A Preliminary Estimation of the Sambar Deer (Rusa unicolor unicolor) Abundance in Horton Plains National Park, Sri Lanka

Abstract

Grasslands are one of the tropics’ most critically threatened habitats, while conservation attempts are rarely concentrated at these ecologically important landscapes. Sambar deer is a large wild ruminant found throughout Sri Lanka, in both grassland and forest ecosystems. Amidst their key position in the trophic web in ‘wet patana’ grasslands of the Horton Plains National Park (HPNP), Sri Lanka, population of sambar deer has not been estimated during recent decades. In this research, field surveys were performed in the total grassland area of 9.4 km2 in HPNP to estimate the density of Sambar deer, for a period of six months, from 1st of January to 31st of June 2018. Sambar deer were sampled along line transects from 1600 hrs -1830 hrs for up to 300m of maximum distance from the line and the distance sampling technique was used to solve imperfect detection for the first time. Counting was carried out for three days per month along a 6.71 km road transect through grasslands. Collected data on sambar deer observations along the transect was analyzed by using the DISTANCE 7.2 computer application. The highest sambar deer density in HPNP was estimated as 113.45 ±11.79 individuals/km2 with a detection probability of 28% in January with an estimated absolute abundance of 1066 ± 110.82 individuals. Our findings indicate consequences of imperfect detection of a statistically strong model.Sambar deer density estimates from this research lays the context for regular surveillance of their population,examining the effects of habitat alterations and assessing the long-term viability of ‘wet patana’ grassland in HPNP, offering insight on the conservation of the fragile habitat of the resident sambar deer population.