

43

Owen-Smith, N., 2014. Spatial ecology of large herbivore populations.

Ecography, 37(5), pp.416–430.

Owen-Smith, N., Fryxell, J.M. & Merrill, E.H., 2010. Foraging theory

upscaled: the behavioural ecology of herbivore movement.

Philosophical Transactions of the Royal Society of London - Series B:

Biological Sciences, 365, pp.2267–2278.

Owen-Smith, N. & Novellie, P., 1982. What should a clever ungulate eat?

The American Naturalist, 119(2), pp.151–178.

Palo, R.T., 1984. Distribution of birch (Betula SPP.), willow (Salix SPP.),

and poplar (Populus SPP.) secondary metabolites and their potential

role as chemical defense against herbivores. Journal of Chemical

Ecology, 10(3), pp.499–520.

Palo, R.T., Bergström, R. & Danell, K., 1992. Digestibility, distribution of

phenols, and fiber at different twig diameters of birch in winter.

Implication for browsers. Oikos, 65, pp.450–454.

Parker, G.A. & Stuart, R.A., 1976. Animal behavior as a strategy optimizer:

evolution of resource assessment strategies and optimal emigration

thresholds. The American Naturalist, 110(976), pp.1055–1076.

Pastor, J. et al., 1999. Further development of the Spalinger-Hobbs

mechanistic foraging model for free-ranging moose. Canadian Journal

of Zoology, 77, pp.1505–1512.

Pedersen, S. et al., 2014. Small mammal responses to moose supplementary

winter feeding. European Journal of Wildlife Research, 60, pp.527–

534.

Pehrson, Å., 1983a. Caecotrophy in caged mountain hares (Lepus timidus).

Journal of Zoology, 199(4), pp.563–574.

Pehrson, Å., 1983b. Digestibility and retension of food components in caged

mountain hares Lepus timidus during the winter. Holarctic Ecology,

6(4), pp.395–403.

Pehrson, Å., 1979. Winter food consumption and digestibility in caged

mountian hares. In K. Myers & C. D. MacInnes, eds. Proceedings of

44

the World Lagomorph Conference. Guelph University Press, pp. 732–

742.

Pond, K.R., Ellis, W.C. & Akin, D.E., 1984. Ingestive mastication and

fragmentation of forages. Journal of Animal Science, 58(6), pp.1567–

1574.

Pulliainen, E., 1982. Habitat selection and fluctuations in numbers in a

population of the arctic hare (Lepus timidus) on a subarctic fell in

Finnish forest Lapland. Z. Saugetierkd, 47(3), pp.168–174.

Pulliainen, E. & Tunkkari, P.S., 1987. Winter diet, habitat selection and

fluctuation of a mountain hare Lepus timidus population in Finnish

Forest Lapland. Ecography, 10(4), pp.261–267.

Putman, R.J. & Staines, B.W., 2004. Supplementary winter feeding of wild

red deer Cervus elaphus in Europe and North America: justifications,

feeding practice and effectiveness. Mammal Review, 34(4), pp.285–

306.

Rastetter, E.B. et al., 2003. Using mechanistic models to scale ecological

processes across space and time. BioScience, 53(1), pp.68–76.

Rehnus, M., 2014. The 24-hour cycle of the mountain hare Lepus timidus

Linnaeus, 1758. Der Zoologische Garten, 83, pp.140–145.

Renecker, L.A. & Hudson, R.J., 1989. Seasonal activity budgets of moose in

aspen-dominated boreal forests. Journal of Wildlife Management, 53,

pp.296–302.

Renecker, L.A. & Hudson, R.J., 1986. Seasonal foraging rates of free-

ranging moose. Journal of Wildlife Management, 50(1), pp.143–147.

Reynolds, A.M., 2012. Fitness-maximizing foragers can use information

about patch quality to decide how to search for and within patches:

optimal Levy walk searching patterns from optimal foraging theory.

Journal of The Royal Society Interface, 9(72), pp.1568–1575.

Rousi, M., Tahvanainen, J. & Uotila, I., 1991. A Mechanism of resistance to

hare browsing in winter-dormant European white birch (Betula

pendula). American Naturalist, 137, pp.64–82.

45

Rundqvist, S. et al., 2011. Tree and shrub expansion over the past 34 years

at the tree-line near Abisko, Sweden. Ambio, 40, pp.683–692.

Sæther, B.E. & Gravem, A.J., 1988. Annual variation in winter body

condition of Norwegian moose calves. Journal of Wildlife

Management, 52(2), pp.333–336.

Sahlsten, J. et al., 2010. Can supplementary feeding be used to redistribute

moose Alces alces? Wildlife Biology, 16, pp.85–92.

