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Elephants & Big Trees: Mitigation Methods
Summary Document of the Thornybush Workshop – 08
November 2018
Compiled by: Dr Michelle Henley (Elephants Alive Director & Principal Researcher)
Mr Robin Cook (Elephants Alive Big Trees Project Manager)
1 | P a g e
Protecting both big trees and elephants
What is the individual importance of big trees in ecological terms? (Kerley and
Landman 2006; Ludwig et al. 2008; Treydte et al. 2008; Vogel et al. 2014; Edge et al.
2017)
buffering against climatic imbalances
Important nutrient pumps
Crucial to prevent flooding and erosion
Important as a food source
Aesthetic and iconic value
Home and/nesting site to many faunal components
What is the individual importance of elephants in ecological terms?
Key stone species – some ecosystem functions cannot happen without elephants (digging
of water wells, dispersing mega-faunal fruits of certain tree species)
Umbrella species – because of their large space and nutritional requirements, when you
conserve elephants you will automatically be creating suitable habitat for many other
smaller animals that share the landscape with elephants
Path finders and makers – elephants play a very important role in promoting landscape
connectivity and with South Africa’s mandate to try and increase land under protected
area status, elephants and their travelling paths can play a vital role in defining corridors
to link conservation areas
Mega-composting agents – elephants play a critical role in nutrient recycling as they can
carry up to 140kg of dung against the gradient which is important as the ancient soils of
the APNR have been leached of minerals over many centuries
Aesthetic and iconic value
Mega-pruning agents – elephants’ lighter feeding habits play a critical role in lowering the
canopy to make more browse available to other animals, also to promote micro-climates
under felled trees (when Acacias then a protective thorn cage is formed which enables
valuable grass swards to be ‘banked’ during the dry season) that promote the growth of
particular grass species.
2 | P a g e
What is the interactive importance of big trees and elephants?
Big trees provide shelter and shade to elephants, which is vital to their thermoregulation.
Big trees offer elephants security in places where they are persecuted i.e. out tracking
data shows that elephants hide out in the ironwood forests of Mozambique during the
day to avoid people and only leave the forests at night when people are sleeping.
Big trees directly offer a valuable food source to elephants (browse primarily during the
dry season).
Big trees indirectly also offer a valuable food source to elephants as they function as
nutrient pumps, you get certain grass species growing under large trees that you wouldn’t
find in the open veld.
Elephants are valuable fertilising agents, making allowance for many large trees to
germinate in the compost they provide and disperse widely over the landscape.
Elephants are critical mega-faunal fruit dispersers with an ability to carry seeds up to
65km from their source (bulls) and deposit the seed in a nutrient rich package (Bunney et
al. 2017).
Elephants are vegetation modifying agents with their feeding habits often promoting the
foraging habits of other species as moderate to light feeding habits can either promote
new shoot growth or change the chemical composition of the vegetation to make it more
nutrient rich (Makhabu et al. 2006, Kohi et al. 2011).
What is the similarities between big trees and elephants, which make them both
vulnerable ecosystem components?
Both large is size
Both long lived
Both have slow recruitment into older age classes
Both of economic value to man (trees for furniture and fuel; elephants for tusks, tourism
and trophies)
Both are vulnerable to over-exploitation
3 | P a g e
Why are we worried about big trees and elephants when looking into the future
and outside our borders?
Big trees (Geist and Lambin 2001; Parrikka 2004)
Wood fuel (charcoal and firewood) demands have led to 68% of deforestation in Africa
Wood fuel constitutes up to 85% of household energy consumption in Sub-Saharan
Africa
With a 1% increase in urbanisation there is a concurrent 14% increase in charcoal
demands
By 2025 more than 50% of Africans will be urbanised
Charcoal consumers use 4-6 X more wood than firewood users
Charcoal demands causes the greatest loss of natural forests & woodlands because of
the selection for living old growth species
Elephants (Wittemyer et al. 2014; Chase et al. 2016)
Continental scale
More than 30 years ago the Southern states (including SA) held 21% of the continental
population. Due to excessive poaching in Central and East Africa, the southern states now
hold 55% of the continental population. Poachers will turn their efforts south for the best
catch per unit effort.
