Habitat proximity, next steps to protect the Nilgiri Taars

The Nilgiri Taars were once spread across the Nilgiri and Western Ghats, even as far as Karnataka. |Photo credit: M. SATHYAMOORTHY

with Nilgiri Taal (LoachAs populations have stabilized or even increased in parts of the Western Ghats over the past few decades due to better conservation measures, wildlife biologists and experts say the next step in protecting the species is to ensure continuity of habitat across its geography. Different populations of the range can interbreed, ensuring genetic diversity.

ERC Davidar wrote in the Centenary Volume of the Nilgiri Wildlife and Environment Society (1877-1977) that according to historical records, the Nilgiri Taars were once widely distributed in the Nilgiri and Western Ghats, and their range even extended to Karnataka. Two centuries ago, the Nilgiri Tahr population may have numbered in the tens of thousands. Field surveys conducted between 2007 and 2011 showed that the Nilgiri Tahr population has declined to more than 3,000 individuals, and many small populations have become extinct. .

However, noted conservation biologist Priya Davidar stated that due to intensive conservation measures, their numbers have increased since Davidar’s (1978) estimate of 2,230 individuals. Only two groups, the Eravikulam and the Nilgiri, have large numbers of individuals, she said, while the remaining groups are much smaller and usually represented by a single group. “There are documented cases of these small groups becoming extinct,” she said.

Conservation biologists such as David Dahl believe that the future of the Nilgiri Tahr has to do with genetics and climate change, arguing that for the species to continue to survive in the coming decades, ensure that the distance between areas where the animal is found is Habitat continuity will be critical to maintaining genetic variability. “Genetic studies by Lewis et al. (2016) show that Western Ghats populations have lower levels of genetic variation, which increases their risk of extinction. Paper “Genetic diversity and population structure of the Nilgiri Taars of the Western Ghats ” analyzed 191 fecal samples of 100 Tatars across the range of Kerala and Tamil Nadu states, stating: “The single largest group of Nilgiri Taars (approximately 700 individuals), incidentally, Eravikulam State The park also has the highest genetic diversity.

genetic variation

“Genetic variation increases with population size, and the Nilgiri Tahr must be maintained in large, interconnected populations to reduce its risk of extinction. Because many populations in the Western Ghats are small and isolated , and are therefore prone to genetic drift and inbreeding. Genetic drift is a process in which small isolated populations lose genes due to random factors, and mating with relatives increases inbreeding, which adversely affects the survival of the individual. ,” Ms. Davidal said. A recent paper from 2023 (Kanagaraj et al.) also predicts that the Tahr may lose 55.5% of its habitat due to climate change by 2070, leading to an increased risk of extinction. Experts believe that “the proximity of habitat also provides opportunities for the Tahr to migrate to more suitable habitats amid human-induced habitat loss and climate change.”

However, other researchers believe that while inbreeding in isolated populations can be a concern, genetic inbreeding depression has so far not been apparent in the Nilgiri Tahr antelope population. “In the 1980s, some individual animals from the Trivandrum Zoo were brought to the United States and bred in captivity, and others also entered private ownership. In 2017, descendants of this small group are still alive and appear to be Thriving in captivity suggests that inbreeding may not pose a direct threat to the species.

Predit said the more pressing issues were man-made pressures and infectious diseases, which he believed had wiped out the populations of Megamalai and Vengoli in Parabikulam. “A lack of genetic diversity may make individuals and herds more susceptible to infectious diseases such as foot-and-mouth disease, but further research is needed to reach this conclusion,” he said, adding that while ensuring that the gap between Tahr groups is Genetic flow is important, but it can also increase the risk of infectious disease spreading throughout a population.

Determining factors

Jean-Philippe Puilavo, a landscape ecologist at the Sigurds Nature Trust, said two factors that determine the future of a species are the number of individuals in the largest population and its genetic diversity. “On both counts, the Nilgiri Tahr is doing very poorly. The idea that the species is doing better due to increased numbers is only marginal progress. What should happen is to promote larger populations that bring them closer to each other.” There is better connectivity, allowing two or more isolated populations to become a larger population, which also increases their genetic diversity,” he said.

MG Ganesan, program director of the government’s Nilgiri Tahr program, said that while concerns about improving the species’ genetic variability were legitimate, the task was challenging due to the “complex” terrain and habitat the animal currently occupies. “What we are looking at is habitat modification, such as removing invasive species and improving grasslands, which allows Tahr sheep to move between habitats,” he said. The Advanced Institute of Wildlife Conservation is studying these aspects, he added, adding that the Tahr have already recolonized certain habitats, especially in the Nilgiris and Kanyakumari.