Saracco, J.F., Collazo, J.A. & Groom, M.J., 2004. How do frugivores track

resources? Insights from spatial analyses of bird foraging in a tropical

forest. Oecologia, 139, pp.235–245.

Schneider, D.C., 2001. The rise of the concept of scale in ecology.

BioScience, 51(7), pp.545–553.

Searle, K.R., Hobbs, N.T. & Shipley, L.A., 2005. Should I stay or should I

go? Patch departure decisions by herbivores at multiple scales. Oikos,

111(3), pp.417–424.

Seiler, A., 2005. Predicting locations of moose-vehicle collisions in

Sweden. Journal of Applied Ecology, 42(2), pp.371–382.

Senn, J. & Haukioja, E., 1994. Reactions of the mountain birch to bud

removal: effects of severity and timing, and implications for herbivore.

Functional Ecology, 8(4), pp.494–501.

Shipley, L., 1999. Grazers and browsers: how digestive morphology affects

diet selection. In K. L. Lanchbaugh, K. D. Sanders, & J. C. Mosley,

eds. Grazing behavior of livestock and wildlife. Moscow: Idaho forest,

Wildlife and Range Experimental Station Bulletin 70. University of

Idaho, pp. 20–27.

Shipley, L.A., 2010. Fifty years of food and foraging in moose: lessons in

ecology from a model herbivore. Alces, 46, pp.1–13.

Shipley, L.A., 2007. The influence of bite size on foraging at larger spatial

and temporal scales by mammalian herbivores. Oikos, 116(12),

pp.1964–1974.

46

Shipley, L.A. et al., 1994. The scaling of intake rate in mammalian

herbivores. The American Naturalist, 143(6), pp.1055–1082.

Shipley, L.A., Blomquist, S. & Danell, K., 1998. Diet choices made by free-

ranging moose in northern Sweden in relation to plant distribution,

chemistry, and morphology. Canadian Journal of Zoology, 76(9),

pp.1722–1733.

Shipley, L.A., Forbey, J.S. & Moore, B.D., 2009. Revisiting the dietary

niche: when is a mammalian herbivore a specialist? Integrative and

Comparative Biology, 49(3), pp.274–290.

Sievert, P. & Keith, L., 1985. Survival of snowshoe hares at a geographic

range boundary. The Journal of wildlife management, 49(4), pp.854–

866.

Skogland, T., 1985. The effects of density-dependent resource limitations on

the demography of wild reindeer. Journal of Animal Ecology, 54,

pp.359–374.

Skogland, T., 1984. Wild reindeer foraging-niche organization. Holarctic

Ecology, 7, pp.345–379.

Van Soest, P.J., 1996. Allometry and ecology of feeding behavior and

digestive capacity in herbivores: a review. Zoo Biology, 15, pp.455–

479.

Van Soest, P.J., 1967. Development of a comprehensive system of feed

analyses and its application to forages. Journal of Animal Science,

26(1), pp.119–128.

Van Soest, P.J., 1994. Nutritional ecology of the ruminant, Ithaca, New

York: Cornell University Press.

Sorensen, A., Van Beest, F.M. & Brook, R.K., 2014. Impacts of wildlife

baiting and supplemental feeding on infectious disease transmission

risk: A synthesis of knowledge. Preventive Veterinary Medicine, 113,

pp.356–363.

47

Spalinger, D.E. & Hobbs, N.T., 1992. Mechanisms of foraging in

mammalian herbivores: new models of functional response. The

American naturalist, 140(2), pp.325–348.

Stark, S., Julkunen-Tiitto, R. & Kumpula, J., 2007. Ecological role of

reindeer summer browsing in the mountain birch (Betula pubescens

ssp. czerepanovii) forests: effects on plant defense, litter

decomposition, and soil nutrient cycling. Oecologia, 151(3), pp.486–

498.

Stephens, D.W. & Krebs, J.R., 1986. Foraging Theory, Princeton: Princeton

University Press.

Steuer, P. et al., 2013. Fibre digestibility in large herbivores as related to

digestion type and body mass- an in vitro approach. Comparative

Biochemistry and Physiology - A Molecular and Integrative

Physiology, 164(2), pp.319–326.

Stewart, A. & Komers, P.E., 2012. Testing the ideal free distribution

hypothesis: moose response to changes in habitat amount. ISRN

Ecology, 2012, pp.1–8.

Steyaert, S.M.J.G. et al., 2014. Behavioral correlates of supplementary

feeding of wildlife: can general conclusions be drawn? Basic and

Applied Ecology, 15, pp.669–676.

Stolter, C. et al., 2005. Winter browsing of moose on two different willow

species: food selection in relation to plant chemistry and plant

response. Canadian Journal of Zoology, 819, pp.807–819.

