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. 2015 Aug 31;10(9):e0134815.
doi: 10.1371/journal.pone.0134815. eCollection 2015.

Face Value: Towards Robust Estimates of Snow Leopard Densities

Justine S Alexander  1 , Arjun M Gopalaswamy  2 , Kun Shi  1 , Philip Riordan  3
Affiliations

Face Value: Towards Robust Estimates of Snow Leopard Densities

Justine S Alexander et al. PLoS One. .

Abstract

When densities of large carnivores fall below certain thresholds, dramatic ecological effects can follow, leading to oversimplified ecosystems. Understanding the population status of such species remains a major challenge as they occur in low densities and their ranges are wide. This paper describes the use of non-invasive data collection techniques combined with recent spatial capture-recapture methods to estimate the density of snow leopards Panthera uncia. It also investigates the influence of environmental and human activity indicators on their spatial distribution. A total of 60 camera traps were systematically set up during a three-month period over a 480 km2 study area in Qilianshan National Nature Reserve, Gansu Province, China. We recorded 76 separate snow leopard captures over 2,906 trap-days, representing an average capture success of 2.62 captures/100 trap-days. We identified a total number of 20 unique individuals from photographs and estimated snow leopard density at 3.31 (SE = 1.01) individuals per 100 km2. Results of our simulation exercise indicate that our estimates from the Spatial Capture Recapture models were not optimal to respect to bias and precision (RMSEs for density parameters less or equal to 0.87). Our results underline the critical challenge in achieving sufficient sample sizes of snow leopard captures and recaptures. Possible performance improvements are discussed, principally by optimising effective camera capture and photographic data quality.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Study Area.
Location of camera traps in QNNR, Gansu Province, China.
Fig 2
Fig 2. The mean pixel-specific abundance plotted against standardized covariates.
Fig 3
Fig 3. Snow leopard individual identification.
B and C are photos of the same individual from different camera traps with C taken at night with infrared. A is a photo of a different individual. Identification is based on distinct spot patterns on the face.
Fig 4
Fig 4. The map of the spatial distribution of snow leopards across the study area.
A pixelated density map produced in SPACECAP showing estimated snow leopard densities per pixel of size 1.96 km2.
See this image and copyright information in PMC

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