Journal of Threatened Taxa | www.threatenedtaxa.org | 26 May 2019 | 11(7): 13815–13821
Cats, canines, and coexistence: dietary differentiation between the sympatric Snow Leopard and Grey Wolf in the western landscape of Nepal Himalaya
Abstract: Understanding the dietary habits of sympatric apex carnivores advances our knowledge of ecological processes and aids their conservation. We compared the diets of the sympatric Snow Leopard Panthera uncia and Grey Wolf Canis lupus using standard micro-histological analyses of scats collected from the western complex of Nepal Himalaya. Our study revealed one of the highest recorded contributions of livestock to the diet of top predators (55% for Grey Wolf and 39% for Snow Leopard) and high dietary overlap (0.82) indicating potential exploitative or interference competition. Their diet composition, however, varied significantly based on their consumption of wild and domestic prey. Limitation in data precludes predicting direction and outcome of inter-specific interactions between these predators. Our findings suggest a high rate of negative interaction with humans in the region and plausibly retaliatory killings of these imperilled predators. To ensure the sustained survival of these two apex carnivores, conservation measures should enhance populations of their wild prey species while reducing livestock losses of the local community through preventive and mitigative interventions.
Keywords: Canis lupus, dietary pattern, dietary overlap, livestock, Naur, negative interaction, Panthera uncia, scat analysis, sympatry.
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doi: https://doi.org/10.11609/jott.4217.11.7.13815-13821
Editor: Jim Sanderson, Small Wild Cat Conservation Foundation, Corrales, USA. Date of publication: 26 May 2019 (online & print)
Manuscript details: #4217 | Received 23 April 2018 | Final received 30 April 2019 | Finally accepted 13 May 2019
Citation: Shrestha, A., K. Thapa, S.A. Subba, M. Dhakal, B.P. Devkota, G.J. Thapa, S. Shrestha, S. Malla & K. Thapa (2019). Cats, canines, and coexistence: dietary differentiation between the sympatric Snow Leopard and Grey Wolf in the western landscape of Nepal Himalaya. Journal of Threatened Taxa 11(7): 13815–13821. https://doi.org/10.11609/jott.4217.11.7.13815-13821
Copyright: © Shrestha et al. 2019. Creative Commons Attribution 4.0 International License. JoTT allows unrestricted use, reproduction, and distribution of this article in any medium by adequate credit to the author(s) and the source of publication.
Funding: WWF UK.
Competing interests: The authors declare no competing interests.
For Author details, Author contribution and Acknowledgements, see end of this article.
INTRODUCTION
Dietary habits of sympatric apex carnivores advance our understanding on ecological processes and regulation of the ecosystem functions, aiding their conservation (Macdonald 1983). In Nepal Himalaya, inter-specific interactions between apex predators have consequences for predator-prey relationships, habitat, and the entire ecosystem; this can also have a spillover effect on their relation to humans, through livestock depredation and retaliatory killing (Chetri et al. 2017). Information on dietary overlap and interactions of sympatric carnivores, however, is limited in these mountainous landscapes and nonexistent from the western complex of Nepal Himalaya.
With this background, we studied the dietary habits of the Snow Leopard Panthera uncia and Grey Wolf Canis lupus (hereafter referred to as ‘Wolf’) which live sympatrically in the western complex of Nepal Himalaya. Snow Leopards are twice the body size of Wolves (Jnawali et al. 2011) and are solitary hunters with a stalking ambush hunting behaviour (Jackson & Hunter 1996). In contrast, Wolves are coordinating cursorial pack-hunters (Viripaev & Vorobiev 1983).
We specifically investigated (a) the dietary pattern and relative importance of prey types for the sympatric Snow Leopard and Wolf, and (b) their dietary overlap in the western complex of Nepal Himalaya.
MATERIALS AND METHODS
Study area
Our study was carried out in the western landscape of Nepal Himalaya (83.281–28.493 in the east to 80.586–29.542 in the west) across the potential habitat of the Snow Leopard and the Wolf (Fig. 1). This covers an area of over 38,312km2 with an altitude range of 3,000–5,500 m. Of the total study area, barren area (22%) is the most dominant land cover, followed by rugged and broken snow-capped mountains and glaciers (17%), alpine rolling grasslands (17%), and agriculture and settlement (12%) (ICIMOD 2010). The total potential habitat within the western landscape covers an area of 11,261km2. The western landscape is one of three priority landscapes identified by The Global Snow Leopard and Ecosystem Protection Program (GLSLEP) (DNPWC 2017).
