CAUSES AND CONSEQUENCES OF GROUP DOMINANCE IN SOCIAL-

TERRITORIAL SPECIES: A STUDY OF EASTERN WOLVES (CANIS LYCAON)

IN ALGONQUIN PROVINCIAL PARK, ONTARIO, CANADA

A Thesis Submitted to the Committee on Graduate Studies

in Partial Fulfillment of the Requirements for the Degree of Master of Science

in the Faculty of Arts and Science

TRENT UNIVERSITY

Peterborough, Ontario, Canada

© Copyright by Thelma Jean Marie Arseneau 2010

Environmental and Life Sciences M.Sc. Program

May 2010

ii

ABSTRACT

Causes and consequences of group dominance in social-territorial species: a study of

eastern wolves (Canis lycaon) in Algonquin Provincial Park, Ontario, Canada

Thelma Jean Marie Arseneau

Previous studies of intergroup competition in social-territorial species have

largely focused on short-term responses to simulated intruders, and have failed to

consider the effects of prolonged competition with multiple neighbours. We formulated a

conceptual model predicting both the causes and consequences of intergroup competition,

and validated it using data from a population of eastern wolves (Canis lycaon) in

Algonquin Provincial Park, Canada. We monitored space use and movement patterns for

17 packs between 2005 and 2007, and further investigated how these were influenced by

the presence and size of surrounding groups. A body of largely anecdotal evidence

suggests group size is a strong indicator of competitive ability in social species. Our

results show that larger packs spent more time in peripheral territory areas and were more

likely to intrude into neighbouring territories, showing they were less averse to the higher

risk of intergroup encounters in these areas. Habitat quality, as indicated by prey density

was the strongest predictor of group size. Numeric superiority was associated with

greater access to both on- and off-territory resources, and allowed more pups to remain

within the pack for longer time periods. The larger body size and hunting experience

associated with delayed dispersal may have led to greater survival and breeding success

post-dispersal; thus, competitive ability may have consequences for lifetime reproductive

success. Results support our conceptual model but its broader applicability should be

validated using other populations and social-territorial species.

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KEYWORDS

intergroup competition, numeric advantage, group dominance, social, territorial,

migration, intrusion, eastern wolves, Canis lycaon, hybridization

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ACKNOWLEDGEMENTS

“When we try to pick out anything by itself, we find it hitched to

everything else in the universe.” - John Muir

I have loved wildlife since I was very young. At the wee age of four, I used a

patented Donald Duck technique to trap a squirrel (he used it to catch Chip and Dale)

while camping with my family. I did not realize I could make a career out of such

endeavours until many years later, when I enrolled in a Conservation Biology program. I

quickly learned in undergrad, that I loved any class with “ecology” on the end. I look

forward to spending a lifetime studying the complexities of the natural world, and the

way the organisms within it interact with each other and their environment. My time at

Trent is what I hope will be but a few years among many in such pursuit.

I would like to thank a very long list of people who have made my graduate

experience both successful, and happy. Dennis Murray and Brent Patterson have advised

me throughout this journey, providing insight and constructive criticism along the way. I

have learned much about conducting research in ecology, writing scientifically, and am

prepared to answer, “What is science?” to anyone who may ask. In addition, thank-you to

Jeff Bowman, who provided valuable feedback that had a significant impact on the final

scope of my project. Additionally, thank-you to Marty Obbard who gave helpful

suggestions in the final stages of my thesis. I am very grateful to the many researchers

who collected the data that I relied upon for my analysis, including Ken Mills, Karen

Loveless and everyone on their field crews. In particular, I give sincere thanks to Karen

for not only collecting the data, but also for discussing possible ways of processing it,

providing GIS layers and R script, and better grounding my work in the biology of

v

eastern wolves. Linda Rutledge performed most of the genetic analysis and assisted me

greatly in the use and interpretation of the genetic results. I would like to thank NSERC,

who funded my graduate work, but also provided numerous scholarships during my

undergrad that gave me the experience needed to pursue graduate studies, and helped

foster my interest in ecology.

I am grateful to my fellow lab members, who sat through many presentations of

proposed studies, and provided feedback when I started producing results. In addition, I

greatly enjoyed discussing all of your research, brainstorming ideas, and critiquing

others‟ work. I feel like I learned a lot from our meetings and broadened my graduate

school experience. I would particularly like to thank Thomas Hossie for his indestructible

keenness and enthusiasm, Stacey Lowe for her sarcastic wit, Amanda Sparkman for great

discussions about women, life histories, statistics and academia, Allan Brand for his

statistical/analytical prowess, and Julia Phillips for being Julia Phillips. Additionally,

Bruce Pond, brainstormed ideas with me, gave me GIS tips, and always provided kind

support and a ready smile.

Many people contributed to my happiness during my time at Trent. These past

few years would not have been the same without my girls. Katy, Allison, Jenn, Rathika

and Kat made holidays, special occasions, and all the days in-between upbeat,

entertaining and exciting. I also give my sincere thanks to my mom and my gramma. I

would not be here today without their support and enthusiasm for my chosen career path.

They have taught me much about what it means to be a strong woman. Last, but certainly

not least, I especially want to give my sincere thanks to Nicholas Robar, who contributed

to the following masterpiece in numerous ways. He significantly improved the content by

vi

brainstorming with me, giving me statistical advice, and editing tirelessly. Perhaps more

importantly, he kept my spirits high, made me laugh, and gave me confidence throughout

my graduate career.

vii

TABLE OF CONTENTS

Abstract ...............................................................................................................................ii

Keywords ...........................................................................................................................iii

Acknowledgements ............................................................................................................iv

Table of Contents ..............................................................................................................vii

List of Tables .....................................................................................................................ix

List of Figures .....................................................................................................................x

Chapter 1: General Introduction .........................................................................................1

Intraspecific Competition in Social Species ...............................................1

Group Dominance .......................................................................................1

Intergroup Communication .........................................................................2

The Conceptual Model ................................................................................3

Alternative Strategies of Food Acquisition .................................................7

Study System ..........................................................................................................8

Study Objectives .....................................................................................................9

Chapter 2: Causes and consequences of group dominance in social-territorial species: a

study of the eastern wolf (Canis lycaon) in Algonquin Provincial Park, Ontario, Canada.

............................................................................................................................................11

Abstract .................................................................................................................12

Introduction ...........................................................................................................13

Study Area ................................................................................................18

Methods .................................................................................................................18

Capture and Monitoring ............................................................................18

Territory Estimation and Dominance ........................................................19

Prey Availability .......................................................................................21

Migration ...................................................................................................21

Pup Retention ............................................................................................22

Genetic Analysis .......................................................................................23

Data Analysis ............................................................................................23

viii

Results ...................................................................................................................25

Dominance ................................................................................................25

Validating the Conceptual Model .............................................................26

Migration vs. Expansion............................................................................27

Discussion .............................................................................................................28

Chapter 3: General Discussion ..........................................................................................42

References .........................................................................................................................47

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LIST OF TABLES

Table 2.1: Models of among pack variability in time spent patrolling, in a population of

eastern wolves (Canis lycaon) in Algonquin Provincial Park (2005-2007). ....................34

Table 2.2: High-ranking models (wi> reduced model) of variability in pack sizes of

eastern wolves (Canis lycaon) in Algonquin Provincial Park (2005-2007). Reduced

model is the constant only model. .....................................................................................35

x

LIST OF FIGURES

Figure 2.1: Conceptual model of group size, habitat quality relationships. The positive

feedback loop illustrates that habitat quality drives group size, group size determines the

dominance of the group and therefore their ability to maximize net resource intake,

thereby maintaining larger group size. Costs associated with sociality act as negative-

feedback mechanisms to decrease recruitment or birth rates, and/or increases dispersal

and juvenile mortality, making further increases to group size unstable. .........................36

