By Rizwan Mithawala
The business of biogeography is to inquire and ascertain where a species exists, where it doesn’t, and why? Though enough work has been done to record and report the geographic distribution of species in India, our forests still hold secrets. That the forested hill range of Satpura, in the heart of India, is a biodiversity hotspot, is undisputed. But to say that all life forms, or even the mammals in these forests, have been fully documented and catalogued, would be a gross overstatement.
The Satpura hill-forests are home to mammals that glide across treetops – squirrels, and mammals that swim its rivers... otters. While the smooth-coated otter, found throughout south and Southeast Asia, has been well documented in Satpura, the other two species known from India – the Asian small-clawed and the Eurasian – had never been reported from central India. Moreover, there was no photographic evidence of the presence of the Eurasian otter in India until October 2016.
“Ek choti si, alag si udbilao dikhti hai kabhi kabhi,” a forest guard revealed to researchers from the Wildlife Conservation Trust (WCT), who were installing camera traps as part of the yearly tiger estimation exercise in the Satpura Tiger Reserve in December 2015. While installing camera traps, they had come across signs of otter presence along the rivers and streams – footprints and spraints (otter dung). This got the researchers curious, and the guard’s revelation, though not clear-cut, piqued their curiosity further. Unable to ascertain the species based only on the footprints and spraints, they decided to place camera traps for otters. With years of experience in camera trapping for tiger estimations, these boys and men have become wizards of their science. But installing camera traps for otters is a different ball game. For scientific estimation of tiger numbers, camera traps are never placed along streams; for otters, this is exactly what was needed to be done.
Around rock boulders where they had seen spraints, along sandy river and stream banks where they had come across footprints, and on the slopes flanking the deep pools in the streams, camera traps were installed and kept for 25-30 days. Twenty one such sites were chosen where camera traps were installed simultaneously. The efforts paid-off when, from three of these locations, along the hill streams, nine cameras captured a species that turned out to be the Eurasian otter Lutra lutra – a species of which there had been no record ever from India. This maiden photographic evidence of the species from India also extended its known geographical range to the central Indian landscape. Subsequently, in the same year, following a similar trail of indirect evidences, the research team managed to photo capture a Eurasian otter in a camera trap deployed along a deep stream-pool in the Balaghat Forest Division, which forms part of the vital Kanha-Pench corridor.
Though it inhabits a wide variety of aquatic habitats across its geographic range, in the Indian subcontinent, the Eurasian otter is only known to inhabit cold mountain streams and rivers, being a habitat specialist of sorts when compared with the smooth-coated otter, which is found across a much-wider altitudinal range. According to historical records from the Himalaya, the species is known to move upstream in summer, and is recorded at up to 3,663 m. above sea level. The camera-trapping study in Satpura also confirmed its preference for high-altitude streams. While smooth-coated otters were photo-captured in lowland areas at altitudes ranging from 300 to 480 m., Eurasian otters were recorded in camera traps along hill streams at altitudes of 550 to 700 m.
The Eurasian otter has the widest distribution of all otter species, covering parts of Europe, Asia and Africa. But throughout its range, the species is feared extinct from many regions or has been reduced to small, isolated, unviable populations. According to the IUCN Otter Specialist Group, water pollution has been the major driver of local extinctions of the species across its European range. Research has repeatedly confirmed that the species is extremely sensitive to man-made changes to its aquatic habitats. Throughout its range, canalisation of rivers, removal of bank-side vegetation, construction of dams, draining of wetlands, aquaculture activities and associated man-made impacts on aquatic systems have been recognised as threats to the survival of the species.
The new photographic evidence of Eurasian otters from central India comes from hill-streams in the ‘core area’ of the Satpura Tiger Reserve, and the least-disturbed areas of Balaghat Forest Division; these forests and rivers are relatively free from human disturbance. Could these populations be stranded relicts of what was once a much wider and contiguous distribution? Could there be other river systems harbouring such isolated populations in central India? To answer these questions, targeted, systematic sampling of riparian habitats in forested hill regions is needed. Dedicated camera-trapping efforts, taking into account species habits, can help document mammalian diversity which is often overlooked during estimation exercises for large carnivores.
The discovery of Eurasian otters in the Satpura Tiger Reserve is yet another heartening validation of the umbrella species model of conservation, and their presence in Balaghat emphasises the importance of wildlife corridors. Awarding protection to Satpura under Project Tiger has prevented the dismantling of its ecosystems at the hands of humans, and ensured the survival of all the species that call this wilderness their home. The otters, it seems, have a message – protect large landscapes to preserve the riches of fully-functioning ecosystems. For uninterrupted ‘ecosystem services’ will ensure the survival of Homo sapiens. Are the policymakers listening?
Author: Rizwan Mithawala