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Predator-Prey Dynamics: The Role of Predators in the Control of Problem Species Tashi Wangchuk between 2004-06 and 2004-08

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 Predator-Prey Dynamics: The Role of Predators in the Control of
Problem Species
Tashi Wangchuk*
Abstract
A study was conducted to look at the relationship between
presence and numbers of wild dog (Cuon alpinus) and
presence and abundance of wild boar (Sus scrofa). This was
corroborated with scat analysis to get percentage of the prey
consumed by wild dogs and other predators. A preliminary
nationwide presence-absence survey of C. alpinus population
showed that with the exception of Trashigang, Samdrup
Jongkhar and Pemagatshel, all the other dzongkhags reported
presence of wild dogs. Wild dog density was then compared
with relative wild boar density using a simple linear
regression analysis.
A negative relationship between increasing wild dog numbers
and decreasing wild boar density was detected. The R2 value
for the regression was 0.60 — meaning that about 60% ofthe
relative amount of variance in wild boar density is explained
by the number of wild dogs present in an area. The
unexplained 40% could be due to other factors such as
habitat conditions, food availability, control measures, other
large predators, diseases, and so on.
An analysis of variance (ANOVA) carried out on the
relationship gave a significant value (F= 12.30 >> Fs = 0.007),
meaning that the average number of boars in the different
study areas are significantly different from each other, or that
different pack sizes of wild dogs have significantly different
effects. The slope ofthe regression line was negative 0.1. Thus
for every unit increase in wild dogs presence there is a 0.1
unit decrease in relative wild boar density.
+ Bhutan Museum of Natural History, Department of Forestry,
Thimphu
68
 Predator-Prey Dynamics: The Role of Predators in the
Control of Problem Species
About 37% of wild dog diet consists of domestic animals such
as cattle and horses. The other 63% is wildlife. Of this 63%,
65 numbers of scat found contained wild boar remains. This
indicates that from the wild herbivores preyed, about 58% of
wild prey consumed are wild boar. Overall, including
domestic animals, wild boars make about 36% of the wild
dog's diet.
In terms of resource partitioning based on sign densities, the
three predators (tiger, leopard, and wild dog) avoid conflict
with wild boars by using different habitats and through
engaging in vastly different hunting behaviour. For instance,
leopards have more fixed and stable home ranges, closer to
human habitation while tigers have larger home ranges but
well away from any human settlement. Wild dogs are more
transient and travel frequently over a large distance; their
home ranges overlap with that of tigers and leopards. Since
their presence is fleeting, they rarely come in conflict with the
other predators.
Introduction
As tertiary consumers predators play an important role in
regulating prey species such as herbivores and omnivores
(Carbone et al, 1999.) Such predator-prey dynamics maintain
the health and balance of ecosystems. Any disturbance of this
balance due to human or other interventions lead to
population explosions or crashes. One significant event in the
ecological history of Bhutan has been the poisoning of wild
dogs (Cuon alpinus) in the early 1980s and the subsequent
explosion of wild boar (Sus scrofa) population (Wangchuk,
1996). Though the wild boar continues to be the main enemy
in Bhutan's agrarian societies, a little is understood about the
dynamics of this predator-prey system.
There is an urgency to understand the C. alpinus-S. scrofa
dynamics and find sustainable solutions to the prey
population boom all over the country.
69
 Journal of Bhutan Studies
Anecdotal information and a small scale survey in Jigme Dorji
National Park (Wangchuk, 1996) suggest that there is no crop
depredation issues due to wild boars and other herbivores in
places where there are wild dogs. A clear understanding of
this particular predator-prey dynamics is essential to quantify
the impact of C. alpinus in regulating S. scrofa population.
This study complements an ongoing project financed by the
Bhutan Trust Fund for Wildlife Conservation (BTF) which is
testing the effectiveness of culling by trapping and shooting
wild boars at two pilot sites. The present study looks at the
effectiveness of predators such as C. alpinus in regulating
prey population like S. scrofa. A natural regulatory
mechanism backed by trapping and culling, where necessary,
may provide a sustainable and long-term solution to the S.
scrofa problem.