Fgure 2.2: Map of eastern wolf (Canis lycaon) packs in Algonquin Provincial Park

(dashed line), Canada, from 2005-2007. Black outlined polygons represent 99% contour

home ranges for 17 packs monitored using GPS radiotelemetry. Polygons with a double

outline are MCP territories for packs having only VHF collar information. Grey polygons

are known deeryards. ........................................................................................................37

Figure 2.3: Frequency of wolf pack sizes observed in Algonquin Provincial Park from

2005-2007 (2005-2006, N = 17; 2007, N = 15). ...............................................................38

Figure 2.4: Relationships between relative pack size of eastern wolves in Algonquin

Provincial Park, number of intrusions made into neighbouring territories, and the total

duration (hrs) of all intrusions, during November 1- April 30 2005-2007. Relative pack

size was calculated as pack size of the intruding pack minus size of the resident pack;

positive values indicate numeric advantage for the intruding pack. .................................39

Figure 2.5: Projected increase in eastern wolf territory quality as represented by number

of moose contained therein when territory size is increased 5% (diamond), 10% (black

target), 15% (black square), or 20% (black circle). The dotted line represents average

number of moose-equivalents (of edible deer biomass) that packs migrating to deeryards

outside Algonquin Provincial Park have obtained. ...........................................................40

Figure 2.6: A) Projected increase in territory size resulting from expansion of 5, 10, 15

and 20%. B) Illustration of unidirectional expansion by 34 km2, which represents the

average territory growth necessary for gross prey benefits to equal those acquired by

migrating to deeryards in winter. ......................................................................................41

1

CHAPTER 1: GENERAL INTRODUCTION

Intraspecific Competition in Social Species

Many studies have used foraging theory to explain the evolution and maintenance

of sociality in group-living animals (reviewed by Giraldeau & Caraco 2000). Sociality

may also yield inclusive fitness benefits, effective scavenger expulsion, protection of

young, and territory defence against conspecifics (Clark & Mangel 1986, Packer et al.

1990, Vucetich et al. 2004, Mosser & Packer 2009). The specific role of territory defence

as a selective force has received limited research attention until recent work on lions

(Panthera leo) found that larger group sizes promote improved territory quality and

increased lifetime reproductive success in adult females (Mosser & Packer 2009). This

research highlights the need to further consider intraspecific competition and the selective

pressure it can exert in other social carnivore species.

Group Dominance

The intensity of intraspecific competition is regulated by population density

(Ridley et al. 2004, López-Sepulcre & Kokko 2005). Group competitive ability, however,

determines the degree to which each social group experiences resource limitation. There

is a lack of standard terminology to describe group competitive ability, but we use the

term “group dominance”. Dominance typically refers to the ability to use the potential

niche space of another species (McNaughton & Wolf 1970) or to individuals that are

likely to win a competitive interaction (Rowell 1974). In the context of a social species,

dominance implies groups are able to evaluate the probable outcome of an interaction

2

with other groups, and behave dominantly or submissively according to the perceived

risks and potential gains of conflict.

Group size is an important determinant in the outcome of an intergroup

interaction (Adams 2001). Observed encounters between neighbours (Sillero-Zubiri &

Macdonald 1998, Creel & Creel 2002, Packard 2003), or simulated intrusions

(Harrington & Mech 1979, McComb et al. 1994, Grinnell et al. 1995) indicate that social

species act in a more dominant manner when in larger groups. For example, smaller

packs of wolves (Canis lupus) and African wild dogs (Lycaon pictus) retreat when they

detect the presence of a larger pack, whereas larger packs advance towards smaller

groups (Creel & Creel 2002, Packard 2003). During intergroup encounters, larger wild

dog packs pursue and attack smaller packs, and serious injuries commonly result (Creel

& Creel 2002). Similarly, larger Ethiopian wolf (Canis simensis) packs are more likely to

win in encounters at territory borders (Sillero-Zubiri & Macdonald 1998). Male lion

coalitions are more likely to chase and attack intruding groups when at a numeric

advantage (McComb et al. 1994, Grinnell et al. 1995), and wounding and mortality rates

are lower for larger groups of females (Mosser & Packer 2009).

Intergroup Communication

The size of neighbouring groups may be communicated through both vocal and

olfactory signals; scent-marking and calling may also confer the age, sex, or identity of

group members (Hurst et al. 2001, Fischer et al. 2002, Frommolt et al. 2003). Information

on individual group members may be important when all individuals do not participate

equally in territory defence. For example, in chimpanzees (Pan troglodytes) the number

3

of adult males indicates the fighting power of a group (Mitani & Watts 2005); juvenile

lions are also less likely to respond to intruders than adults (Heinsohn et al. 1996). In

such cases, group size alone may not be an adequate measure of group competitive

ability, and group composition must be considered.

In addition to group size and composition, scent-marks may also convey

information on dominance behaviour. The density of marks, their freshness and the speed

that neighbours‟ signs are counter-marked, all indicate patrolling effort (Hurst et al.

2001). Larger packs tend to patrol territory boundaries more frequently (Harrington &

Mech 1979, Sillero-Zubiri & Macdonald 1998, Mitani & Watts 2005). It has been

proposed that larger groups are aware of their numeric advantage, and are more likely to

spend time in areas where high-risk encounters are more probable (Harrington & Mech

1979). Non-numeric factors influencing dominance behaviour in social groups are poorly

understood, although individual variability does exist (Heinsohn & Packer 1995).

The Conceptual Model

Both models and empirical studies predict a positive relationship between group

size and habitat quality (e.g., resource density, prey vulnerability) (Macdonald 1983,

Johnson et al. 2002, Mosser & Packer 2009), but determining cause and effect

relationships between these variables is difficult. Two opposing hypotheses could explain

the correlation. The “Competition Hypothesis” predicts that large groups live in high

quality habitat because their dominance allows them to acquire and defend the best

territories. This hypothesis follows the ideal despotic distribution (Fretwell 1972) in

which a necessary assumption is that interference competition occurs for territory

4

ownership. As such, this theory implies dominant groups have a competitive advantage,

which allows them to oust subordinate groups. Alternatively, the “Habitat Quality

Hypothesis” assumes territory competition is pre-emptive and that occupation by

residents prevents others from using the territory. This hypothesis is stems from the ideal

pre-emptive distribution (Pulliam & Danielson 1991) in which competition for territories

is exploitative. This hypothesis proposes high-quality habitat simply supports more

individuals. When resource density is high, search time may decrease as encounters with

prey become more frequent; therefore, the net energy gained per food item would be

maximized and a given resource base could support more group members (Holling 1959).

Below, we examine patterns of territory acquisition in multiple social carnivores to

determine the most defensible hypothesis.

When social carnivore populations are near carrying capacity, territories are

primarily acquired through inheritance, budding, or opportunistically when a territory is

vacated (Adams 2001, Theberge & Theberge 2004, López-Sepulcre & Kokko 2005). In

lions and spotted hyaenas (Crocuta crocuta) females are largely philopatric indicating

that they inherit natal territories (Heinsohn et al. 1996, Boydston et al. 2001). Wolf

territories are also inherited or formed through expansion and budding (Theberge &

Theberge 2004, Vonholdt et al. 2008, Rutledge et al. 2010a). Alternatively, the

displacement of resident groups through contest is atypical among social-territorial

animals. We suggest two important mechanisms that may explain the lack of such

occurrences. First, a strong prior resident effect, in which territory owners are more likely

to win contest competitions than non-resident floaters (e.g. Holberton et al. 1990, Haley

1994), may inhibit eviction of social groups. The prior resident effect is likely

5

exaggerated in social species because floaters and dispersers are typically solitary or in

small groups (Mech & Boitani 2003), and are at a numeric disadvantage to resident

groups. Secondly, entire social groups may show strong fidelity to established territories

because of the risk and energy expenditure required to relocate. Searching for higher

quality habitat may increase the probability of a high-risk encounter with conspecifics,

requires energy to search new habitats, and carries a risk of failure to find higher-quality

habitat (Johnson & Gaines 1990, Kramer & Chapman 1999). Additionally, the settlement

and establishment of a new territory is both energetically costly and risky as adjacent

residents may behave more aggressively towards newcomers than expanding neighbours

(McDougall & Kramer 2006). When territories are not won through contest, but rather

are inherited or acquired opportunistically, group competitive ability does not determine

habitat quality within initial territories. Thus, patterns of territory acquisition support the

Habitat Quality Hypothesis. Importantly, this conclusion suggests that habitat quality

may influence group dominance in social species through mechanisms regulating group

size.

