Site occupancy of the Indian giant squirrel Ratufa indica (Erxleben) in Kalakad-Mundanthurai Tiger Reserve, Tamil Nadu, India

摘要

The status report on the Indian giant squirrel speculates a declining population trend for the species and suggests that a further decline can be expected. Given the wide distribution of the species and the limited resources to accurately estimate abundances to monitor population trends, the proportion of the area occupied by the species could be used as an alternate state variable. Arriving at occupancy rates involves repeated detectionon-detection surveys and analysis of the data in a capture-recapture framework. We estimate the site occupancy rates for unstudied populations of Indian giant squirrel within the Kalakad-Mundanthurai Tiger Reserve (KMTR) using a model that allowed us to estimate this parameter even when the species was not detected. About 180 evidences of the occurrence of the species were recorded from 486 km of trails. The estimated occupancy rate for Indian giant squirrel in KMTR was 0.82 (with a SE of 0.08) with a detection probability of 0.71 (+/- 0.05). An examination of the species habitat relationship showed that contiguous patches of moist deciduous and evergreen forests were preferred by the species. The occupancy rates were low in areas with degraded dry deciduous forests and scrub, which were associated with high levels of human disturbance. The estimates from this study provide a benchmark for long-term monitoring and metapopulation studies.