4 | P a g e
In 7 years ranging from 2007-2014 we have lost 30% or 144 000 elephants
Continue at present rate, no elephants in places in 20 years’ time
Figure 1: Continental decline in the African elephant from 5 million at the turn of the century to
below 450 000 at present.
Our neighbour
50 000 in 1970 now only 19 600
Poaching on an industrialised scale
1500-1800 poached per year
Niassa, their biggest reserve, 63% decline in 3 years, second highest carcass ratio in
Africa
48% decline in 5 years
In South Africa
In the Kruger National Park close to 200 elephants have been poached since September 2015,
these are the highest poaching incidents in their history and they are indicative that we are
not immune to the potential risks.
In the APNR
The APNR density has increased over time and the individual reserve densities have reflected
the expansion of the protected areas westwards. In comparison, the APNR densities have
historically always been higher than those of the Kruger National Park (Figure 2). Within a
national context, the APNR plays an important role (Figure 3).
5 | P a g e
Figure 2: Changes in elephant densities together with the expansion of the Protected Area over time.
Figure 3: Elephant distribution in South Africa.
0,59 1,41 0,95
0,69
APNR density in 2017: 1.11 elephants/km2 KNP density in 2017: 1.05 elephants/km2
KNP density when culled: 0.32 elephants/km2 from 1967 to 1995/1996
6 | P a g e
Will reducing elephant numbers save large trees?
We are dealing with complex systems with many factors that influence large tree
survival rate.
Fence line contrasts are often used as illustration why elephant numbers need to be
reduced.
Below the roan antelope enclosure has a healthy age structure for trees inside the
enclosure while the surrounding landscape has very few large trees and almost no
younger trees of particular species.
The enclosure was erected at the time when culling was implemented and yet
reducing elephant numbers did not save the big trees.
Rather than illustrate the efficacy of culling as a management option, the enclosure
clearly illustrates just how complex the system is and that controlling elephant
numbers does not ensure the survival of big trees.
Inside the roan enclosure no hot fires were lit and there was also an absence of any
other smaller browsers other than elephants, save for a few steenbuck and duiker.
Already from just this example we can conclude that fire and herbivory (from a number
of species) are playing a very important role in tree population dynamics.
Fence line contrast, which always illustrate the extreme points along an ecosystem continuum. You
can never expect to achieve the same outcome for one side of the fence with a particular suite of
ecosystem drivers by comparing it with the other side, lacking those same ecosystem drivers. You
would first need to know which drivers are contributing towards the observed difference and then
attempt to remove all those same drivers. Within complex systems such as African savannahs, we are
only beginning to identify the potential drivers and are very far off from fully understanding how they
tie into each other.
7 | P a g e
Asner et al. (2016) used an airborne Light Detection and Ranging technique known as
LiDAR, to monitor 10.4 million woody plant species canopies in Kruger to determine
what environmental and management factors were influencing tree-fall rates.
Tree-fall rates were found to vary over space and time and have been occurring since
the 1940s, irrespective of the elephant management intervention that has been
applied.
In chronological order: elevation, soil type, elephants, fire were found to be the best
predictor of tree-fall rates.
The scale of this monitoring technique is unmatched but is still limited as additional
factors that are only obtainable by on-the ground census techniques are still required
to determine whether insect attack, herbivory (especially of younger woody species),
natural senescence and/or wind-fall could have affected tree-fall rates.
A conceptual model clearly outlines the numerous factors that could play a role in the
survival rates of large trees (Henley and Cook, in review) and once the complexity of
the possible causal factors are grasped, it becomes apparent why a number of
scientists have failed to find a linear relationship between elephant impact and
elephant density.
Specific life history- and phenotypic characteristics of the plant species under
consideration affect survival rate (germination rate from seed, seedling protection
mechanisms, ability to recoppice, susceptibility to disease, natural life span length,
palatability, root structure and bark structure).
Various abiotic factors influence survival rates (fire, climatic factors such as drought,
floods, rainfall, increased carbon levels which favour woody species due to our actions
and wind, edaphic determining factors such as soil type, elevation and topography)
Various biotic factors influence tree survival rates and include the surrounding plant
community type and herbivory.