Although social groups do not control habitat quality in budded or natal

territories, group dominance will determine ability to expand territory boundaries (Adams

2001). For the purpose of this thesis, we define „territory quality‟ as the total number of

prey available to a group within their territory. Because prey availability is a function of

both prey density and territory size, it follows that territory expansion should increase

territory quality. Depending on the species' life history, fluctuations in resource

availability affect birth, death, dispersal, or recruitment rates. Dispersal is an important

mechanism regulating social group size because subordinate individuals emigrate when

6

intragroup food competition is high (Messier 1985, Mech & Boitani 2003). As such,

dispersal is a mechanism by which changes in territory quality cause group size to

fluctuate, implying that dominant groups that are able to increase their resource base are

also able to maximize food intake and further maintain larger group sizes.

Ultimately, under this scenario, a positive-feedback loop involving group size and

territory quality emerges. Efficient foraging in high-quality habitat can promote larger

group sizes, and large groups are better able to increase territory quality, thereby

supporting larger group size (see Chapter 2, Fig. 2.1). Conversely, many factors may

concurrently select for smaller group sizes, thus limiting group size. For example,

intragroup competition for limiting resources, such as food and mates, and the increased

transmission of diseases in larger groups are known costs of group living (Côté & Poulin

1995, Mosser 2008, Zhao et al. 2008). Additionally, territories may become so large as to

no longer be economically defensible, limiting further increases to group size.

Based on our conceptual model we predicted that (i) group size relates positively

to prey density, until further increases in group size are unstable; (ii) group size is

positively associated with dominance behaviour; (iii) dominance relates positively to both

territory size and territory quality (estimated as total number of prey available); and (iv)

territory quality is negatively related to dispersal, such that more juveniles remain with

their natal group in high-quality territories for longer periods. In other populations, the

effects territory quality has on reproductive, survival and recruitment rates may be more

important. We tested the above predictions using data on a population of eastern wolves

(Canis lycaon) in Algonquin Provincial Park (APP), Ontario, Canada. Within this study

7

system, two factors potentially confounding these predicted relationships include

seasonal changes in the distribution of prey and hybridization among wolves and coyotes.

Alternative Strategies of Food Acquisition

Traditional territory models often assume that territories are not contiguous, and

population density is low (Adams 2001). At high density, however, intense intraspecific

competition causes territories to become compressed (Ridley et al. 2004). As resources

become limiting, owners defend compressed territories more aggressively, and can do so

more efficiently (Huxley 1934, Stuart-Smith & Boutin 1994, Adams 2001). In high-

density populations, field experiments often show rapid territory expansion when gaps

occur in the territory mosaic (e.g. Krebs 1971, Boutin & Schweiger 1988, Butchart et al.

1999), but expansion without perturbation may be more difficult. The high cost of

territory expansion in saturated populations may promote alternative strategies of food

acquisition, such as acquiring resources off-territory.

Spotted hyaenas and wolves both exhibit migratory behaviour in which

individuals or groups take foraging excursions off-territory (Messier 1985, Hofer & East

1993, Cook et al. 1999). In both cases, the strategy is feasible because prey aggregate

predictably (Hofer & East 1993, Cook et al. 1999). When resources are acquired off-

territory, traditional measures of territory quality do not accurately represent resource

intake; therefore, we adapted our conceptual model to include a migration strategy (See

Chapter 2, Fig. 2.1). We hypothesized that migration provides an effective method of

increasing resource intake without expanding territory boundaries. During our study,

migrating packs traversed as many as four territories to reach deeryards where deer

8

aggregate in the winter. We observed deaths of trespassing individuals, indicating that

migration is risky (Patterson et al., unpublished data). Therefore, we hypothesized that

competitive ability would mediate migratory behaviour, and predicted a positive

relationship between group dominance and tendency to migrate to seasonally aggregated

prey sources.

Study System

The eastern wolf was previously listed as a subspecies (Canis lupus lycaon) of the

grey wolf (COSEWIC 2001), however, genetic analyses indicate they should be

considered a distinct species (Canis lycaon; Wilson et al. 2000, Kyle et al. 2006). Wolves

in the APP population maintain a higher proportion of eastern wolf ancestry than is seen

outside the park, where hybridization with both grey wolves and eastern coyotes (C.

latrans) occurs to a greater extent (Wilson et al. 2009, Rutledge et al. 2010b). A wolf

harvest ban imposed in areas surrounding the park in 2001 stabilized pack structure

increasing within pack relatedness and decreasing adoption of unrelated individuals

(Rutledge et al. 2010a). As a result, the frequency of hybridization in this population may

decrease in the future.

Current levels of introgression (gene flow from one species into another) may

confound the relationship between pack size and behavioural dominance, and therefore

we considered potential effects of genetic admixture on wolf behaviour in our study. To

our knowledge, the relative contribution of group size and individual quality to group

9

dominance has not been addressed. Body size, however, is an important factor in

individual quality in asocial species (Haley 1994, Stuart-Smith & Boutin 1994) and may

influence group competitive ability when there is little numeric difference between

competing groups. Eastern wolves are of intermediate body size between larger grey

wolves and smaller eastern coyotes (Rutledge et al. 2010b). Larger animals are able to

kill large prey more efficiently (Sand et al. 2006, MacNulty et al. 2009); thus,

introgression may influence pack size indirectly by affecting net food intake efficiency.

Study Objectives

Previous research has focused primarily on the short-term effects of intergroup

competition by examining the manner in which residents respond to intruders (e.g.

Grinnell et al. 1995, Sillero-Zubiri & Macdonald 1998). The purpose of the present study

was to further our understanding of both the causes and long-term consequences of

continuous competition between neighbours. Our overall goals were to (i) investigate

primary factors influencing group size; (ii) better understand mechanisms by which

numeric advantage influences dominance behaviour; (iii) explore how dominance

influences a group‟s potential to acquire resources on- and off-territory; and, (iv) explore

the possible fitness benefits of resource acquisition.

Using GPS radiotelemetry, we intensively studied movement patterns, space use,

and group size of wolves in APP from 2004 to 2007. Importantly, many of the packs we

monitored were located in a contiguous mosaic (See Chapter 2, Fig. 2.2), allowing us to

10

investigate the influence of surrounding neighbours on space use and behaviour. High-

frequency movement data allowed us to delineate territory boundaries precisely, as well

as determine movements off-territory.

11

CHAPTER 2

CAUSES AND CONSEQUENCES OF GROUP DOMINANCE IN SOCIAL-

TERRITORIAL SPECIES: A STUDY OF EASTERN WOLVES (CANIS LYCAON)

IN ALGONQUIN PROVINCIAL PARK, ONTARIO, CANADA

12

Abstract

Previous studies of intergroup competition in social-territorial species have

largely focused on short-term response to intruders and have failed to consider the effects

of prolonged competition. We formulated a conceptual model predicting high-quality

habitat would support larger, more dominant groups, thereby increasing their ability to

access resources and retain group members. The model was validated using data from a

population of eastern wolves (Canis lycaon) in Algonquin Provincial Park, Canada, in

which we monitored space use and movement patterns of 17 packs from 2005 to 2007.

We found that group size was positively related to habitat quality and that larger groups

behaved more dominantly, as they spent more time in peripheral territory areas and were

more likely to intrude into neighbouring territories. These behaviours illustrated use of

high-risk areas where intergroup encounters were more probable. Numeric superiority

was also associated with greater access to both on- and off-territory resources, by

promoting territory expansion and seasonal migration to aggregated prey sources. Higher

resource availability allowed more pups to remain within the pack for longer, which may

infer greater survival and breeding success post-dispersal. Canis latrans introgression

was a confounding factor of both group size and intrusion behaviour, indicating

individual quality (e.g., body size, hunting ability) also influenced group dominance.