Wild prey species recorded in the study area included Bharal/ Blue Sheep/ Naur Pseudois nayaur, Himalayan Tahr Hemitragus jemlahicus, Kiang Equus kiang, Tibetan Argali Ovis ammon, Alpine Musk Deer Moschus chrysogaster, Tibetan Gazelle Procapra picticaudata, pika Ochotona spp., marmot Marmota spp., and Woolly Hare Lepus oiostolus.
With pastoralism as the main occupation of the local community, this region harbours a high density of livestock (73 head per km2), including domestic yak Bos grunniens, cow Bos spp. and hybrid, horse Equus ferus caballus, goat Capra hircus, sheep Ovis aries, and pig Sus scrofa domesticus (CBS 2011).
Scat survey
We systematically collected putative Snow Leopard and Wolf scat samples from each of the 56 grids measuring 16km2 (4km x 4km; effective sample area ~896km2; Fig. 1) spread across 11,261km2 following standard protocol (Thapa 2007) during the late spring season (April–May) in 2014. Within each grid, at least two transects (0.4–2.8 km) were laid 1.0–1.5 km apart (Jackson & Hunter 1996) and surveyed. Upon encounter of fresh scat samples, a few grams were collected and stored in 15ml tubes containing silica desiccant for micro-histological studies; the remaining scat was left in the field to avoid disturbing the regular movements and territorial marking of the predators (Lovari et al. 2009). All putative scat samples (n=265) were screened for species identification through molecular scatology (Kelly et al. 2012).
DNA extraction
DNA was extracted from scat samples using commercially available DNA stool kit (QIAGEN Inc.) following manufacturer instructions. We kept one negative control (water) in each batch of samples to monitor contamination during DNA extraction.
Species identification
All the samples were screened for PCR-based species identification using mitochondrial DNA (mtDNA) cytochrome-b segment Snow Leopard-specific primers (Janecka et al. 2008, 2011). All Snow Leopard-negative samples were further screened using D-Loop section of mtDNA (MIT forward/ reverse) with Wolf specific primers (Parra et al. 2008; Pilot et al. 2010). All PCR reactions for both Snow Leopard and Wolf were performed in duplicate for confirmation. Similar results in duplicate PCR runs were considered (Snow Leopard/ Wolf) positive samples. Non-conformity and/or discrepancy in two PCR runs were verified with a third run for confirmation.
Diet analysis
Species-positive scat samples for Snow Leopard and Wolf were analyzed using a standard micro-histological study method (Oli et al. 1993; Devkota et al. 2013). Prey species were identified by comparing hair samples collected from these species-positive scat samples with reference to hair samples of all potential prey species (Oli et al.1994; Wegge et al. 2012).
We calculated and compared relative frequencies of occurrence of each prey species:
No. of occurrences of each food item when present
[(–––––––––––––––––––––––––––––––––––––––––––) x100]
Total no. of occurrences of all food items
(Lucherini & Crema 1995) for all mammalian prey items, which were identified to species level. To investigate the relative importance of prey type, we used χ2 analysis to compare differences in frequencies of occurrence of prey items between the diet of the Snow Leopard and Wolf in terms of wild versus domestic prey (Azevedo et al. 2006).
We also calculated Pianka’s index to measure the dietary overlap between Snow Leopard and Wolf (Pianka & Pianka 1970):
DO =
where, DO is dietary overlap and Pij and Pik are the respective proportions of prey category i in the diet of the two predators ‘j’ and ‘k’. The value ranges from zero to one, indicating no dietary overlap (DO=0) to complete overlap (DO=1), respectively.
RESULTS
Diet composition of carnivores
Of the 265 putative scat samples collected and genetically screened, 35 (13%) belonged to Snow Leopards and 24 (9%) to Wolves; the rest (78%) belonged to other species. Five wild prey species—Bharal, hare, pika, marmot, and Musk Deer—were identified in both Snow Leopard and Wolf scat samples. Of the domestic prey species identified, Snow Leopard scat was found to have goat, sheep, domestic yak, cow, dog, and horse, while Wolf scat had five of these, excluding horse. Spatial distribution of genetically screened scat samples as Snow Leopard, Wolf, and negative is shown in Fig. 1.