Herbivory includes all browsers of which elephants are but one and which are known
to target trees of particular size and stem diameters (Moe et al. 2009)
When it comes to elephant impact, two factors could directly influence big tree
survival rate and they include encounter rate and density of elephants.
Encounter rates are determined by the spatial distribution of elephants while densities
of elephants are influenced by their numbers.
8 | P a g e
Densities of elephants are more inclined to influence the frequency of encounter rates
while their spatial distribution will influence the duration of the encounter rate
(O’Connor et al. 2007).
Elephants do not spread their impact evenly across the landscape unless their
distribution is controlled or influenced by regularly spaced artificial water points.
Densities of elephants are not as important as their spatial distribution as a few
elephants in an area with a high density of their favoured species will have more of an
effect in that particular patch than many elephants over a large area surrounded by
staple food species.
There are various lethal (culling, poaching, disease, drought) and non-lethal ways
(contraception and translocation) to control elephant numbers.
The spatial distribution of elephants can be controlled by the closing of artificial
waterholes, by erecting barriers, by expanding their range, by attracting them away
from sensitive areas or by frightening them away (creating fear-landscapes)
Both management methods aimed at controlling elephant numbers or their special
distribution have their pros and cons, which could be evaluated against ethical
concerns (Henley and Cook, in review).
Alternatively, one can focus on the age and size class of trees that elephants are known
to target and directly protect the resource.
There are no ethical concerns involved if focussing on iconic tree specimens with
aesthetic appeal or on a spatial scale that only aims to protect various adults of specific
age and sex to ensure seed production throughout the landscape or the maintenance
of large tree nesting bird sites.
By so doing one could promote the interactive importance between various species
and not try to change important linkages between species, which we do not yet fully
understand.
Since 2004, Elephants Alive has investigated various mitigation strategies to protect
iconic big trees throughout the APNR.
Our big tree monitoring includes 3500 large trees spread throughout the APNR.
9 | P a g e
Big Tree Population Dynamics Woody cover is influenced by a number of factors (Osborne et al. 2018):
Land clearance
Herbivory
Fire
Climate change and rising carbon dioxide
A single marula tree population can experience pressures and bottlenecks at various
stages in its life history (Cook et al. 2017):
Seed predation
Seedling recruitment
Elephant impact
Elephants and Big Trees
Forms of monitored elephant impact
Bark-stripping
Branch breakage
Main stem snapping
Uprooting
Encounter rates
Strategy is reduce encounter rates between elephants and big trees
10 | P a g e
Encounter rates affected by artificial boundaries, proliferation of water points and a
weakened density-dependent regulation of elephant populations (O’Connor et al. 2007)
Landscape approach
Manage how and where elephants use the landscape (Ferreira et al. 2015)
Waterhole closures to promote landscape heterogeneity (Sianga et al. 2017; Dzinotizei
et al. 2018)
Small-scale approach
Individual tree protection = directly protecting the resource
Not a landscape solution
Ideal for small reserves that are unable to manipulate elephant movements through
waterhole closures
Ideal for lodges/management wishing to protect particular iconic trees
11 | P a g e
Big Tree Mitigation Methods
Wire-netting
Beehives
Rock packing/Pyramids
Creosote
Bee pheromones
Bioneem oil
Chilli oil
Dung paste
Wire-Netting
Purpose: protect tree against ring-barking
Ring barking
Prevents nutrient flow
Tree becomes vulnerable to insect invasions and fire damage
Tree may be hollowed out from the inside
Variety of methods/techniques used within the Associated Private Nature Reserves
12 | P a g e
Elephant Alive method (as shown by Bateleur Safari Camp)
Double-wrapping method
13 mm Chicken mesh: 1.8 m tall
Measurement of length of mesh required: (Tree circumference x 2) + 50 cm
Fold mesh in half and then wrap around tree’s main stem, starting 50 cm above the
ground
End of chicken mesh are stapled to tree using 150-200 mm U-staple nails
Ensure that tree has a small amount of room to grow, i.e. tree must not be strangled
Important to monitor wire-netting over time
Remember: Wire-netting is only effective against bark-stripping
Our method of wire-netting not an eye-sore for tourists (Edge et al. 2017)
Longevity Up to 5 years (but ensure that tree is never
strangled)
Cost ± R100.00 per tree
Results Henley (2013): increased tree survival over
3000 days versus unwired trees
Derham et al. (2016): Bark-Stripping: 1.7%
wired vs 25% unwired trees after 12 years
Cook et al. (2017): Bark-Stripping: 2% wired