Recent news stories report the re-emergence ofthe wild dog in
certain parts of Bhutan and the subsequent loss of livestock
to wild dogs. Understanding the impact of predators on prey
in the forests of Bhutan has become more critical in light of
this evidence before another mass predator eradication
programme is done, formally or otherwise.
A little hard data on the predator-prey dynamics of C. alpinus
and S. scrofa exists at the moment. Therefore, it is difficult to
assess the impacts of C. alpinus in controlling S. scrofa
population. Should the anecdotal reports prove true, it is
critical to ensure that wild dogs are not killed, mainly through
poisoning of carcasses. However, if livestock losses are high
and there is no reduction in wild boar population, then the
wild dog may simply be a menace to both farmers and
wildlife.
Studies of the wild dog or Dhole in south India indicate that
preferred prey species of dhole (more than 70% of kills) are
smaller than 50 kg in size (Johnsingh, 1992; Venkataram et
al. 1994, Karanth and Sunquist, 1995). Since chital (Axis
axis) was the most abundant prey species in the study area
70
 Predator-Prey Dynamics: The Role of Predators in the
Control of Problem Species
and wild pigs were the least abundant in the less than 50 kg
prey class (ratio of 23 chital to 1 wild pig), it is possible that
in Bhutan wild boars may substitute the chital as the most
abundant preferred prey class. Johnsingh (1992) also found
that 69% of leopards that kill in the same area were of prey in
the less then 50 kg class. Tigers, however, preferred prey that
was greater than 100 kg.
In Bhutan too where these three predators exist in sympatry,
it is possible that a similar resource partitioning takes place.
However, none of these questions have been answered for the
wild dog and other predators in Bhutan.
The present study attempts to address this data gap. A
preliminary nationwide survey of C. alpinus populations was
conducted. Details such as number of wild dogs, location of
packs, and reported loss of livestock were collected. Based on
this information, a representative field sites in Zhemgang,
Gasa, Punakha, Paro, and Thimphu dzongkhags were visited
and surveyed. Relative densities of both wild dog and wild
boars by habitat types were estimated.
Ten study sites for intensive monitoring were selected in
Gasa, Zhemgang, Thimphu, Paro and Punakha based on the
preliminary work. In the study areas predator scat was
collected from the monitoring sites to analyze the prey
content. The study mapped the over-lapping ranges of tigers
and leopards, and wild boars. Transects for scat and sign
collection were laid in these areas. Habitat and resource use
partitioning among these three top carnivores were mapped.
Correlation of wild dog presence and numbers with wild boar
presence, abundance, and crop damage reported by farmers
were also done. This was corroborated with scat analysis
which showed percentage of prey consumed by wild dogs and
other predators.
71
 Journal of Bhutan Studies
Methods
The initial stage of this preliminary nationwide survey was
conducted by contacting the offices of parks, wardens,
divisional, ranges, dzongkhag forestry and beat officers in the
country by phone, fax and email. Sixty-seven such interviews
were conducted between September and October 2003.
Concurrent visits to 18 villages in Trongsa, Zhemgang,
Wangdue, Punakha, Gasa, Thimphu, Paro were made as part
of the preliminary survey. The details such as presence of
wild dogs, leopards and tigers in the areas, location of the
wild dog packs, reported losses of livestock, and reported
reductions in wild boar crop depredation were collected using
Data Form 01 (see annex).
The second part was to verify these reports by visiting
representative sites in the country. Detailed surveys of the
sites and predator presence/absence were conducted, and
counts authenticated through use of local informants and
transect-laying in the reported areas. The sites were chosen
on the basis of the number of wild dogs reported. Some
villages reported a high incidence of wild dog occurrence
while there was a medium or low wild dog activity in other
areas.
Data Forms 02 and 03 (see annex) were used to collect
relative mammal sign abundance and scat content. The forms
recorded animal sign such as footprint, scat, wallow,
rubbings, etc by species. Detail of the habitat types was
recorded where each mammal sign was observed. Animal sign
information was collected along transects that were randomly
selected within a 10 km radius of the study villages.
Agricultural areas around villages were excluded from the
survey area and the 10 km radius was measured from the
edge of agricultural fields. This had the advantage of covering
a reasonable amount of forest around the villages. 10 km was
an adequate distance to move away from scrub forests to
72
 Predator-Prey Dynamics: The Role of Predators in the
Control of Problem Species
undisturbed forests at the top of ridges or valley floors and
away from disturbance as well.