Results support our conceptual model but its broader applicability should be validated

using other populations and social-territorial species.

13

Introduction

Even though competition is an important process in ecology, the role of

intergroup competition in regulating resource access for social-territorial species has

received limited research attention (Mosser & Packer 2009). To date, studies have largely

focused on the short-term response by social groups to intruders (e.g. Harrington & Mech

1979, Grinnell et al. 1995, Sillero-Zubiri & Macdonald 1998) but have not considered

longer-term consequences of continuous competition with multiple neighbours. Recent

work, however, linked intergroup competition in lions (Panthera leo) to territory quality

and fitness (Mosser & Packer 2009), highlighting the need to further consider the

selective pressure that intraspecific competition can exert on other social-territorial

species. We developed a conceptual framework for the causes and consequences of

differential group competitive ability, and evaluated the validity of our hypotheses using

data from a population of eastern wolves (Canis lycaon) in Algonquin Provincial Park,

Canada.

During intergroup conflict, members of smaller groups are more likely to suffer

injury or death (Ethiopian wolves (Canis simensis), Sillero-Zubiri & Macdonald 1998;

African wild dogs (Lycaon pictus), Creel & Creel 2002; lions, Mosser & Packer 2009).

As a result, social groups tend to approach or chase intruders when at a numeric

advantage, whereas smaller groups retreat upon detecting a larger group (lions, McComb

et al. 1994; African wild dogs, Creel & Creel 2002; grey wolves (Canis lupus), Packard

2003). This evidence indicates that territorial groups evaluate the size of intruding

groups, and respond “dominantly” when at a competitive advantage.

14

The manifestation of dominant and subordinate responses into changes in territory

size and resource access is poorly understood. Awareness of numeric advantage may

promote use of areas in which risk of intergroup encounters is higher, such as along the

territory periphery. Indeed, larger groups tend to spend more time patrolling territory

boundaries (Harrington & Mech 1979, Mitani & Watts 2005). We propose that numeric

superiority largely determines group dominance behaviour, and as a result facilitates

increased resource access. To test this hypothesis we investigated relationships between

group size and two dominance-related behaviours: time spent patrolling and intrusions

into neighbouring territories. The latter behaviour reveals use of space and resources

defended by other groups, and may therefore represent capacity to seize space.

Using information on the ecology of multiple group-territorial species, we

developed a priori predictions of the causes and consequences of group dominance (Fig.

2.1). Although group size should relate positively to habitat quality (e.g., resource

density, prey vulnerability) (Johnson et al. 2002, Mosser & Packer 2009), two opposing

hypotheses could explain this correlation. The “Competition Hypothesis” predicts that

large groups live in high quality habitat because their dominance allows them to acquire

and defend the best territories. Following the ideal despotic distribution (Fretwell 1972),

an important implication is that interference competition for territory ownership occurs,

with dominant groups ousting subordinate groups. Alternatively, the “Habitat Quality

Hypothesis” assumes territory competition is pre-emptive and that occupation by

residents prevents others from using the territory. This hypothesis is comparable to the

theory behind the ideal pre-emptive distribution (Pulliam & Danielson 1991) and implies

competition for territories is exploitative. This hypothesis proposes high-quality habitat

15

simply supports more individuals. When habitat quality is a product of prey density,

factors such as decreased search time increase hunting efficiency. The associated increase

in net food intake may increase birth rates, decrease dispersal rates, or increase

recruitment rates, effectively increasing group size.

Observed patterns of territory acquisition support the Habitat Quality Hypothesis,

as competitive ability does not appear to determine habitat quality in newly formed

territories. In high-density social carnivore populations, territories are acquired through

inheritance, expansion and budding, or opportunistically when a territory is vacated

(lions, Heinsohn et al. 1996; spotted hyaenas (Crocuta crocuta), Boydston et al. 2001;

eastern wolves, Theberge & Theberge 2004; grey wolves, Vonholdt et al. 2008). In the

former two scenarios, habitat quality is determined by the location of the natal territory or

the adjacent habitat. In opportunistically acquired territories, habitat quality is whatever

becomes available. Alternatively, there is little evidence suggesting larger, more

dominant groups seize high-quality territories through interference competition. We

suggest two mechanisms to explain the lack of such occurrences. First, it is likely that

numeric advantage exaggerates the prior resident effect (e.g. Holberton et al. 1990, Haley

1994), such that resident groups are more likely to win in contest competition than are

floaters who typically are solitary or travel as a small group. Secondly, entire social

groups may show strong fidelity to established territories because of the risk and energy

expenditure required to relocate. Searching for higher quality habitat may increase the

probability of a high-risk encounter with conspecifics, requires energy to search new

habitats, and carries a risk of failure to find higher-quality habitat (Johnson & Gaines

1990, Kramer & Chapman 1999). Additionally, the settlement and establishment of a

16

new territory is both energetically costly and risky as adjacent residents may behave more

aggressively towards newcomers than expanding neighbours (McDougall & Kramer

2006). The observed patterns of territory establishment indicate that group competitive

ability does not facilitate acquisition of high-quality habitat, but are rather a product of it;

importantly, this conclusion suggests that habitat quality may influence group dominance

in social species through mechanisms regulating group size.

Group dominance will determine the ability to expand or shift territory boundaries

(Adams 2001, Mosser & Packer 2009), thereby increasing resource availability and

overall territory quality. Fluctuations in resource availability affect dispersal (or

recruitment) rates, as subordinate individuals emigrate when intragroup food competition

is intense (Messier 1985, Mech & Boitani 2003). Because resource availability regulates

group size, dominant groups that are able to increase territory quality can maximize food

intake and further support larger group sizes.

Ultimately, a positive-feedback loop establishing the mechanisms underlying

group size formation and maintenance becomes apparent (Fig. 2.1). Foraging efficiency

in high-quality habitat supports larger groups that are better able to increase territory

quality, further maintaining large group sizes. Conversely, costs to group living, such as

intragroup competition for limiting resources such as food and mates and the increased

transmission of diseases in larger groups, may exert selective pressure for smaller group

sizes (Côté & Poulin 1995, Mosser 2008, Zhao et al. 2008). Additionally, territories may

become so large as to no longer be economically defensible, limiting further increases to

group size. These factors create a negative-feedback effect, counteracting the positive

17

pressure intergroup competition exerts on group size, and regulate maximum group size

(Fig. 2.1).

Within our study system, group size and territory maintenance behaviour are

potentially confounded by hybridization among wolves and coyotes and the seasonal

migration of prey. First, variability in body size, associated with eastern wolf

hybridization with eastern coyotes (Canis latrans) and grey wolves (Rutledge et al

2010b), may directly influence group dominance when groups are numerically equal.

Additionally, body size may indirectly affect pack size by influencing hunting efficiency

(Sand et al. 2006, MacNulty et al. 2009). Second, many packs exhibit an alternative

strategy of food acquisition, migrating off-territory to obtain seasonally aggregated prey

(Cook et al. 1999). Because this strategy can increase net food intake, it may also have a

positive effect on the maintenance of larger group sizes (Fig. 2.1). Based on our

conceptual model, we predicted:

P1: Habitat quality determines group size such that pack size will relate positively to prey

density until density dependent factors, mate competition, or economic defensibility

of large territories make larger group sizes unstable.

P2: Numerically dominant packs spend more time in peripheral territory area and are

more likely to trespass in neighbouring territories.

P3: Dominance affects ability to increase territory quality and therefore both territory size

and prey availability on- territory will relate positively to pack size.

P4: Migration effectively increases resource intake but is regulated by relative

competitive ability such that packs will be more likely to migrate when at a numeric

advantage compared to neighbouring packs.

18

P5: Resource availability regulates dispersal age such that greater access to either on- or

off-territory resources increases juvenile retention through the following winter.

