Estimating Asian Elephant, Elephas Maximus, Density Through Distance Sampling in the Tropical Forests of Biligiri Rangaswamy Temple Tiger Reserve, India

Abstract

To determine abundance, density and distribution of wild animals, it is crucial to estimate populations using reliable sampling techniques. In most earlier studies, elephant populations were estimated employing block counts or dung counts, which provide biased estimates due to limitations of the methods. We estimated an Asian elephant population using distance sampling, a quantitatively robust technique, in Biligiri Rangaswamy Temple Tiger Reserve, a critical elephant conservation area in the Nilgiri Biosphere Reserve in south India. We laid 33 transects with a total length of 93 km. We walked these transects five to 11 times amounting to a total of 795.5 km of walks. We collected data on location, number and age-sex classes through direct elephant sightings, using rangefinders, global positioning systems and compass. We used DISTANCE software for analysis. We estimated per km2 cluster density as 0.69 elephant herds, mean cluster size as 2.44, and elephant density as 1.7 animals. This amounts to a total of 713 elephants in 610 km2 of the sanctuary. A high percentage of males less than 30 years old and a low immature:adult female ratio indicated the severity of poaching in the recent past in the study region.