Snow Leopard diet
The Snow Leopard diet was dominated by wild prey comprising about 61%, followed by domestic livestock making up for 39% of the total identified species (Fig. 2). Bharal was the most significant prey of Snow Leopard, contributing 29%, followed by goat (21%), hare (15%), pika (5%), domestic yak (5%), domestic cow (4%), and others (Fig. 3). About 54% of the confirmed Snow Leopard scats comprised a single prey species, followed by 32% with two species and 14% with three species.
Wolf diet
Domestic livestock contributed more than half (55%) of the Wolf’s diet while wild prey comprised only 45% (Fig. 2). Wolf diet was dominated by Bharal (28%), followed by domestic cow (15%), sheep (15%), goat (10%), dog (8%), domestic yak (8%), marmot (7%), and others (Fig. 3). About 46% of the confirmed Wolf scat comprised of a single prey species, followed by 29% comprising two species and 25% with three species.
Diet overlap between Snow Leopard and Wolf
High diet overlap (DO=0.82) was found between the sympatric Snow Leopard and Wolf. The diet composition (wild prey vs. domestic prey) of Snow Leopard and Wolf, however, varied significantly (X2=5.13, d.f.=1, P<0.023).
DISCUSSION
This appears to be the first study on Snow Leopard (Image 1) and Grey Wolf (Image 2) dietary pattern in western Nepal Himalaya applying standard micro-histological analysis of genetically confirmed scats. We compared our results specifically with similar studies that employed genetic screening to avoid biases (Weiskopf et al. 2016).
Our results showed that the diet of the Snow Leopard in the western landscape of Nepal Himalaya was dominated by wild herbivores (61%), with majority contributed by one principle prey species, i.e., Bharal, followed by livestock. This is consistent with the dietary pattern of the Snow Leopard in the central landscape of Nepal Himalaya (Wegge et al. 2012; Aryal et al. 2014). Similar trends were also recorded in other Snow Leopard range states, except that the principal prey species was not Bharal (Jumabay-Uulu et al. 2014; Weiskopf et al. 2016). The proportion of livestock (39%) and small mammals (30%) in Snow Leopard diet, however, was found to be higher in the present study as compared to other similar studies (Shehzad et al. 2012; Lovari et al. 2013; Aryal et al. 2014; Jumabay-Uulu et al. 2014; Weiskopf et al. 2016; Chetri et al. 2017).
As a whole, more than half of the Wolf’s diet (55%) was dominated by domestic livestock, but the single-most frequently encountered species was wild prey—Bharal (28%). Our findings confirm the preference of large prey by pack-living Wolves (Chetri et al. 2017) but differ in the proportion contributed to their diet by the cliff-dwelling primary wild prey, Bharal. Further detailed studies are needed to understand the underlying reason for this observation. As compared to other studies, the contributions of livestock to Wolf diet recorded here were among the highest (Jumabay-Uulu et al. 2014; Wang et al. 2014; Chetri et al. 2017). Interestingly, the contribution of wild prey and small mammals to Wolf diet was less in our study as compared to other studies (Jumabay-Uulu et al. 2014; Chetri et al. 2017). These findings may be an outcome of local circumstances; further research will be needed to verify the causes and effects of these findings.
Our study revealed a very high dietary overlap (0.82) between these sympatric predators. This differs significantly from a recent study carried out in the central landscape of Nepal Himalaya wherein a dietary overlap of 0.44 was recorded (Chetri et al. 2017).
High dietary overlap along with their dependence on one primary wild prey species, Bharal (contributing one-third of their diet), may warrant higher potential exploitative or interference competition between Snow Leopards and Wolves in the western landscape.
Interestingly, the finer scale dietary pattern showed a higher contribution of wild prey to the diet of Snow Leopard as compared to that of the Wolf; domestic livestock was dominant in the diet of the latter. The direction and outcome of the interaction between these two predators, however, are difficult to predict from our current study due to our limited sample size, restricted collection season (limited to spring), and lack of information on the population density of the prey species.
