PILOT STUDY OF NILGIRI TAHR IN GRASS HILLS NATIONAL PARK
- As a prelude to a synchronised survey of Nilgiri Tahr, a pilot survey was conducted to standardize the protocols for population estimation methods. The exercise was carried out at Grass Hills National Park in Anamalai Tiger Reserve to test the four different population estimation methods namely Total sampling method, Double Observer, Bounded count method and aerial survey using drones.
- By applying the above methods in the field, the pros and cons of each protocol and practical feasibility were assessed thoroughly.
- This multifaceted approach contributed to expedient a standard methodology which is also statistically robust for surveying of the Nilgiri Tahr population across its habitats.
- The results revealed that in Grass Hills National Park, the Nilgiri Tahr population was arrived as 220 individuals based on the total sampling method whereas the Drone survey yielded 187 numbers. Similarly, the Bounded count estimated 350 numbers whereas the lower limit is 285 and the upper limit of the population is 545. The statistical analysis of the double observer method enumerated the Nilgiri Tahr population in Grass Hills to be 323 individuals with a range of 113-652 (95% Confidence Interval) and the average number of groups being 11 with a mean group size of 29. The derived estimates indicated that the Double Observer method is more compatible for surveying large populations in contiguous habitats, whereas Bounded Count method could be adopted to enumerate pocketed populations in fragmented habitats.