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Pollution along river systems in the Nilgiris could pose threats to otters, warn researchers

September 07, 2022 03:22 pm | Updated September 15, 2022 12:34 pm IST - UDHAGAMANDALAM:

A group of Indian smooth-coated Otters in Nilgiris.

A group of Indian smooth-coated Otters in Nilgiris. | Photo Credit: Special Arrangement

With anthropogenic pressures on the rise in riverine ecosystems in the Nilgiris, researchers and conservationists have called on the state forest department to increase restrictions that will safeguard the populations of two species of river otters in the district.

The Nilgiris is home to the smooth-coated otter ( Lutrogale perspicillata) and the Asian small-clawed otter ( Aonyx cinereus), both listed as “vulnerable” to extinction by the International Union for the Conservation of Nature (IUCN). Based on estimates by researchers and the forest department in the Nilgiris, there are believed to be a few hundred individuals from both species inhabiting both the Moyar river basin and streams and lakes in the Upper Nilgiris.

According to K. Narasimmarajan, a wildlife biologist and associate with the zoology department at the Madras Christian College (MCC), Chennai, the smooth-coated otters prefer perennial rivers like the Moyar as part of their habitat, while the Asian small-clawed otters, which is the smallest species of otter in the world, inhabits smaller streams further up the Nilgiri slopes.

Asian small-clawed otter. File photo

Asian small-clawed otter. File photo | Photo Credit: Special Arrangement

Due to the elusive nature of the animals, the population health of the two species, which are key indicators of the health of the rivers which they inhabit, remains extremely difficult to understand, state researchers. Mr. Narasimmarajan said that threats such as hydroelectric dams, which arbitrarily alter water flows along rivers have always been a significant factor that researchers believe could affect the population of the two species. “However, in the recent past, pollution of the rivers with the usage of chemical pesticides used by farmers, as well as effluents from a Laundromat located near the Mudumalai Tiger Reserve (MTR), could potentially exacerbate such pressures on the existing population,” said Mr. Narasimmarajan, who studied otters in the Nilgiris between 2015 and 2017.

M. Murali, a wildlife photographer who has been documenting birds and mammals in the Sigur plateau said that he had photographed smooth-coated otters frequently during the COVID-19 lockdown. “In certain areas, where fishing had been completely stopped, there had been a noticeable increase of smooth-coated otters using stretches of the Moyar and Sigurhalla Rivers during the lockdown,” he said. However, Mr. Murali added that since the lifting of restrictions, fishing had resumed in these stretches of river, which coincided with a decrease in sightings of the river otters. “This could be due to competition from fishermen, who are overfishing stretches of the river, like near the Maravakandy Dam,” added Mr. Murali.

Conservationists have called for better monitoring and collecting records of sightings of river otters by the forest department to gain a better understanding of the populations of the two species, and to also identify whether the population was decreasing or was stable.

When contacted, the Field Director of Mudumalai Tiger Reserve, D. Venkatesh, said that population estimation of the two species was incredibly hard due to them being extremely shy animals. He however added that the forest department was recording the frequency of sightings of the two species, and said that only through further studies could the department come to an understanding as to whether there needed to be increased protections for the otters along stretches of rivers in which they had been recorded.

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