Stöcklin, J. & Körner, C., 1999. Recruitment and mortality of Pinus

sylvestris near the nordic treeline: the role of climatic change and

herbivory. Ecological Bulletins, 47, pp.168–177.

Sutherland, W.J., 2006. Predicting the ecological consequences of

environmental change: a review of the methods. Journal of Applied

Ecology, 43(4), pp.599–616.

Sweanor, P.Y. & Sandegren, F., 1989. Winter range philopatry of seasonally

migratory moose. Journal of Applied Ecology, 26, pp.25–34.

48

Telfer, E.S. & Kelsall, J.P., 1984. Adaptation of some large North American

mammals for survival in snow. Ecology, 65(6), pp.1828–1834.

Tenow, O., 1996. Hazards to a mountain birch forest- Abisko in perspective.

Ecological Bulletins, 45, pp.104–114.

Tenow, O. & Bylund, H., 2000. Recovery of a Betula pubescens forest in

northern Sweden after severe defoliation by Epirrita autumnata.

Journal of Vegetation Science, 11, pp.855–862.

Thirgood, S.J. & Hewson, R., 1987. Shelter characteristics of mountain hare

resting sites. Holarctic Ecology, 10(4), pp.294–298.

Thomas, V.G., 1987. Similar winter energy strategies of grouse, hares and

rabbits in northern biomes. Oikos, 50, pp.206–212.

Tømmervik, H. et al., 2009. Above ground biomass changes in the mountain

birch forests and mountain heaths of Finnmarksvidda, northern

Norway, in the period 1957-2006. Forest Ecology and Management,

257(1), pp.244–257.

Ungar, E.D. & Noy-Meir, I., 1988. Herbage intake in relation to availability

and sward structure: grazing processes and optimal foraging. Journal

of Applied Ecology, 25(3), pp.1045–1062.

WallisDeVries, M.F., Laca, E.A. & Demment, M.W., 1999. The importance

of scale of patchiness for selectivity in grazing herbivores. Oecologia,

121(3), pp.355–363.

Valone, T.J. & Brown, J.S., 1989. Measuring patch assessment abilities of

desert granivores. Ecology, 70, pp.1800–1810.

Wam, H.K. & Hjeljord, O., 2010. Moose summer and winter diets along a

large scale gradient of forage availability in southern Norway.

European Journal of Wildlife Research, 56, pp.745–755.

Wang, X., Blanchet, F.G. & Koper, N., 2014. Measuring habitat

fragmentation: an evaluation of landscape pattern metrics. Methods in

Ecology and Evolution, 5(7), pp.634–646.

49

Veen, G.F., Geuverink, E. & Olff, H., 2012. Large grazers modify effects of

aboveground-belowground interactions on small-scale plant

community composition. Oecologia, 168(2), pp.511–518.

Weih, M. & Karlsson, P.S., 2002. Low winter soil temperature affects

summertime nutrient uptake capacity and growth rate of mountain

birch seedlings in the subarctic, Swedish lapland. Arctic Antarctic and

Alpine Research, 34, pp.434–439.

Welch, J.G., 1982. Rumination, particle size and passage from the rumen.

Journal of animal science, 54(4), pp.885–894.

Vidus-Rosin, A. et al., 2012. Habitat selection and segregation by two

sympatric lagomorphs: the case of European hares (Lepus europaeus )

and Eastern cottontails (Sylvilagus floridanus ) in northern Italy. Acta

Theriologica, 57(4), pp.295–304.

Wiens, J., 1989. Spatial scaling in ecology. Functional Ecology, 3, pp.385–

397.

Williams-Linera, G., 1990. Vegetation structure and environmental

conditions of forest edges in Panama. Journal of Ecology, 78(2),

pp.356–373.

Wilson, R.P. et al., 2013. Turn costs change the value of animal search

paths. Ecology Letters, 16(9), pp.1145–1150.

Vivås, H.J. & Sæther, B.E., 1987. Interactions between a generalist

herbivore, the moose Alces alces, and its food resources: an

experimental study of winter foraging behaviour in relation to browse

availability. Journal of Animal Ecology, 56, pp.509–520.

Zangerl, A.R. & Bazzaz, F.A., 1992. Theory and pattern in plant defense

allocation. In R. S. Fritz & E. L. Simms, eds. Plant resistance to

herbivores and pathogens: ecology, evolution, and genetics. Chicago:

University of Chicago Press, pp. 363–391.

Öhmark, S.M., Iason, G.R. & Palo, R.T., 2015. Spatially segregated

foraging patterns of moose (Alces alces) and mountain hare (Lepus

timidus) in a subarctic landscape: different tables in the same

restaurant? Canadian Journal of Zoology, 93, pp.391–396.