However, in some instances tiger sign may have been missed
since tigers prefer to stay away from human settlement. It
may not come within the 10 km radius of the survey area.
Topo sheets (1:50,000) were used to generate the random
transects to cover a minimum of 25% of the area (78,500m2).
Transect lengths varied between 400 m to 1000 m, although
an ideal length of 1000 m was preferred. Some transects were
shorter since steep cliff, gorges, or dense bamboo thickets
were inaccessible after a certain length. Therefore, the
number of transects in each study village varied by conditions
but care was taken to ensure a minimum coverage of 25% of
the area. Also, randomization allowed coverage of all habitat
types in the area to a certain degree. Transect width was
maintained at 10 m (5 m on either side) to cover an area of
10,000 m2 in each transect. Eight random transect of 1000 m
length and 10 m width were aimed in each study area to
cover an area of 80,000 m2 per study area since the total area
surveyed per study area was 314,000 m2.
In each plot, the number of sign made by different species
was recorded. These sign were then used to generate a
relative density per transect for the area by species. Special
attention was paid to wild dogs and wild boars. Wild dog
density was then compared against wild boar density in the
selected areas and a linear regression analysis was done to
see the functional relationship between the density of wild
dogs and wild boars. Since wild dog numbers were available
through actual sightings and observations by villagers, the
actual number of wild dogs present in an area was used
rather than the relative density estimates based on sign. Also,
the relative density estimate of wild dogs fit well with the
actual numbers of wild dogs in the area, indicating that
transects accurately recorded animal sign.
73
 Journal of Bhutan Studies
The following villages listed in Table 1 were visited for detailed
field surveys and verification.
Table 1: Survey Sites
Location
Reported Wild
Dog
Abundance
Dominant
Vegetation
Goenshari, Punakha
Low
Warm/Cool
Broadleaf
Sha Gangshikha, Wangdue
None
Warm Broadleaf
Tamey Damchu, Punakha
Medium
Warm/Cool
Broadleaf
Kuenga Rabten, Trongsa
None
Cool Broadleaf
Remee, Gasa (Revisited in
March 2004)
High
Cool Broadleaf
Chamayna, Thimphu
Medium
Mixed Conifer
Helela/Talakha, Thimphu
Medium
Mixed Conifer
Kharibjee, Paro
Low
Mixed Conifer
Dunmang, Zhemgang
Medium
Warm/Cool
Broadleaf
Langdurbi, Zhemgang
High
Warm / Cool
Broadleaf
Sign from other predators such as leopard and tiger were
recorded and mapped by relative density by location to derive
habitat use patterns. The habitat and resource partitioning of
the three main predators in two selected study areas
(Dunmang and Tamey Damchu) were done since these two
areas had sign made by all three predators. In each area
relative sign density in a transect that fell close to a village,
another that fell midway (about 5 km) and a third close to the
outer limits of the survey area were selected to study
distribution. Habitat use patterns of tiger, wild dog and
leopard could be done to a certain extent through the
distribution of sign in these selected transects. However, this
provides only a general and preliminary distribution pattern
and in-depth analysis was avoided. It was simply assumed
that where  sign were  present,  the  particular  species was
74
 Predator-Prey Dynamics: The Role of Predators in the
Control of Problem Species
active in that area and where there was no sign, the
particular species avoided that habitat.
This also allowed estimation of home range size through sign
distribution and density analysis. In south India the home
range size for dholes varied between 54.2 and 83.3 km2
(Venkataram et al. 1994). In Bhutan based on anecdotal
information, in some areas 2 or 3 packs may have
overlapping ranges with a rough estimate of 50 km2 home
range size (Wangchuk, 2003).]
Another important determinant has been the diet analysis of
wild dogs, tigers, and leopards. This was done by collecting
predator scat along transects and analyzing scat contents for
prey species using Data Form 02. Scat found along transects
were identified by species. Predator scat were analyzed for
prey content on the basis of indigestible animal remains in
the scat such as hair, bones, hooves, feathers, and skin. In
scat, hair is a good indicator of prey consumed (Schaller,
1967), and it was compared against a reference collection of
hairs from the Bhutan Natural History Collection (BNHC).
