3.4 Snow leopard-prey availability
An annual food requirement for one snow leopard is 1343 kg. Standing available food biomass of both wild and domestic livestock was calculated at 355, 236 kg. Naur, the snow leopard’s staple food in the KCA, was calculated at 47, 736 kg and domestic yak, 307, 500 kg. Harvesting rate of the estimated 24 snow leopards was about 7% per annum. If a snow leopard killed 21 Naur annually then the extant 24 snow leopards would require 504 Naur per annum. Without the biomass contribution of small mammals and livestock, the estimated available Naur biomass of 47, 736 kg gives a predator- prey ratio of 1:59 in KCA on a weight basis. Here in the KCA the proportion of young (Naur) is estimated at 17%, but predation rate is almost double at 28%.
DISCUSSION
The study estimated snow leopard density at 3.9/ 100 km2 (95% CI= 3.1- 4.8; SD: 0.8) in the KCA. This estimate is lower than the densities recorded in the Phu valley by Wegge, et al., 2012 (6 individuals/125 km2), by Janecka et al., 2011 in Mongolia (5.9 individuals/100 km2; 95% CI= 3.4- 8.0) and Oli, 1994 in Manang 4.8-6.7/100 km2. Jackson & Ahlborn (1989) estimated 5-10 snow leopards/100 km2 in the prime habitat of the Langu valley and then extrapolated this estimate to a country-wide density of less than 0.1- 0.5 snow leopards/100 km2 in most parts of Nepal. The studies such as Jackson and Ahlborn (1989) and Oli (1997) which were based on expert opinion, sign evidence, VHF radio telemetry, and their extrapolations may be less reliable (McCarthy & Chapron, 2003). Chetri et al. (2019) however, estimated a lower density of 1.07 individuals/100 km2 (95% CI: 0.71- 1.62) in Annapurna and 1.16 individuals/100 km2 (95% CI: 0.73- 1.87) in Manaslu of Nepal by modeling genetic sampling over a larger area. This lower density was likely due to Chetri et al. (2019) including the high mountain zone up-to 6000 m as potential snow leopard habitat in their study rather than the 3000-5400 m range considered (prime and fair) suitable snow leopard habitat in Nepal (Jackson & Hunter, 1996). Recently, Khanal et al., 2020 estimated lower densities using remote camera traps compared to our estimates i.e., 2.51/100 km2 (95% CI: 1.36= 4.60) in Upper Dolpa and 1.21/100 km2 (95% CI: 0.58-2.54) in Lower Dolpa of SPNP west Nepal. The estimated lower snow leopard density in western Nepal compared to the KCA could be a result of camera trap analysis from this study excluding sub-adult and young in density estimates.
Based on food requirements, 24 snow leopards would need an annual biomass of 32,232 kg in the KCA. Snow leopard diet in this study comprised both wild (49%) and domestic (45%) prey. Our estimates were consistent with that of Bagchi & Mishra (2006) and Wegge et al. (2012), with 58% and 42% livestock in India and Nepal respectively. Chetri et al., 2017 estimated 57% of Naur and 31% livestock in snow leopard diet within the Annapurna-Manaslu region, similar to the estimates of Lovari et al. (2013) and Ferretti et al. (2014) in the Mt Everest region (25% livestock and 56% Himalayan tahr). Within the Dolpa region of western Nepal however, Devkota et al., 2013 found that snow leopard diet consisted of only 30% Naur where marmot (buffer prey) and small livestock are plentiful. Oli (1994) stressed that snow leopards killed livestock because they are abundant and easy to kill compared to wild prey, not because they were a preferred food source. These findings are consistent with the results of our study in the KCA, particularly with the standing biomass of yak representing approximately 2/3 of the total volume (with Naur occupying the other 1/3).
Based on the estimate of Jackson & Ahlborn (1989), that an adult snow leopard requires 20-30 Naur annually to survive, 24 snow leopards would need to consume 480-720 Naur per year. Jackson and Ahlborn (1989) hypothesized that a single snow leopard requires an estimated population of 150- 230 Naur to achieve this (possibly less in areas where other prey species are easily available). In the KCA snow leopards were estimated to harvest 28% of the Naur population annually, nearly twice the amount estimated (15.1%) by Wegge et al. (2012) in the Phu valley, however the proportion of young Naur was found to be similar between the KCA and Phu (17% compared to 18.4%; Wegge et al., 2012). This difference could be explained by the greater availability of small livestock in the Phu Valley (Wegge et al., 2012; Thapa, 2005) compared to the KCA, providing snow leopards with a smaller prey target. The higher proportion of prey to predators around Manang (159:1; Oli, 1994) compared to KCA (59:1) could also explain this difference in Naur consumption. As well as the KCA having less “easy” small livestock prey available compared to Dolpa, Manang and the Phu Valley (Devkota et al., 2013; Wegge et al., 2012; Oli, 1994), snow leopards in the area also share habitat with two other apex predators, the common leopard along the forested- edge habitat in the south (Thapa et al., 2013) and grey wolf (Subba et al., 2017) in the north which will add significantly to the competitive pressures on Naur populations. Further long-term studies examining snow leopard, common leopard and wolf interactions are therefore needed.
The current situation indicates that available wild prey biomass is insufficient to support the estimated snow leopard population in the KCA. Therefore, livestock play an important role for the survival of snow leopard here in Nepal and elsewhere (Khanal et al., 2020; Mishra et al., 2016; Johansson et al., 2015; Sharma et al., 2015; Wegge et al., 2012; Shehzad et al., 2012; Oli et al., 1993). In most of the snow leopard’s range, current community conservation initiatives focus on compensation and incentive, rather than preventative measures. Recently introduced Community- Managed Livestock Insurance Schemes in the KCA are offering huge promise for the long-term survival of snow leopards in the area by reducing the incentive for retribution killings (Gurung et al., 2011). However, financial compensation for livestock losses alone will not solve the problem (Thapa, 2006; Jackson, 2015). Along with this scheme improvement, there needs to be a focus on preventive measures such as improved livestock guarding as well as engaging and educating local people to be citizen scientists on the importance of snow leopard conservation, involving them in long-term monitoring programs and promotion of ecotourism.
ACKNOWLEDGEMENTS Permission was granted to conduct the study by the Department of National Parks and Wildlife Conservation (Ref.: 689/069/070). We are grateful to WWF International for awarding us the PRINCE BERNHARD scholarship (Grant no. 9Z0533.01) and WWF Nepal for the research grant to undertake this study. We also want to thank the Nepal Engineering College (nec-cps) especially the Director Prof. Dr. Khem Raj Sharma, Associate Prof. Dr. Narayan Kumar Shrestha, Associate Prof. Jhamak Bahadur Karki and Asst. Prof. Mr. Robert Dongol including Prof. Mukesh Kumar Chalishe (TU) for their guidance and critical review during drafting the paper.
Our sincere thanks go to members of the Snow Leopard Conservation Committees of KCA who collected the scat samples and also assisted us in gathering the Naur and domestic stock data in the field. We also acknowledge the Kangchenjunga Conservation Area Management Council and Kangchenjunga Conservation Area Project for mobilizing the Citizen Scientists who helped us gather reliable data from field. The team at the Center for Molecular Dynamics Nepal (CMDN) generously processed and analyzed our fecal samples in the lab. Finally, we are grateful to Mr. Gokarna Jung Thapa (GIS expert, WWF Nepal) for assisting us in preparing the map.