Towards a reliable assessment of Asian elephant population parameters: the application of photographic spatial capture–recapture sampling in a priority floodplain ecosystem

• Published in: Scientific reports 2019-06, Vol.9 (1), p.8578-8578, Article 8578
• Main Authors: Goswami, Varun R., Yadava, Mahendra K., Vasudev, Divya, Prasad, Parvathi K., Sharma, Pragyan, Jathanna, Devcharan
• Format: Article
• Language: English
• Subjects: 631/158/1745; 631/158/672; Adults; Animal populations; Animals; Bayesian analysis; Capture-recapture studies; Conservation of Natural Resources; Ecosystem; Ecosystems; Elephants; Elephants - physiology; Estimates; Female; Floodplains; Heterogeneity; Humanities and Social Sciences; India; Male; Males; Megafauna; multidisciplinary; National parks; Photography; Population; Population Dynamics; Population status; Sampling; Science; Science (multidisciplinary); Spatial heterogeneity
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-019-44795-y

The hitherto difficult task of reliably estimating populations of wide-ranging megafauna has been enabled by advances in capture–recapture methodology. Here we combine photographic sampling with a Bayesian spatially-explicit capture–recapture (SCR) model to estimate population parameters for the endangered Asian elephant Elephas maximus in the productive floodplain ecosystem of Kaziranga National Park, India. Posterior density estimates of herd-living adult females and sub-adult males and females (herd-adults) was 0.68 elephants/km 2 (95% Credible Intervals, CrI = 0.56−0.81) while that of adult males was 0.24 elephants/km 2 (95% CrI = 0.18−0.30), with posterior density estimates highlighting spatial heterogeneity in elephant distribution. Estimates of the space-usage parameter suggested that herd-adults ( σ ˆ H A  = 5.91 km, 95% CrI = 5.18–6.81) moved around considerably more than adult males ( σ ˆ A M  = 3.64 km, 95% CrI = 3.09–4.34). Based on elephant movement and age–sex composition, we derived the population that contributed individuals sampled in Kaziranga to be 908 herd-adults, 228 adult males and 610 young (density = 0.46 young/km 2 , SD = 0.06). Our study demonstrates how SCR is suited to estimating geographically open populations, characterising spatial heterogeneity in fine-scale density, and facilitating reliable monitoring to assess population status and dynamics for science and conservation.