Occupancy Estimation of Sloth Bear (Melursus Ursinus) in Chitwan National Park, Nepal

Abstract

Effective conservation plan for Sloth Bear requires detailed information regarding their distribution and habitat use.There is limited information available on the species ecology in response to different site covariates in Nepal.The aim of the study was to assess occupancy,distribution pattern and habitat preference of Sloth Bear in Chitwan National Park. The study was carried out during April -May 2012 using single season model of occupancy estimation based on sign survey.The study area was divided into 74 grids each measuring 16 Km . Of the total grids, 35 were randomly selected for sampling.A total of 288 spatial replicates were sampled in 35 different grids recording 87 evidences of Sloth Bear presence.An occupancy-based approach was used in which separate models were developed to determine the influence of habitat covariates on occupancy and detection probability. A total of 12 models for detection probability and 18 models for occupancy estimation were created. Models were ranked on the basis of AIC values and model average was undertaken from the models having ∆AIC< 2. The estimated occupancy of Sloth Bear in the study area was 0.90 (with SE of 0.08, 95% CI 0.34-0.97), 25% higher than naïve estimate. The major predictors for the occupancy of Sloth Bear were habitat types(0.45), distance to water(0.22), distance to road(0.15)and altitude(0.16). 37% of the surveyed grids had occupancy rates lower than the averaged rate(0.90).There was no relationship found between distance to settlement and occupancy(0.0015). Model averaged detection probability was 0.44 ± 0.09 ranged between 0.05 and 0.77. The detection of animal was negatively correlated with disturbances. The general distribution pattern of Sloth Bear was clumped. Mixed forest(RPI =0.42)was found to be most preferred by the animal followed by grassland(0.21). Sal forest(-0.11) andriverine forest(-0.25)was less preferred. The status of Sloth Bear in Chitwan National Parkwas found satisfactory in term of habitat use though anthropogenic disturbances could be potential threat for long term conservation of the species. This study provides the present status of Sloth Bear in term of habitat use and distribution. Detailed multi-season occupancy analysis is essential to evaluate the effect of ground covariates throughout the year.