Study Area

We studied wolves in Algonquin Provincial Park (APP), which covers 7571 km2

in south-central Ontario, Canada (45° 27‟ N 78° 27‟ W). APP lies between the boreal and

mixed-deciduous forest ecotones on the southern edge of the Canadian shield (Pimlott et

al. 1969, Patterson et al. 2004). Eastern wolves occur throughout APP, and although prior

hybridization with grey wolves and eastern coyotes is evident (Rutledge et al 2010b),

wolves within the park have higher proportions of eastern wolf ancestry than is typically

seen outside park boundaries (Wilson et al. 2009). The population is believed to be near

carrying capacity because of the contiguous configuration of packs on the landscape (Fig.

2.2) and observed stationary population size since 2001 (Rutledge et al. 2010b).

Dominant prey species include moose (Alces alces), white-tailed deer (Odocoileus

virginianus) and beaver (Castor canadensis).

Methods

Capture and Monitoring

We monitored 257 wolves between 2003 and 2007 as part of a larger research

project on wolf ecology in APP (Patterson et al. 2004). Adult wolves were captured using

foothold traps, neck snares and aerial net-gunning. Most wolves were collared with VHF

19

radio-transmitters, but a subset of packs (2005, N = 6; 2006, N = 9; 2007, N = 5), were

monitored via GPS collars (Model 4400, Lotek Wireless Inc. 2007) programmed with a

1- 1.5hr fix interval through the winter (November 1-April 30). VHF collared individuals

were monitored from the air weekly. Locations imported into GIS (ArcView 3.2,

Environmental Research Institute Inc. 1999) revealed a high transmitter fix-success rate

(81%±2.3 SE) (J. Arseneau, unpublished data). A stationary collar test indicated location

accuracy ranging from 7.9 m (±11.3 SD) to 15.5 m (±27.9 SD) depending on cover type

(Maxie 2009). In 2004 and 2005, pups were captured at the den and implanted with VHF

radio-transmitters (Advanced Telemetry Systems, Isanti, MN, or Telonics, Mesa, AZ)

(Mills et al. 2006).

We identified clusters of GPS points (hereafter “clusters”) where collared wolves

remained within a 100 m buffer for at least three hours. We ground-truthed 94% (N =

1572) clusters and found that 25% constituted prey kill sites, whereas the remainder were

bedding or resting sites (Loveless 2010). We deployed 2 GPS collars concurrently within

a pack and found no difference in cluster locations between individual pack members

(Loveless 2010), implying that coarse-scale movement patterns were comparable among

pack members despite finer scale variability in movements (Peterson et al. 1998,

Mallonée 2008).

Territory Estimation and Dominance

Because wolf packs in APP exhibit extra-territorial movements (Cook et al.

1999), we defined a territory as the area occupied during seasons when site fidelity was

greatest. We created data-subsets using locations from a 43-day period in either spring or

20

fall, as this was the longest period when site fidelity was observed. We randomly

subsampled each data-subset to standardize the number of telemetry locations to the

minimum observed (N = 343) because preliminary analyses showed that estimated time

spent patrolling was sensitive to number of locations.

To overcome autocorrelation among consecutive locations, we used the Brownian

Bridge Movement Model (BBMM) to estimate territory size (Bullard 1999, Horne et al.

2007). The BBMM method is sensitive to standard deviation of the telemetry error (δ)

and an animal‟s movement rate (σ2

m) (Bullard 1999, Horne et al. 2007). We used δ = 30

m, which was accurate for locations in conifer stands and conservative for other forest

types (Maxie 2009). Territory boundaries were defined by the 99% contour. We also

calculated minimum convex polygons (MCPs) for VHF packs using time-periods when

site fidelity was shown (April 1 – November 30), to better determine configuration of

wolf packs on the landscape.

We used pack size to indicate numeric dominance of a focal pack, and relative

pack size (i.e. focal pack size – neighbouring pack size) when investigating a pairwise

interaction such as an off-territory intrusion or migration. Pack size was enumerated

during 2-3 winter telemetry flights, and opportunistic snow tracking events. The

maximum pack size observed was assumed representative for the entire winter. Pack size

was compared to (i) time spent patrolling, and (ii) intrusion into neighbouring territories.

Patrolling behaviour was measured as the proportion of time spent in the outer 30% of

the territory, which we calculated using movement paths (Hawth‟s Tools, Beyer 2004)

and the time elapsed between successive locations. We assumed that among pack

variability in the time contributed to maintenance behaviours (e.g., scent-marking) when

21

in the outer 30% was negligible. Number and total duration of intrusions into

neighbouring territories was determined using GPS location clusters, which indicated a

prolonged intrusion. We quantified intrusion duration as the total time spent at a cluster

in a foreign territory, and summed all intrusions for each pack to get the total duration of

intrusions. Intrusion variables were standardized by the proportion of the study year the

pack was monitored (range 52-100%).

Prey Availability

We categorized a territory as having high deer densities if it overlapped spatially

with known deeryards (Fig. 2.2). Moose density was determined from helicopter transects

flown after fresh snowfalls in 2001, 2003 and 2006 (Bisset and McLaren 1999). To deal

with partial surveys in 2001 and 2006, we kriged counts from surveys in 2001/2003 and

2003/2006, and then averaged kriged layers to weight the 2003 survey. We used average

moose density in the territory to represent habitat quality, and because this value was

resilient to changes in territory area, we determined mean moose density for both GPS

and VHF packs. Total number of moose within territories represented their overall

territory quality for packs not residing in deeryards. We estimated total number of moose

using the kriged moose layer. This parameter was only calculated for GPS-collared packs

having precise estimates of territory size.

Migration

Packs that migrated at least once between November 1 and April 30 were

categorized as migratory for that year. We determined relative size of each pack to the

22

neighbour “blocking” its direct migration path to known deeryards, which indicated

competitive cost of migration. We also qualitatively investigated the change in relative

pack sizes when a single pack altered migration behaviour between years.

We conducted a simulation exercise to contrast gross benefits of territory

expansion with those of migration in terms of prey access. The potential increase in

moose availability for multiple expansion scenarios was simulated by buffering territories

by 5, 10, 15, and 20% of their estimated area. These simulated increases in prey were

compared with observed predation rates for packs either residing in, or migrating to

deeryards. We used predation rates from 2006 and 2007 (K. Loveless, unpublished data)

to determine the number of deer that could be acquired by using deeryards. To directly

compare moose and deer, we converted deer to moose equivalents using reported body

sizes (Kolenosky 1972, Quinn & Aho 1989), and percent edible biomass (Hayes et al.

2000, Kolenosky 1972) (following Fuller 1989); our conversion was 1 moose: 4 deer.

Pup Retention

We identified den sites from movements of monitored adults, and captured pups

when 4-6 weeks old (Mills et al. 2006). VHF implants allowed us to track pup dispersal

and mortality events, and although mortality rates were low, we observed dispersal as

early as 15 weeks of age. When packs were enumerated the following January, we

determined retention as the number of pups still with the pack. Because off-territory prey

sources were used by many packs, territory quality did not accurately represent potential

resource intake; consequently, we tested the indirect relationship between pack size and

pup retention.

23

Genetic Analysis

Throughout the study, we collected blood and hair samples from captured wolves,

as well as scat samples opportunistically. We determined levels of introgression of C.

lupus and C. latrans genes in eastern wolves using methods described previously

(Rutledge et al. 2010a, b). Admixture analysis was performed using a Bayesian approach

in STRUCTURE 2.1 (Pritchard et al. 2000, Falush et al. 2003) to assign probability of

population of origin to each individual, without a priori population assignments.

Outgroups included the APP population, northeast Ontario/Quebec population

(predominantly C. lupus), and the Frontenac Axis region (predominantly C. latrans).

Assignment was corroborated using factorial correspondence analysis in GENETIX 4.05

(Belkhir et al. 2004). We assigned animals to populations using a conservative likelihood

of membership threshold (q = 0.8) because of the high level of hybridization (Pierpaoli et

al. 2003, Adams et al. 2007), and used likelihood of membership to C. lupus and C.

latrans as continuous variables indicating degree of introgression. To calculate pack

admixture, we averaged q values among two or more adult pack members, except in three

cases where only a single individual was sampled.