(tusking) vs 26% unwired trees after 2 years
Scale Can be applied on a large scale across a
property
13 | P a g e
Beehives
African honeybees have been used to successfully protect crops (King et al. 2017)
and trees (Cook et al. 2018) from elephants
Information on setting up beehives in trees available in a manual on the Elephants
Alive website (www.elephantsalive.org)
Two types of hives have been tested:
Longevity Wooden: > 3 years
Beepak: > 10 years
Cost Wooden: R620 per tree
Beepak: R5000 per tree
Results (Cook et al. 2018) –
2 year study
(Jejane Private Nature
Reserve)
Impact-type
Bark-stripping
Stem snapping
Uprooting
Branch
breakage
Bees
0%
0%
2%
6%
Wire-netting
2%
12%
4%
40%
Control
26%
4%
4%
48%
Scale Small-scale: Handful of iconic trees around property
14 | P a g e
Feeding may be required during droughts
Risks: bee-stings (allergies); Drought; Insecticides
Honey production potential for tourists/staff
Rock packing/Pyramids Rings of rocks or pyramids stacked around the main stem of a tree
15 | P a g e
Problems identified in the Associated Private Nature Reserve: not enough
distance between tree’s main stem and end of pyramids/rocks
Noticeable trend that elephant impact decreases as pyramid radius around tree
increases
Calculating cost of method
Total cost = Single pyramid cost x Number of pyramids in a square metre x
𝛑(Desired radius)²
Rocks/pyramids need to be tightly stacked to prevent elephants manoeuvring
between gaps
Rocks/pyramids should try keep elephants 4-5 m away from tree’s main stem
Caution should be taken for the number of large natural rocks moved around
(micro-habitat disturbance)
Longevity 10-20 years (or more) if maintained
Cost R4.50 per pyramid made (concrete + labour costs)
= > R2000 per tree
Scale Small-scale application around particular iconic
trees
16 | P a g e
Creosote
Tins/jars of creosote nailed to the main stem of a tree
What is creosote? (Choudhary et al. 2002)
Coal-creosote is a residue produced during the distillation of coal tar, which is a
by-product of the carbonization of coal
Creosote is a thick, oily and flammable liquid, and does not easily dissolve in
water
Creosote has suspected carcinogenic properties and the breakdown of creosote
in soil can take months to years to occur
In the United States of America, spills of creosote into the environment which
exceed 0.454 kg need to be reported to the Environmental Protection Agency
Assessment on 100 trees creosote trees over 9-month period
Category Result
Number of trees still alive 96
Number of trees dead 4
Number of trees impacted since method went up 23
Number of creosote jars broken 25
Concern over the spillage of creosote into the environment and breakage of
tins/glass
Comparison to trees without creosote in the same property: No statistically significant
difference between the likelihood of a tree being impacted with or without creosote
Results suggest that creosote is not an effective method for protecting trees against
elephant impact and should be replaced with a more suitable method
17 | P a g e
Bee Attack Pheromone
Bee attack pheromone help bees recruit more bees from their colony to
handle large predators (Nouvian et al. 2016)
Bee attack pheromone is comprised of iso-amyl acetate and 2-heptatone
compounds which have been synthetically turned into a synthetically
produced Specialised Pheromone and Lure Application Technology
(SPLAT) paste
Developed by Prof. Mark Wright (University of Hawaii at Manoa) and Dr
Agenor Mafra-Neto (ISCA Technologies)
Research carried out in Balule with Transfrontier Africa and Elephants
Alive (Wright et al. 2018)
86% of elephants encountering smell in Jejane Private Nature Reserve
displayed avoidance behaviours (Jejane is the beehive project study site)
Results suggest that this method may be effective if elephants have prior
knowledge of bee attacks (learnt association)
Early research phase - not yet available to public
Can last up to 2 months when applied (weather dependant)
18 | P a g e
Bioneem Oil What is Bioneem? (Benmhend et al. 2012)
Bioneem is pressed directly from seeds of the Neem tree (Azadirachta indica),
which is a tropical evergreen tree native to India
Bioneem is an insecticide that controls insects which are harmful in agriculture,
forestry and horticulture, and can be used in place of chemical insecticides
Bioneem is effective against more than 400 pests of economic importance
Half-life of bioneem: 3-22 days (45 minutes in water exposure)
Method
Bioneem is sprayed over the branches and stem of a tree as an elephant
deterrent
Hypothesis: Elephants do not like the smell/taste of bioneem and will not impact
the tree
Bioneem effects (Benmhend et al. 2012)
Anti-feedant and repellent: deters insects from feeding on treated plant
Insect growth regulation: disrupts insect development. Insects do not reach
adulthood
Oviposition deterrent: insects are prevented from laying eggs on bioneem plants
Honeybees and other pollinators avoid plants with bioneem
Risks
What else in the environment is affected if an insecticide is used solely as an
elephant repellent?