Results
The preliminary survey of C. alpinus populations in all 20
dzongkhags showed that with exception of Trashigang,
Samdrup Jongkhar and Pemagathsel, other dzongkhags
reported wild dog presence. The last report of wild dog in
Trashigang was in Wamrong in 2002. Nine wild dogs were
killed by poisoning and their tails handed over to the Nature
Conservation Division (NCD). Interestingly, these three
dzongkhags lie east of the Drangmichhu which may have
acted as a barrier. The river certainly prevented further
colonization of the areas by dispersing wild dogs from other
dzongkhags where wild dogs are present. Recolonization may
take some time as wild dogs have to either find their way
across the Drangmichhu or from the neighbouring Indian
states of Assam and Arunachal Pradesh.
75
 Journal of Bhutan Studies
The other 17 dzongkhags reported presence of wild dogs. The
wild dog packs were distributed in patches and did not cover
entire dzongkhags. For instance in Wangdue, there is no wild
dog in villages along the Dangchhu, unlike higher villages like
Phobjikha and Gogona which reported the presence of a pack
of 13 wild dogs. Surveys in the Dangchhu area revealed that
most cattle were at the summer pastures in the higher
altitude areas of Phobjikha and Gogona. The cattle move
down to the Dangchhu area in the winter (Ninth Bhutanese
month). Farmers reported that they have been having wild
boar problems for the last 20 years, beginning 1983.
Interestingly, the last wild dogs were extirpated from the area
by poisoning that same year. Since then the people have to
guard their paddy fields. The usual practice in the past had
been to transplant the paddy and return to Phobjikha. But
with the presence of wild boars, farmers are compelled to stay
behind to guard their crops.
In Trongsa too, some areas reported presence of wild dogs
while others did not. For instance, wild dogs were present
about 15 years ago in Kuenga Rabten area, but the last pack
was killed by using rat poison distributed by agriculture
officers. About 10 years ago, wild boars became a major
problem in the area. Some agricultural fields above the village
and close to the forests had been abandoned since they could
not guard crops from wild boars. However, in the Chendebji
area, two packs of 4 and 8 wild dogs are present. The packs
have killed cattle and yaks in the area in November 2003
when the survey was conducted.
Lhuntse and Trashiyangtsi seemed to share the same pack.
When wild dogs appeared in Yangtse, there was no report in
Lhuntse, and vice versa.
Gasa and Zhemgang reported the highest cases of wild dog
depredation of livestock (and therefore, its presence). Even in
Gasa some areas in Khatey reported high occurrence, while
others such as Lunana and Khamey reported occasional
presence only.  Likewise in Zhemgang, Bardo reported high
76
 Predator-Prey Dynamics: The Role of Predators in the
Control of Problem Species
occurrence while there was no report in villages around
Zhemgang Dzong.
Farmers in all survey areas report that there is a direct
correlation between presence of wild dogs and wild boars.
Where there are many wild dogs, there are a few wild boar
numbers and vice versa. This is further corroborated by
farmers' reports of reduced crop depredation by wild boar,
but increased livestock loss to wild dogs. Farmers have
responded by changing their animal herding behaviour. Many
said that they now have a full time cattle herder, while horses
and mules are stabled and corralled at night. Such changes
have reduced loss of livestock to wild dogs. Farmers complain
that employing full time cattle herder is an additional burden
to their already strained manpower. Also, mule and horse
owners complained of the loss of night time foraging
opportunity when animals are kept in stables. Loss of mules
and horses in Gasa and cattle in Zhemgang are huge losses of
income for the people. In Gasa, portage by horses and mules
are the main source of income and a loss of these animals
meant a big loss to the family. In Zhemgang cattle provide
valuable diary products that are sold or bartered.
In Khatey Gewog of Gasa, a pack of 15 wild dogs have been
active since 2002. In 2001 only a male and female dogs were
sighted. Within a short span of two years the pack had
multiplied to 15 in 2003. The highest density of sign,
including group defecation sites or communal latrines, was
found in the forest around Remee, about three kilometers
from Gasa Dzong; this suggests that the animals have a
denning site near Remee village. In Khamey Gewog, a pair has
been sighted since last year near Tashithang. Likewise,
another pair has been sighted this year in Laya Gewog. It is
possible that these will grow over the subsequent years.
