A Habitat Suitability Index Model for Nilgiri Tahr (Hemitragus hylocrius Ogilby) in Eravikulam National Park, Kerala

The Nilgiri tahr, Hemitragus hylocrius Ogilby, is an endangered mountain goat distributed in southern Western Ghats of Peninsular India. Monitoring tahr habitats and selection of sites for management interventions and reintroduction of the tahr in their natural environment require an understanding of habitat suitability and hence this study was undertaken. The estimated tahr population in Kerala was around 1,000 individuals on 11 sites. The Eravikulam National Park (ENP) was chosen for developing the Habitat Suitability Index (HSI) model since it has the sole viable population of about 700 individuals. Based on the habitat utilization, the ENP was divided into different blocks. The relational trends between block-wise tahr density and the critical habitat variables viz., altitude, extent of cliff and availability of principal food species were examined through correlation analysis for evolving habitat suitability criteria. This formed the basis for deriving suitability indices, ranging from 0 to 1, which were subsequently used for developing the HSI models. In order to find out how well the HSI models captured variation in tahr density, they were subjected to regression analysis. The analyses indicate that the HSI models were satisfactory considering the limited number of factors involved. However, the models should be evaluated in other habitat conditions especially in fragmented habitats considering their degradation factors such as human disturbance, grazing pressure.