Is Assam’s NH715 our deadliest highway? Ask the local animals

A recent study (published in the journal Nature Conservation in March 2022) set out to count just how many animals end up as roadkill when a highway cuts through a forest, and emerged with an astounding number. By their estimate, just one 64-km stretch in Assam saw 6,036 deaths in one year (October 2016 to September 2017).

This highway, NH715, is particularly invasive, cutting through the Kaziranga National Park on one side and the North Karbi-Anglong Wildlife Sanctuary on the other. Over 12 months, the researchers set out to tally every life lost, no matter how small. They started their count where forest departments typically end theirs.

“Forest departments usually do not keep any record of deaths of smaller groups of animals,” says doctoral fellow Somoyita Sur, who carried out the study with zoology professors Prasanta Kumar Saikia and Malabika Kakati Saikia of Gauhati University. “Their focus has to be on the larger, more spectacular animals like rhinos, elephants and tigers.”

Among amphibians, the common Indian toad was found to be the most-affected, accounting for 54% of all amphibians fatalities. Among reptiles, the oriental garden lizard and striped keelback snake accounted for the highest fatalities (a combined 16%).

“There are multiple factors that make reptiles and amphibians more vulnerable. They are slower and they’re smaller, which makes it difficult for drivers to see them. Amphibians also tend to go towards light, chasing insects. This can be street lights or vehicle headlights,” says Sur.

The research team noted seasonal variations in roadkill. Nearly 63% of deaths occurred during the pre-monsoon and monsoon months of April to September. “In these months, animals typically move from the low-lying floodplains of Kaziranga to the higher elevations of the Karbi Anglong hills, and the highway runs right across their path,” Sur says.

A simple first-step solution, of course, is to build wildlife bridges and tunnels so that animals can avoid the highway altogether. Until then, one way to make things better is to drive with more caution in or near a reserve or national park. “Just slow down a bit. It could save lives,” Sur says.