Farmers in Khatey Gewog, with the highest density of wild
dogs, reported that in the spring of 2003 they had a good
wheat harvests, which in normal years would have been
ravaged by wild boars. Disturbingly, in March 2004, a revisit
to Remee village revealed the presence of old wild dog sign
77
 Journal of Bhutan Studies
only. The wild dogs had either moved to another location, or
perhaps been poisoned since the economic damage in terms
of horses and mules loss was too severe. The officials of
District Animal Husbandary, Gasa, reported that villagers
had made a request for a stringent poison tablets. The
villagers denied making any such requests.
In Bardo and Nangkor Gewog of Zhemgang, wild dog densities
were highest in Langdurbi village where at least three packs
were reported. Two packs (seven and 14 respectively) seemed
to remain on the east bank of the Chamkharchhu basin,
roving between Khomshar, Langduribi, and Digala, while
another pack of 12 dogs traveled back and forth between
Dunmang/ Kamjang and Langdurbi/Digala. During interviews
farmers reported the loss of more than 70 livestock, mostly
cattle and a few horses. In one instance, wild dogs came right
up to the doorstep and killed a pig.
It was interesting to note that some wild boars were still
present in the Langdurbi area (a herd of four was sighted),
but farmers reported that they did not lose any crops to wild
boars this year.
In Khengkha, wild dogs are called Tsa Wa Reng and nick
named A-shang Gelong because of their red coats. A pair is
called omrang and usually omrang is reported colonizing an
area and producing a litter in the following year. Livestock
owners in Kamjang reported the presence of an omrang this
year. The people believe they arrived from the Langdurbi.
A pack of 10 wild dogs share the forests above the villages of
Chamayan and Kabjisa in Thimphu. In 2003 people did not
have to guard their potato. Wild dogs appeared this year only
and last year people suffered sever loss of potato to wild
boars. It seems that the pack may be a transient between
other side of Sinchula which might have migrated from the
Kabji-Punakha area.
78
 Predator-Prey Dynamics: The Role of Predators in the
Control of Problem Species
The anecdotal information collected from villagers especially
about the presence relationship between wild dogs and wild
boars is verified through the transect sign survey data.
Transect sign survey from 10 study sites in Zhemgang, Gasa,
Thimphu, Paro, and Punakha dzongkhags revealed the
following relative densities of wild dogs and wild boars (Table
2). Table 2 also shows the actual numbers of wild dogs
confirmed from the study sites.
Table 2: Relative densities of wild boars and wild dogs and confirmed
number of wild dogs by study site
Location
Relative
Density Wild
Boar
Avg. #
sign/m2
Relative
Density Wild
Dogs
Avg. #
sign/m2
Actual #
Wild Dogs
Goenshari
1.40
0.40
4
Gangshikha
2.90
0.00
0
Kuenga
Rabten
3.10
0.00
0
Kharibjee
1.00
0.22
2
Dunmang
0.80
0.75
8
Tamey
Damchu
0.70
0.65
6
Chamayna
0.70
0.99
10
Talakha
0.90
1.00
10
Remee
0.10
2.10
18
Langdurbi
0.05
2.76
26
Gangshikha in Wangdue had the highest wild boar sign
recorded with an average of 2.90 sign/m2 of transect area
surveyed, while Langdurbi in Zhemgang had the lowest with
0.05 sign/m2. Contrarily, Langdurbi had the highest number
of wild dog sign and Gangshikha had the lowest.
Since actual wild dog numbers in the study areas could be
confirmed through corroborated observations by villagers, the
79
 Journal of Bhutan Studies
actual number of wild dogs present in an area could be
compared against the relative density of wild dogs in the same
area estimated through sign. A Pearson correlation coefficient
was generated to test for the fit between observed and
estimated wild dog numbers. The correlation coefficient ractuai-
rei.density is 0.996542 indicating an almost perfect positive
association.