Short half-life means that trees will need to be continuously sprayed
Far more research is required on this product before being used in a protected
area
19 | P a g e
Chilli Oil
Chillies have been used as elephant detergents in sprays (Osborn and Rasmussen
1995), chilli-grease covered fences (Osborn and Parker 2002) and dung balls
Hessian ropes soaked in chilli oil (capsicum mixed with oil) is now being tested on
trees in Olifants North (Balule)
Thornybush are directly paste chilli oil onto tree stem
Reapplication every 2-4 weeks (weather dependent)
Oil-based chilli lasts longer than water-based chilli
Study sites require evaluation to test the effectiveness of the hessian ropes
(Olifants North) and direct pasting (Thornybush) methods
More data is required at a manageable scale
Elephants Alive have a product in small quantity measuring 2 million Scoville Heat
Units (SHU)
20 | P a g e
Dung Paste
Tree healing properties
Alteration of the old cow dung and clay tree healing method
Anti-bacterial properties and adhesion constituents
Seals tree wounds and prevents pathogens to otherwise exposed surfaces
Suggested method: Clay + buffalo/cattle dung mixed with fermented elephant
dung (amounts can be reduced for small quantities of trees)
Fresh buffalo/cattle manure gathered in 100kg or ¾ 200Ltr drum (no oil or
chemicals inside)
Elephant manure 100kg in 200ltr (CLEAN NB) drum filled water ¾. Add 2kg sugar
press through to dissolve and keep doing for 3 days or so until fermentation
stops. Press plug forming at top down as much as needed
200kg clay – from destroyed anthills or ones not in use
On day of use, mix the fresh buffalo/cattle manure with the clay and add the
fermented elephant ‘tea’ to the mixture. Ensure the final mix is not too fluid-like
Use a brush to paint the tree’s main stem, covering as much as you can
NB: Primarily a tree healing method, however,
elephants have been observed avoiding dung pasted
trees in Botswana
Aesthetically pleasing: tree has a rubbing post
appearance
Longevity may be affected by rainfall
21 | P a g e
Conclusions
Summary table of methods
Identifying method of use
What is my purpose for protecting the trees? Vulture nest? Aesthetic/Ecological
purposes/Tree propagation purposes?
How many trees am I wanting to protect and what am I prepared to spend on a
mitigation method?
What species or size classes of trees am I wanting to protect?
What type of elephant impact am I trying to protect against?
Is my property exposed to intense fires?
How close are the trees to my property or lodge?
Tourist perceptions – what am I willing to let my tourists see in/on/around the
trees?
22 | P a g e
Summary
Tree populations are affected at various demographic stages
Landscape management approaches can manipulate elephant encounter rates
with big trees
Methods are available to protect individual trees against impact
Method of choice is dependent on your management requirements and
available resources
Certain methods are still undergoing testing and caution is required before large-
scale usage
No method is fool proof but survival rates of big trees can be increased if
methods are applied correctly
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