Nevertheless, in our study area, the relative contribution of livestock to the diet of both top predators (55% for Wolves and 39% for Snow Leopards) was higher as compared to other studies (Chetri et al. 2017). Further exploration would be necessary to establish if seasonality and local herding practices had a role in bringing this about.
Additionally, prime habitats of these species in the study area see very high anthropogenic activity in the form of Caterpillar Fungus Ophiocordyceps spp.(‘yarsagumba’) collection during the latter part of the scat collection season (April–May). This may also have had direct or indirect impacts on wild and domestic prey availability or accessibility, leading to greater livestock in the predator diet.
Increased dependence of both apex carnivores on livestock may lead to further escalation of human-carnivore negative interactions in the long run. This may trigger retaliatory killings of Snow Leopard and Wolf, as was reported from the region, thereby affecting the abundance of these predators in the region. Conservation measures focusing on preventive and mitigative measures that aid in securing people’s livelihoods can potentially reduce retaliation against the predators. We recommend further detailed research on population trends of both predators and their principal prey species in the region to determine the degree of their interaction and ramification on livestock depredation in the area.
For figures & images – click here
REFERENCES
Aryal, A., D. Brunton, W. Ji, D. Karmacharya, T. McCarthy, R. Bencini & D. Raubenheimer (2014). Multipronged strategy including genetic analysis for assessing conservation options for the Snow Leopard in the central Himalaya. Journal of Mammalogy 95(4): 871–881. https://doi.org/10.1644/13-MAMM-A-243
Azevedo, F., V. Lester, W. Gorsuch, S. Lariviere, A. Wirsing & D. Murray (2006). Dietary breadth and overlap among five sympatric prairie carnivores. Journal of Zoology 269: 127–135. https://doi.org/10.1111/j.1469-7998.2006.00075.x
CBS (2011). Statistical Year Book of Nepal. Central Bureau of Statistics. Government of Nepal, National Planning Commission Secretariat, Kathmandu, Nepal, 278pp.
Chetri, M., M. Odden & P. Wegge (2017). Snow Leopard and Himalayan Wolf: food habits and prey selection in the central Himalayas, Nepal. PLoS ONE 12(2): e0170549. https://doi.org/10.1371/journal.pone.0170549
DNPWC (2017). Snow Leopard Conservation Action Plan (2017–2021). Department of National Parks and Wildlife Conservation, Kathmandu, Nepal, 38pp.
Devkota, B.P., T. Silwal & J. Kolejka (2013). Prey density and diet of Snow Leopard (Uncia uncia) in Shey Phoksundo National Park, Nepal. Applied Ecology and Environmental Sciences 1(4): 55–60. https://doi.org/10.12691/aees-1-4-4
ICIMOD (2010). The Landcover of Nepal. Regional Database System. International Center for Integrated Mountain Development, Kathmandu, Nepal. Retrieved from http://rds.icimod.org/Home/DataDetail?metadataId=9224. Downloaded on 04 April 2019.
Jackson, R.M. & D.O. Hunter (1996). Snow Leopard Survey and Conservation Handbook.International Snow Leopard Trust and US Geological Survey, Fort Collins, 154pp+appendices.
Janecka, J.E., R. Jackson, Z. Yuquang, L. Diqiang, B. Munkhtsog, V. Buckley-Beason & W.J. Murphy (2008). Population monitoring of Snow Leopards using noninvasive collection of scat samples: a pilot study. Animal Conservation 11(5): 401–411. https://doi.org/10.1111/j.1469-1795.2008.00195.x
Janecka, J.E., B. Munkhtsog, R.M. Jackson, G. Naranbaatar, D.P. Mallon & W.J. Murphy (2011). Comparison of noninvasive genetic and camera-trapping techniques for surveying Snow Leopards. Journal of Mammalogy 92(4): 771–783. https://doi.org/10.1644/10-MAMM-A-036.1
Jnawali, S., H.S. Baral, S. Lee, K.P. Acharya, G.P. Upadhyay, M. Pandey, R. Shrestha, D. Joshi, B. Laminchhane & J. Griffiths (compilers) (2011). The Status of Nepal Mammals: The National Red List Series. Department of National Parks and Wildlife Conservation Kathmandu, Nepal, viii+266pp.