30 i
0.5 1 1.5 2
Rel. Density Wild Dogs
2.5
Figurel: Close fit between actual number of wild dogs observed and
the relative density of wild dogs estimated from sign (ractuai-reidensity =
0.996542)
Figure 1 shows the close fit between actual number of wild
dogs observed and the relative density of wild dogs estimated
from sign. This close fit between observed and estimated
numbers indicates that transects accurately recorded animal
sign. Wild dog density was then compared against relative
wild boar density using a simple linear regression analysis.
80
 Predator-Prey Dynamics: The Role of Predators in the
Control of Problem Species
Figure 2: Negative relationship between increasing wild dog numbers
and decreasing wild boar density (R2 = 0.60, b = -0.09857)
♦ Rel. Wild Boar Density
10 15 20
#WldDogs
25 30
Figure 2 shows the negative relationship between increasing
wild dog numbers and decreasing wild boar density. The R2
value is 0.60 meaning that about 60% of the relative amount
of variance in wild boar density is explained by the number of
wild dogs present in an area. The unexplained 40% could be
due to other factors such as habitat conditions, food
availability, control measures, other large predators, diseases,
and so on.
An analysis of variance (ANOVA) carried out on the
relationship gave a significant value (F= 12.30 >> Fs = 0.007),
meaning that the average number of boars in the different
study areas are significantly different from each other or that
different pack sizes of wild dogs have significantly different
effects; larger size has a larger effect and vice versa. The slope
81
 Journal of Bhutan Studies
of the regression line is - 0.09857 or close to - 0.1. Thus for
one unit increase in wild dogs there is a 0.1 unit decrease in
relative wild boar density. As the ANOVA significance test
showed, this is a significant relationship.
In terms of resource partitioning based on sign densities, the
three predators (tiger, leopard, and wild dog) avoid conflict by
using different habitats and by engaging in vastly different
hunting behaviour. For instance, leopards have more fixed
and stable home ranges, closer to human habitation, while
tigers have larger home ranges but well away from any
human settlement. Wild dogs are more transient and
frequently travel over large distances; their home ranges
overlap with those of tiger and leopard. But they rarely come
in conflict with the other predators due to their fleeting
presence. In any case, they were known to kill leopards and
even tigers if the pack is big.
Table 3 and Figure 3 show the sign density by species in two
of the study areas. More detailed and long term studies are
necessary to understand this complex relationship.
Table 3 Relative sign density by predator species in Tamey Damchu
and Dunmang
Location
Distance
from
village
Predator sign density / m2
Tamey Damchu
1 km
L= 0.12, W= 0.64,T= 0.00
5.6 km
L= 0.09, W=0.64, T=0.03
9.9 km
L= 0.07, W=0.66, T=0.09
Dunmang
0.9 km
L= 0.15, W= 0.74,T= 0.00
5.0 km
L= 0.1, W=0.76, T=0.04
9.5 km
L= 0.04, W=0.75, T=0.1
L= Leopard, W = Wild Dog, T = Tiger
82
 Predator-Prey Dynamics: The Role of Predators in the
Control of Problem Species
Figure 3 Relative sign density by predator species in Tamey Damchu
and Dunmang
0.8 1
0.7
0.6
0.5
0.4
0.3
1 km     5.6 km
Tamey    Tamey
Damchu Damchu
9.9 km
Tamey
Damchu
0.9 km
Dunmang
■    J I
t
1 Leopard
I Wild Dog
I Tiger
5.0 km    9.5 km
Dunmang Dunmang
Scat Content
Of 178 wild dog scats that were found, 112 contained
remains of wild herbivores, one Kaleej pheasant and 65
domestic animals. This shows that about 37% of wild dog diet
consists of domestic animals such as cattle and horses. The
other wildlife constitutes 63%. Of this 63%, 65 numbers of
scat found contained wild boar remains. This indicates that
from the wild herbivores preyed, about 58% of wild prey
consumed is wild boar. Overall, wild boars, including
domestic animals, make up about 36% of the wild dog diet.
Since less than 10 tiger scat was encountered, tiger scat
analysis is excluded from the present study. Fifty eight
leopard   scats   were   found   along   transects.   Of this,   76%
83
 Journal of Bhutan Studies
consisted of wild game, mostly of muntjac. No wild boar
remains were found in the leopard scat. The remaining 24%
consisted of domestic animals.
DISCUSSION
The study shows that wild dogs are making a slow comeback
in Bhutan. They are present in all dzongkhags with the
exception of three eastern dzongkhags east of Drangmechhu.