Data Analysis

We used linear regression to investigate the relationship between pack size, or

relative pack size, and our behavioural, genetic, and habitat-related measurements.

Although a non-linear relationship between habitat quality and group size was predicted,

we lacked a large enough sample size to rigorously test for a non-linear relationship. We

used Fisher‟s exact test to investigate the importance of pack size relative to the blocking

24

pack (positive/advantage vs. equal or negative/disadvantage) in driving migratory

behaviour, and logistic regression was used to test the impact of C. latrans and C. lupus

admixture. Analysis of the relationship between habitat quality and pack size focused on

the average pack size (2005-2007) supported by average moose density during the study.

We used an information-theoretic approach to evaluate the effect of genetic

admixture on pack size and time spent patrolling. We censored candidate variables that fit

the data poorly (P < 0.10), and calculated Akaike‟s Information Criteria (corrected for

small sample sizes; AICc), cumulative weights (∑w), model-averaged coefficients and

unconditional confidence intervals (Burnham & Anderson 2002). We used one-tailed (α

= 0.05) tests where we had a priori hypotheses (Fig. 2.1). In two analyses, we removed

outliers that could not be corrected via transformation and exerted strong leverage in the

regression (Cook 1977, Belsley et al. 1980). One outlier likely resulted from over-

estimation of moose densities, in high-density areas, during the kriging process. The

second outlier was a territory of large size, which budded into three smaller territories the

following year, possibly indicating that territory was unstable. All statistics were

conducted in R (R Development Core Team 2008). Means are presented with standard

deviation unless otherwise stated.

25

Results

Dominance

The median wolf pack size during our study was 5.0 in all years, although within-

pack size was consistent for only 27% (N = 25) of packs with the remainder varying on

average by 2.2 ± 1.1 individuals among years. We observed greater inter-pack variability

in group size in 2005 and 2006, than in 2007 (Fig. 2.3). Pack size was closely related to

our measure of patrolling effort (∑wi = 0.97, β = 0.54, 1-tail CI = 0.30, N = 17), with

larger packs spending a greater proportion of time in the outer 30% of their territories

(Table 2.1). There was little support for the influence of C. latrans admixture on the

proportion of time spent patrolling (∑wi = 0.28, β = -2.86 ± 5.31, N = 17), and C. lupus

admixture was also not important (linear regression, P > 0.70). We did not detect

influence of an individual‟s breeding status or gender, or of season or year, on time spent

patrolling (Welch‟s t-test: all P > 0.26).

Relative pack size between intruding and resident packs influenced both the

number of intrusions (linear regression: R2adj

= 0.37, F1,8 = 6.23, β = 1.72, 1-tail CI =

0.44, P = 0.019), and the total duration of intrusions (R2adj

= 0.29, F1,8 = 4.62, β = 19.04,

1-tail CI = 2.55, P = 0.032) (Fig. 2.4). The average duration of each intrusion was 11.7

hrs (± 3.9), and was not related to relative pack size (R2adj

= -0.05, F1,8 = 0.56, β = 0.57,

1-tail CI = -0.84, P = 0.24).

Canis latrans introgression had a negative relationship with the total duration of

intrusions when all packs were considered (linear regression: R2adj

= 0.48, F1,10 = 10.95,

β = -183.31 ± 123.45 , P = 0.008). Because they may be less likely to move off-territory

26

as they have access to an aggregated prey resource, we repeated this analysis after

censoring packs residing in deeryards (N = 4) and found C. latrans introgression was still

negatively related to the total duration of all intrusion (R2adj

= 0.56, F1,7 = 11.12, β = -

506.41 ± 359.10, P = 0.013). Canis lupus introgression had no effect on intrusion

behaviour (R2adj

= -0.10, F1,10 = 0.01, β = 6.52 ± 161.92 , P = 0.93).

Validating the Conceptual Model

Average moose density within the territory explained much variability in average

pack size (∑wi = 0.75, β = 8.62, 1-tail CI = 0.56, N = 16), with higher-quality habitat

supporting larger groups. Although the model including moose density, C. latrans

admixture, and C. lupus admixture was strong (Table 2.2), we found only moderate

overall support for C. latrans admixture (∑wi = 0.55, β = -14.06 ± 19.31, N = 16), and

little support for C. lupus admixture (∑wi = 0.38, β = 3.19 ± 37.31, N = 16) as

determinants of pack size. The average size of primarily C. lycaon packs was 5.1 ± 1.5,

whereas highly C. lupus admixed packs tended to be larger (5.9 ± 1.7) and highly C.

latrans admixed packs tended to be smaller (4.1 ± 1.0).

We investigated the impact of competitive ability on territory size and the number

of moose per territory for packs residing outside deeryards. Group size was positively

related to both territory size (linear regression: R2adj

= 0.30, F1,14 = 7.45, β = 20.47, 1-tail

CI = 7.27, P = 0.008), and the number of moose (territory quality) (R2adj

= 0.45, F1,9 =

9.07, β = 9.59, 1-tail CI = 3.75, P = 0.007).

When pups were excluded from our pack count estimates, we found that group

size showed little variability (range 2-4 individuals), indicating the importance of pups on

27

pack size. We found that pack size in the previous winter was related to number of pups

retained the following winter (R2adj

= 0.23, F1,11 = 4.50, β = 0.41, 1-tail CI = 0.06, P =

0.029).

Migration vs. Expansion

During 2006 and 2007 combined, approximately half of monitored packs

migrated to deeryards during winter. Numeric advantage was a significant predictor of

migration (Fisher‟s exact test: χ2= 7.43, 1-tail P = 0.008, N = 31); 80.0% of migrating

packs (N = 15) were larger than the blocking pack, whereas 68.3% of the non-migrating

packs (N = 16) were at a numeric disadvantage. The strength of the effect varied between

years (2006: χ2= 4.18, 1-tail P = 0.020, N = 16; 2007: χ

2= 0.28, 1-tail P = 0.21, N = 15),

due to the larger overall number of packs not migrating in 2007. Anecdotally, four of the

packs monitored in both years (N = 15) switched migratory behaviour between years; this

trend was not associated specifically with the year itself, but rather with changes in

relative pack size to the blocking pack. We found little support for either C. latrans or C.

lupus admixture as important factors affecting migration (logistic regression: all P >

0.54).

We determined that packs residing in the deeryards consumed an average of 39.6

deer (± 70.7% SD, N = 4) during the 170 day winter, which represents ~10.0 (± 71.0%)

moose-equivalents of deer biomass. The average moose-equivalents of deer biomass,

killed by migratory packs was ~6.7 (± 40.3%, N = 5), but the maximum observed was

~10.4. Thus, migratory packs were capable of acquiring gross prey biomass equal to that

of the average deeryard resident pack.

28

We related the profitability of a 5, 10, 15 and 20% territory expansion (number of

moose available) to the current number of moose occurring in a territory, which is a

function of both territory size and moose density (Fig. 2.5). This exercise revealed that

packs holding low-quality territories (i.e., <50 moose) experienced little benefit from

further territorial expansion. Furthermore, territory expansion by 5-10% provided less

benefit in terms of gross prey biomass than could be obtained by migrating to deeryards.

Conversely, for packs with territories having >70 moose within the territory, expanding

by 15-20% could provide access to more additional prey than migrating to deeryards.

The mean size of territories with >70 moose was 228 km2

(± 21.5%), indicating that

expansion by 34 km2 (± 20.1%) may equal the gross benefits of migration. Depending on

the size of inter-territorial spaces, expansion of this extent may be feasible with minimal

increased interaction among neighbours (Fig. 2.6).