Jumabay-Uulu, K., P. Wegge, C. Mishra & K. Sharma (2014). Large carnivores and low diversity of optimal prey: a comparison of the diets of Snow Leopards Panthera uncia and wolves Canis lupus in Sarychat-Ertash Reserve in Kyrgyzstan. Oryx 48(4): 529–535. https://doi.org/10.1017/S0030605313000306
Kelly, M.J., J. Betsch, C. Wultsch, B. Mesa & L.S. Mills (2012). Noninvasive sampling for carnivores, pp47–69. In: Boitani, L. & R.A. Powell (eds.). Carnivore Ecology and Conservation: A Handbook of Techniques. Oxford University Press, New York, 506pp.
Lovari, S., R. Boesi, I. Minder, N. Mucci, E. Randi, A. Dematteis & S. Ale (2009). Restoring a keystone predator may endanger a prey species in a human-altered ecosystem: the return of the snow leopard to Sagarmatha National Park. Animal Conservation 12: 559–570. https://doi.org/10.1111/j.1469-1795.2009.00285.x
Lovari, S., I. Minder, F. Ferretti, N. Mucci, E. Randi & B. Pellizzi (2013). Common and Snow Leopards share prey, but not habitats: competition avoidance by large predators? Journal of Zoology 291: 127–135. https://doi.org/10.1111/jzo.12053
Lucherini, M. & G. Crema (1995). Seasonal variation in the food habits of badgers in an alpine valley. Hystrix: The Italian Journal of Mammalogy 7: 165–172.
Macdonald, D.W. (1983). The ecology of carnivore social behaviour. Nature 301(5899): 379–384.
Oli, M., I. Taylor & D.M. Rogers (1993). Diet of the Snow Leopard (Panthera uncia) in the Annapurna Conservation Area, Nepal. Journal of Zoology 231: 365–370. https://doi.org/10.1111/j.1469-7998.1993.tb01924.x
Oli, M.K., I.R. Taylor & M.E. Rogers (1994). Snow Leopard Panthera uncia predation of livestock: an assessment of local perceptions in the Annapurna Conservation Area, Nepal. Biological Conservation 68: 63–68. https://doi.org/10.1016/0006-3207(94)90547-9
Parra, D., S. Méndez, J. Canon & S. Dunner (2008). Genetic differentiation in pointing dog breeds inferred from microsatellites and mitochondrial DNA sequence. Animal Genetics 39: 1–7. https://doi.org/10.1111/j.1365-2052.2007.01658.x
Pianka, E.R. & H.D. Pianka (1970). The ecology of Moloch horridus (Lacertilia: Agamidae) in Western Australia. Copeia 1970(1): 90–103. https://doi.org/10.1186/1471-2148-10-104
Pilot, M., W. Branicki, W. Jędrzejewski, J. Goszczyński , B. Jędrzejewska, I. Dykyy, M. Shkvyrya & E. Tsingarska (2010). Phylogeographic history of grey wolves in Europe. BMC Evolutionary Biology 10: 104.
Shehzad, W., T.M. McCarthy, F. Pompanon, L. Purevjav, E. Coissac, T. Riaz & P. Taberlet (2012). Prey preference of Snow Leopard (Panthera uncia) in South Gobi, Mongolia. PLoS ONE 7(2): e32104. https://doi.org/10.1371/journal.pone.0032104
Thapa, K. (2007). Snow Leopard Monitoring Guideline for Nepal Himalaya. WWF Nepal, 60pp.
Viripaev, V. & G. Vorobiev (1983). The Wolf in Kirghizia. Frunze: Science, 95pp.
Wang, J., A. Laguardia, P.J. Damerell, P. Riordan & K. Shi (2014). Dietary overlap of Snow Leopard and other carnivores in the Pamirs of northwestern China. Chinese Science Bulletin 59(25): 3162–3168. https://doi.org/10.1007/s11434-014-0370-y
Wegge, P., R. Shrestha & Ø. Flagstad (2012). Snow Leopard Panthera uncia predation on livestock and wild prey in a mountain valley in northern Nepal: implications for conservation management. Wildlife Biology 18(2): 131–141. https://doi.org/10.2981/11-049
Weiskopf, S.R., S.M. Kachel & K.P. McCarthy (2016). What are Snow Leopards really eating? Identifying bias in food-habit studies. Wildlife Society Bulletin 40(2): 233–240. https://doi.org/10.1002/wsb.640