There is much speculation within the farming community
that the reemergence of the wild dogs is due to a government
predator release programme.
The wild dogs are called zhungi phou or government wild
dogs, released to control the wild boars. However, to my
knowledge there is no record of a predator release programme
in Bhutan. Some farmers contend that the new wild dogs look
different from the old ones. They are said to be smaller in
size, more reddish in colour and has a different repertoire of
vocalizations from the old ones. Given this observation, it is
possible that after the eradication of wild dogs in the 1980s in
Bhutan, wild dogs from the Indian plains could have re-
colonized the vacant niche.
The sub-species in Bhutan are generally thought to be Cuon
alpinus primevus (Hodgson, 1833, Ellerman and Morrisson-
Scott, 1966) distinguished by their furrier coat, larger body
size, and grayish-reddish pelage. Specimens from the Bombay
Natural History Society Collection show that there is a clinal
variation in appearance with wild dogs from the Indian Duars
which have shorter hair. The India subspecies C. a.
dukhunensis is found south of the Ganges and is probably
not the one that re-colonized vacant niches in Bhutan. Rather
it is likely that the Duars variety of C. a. primevus climbed up
into Bhutan.
Whatever the origin, the present study revealed that the
reemergence of the wild dogs is having a significant ecological
and social impact. The carrying capacity for wild dogs of the
84
 Predator-Prey Dynamics: The Role of Predators in the
Control of Problem Species
community is extremely low since they kill valuable livestock.
Yet the positive role of the wild dog in controlling wild boars
cannot be ignored. As the results indicate, wild dogs have a
significant impact in reducing wild boar numbers.
The regression analysis showed a strong negative relationship
between increasing wild dog numbers and decreasing wild
boar density. The R2 value of 0.60 is statistically significant
and tells that about 60% of the relative amount of variance in
wild boar density is explained by the number of wild dogs
present in an area. Another way to interpret this result in
layman's terms would be that the presence of a pack of wild
dogs in an area can result in a 60% reduction in wild boar
numbers. The slope of the regression line was close to
negative 0.1. Thus for one unit increase in wild dogs there is
a 0.1 unit decrease in relative wild boar density. As the
ANOVA significance test showed, this is a significant
relationship. Wild dogs can effectively control wild boar
numbers.
This is further corroborated by the scat test which revealed
that wild boars make up about 58 % of wild prey consumed
by wild dogs. However, the scat test also showed that overall,
about 37% of wild dog diet consists of domestic animals such
as cattle and horses. However, these figures are observations
from a single point in time and can change due to livestock
care and guarding provided by farmers. For instance in
Remee, Gasa, scat content of domestic animals was more
than 50% in November 2003. By February 2004, the figure
had dropped to about 30% largely because livestock owners
changed their herding behavior. Many said that they now
have a full time herder with cattle, while horses and mules
are stabled and corralled at night. Earlier livestock were set
free in the forest and rounded up only when needed. Such
changes have reduced loss of livestock to wild dogs.
Regarding other predators, the scat test also showed that
leopards have a significant impact on domestic animals but
that they had little or no impact on wild boars.
85
 Journal of Bhutan Studies
Tiger scat results were inconclusive. Future studies could be
designed to cover larger areas and better represent tiger
habitat than the present study did. Also, as pointed out
above, as preying behavior can change over time in response
to herding behavior, longer term studies are recommended to
monitor these dynamics. Longer term studies are also
recommended to better understand the relationship between
the three top carnivores of Bhutan. The present study was
barely able to scratch the surface regarding this important
relationship which may have significant consequences for
wild boar numbers. A multi-varied analysis will be possible if
better data are available and deeper understanding of
predator-prey relationships in Bhutan gained.
Based on the results and discussions above, the following
recommendations are made:
1. Avoid mass predator eradication schemes as was done in
the 1980s through poisoning since this can have severe
consequences such as the wild boar epidemic. However, in
certain areas with a big wild dog numbers in a limited local
carrying capacity, targeted predator control schemes could be
conducted. For instance, if there are three or four packs in
any single area (Langdurbi in Zhemgang), a pack could be
relocated or removed. This would have to be done by trained
professionals, not through random carcasses poisoning since
any animal eating the poison are killed.