Discussion

We found strong support for our conceptual model of the causes and

consequences of group dominance. Group size related positively to habitat quality

(prediction 1), and therefore group dominance. The numeric superiority experienced by

packs residing in high-quality habitat had a positive influence on a pack‟s ability to

increase resource availability in on- and off-territory sources (predictions 3-4), and to

retain subordinate pack members for longer (prediction 5). Larger packs also behaved

more dominantly by exhibiting higher-risk behaviours, including spending more time in

29

territory peripheries, and intruding in neighbouring territories (prediction 2). This

apparently low aversion to risk may be a mechanism by which dominant groups can seize

space and increase resource availability. Canis latrans introgression confounded both

group size and intrusion behaviour, suggesting that individual variability in body size,

aggression, or hunting ability influences group dominance.

We infer that because larger groups are more likely to win in intergroup

interactions (Sillero-Zubiri & Macdonald 1998, Creel & Creel 2002, Mosser & Packer

2009), they are less averse to using high-risk areas. Larger packs spent a larger proportion

of time in patrolling territory peripheries where the chance of encountering conspecifics

was higher. Reduced aversion associated with larger pack size was also apparent in

facilitating off-territory forays as intrusions were made almost exclusively into territories

where the intruding pack was at a numeric advantage. The ability to exhibit dominance

outside defended boundaries likely permits packs to challenge neighbours for space and

thus may be an important mechanism of territory expansion or shifting, increasing

resource availability.

There was variability in time spent patrolling and intrusion tendencies among

equal- sized packs. Some variability likely relates to the identity (i.e., status, sex,

boldness) of the focal animal (Heinsohn et al. 1996, Sillero-Zubiri & Macdonald 1998),

but we typically monitored only one individual per pack and were therefore unable to

account for within-group differences. However, introgression influenced time spent

patrolling and intrusion duration, indicating that individual quality likely impacts group

dominance. The smaller body size in eastern coyotes (Rutledge et al. 2010a) may inhibit

highly admixed packs from behaving dominantly. If correct, this conclusion could have

30

important implications for both the APP population and the reintroduced red wolf (Canis

rufus), as hybridization with eastern coyotes is a conservation concern for both

populations (Stoskopf et al. 2005).

We created a conceptual model to explain not only the drivers of group

dominance, but also its consequences. A key assumption made was that dominant groups

do not displace resident groups when territories are inherited, budded, or

opportunistically acquired; it logically follows that habitat quality determines group size.

Numeric superiority facilitated boundary expansion, and was thus associated with larger

territory size and greater moose availability. A positive relationship between group size

and territory size has also been seen in lions (Mosser & Packer 2009), suggesting that

territory expansion is a common tactic in social-territorial species. In established

populations, this strategy would ensure territory acquisition for offspring and thus

promote long-term fitness, while also decreasing the intensity of inter-territorial conflict

between closely related neighbours (Kitchen et al. 2005).

The benefits of a high-quality territory may include increased reproductive output,

higher retention or recruitment, or higher breeding success of offspring (Bygott et al.

1975, Mosser & Packer 2009). In APP, we observed dispersal as early as 15 weeks, and

given that pups are not sexually mature, intrapack food competition is the probable

trigger of most juvenile dispersal events (Mech & Boitani 2003). Larger packs, however,

retained more pups within the group for longer into the following winter. That larger

packs perpetuate larger packs is a superficial conclusion, but the implication that larger

packs raise pups that are likely bigger and have more hunting experience due to longer

residency in natal packs is biologically significant. These two characteristics may be

31

important in the future survival and breeding success of dispersing individuals. In lions,

synchronous breeding by larger numbers of females (in large prides) results in larger

male cohorts that can experience greater reproductive success later in life (Bygott et al.

1975).

There was a weak effect of introgression on group size when we controlled for

prey density. This may reflect differential hunting ability and efficiency. Larger body size

associated with C. lupus admixture may minimize handling time and allow groups to

target larger prey (e.g. Sand et al. 2006, MacNulty et al. 2009), maximizing consumable

biomass and supporting larger group size. In our study system, introgression has been

shown to influence prey size with C. lupus admixed packs tending to select moose and C.

latrans admixed packs selecting deer (Loveless 2010). Furthermore, larger groups

effectively repel scavengers and maximize biomass consumed (Vucetich et al. 2004),

thereby enhancing a body size effect.

We found that migration was an effective strategy for acquiring prey, providing

gross benefits equal to those obtained by the average deeryard-residing pack. Our

simulation also revealed migration was more profitable than expanding territory size (by

≥ 15%) for approximately half of our observed packs. The net profitability of territory

expansion will depend on the density and distribution of prey in surrounding areas, as

well as energetic costs of maintaining a larger territory. The feasibility of enlarging a

territory ≥ 15% should depend on the number of neighbouring packs, their relative

competitive ability, the size of inter-territorial spaces, and the degree to which

neighbouring territories are compressed.

32

Numeric advantage over the pack blocking a direct route to a deeryard was a

strong predictor of migration behaviour, although packs at a numeric advantage did not

always migrate. Migration behaviour was flexible with some packs switching strategies

between years; switching always coincided with a change in group size relative to

blocking packs, reaffirming the importance of dominance in governing this behaviour.

The apparent year effect, in which fewer packs were observed to migrate in 2007, is

likely the result of a mild winter. Because conditions were not as severe in 2007, deer

aggregation was less confined spatially, increasing on-territory prey availability for packs

residing in close proximity to the deeryards (Loveless 2010). It is reasonable to assume

that migration is affected by the energetic cost of travel, but we did not find evidence that

locomotive costs (i.e., distance to deeryard) influenced the adoption of a migration

strategy. The maximum migration distance we observed was 51 km. Ninety-two percent

(N = 23) of our study packs resided closer to a deeryard than 51 km, indicating migration

is not limited by distance; however, energetic costs may influence the number and

duration of trips.

Our study provides new insight into group dominance by contributing a unique

assessment of off-territory movements, as well as our evaluation of non-numeric factors

influencing dominance behaviour. The conceptual model we developed provides a

general tool for understanding relationships between habitat and group size, clarifying the

causes and consequences of numeric superiority. Our results reinforce findings by Mosser

& Packer (2009) and collectively create a theoretical foundation with empirical support

from two species. Future studies should further test the relationships between habitat

quality, group size, territory quality and reproductive success, in other species and

33

populations to ensure our model is an accurate generalization for social-territorial

animals. Additionally, investigating fitness consequences of altered behaviour, space use,

and resource acquisition is necessary to understand the importance of intergroup

competition at the population level.

34

Table 2.1: Models of among pack variability in patrol effort, in a population of eastern

wolves (Canis lycaon) in Algonquin Provincial Park (2005-2007). Reduced model is the

constant only model.

Model Adjusted R2 K AICc Δi wi

Pack Size 0.39 3 13.367 0.000 0.693

Pack Size + C. latrans 0.39 4 15.514 2.147 0.237

C. latrans 0.15 3 18.972 5.605 0.042

Reduced Model 2 19.781 6.414 0.028

35

Table 2.2: High-ranking models (wi> reduced model) of variability in pack sizes of

eastern wolves (Canis lycaon) in Algonquin Provincial Park (2005-2007). Reduced

model is the constant only model.

Model Adjusted R2 K AICc Δi wi

Moose Density 0.22 3 17.341 0.000 0.242

Moose + C. latrans + C. lupus 0.35 5 17.454 0.112 0.229

Moose + C. latrans 0.21 4 17.475 0.134 0.227

C. lupus -0.04 3 19.521 2.180 0.081

Reduced Model 2 19.656 2.284 0.077

36

Figure 2.1: Conceptual model of group size, habitat quality relationships. The positive

feedback loop illustrates that habitat quality drives group size, group size determines the

dominance of the group and therefore their ability to maximize net resource intake,

thereby maintaining larger group size. Costs associated with sociality act as negative-

feedback mechanisms to decrease recruitment or birth rates, and/or increases dispersal

and juvenile mortality, making further increases to group size unstable.

