About 21 animals died every 10 km and amphibians comprised the majority

The roads that Valparai’s tourists love driving through to spot wildlife also see numerous animal deaths. Road surveys show that almost 3,000 animals died on approximately 1,500 km of roads in Tamil Nadu's Valparai plateau in 2011-12 alone.

Valparai’s road network meanders through rainforest fragments and tea, coffee, cardamom and eucalyptus plantations in the Anamalai Hills of the Western Ghats. Along with people, animals – including endangered Asian elephants and lion-tailed macaques – also live on this high-elevation plateau. However, fragmentation of habitats ensures that wildlife have to cross roads when they move about. A study recorded 73 reptile deaths on the Valparai roads in 2001; mammal and insect deaths are also frequent here.

Scientists of the Nature Conservation Foundation (NCF) walked along eleven road sections passing through various habitats in the Valparai plateau. They noted roadkills of all animal taxa across seasons (surveying totally1473.4 kms, including a State Highway) in 2011-12.

Their results, published in the journal Current Science, show that 2,969 animals died on Valparai’s roads during this time, which translates approximately to an average of 21 animals per 10 km of road. Almost 50% of these kills comprised amphibians — toads, frogs and caecilians (limbless, snake-like amphibians). Rodents and shrews comprised a majority of the 148 mammal kills. The Indian crested porcupine, the brown palm civet (a fruit-eater endemic to the Western Ghats), larger mammals like sambar deer and endemic lion-tailed macaques also figured in the list of mammal roadkills.

When the team compared deaths across seasons, they found that roadkill rates were 2.4 times higher during the monsoons than during summer. This could be because many amphibians breed and move across land during the monsoon, write the authors. What habitat the road passed through also mattered; roads passing through tea plantations, followed by forests habitats, saw the highest deaths at 1,402 and 948, respectively. Forest patches had the highest mammal roadkills.

The team’s findings could help identify specific management measures for different habitats to prevent or reduce roadkills in Valparai and similar places. According to the authors, roads through forest patches need urgent attention because forest-dependant and endemic species died most here. Drains along roadsides with underpasses at regular intervals can also provide safe passages for small-sized taxa like amphibians.

“But mitigation measures have to be taxa- and habitat-specific, and should be implemented on road stretches which see a lot of roadkills,” said P. Jeganathan (NCF), lead author of the study.