The Nilgiri Tahar population once spread across the Nilgiris and Western Ghats, with their range extending into Karnataka. | Photo credit: M. Satyamurthy
Nilgiri Tahar (Nilgiritragus hylocris) population has stabilized and increased in parts of the Western Ghats over the past few decades due to better conservation practices, wildlife biologists and experts say that another program for the conservation of the species was ensuring the suitability of the habitat so that the populations varied across their geographic range. Can inter-breed ensuring genetic diversity.
In the Centenary Volume (1877-1977) of the Nilgiri Wildlife and Environment Association, ERC Devidar writes that according to historical records, the Nilgiri Tahar was once widespread in the Nilgiris and Western Ghats, with their range extending into Karnataka. The Nilgiri tahr, which probably numbered in the tens of thousands two centuries ago, has dwindled to less than 3,000 in field surveys conducted between 2007 and 2011, with many small populations disappearing.
However, due to intensive conservation practices, Davidar’s (1978) estimate has increased the number to 2,230 individuals, noted conservation biologist Priya Davidar said. She said that only two populations in Eravikulam and Nilgiris have large numbers of individuals, the rest are much smaller, often represented by a single herd. “The extinction of these small populations is documented,” she said.
Conservation biologists like Davider argue that the future of the Nilgiris range is linked to genetics and climate change, arguing that for the species to continue to survive in the coming decades, ensuring habitat suitability between areas where the animals are found will be critical. To maintain genetic variability. “A genetic study by Lewis et al. (2016) indicates a low level of genetic variation in the Western Ghats population, which increases their risk of extinction. Genetic diversity and populations of the Nilgiri tahr in the Western Ghats analyzed 191 faecal samples from 100 tahrs from their distribution range in Kerala and Tamil Nadu. “The single largest Nilgiri tahr population (about 700 individuals) is also coincidentally high in genetic diversity,” says the paper titled Structure.
genetic variation
“Genetic variation increases with population size, and the Nilgiri tahr must be kept in large, connected populations to reduce its risk of extinction. As most populations in the Western Ghats are small and isolated, it is subject to genetic drift and inbreeding. “Genetic drift is a process by which small isolated populations lose genes due to random factors, and inbreeding increases inbreeding, which adversely affects individual survival,” said Ms. Davider. The tahr may lose 55.5% of its habitat by , predicting an increased risk of extinction.” Habitat suitability to the tahr Humans also provide an opportunity to move to more suitable habitats in a scenario of habitat loss and climate change,” experts argue.
However, other researchers believe that in-breeding in isolated populations may be a concern, as the expression of genetic in-breeding depression was not yet evident in the Nilgiri tahr population. “In the 1980s, some individual animals from the Thiruvananthapuram Zoo were taken to the United States (US) and bred in captivity, with some individuals also entering private ownership. In 2017, the offspring of this small population, were still alive and thriving in captivity, indicating that there may not be an immediate threat to the breeding species,” said MA Pradit, Associate Coordinator of the Nilgiri Tahr Project, WWF-India.
Mr. Predit said anthropogenic pressure and communicable diseases are more immediate concerns, which he believes have led to the depopulation of Megamalai and Vengoli in Parambikulam. “Lack of genetic diversity may make individuals and herds more vulnerable to communicable diseases such as foot-and-mouth disease, but more studies are needed to reach this conclusion,” he said. He said that while it is important to ensure genetic flow among Tahar populations, it can also increase the risk of communicable diseases spreading through the population.
Determining factors
Jean-Philippe Purevaud, a landscape ecologist at the Sigur Nature Trust, said the two factors that determine the future of a species are the number of individuals in the largest population and their genetic diversity. “The condition of Nilgiri Tahar is very poor in both respects. The assumption that the species is doing well because the numbers are increasing is a modest improvement. What should happen is to promote large populations with good connectivity between them, where two or more isolated populations become one large herd, which also increases their genetic diversity,” he said.
MG Ganesan, project director of the government’s project Nilgiri Tahar, said while the concern to improve the genetic variability of the species was valid, the task was challenging due to the current ‘complex’ topography and habitat occupied by the animal. “We are looking at habitat modification, such as removing invasive species and improving grasslands, which may allow the tahr to move between habitats,” he said. He added that the Advanced Institute for Wildlife Conservation is looking into these aspects, adding that Tahar is already rehabilitating certain habitats, especially in the Nilgiris and Kanniyakumari.
published – December 20, 2024 at 07:33 pm IST