Tamil Nadu: Endangered Otter Habitats Need Protection, Will Save Thamirabarani River's Biodiversity

Tirunelveli: Unknown to many, the Thamirabarani River flowing through Tamil Nadu is home to otters among a plethora of fauna and flora. However, researchers are concerned about their dwindling numbers, as their habitats have been increasingly destroyed over the last few years. Ecologists have often underlined the importance of otters for a healthy river ecosystem.

Originating in the Pothigai Hills in the western part of Tirunelveli district, Thamirabarani River is the only perennial river flowing through the state. It joins the sea at Punnakayal in Thoothukudi district.

Pretty similar to mongoose in looks, otters are shy and playful creatures that live on both land and in water. Mostly active at night, they primarily survive on fish, snails and crabs. During the day, they tend to hide among the vegetation and thickets along the riverbanks.

They use burrows along the riverbanks to give birth. Researchers say that in addition to the main entrance, they construct four to five secret exit routes from their burrows.

Experts say that they help prevent river pollution by feeding primarily on old and diseased fish. Their consumption of fish also helps keep the fish populations in check creating a suitable environment for other aquatic life to thrive.

India's Otter Species

While global research on otters began around 50 years ago, studies in India have been conducted over the last 30 years on the three species of otters that are found here: The Eurasian otter, the smooth-coated otter, and the Asian small-clawed otter.

The Eurasian otter weighs around 5-8 kg and feeds on fish, crabs, snakes and snails. The smooth-coated one is the largest species in the Indian subcontinent. It has webbed feet, similar to those of ducks, and weighs between 12-15 kg. The Asian small-clawed otter weighs between 4-5 kg.

All the three species inhabit the Thamirabarani River. Natural Resource Conservation Centre at Bengaluru has been carrying out studies on the otters in the Thamirabarani over the last two years.

It is learnt that the presence of otters in the Thamirabarani River has been recorded for around four centuries as wall paintings depicting them can be found in the Thiruppudaimaruthur temple near Mukkoodal that was built in the 17th century.

These paintings vividly depict scenes of clashes between otters and ordinary dogs. It is said that as the riverbank thickets, rich in screw pine plants and sedge grasses, have dwindled, the otters habitats have been destroyed, leading to a steady decline in their population.

While otters were once widely distributed along the Thamirabarani River from Papanasam to Srivaikuntam in the Thoothukudi district about 50 years ago, they can now be spotted only in a few specific areas.

Researchers have initiated efforts to revive this endangered species. According to them otters are sighted only within the stretch extending from Papanasam to the Nadiyunni anicut near Manimuthar over 10 km. They say that this area provides the necessary environment for their survival as it contains the dense riverbank thickets and grasses, they require.

Research On The Endangered Species

Researchers Vinoth and Thanigaivel, who have been studying otters along the Thamirabarani River disclosed that the otter habitat has been destroyed due to various factors including the clearing of riverbank thickets, illegal sand mining and the discharge of sewage into the river.

Vinoth pointed out, “We confirmed the presence of the three species in the river using camera traps two years ago. Fishermen have stated that, fifty years ago, otters were found throughout the Thamirabarani.”

He further stated, “We have sighted them only in the stretch between Papanasam and the Nadhiyunni dam.”

The researchers said that since the otters roam at night, they require secluded spots to rest and breed during the day. They need dense, grassy areas along the riverbanks that are no longer found in areas where their habitats have been destroyed.

They disclosed that indirect evidence to determine their location was gathered by searching for signs such as footprints and droppings. “We confirmed the presence of otters by placing an automated camera at a spot where footprints were found. Spotting them in person is extremely rare. Only fishermen or people who regularly frequent the river are likely to see them,” they stated.

Sangam literature, specifically the Natrinai poems, mentions the presence of otters in both the Marutham (agricultural) and Neithal (coastal) landscapes. Currently, they can be spotted in the stretch between Papanasam and the Nithiyunni Anicut. Experts believe that if the government declares this area a 'Biodiversity Heritage Site' and a protected zone, the otters' habitat could be safeguarded.

Protecting Biodiversity

"Protecting otters also helps conserve other river dependent species. The fact that three species of otters can still be found in the Thamirabarani suggests that the river is not yet severely polluted. Therefore, the government must step forward to protect it," Vinoth underlined.

His fellow researcher, Thanigaivel said, "Protecting otters essentially means protecting their habitats. The Thamirabarani River once boasted extensive riparian forests (riverine groves), but these are dwindling rapidly. Such forests remain in good condition at only a few places today. A river ecosystem relies on various interconnected layers.”

“Activities like sand mining and the spread of invasive plant species are causing the area covered by riparian forests to shrink. Native trees characteristic of these groves like Marudham, Kadambu and Iluppai are being replaced by invasive tree species. The presence of otters is directly linked to the extent of these riparian forests,” the researcher added.

The researchers said the government is taking various measures to restore the Thamirabarani River. “In addition, trees native to riparian forests should be planted. By protecting the water body, we can safeguard otter habitats and conserve other forms of biodiversity as well," Thanigaivel underlined.