2. Encourage livestock owners to better guard their livestock
in wild dog prone areas as in Gasa areas. However, formal
government acknowledgement of the problem faced by
livestock owners and repeated public announcements can
inform the people that the problem is recognized, and that the
solution lies with owners themselves.
3. A livestock compensation scheme for livestock killed by
wild dogs, despite their best efforts at guarding, may increase
tolerance   for   wild   dogs   especially,   since   farmers   already
86
 Predator-Prey Dynamics: The Role of Predators in the
Control of Problem Species
understand the relationship between wild dogs and wild
boars and do not have to be educated about such realities.
4. In areas with large numbers of wild boars, targeted culling
which is ongoing in Thinleygang and Bumdeling areas could
be done. As this study showed, wild dogs can at the most
result in a 60% reduction in wild boar numbers in any given
area. The other 40% can be addressed through trapping and
shooting of wild boars if conditions are favourable.
This combination of actions may result in a balanced
approach to the human-wildlife conflicts caused by wild dogs
and wild boars.
Bibliography
Carbone, C. et al (1999). "Energetic constraints on the diet of
terrestrial carnivores" in Nature 402:286-288.
Ellerman, J. R. and T. C. S. Morrison-Scott. (1966). Checklist of
Palaearctic and Indian mammals. London: British
Museum, National History,
Johnsingh, A.J.T. (1982). Reproductive and social behavior ofthe
dhole, Cuon alpinus (Canidae). J. Zool., Lond. 198: 443-
463.
 (1992). Prey selection in three large sympatric
carnivores in Bandipur. Mammalia. 56: 517-526.
Karanth, K. U. and M. Sunquist. (1995). Prey selection by tiger,
leopard and dhole in tropical forests. J. Anim. Ecol. 64:
439-450.
Venkataraman, A.B. et al (1995). The foraging ecology of dhole
(Cuon alpinus) in Mudumalai Sanctuary, southern India.
J. Zool, Lond. 237: 543-561.
Wangchuk, T. (1996). An answer from nature? Kuensel. Oct 19,
1996.
87
 Journal of Bhutan Studies
Annexure
Data Form Ol
Questionnaire for Presence /Absence Survey of Wild Dogs
Phone Interview
Forest Division
Park/Wildlife Sanctuary_
Range Office	
Warden Post	
Beat Office	
Guard Post	
Dzongkhag Forest Office (Dzongkhag/ RNR Center)	
Dzongkhag Agricultural Office (Dzongkhag / RNR Center)_
Phone/ WT Interview
Gup Office (Gewog and Dzongkhag):	
Site Visit Interview
Village / Gewog / Dzongkha:_
Informant name	
Date:	
Enumerator:	
1) Are wild dogs (phou) present in your area?
2) If so in which areas (Gewog, Village) are they found?
3) How Many packs are there? How many individuals are there in each
pack?
4) What are the areas covered by the packs (Villages, gewogs).
5) Is there livestock loss to predators in your area? What are the main
predators?
6) How many livestock losses have occurred within the last one year? What
type of livestock was lost (cows, calves, bulls, horses etc) and what were the
responsible predators? (Enumerator to fill out the form below)
Type of
Livestock Lost
Numbers
Village
Predator
Approximate
Dates
88
 Predator-Prey Dynamics: The Role of Predators in the
Control of Problem Species
7) Are there reports of crop loss in your area? How severe is the problem
and where are the reports of heaviest loss? (Enumerator to fill out the form
below)
Type
of
Crop
Lost
Loss intensity
(High, Medium,
Low)
Village
Responsible Wild life
(deer, wild boar, shou
etc)
Approx.
Dates
Data Form.02
Scat Analysis
Transect #	
Habitat Type:	
Date:	
Location
Enumerator:
Scat Content: Prey
Species
Numbers
Percentage
Comments
Data Form.03
Relative Mammal Sign Abundance
Transect No:	
Transect Length: Location:
Date:	
Enumerator:
Weather: Rain/Cloudy/Sun
 Local Informant:	
No.
Mammal
Species
Sign (footprint, scat,
wallow, rubbing) and
number of sign
Comments (habitat type,
substrate, other relevant
observations)
Notes:

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