37

Figure 2.2: Map of eastern wolf (Canis lycaon) packs in Algonquin Provincial Park

(dashed line), Canada, from 2005-2007. Black outlined polygons represent 99% contour

home ranges for 17 packs monitored using GPS radiotelemetry. Polygons with a double

outline are MCP territories for packs having only VHF collar information. Grey polygons

are known deeryards.

38

Figure 2.3: Frequency of wolf pack sizes observed in Algonquin Provincial Park from

2005-2007 (2005-2006, N = 17; 2007, N = 15).

39

Figure 2.4: Relationships between relative pack size of eastern wolves in Algonquin

Provincial Park, number of intrusions made into neighbouring territories, and the total

duration (hrs) of all intrusions, during November 1- April 30 2005-2007. Relative pack

size was calculated as pack size of the intruding pack minus size of the resident pack;

positive values indicate numeric advantage for the intruding pack.

40

Figure 2.5: Projected increase in eastern wolf territory quality as represented by number

of moose contained therein when territory size is increased 5% (diamond), 10% (black

target), 15% (black square), or 20% (black circle). The dotted line represents average

number of moose-equivalents (of edible deer biomass) that packs migrating to deeryards

outside Algonquin Provincial Park have obtained.

41

Figure 2.6: A) Projected increase in territory size resulting from expansion of 5, 10, 15

and 20%. B) Illustration of unidirectional expansion by 34 km2, which represents the

average territory growth necessary for gross prey benefits to equal those acquired by

migrating to deeryards in winter.

B

A

42

CHAPTER 3: GENERAL DISCUSSION

Although competition for limiting resources is recognized as a strong selective

pressure, its importance in social-territorial species is rarely emphasised. The body of

literature dealing with intergroup competition is limited and generally focuses on short-

term behavioural responses to intruders. Our goal was to make clear hypotheses as to the

causes and consequences of intergroup competition in social-territorial species, and test

their validity using data from a population of eastern wolves in APP. Overall, we found

that numeric superiority was a strong predictor of dominance behaviour. Larger packs

were more likely to exhibit risky behaviours such as spending time in peripheral territory

areas and foraying off-territory. Some of the variability among equal-sized packs

appeared to be due to the influence of introgression. Pack size was predominantly

influenced by habitat quality, although a weak introgression effect was also apparent.

Larger packs maximized resource access by either holding larger territories containing

many moose, or migrating to deeryards where prey aggregate seasonally. Packs that were

able to acquire prey using one of these strategies were able to retain more pups within the

pack for longer time periods. This may provide juveniles with larger body size and

hunting experience needed to survive and successfully gain a breeding position in the

future.

Our study was unique in that we derived a simple model outlining causes and

effects of intergroup competition that was strongly supported by our data, assessed

factors regulating two types of off-territory movements (i.e., trespassing into

43

neighbouring territories and migration), and investigated the potential influence of

individual quality (i.e., hybridization) on group competitive ability.

Although we found intergroup competition had a strong effect on migratory

behaviour, an in-depth cost/benefit analysis is needed to fully understand this strategy‟s

merits relative to expansion. In our study system, migration could yield gross benefits

equal to those obtained by packs residing in areas with an aggregated prey resource;

however, many of the monitored packs would need to increase size substantially (by at

least 15%) to gain them. Net benefits of the two strategies depend on both the costs and

risks associated with each. Expansion feasibility will depend on the number of

neighbouring packs, their relative competitive abilities, the size of inter-territorial spaces,

and degree to which neighbours are already resource-stressed or compressed. The initial

risk of seizing space is high as resident packs may defend their territory more

aggressively against compression than against temporary trespass. Costs extend into the

long-term as expanded borders must be patrolled and defended. Alternatively, a

migration strategy reduces risk and minimizes costs in the long-term. Packs are unable to

acquire information on groups past their immediate neighbours making travel through an

occupied landscape potentially dangerous. Movement patterns observed in this study

suggest wolves may mitigate this risk by travelling in inter-territorial spaces and

switching routes to avoid numerically dominant packs (J. Arseneau, unpublished data).

The energetic costs of migration depend on distance travelled, the number of trips, the

degree of deviation from a direct route, and snow conditions. These costs, however, are

relatively predictable, and are short-term.

44

Our study was somewhat limited in its ability to address individual quality as we

only had one GPS-monitored individual per pack; however, observed effects of

introgression on dominance behaviour indicate individual quality likely influences group

dominance. Differential body size is an important determinant of individual quality

(Haley 1994, Stuart-Smith & Boutin 1994, Adams 2001), and may influence group

dominance. Kyle et al. (2006) suggested hybridization with C. latrans might enhance

adaptive potential of eastern wolves, better enabling them to utilize anthropogenically

modified landscapes. Human impact has facilitated range expansion in white-tailed deer

(Nowak 2002), and both smaller- and larger-bodied canids effectively prey upon these

smaller ungulates. Our results, however, suggest smaller body size may place animals or

groups at a competitive disadvantage, and be selected against in saturated populations

where competition exerts stronger selective pressure. Similarly, when moose are the

dominant prey species, larger bodied animals (C. lycaon and/or C. lupus) will be more

successful (Quinn 2004, Loveless 2010). Thus, selective forces acting on Ontario canids

may be complex and depend on the saturation of the population as well as available prey.

The first important assumption made while conducting this study was that packs

were relatively cohesive, and thus individual movements were representative of the

group. We also assumed that cohesion did not vary with pack size, implying the

proportion of time that collared individuals spent in the outer 30% of their territory did

not vary with group size. We found no relationship between pack size and percapita area

suggesting this was a valid assumption. Secondly, we assumed strong site fidelity was

representative of the defended territory, and that territories estimated in the fall or spring

were representative of the defended area in the following or preceding (respectively)

45

winter. Because off-territory movements were identified using spring or fall territories,

shifts in territory shape during the winter would bias estimates of intrusion duration. We

mitigated this bias by using GPS clusters to identify intrusions rather than movement

vectors, which would be more susceptible to changes in territory size. We also excluded

clusters located in areas of territory overlap. Thirdly, we assumed that because positive

relationships were seen between pack size and number of moose on-territory, as well as

pack size and migration behaviour, that larger packs also had higher gross resource

intake. Thus, individual hunting abilities are presumed to be relatively unimportant.

Our study could have been improved with multi-year data on individual packs. As

we typically had only one winter of data, we assumed larger territory size was a product

of previous expansion. Multi-year data on contiguous packs would allow the shifts in

territory boundaries, with respect to relative group sizes of adjacent packs, to be

quantified.

Future work on intergroup competition should use an experimental approach to

quantify effects of neighbours on behaviour, space use, and resource consumption.

Simulating encroaching neighbours by depositing olfactory signals and playing recorded

vocalizations (Czetwertynski 2001, Müller & Manser 2007) would allow investigators to

test longer-term responses to intrusion. The continuing development of GPS technology

will improve our ability to monitor and quantify pack responses in terms of fine scale

movement and space use. The method would allow (i) permeability of a simulated

barrier; (ii) resident pack‟s behavioural, movement, and spatial response; (iii) resident‟s

resilience to simulated intrusion; and, (iv) relative importance of individual quality to

group dominance to be investigated. These longer-term responses to encroachment are

46

still poorly understood. Some work has been done on social insects (Adams 1990), but

the research would be a unique contribution to social mammal literature.

Investigating fitness consequences of altered behaviour, space use, and resource

acquisition is necessary to understand the importance of intergroup competition at the

population level. In social carnivores, which are relatively long-lived, the duration over

which populations would need to be monitored to obtain fitness data may be prohibitive.

However, GPS radiotelemetry and use of genetic sampling for identifying individuals

will facilitate long-term monitoring. Fitness data, combined with fine scale movement

and space use information will allow better understanding of social mammal response to

intergroup competition, as well as associated selective pressures. It is time to consider

factors other than movement, abundance and distribution of prey as being important in

structuring populations of social predators. Understanding how competition among

neighbours influences populations is necessary to effectively manage these populations in

the future. This is an important consideration as many social-territorial animals are of

conservation concern (i.e. wolves, lions, chimpanzees), at least in some populations.

47

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