Fatal crossings: tigers in 26 reserves under threat

Cats die in accidents on highways without safe passages

Updated - December 01, 2021 06:34 am IST

Published - January 06, 2018 11:12 pm IST - Kochi

In peril:  A tiger walks on a road linking villages at the Tadoba Andhari Tiger Reserve in Maharashtra.

In peril: A tiger walks on a road linking villages at the Tadoba Andhari Tiger Reserve in Maharashtra.

On New Year’s eve, a fast-moving vehicle on Maharashtra’s National Highway 6 killed Bajirao, one of Bor Tiger Reserve’s charismatic, dominant male tigers.

The same day, a team of scientists published the findings from their latest research: roads with high traffic are sounding the death knell for the tiger in this part of the country. Unplanned expansion of national highways without mitigation measures (such as underpasses created for wildlife) could greatly increase the probability of tiger extinction in Central India’s protected areas, home to one of the largest tiger populations. But new and expanded roads continue to slice through most of India’s protected areas.

Second largest

According to the National Highways Authority of India, the country’s road network, at approximately 33 lakh km, is the second largest in the world. Many of these roads — including national and State highways — cut through at least 26 tiger reserves, says a draft guidance document of the Wildlife Institute of India (WII), framed to reduce the impact of roads and railway lines on wildlife.

Leopards, snakes, deer, desert fox, golden jackals, civets and critically endangered amphibians are among the wildlife that perish on roads in States as far flung as Assam, Rajasthan, Uttar Pradesh and Tamil Nadu.

For tigers, like many other species, traversing large areas to move across habitats involves crossing of roads.

This is the only way they can ensure genetic diversity, which is vital for species survival. When scientists from the National Centre for Biological Sciences (NCBS) and other organisations extracted genetic material from the scat of 116 tigers to study genetic diversity across 11 protected areas, they found that human settlements and traffic intensity — which restrict tiger movement between populations — decreased genetic exchange the most.

The areas they looked at included Bor, where Bajirao, or BTR T-2 as he was known to researchers, sired cubs. The study also covered three territorial forests across Madhya Pradesh, Maharashtra and Chhattisgarh.

The team found that if unplanned development continued, it could result in a 56% higher average extinction probability for tigers within protected areas, due to lack of genetic connectivity.

“If the same rate of landscape change as we have seen for the past 12 years continues, small tiger populations like the ones in Bor and Tipeshwar Wildlife Sanctuary are unlikely to survive into the next century,” says author Prachi Thatte from NCBS. “Isolated populations – like the one in Panna – are also likely to go extinct.”

But new roads in protected areas affect and road widening, attract more traffic. In 2001, scientists studying a 9-km stretch of NH 7 which passes through Pench Tiger Reserve in Madhya Pradesh recorded 490 snakes killed in just two years.

In the south, wildlife biologist Sanjay Gubbi and his colleagues studied the impact of vehicular traffic on the use of road edges by large mammals along the Mysore - Mananthavadi highway, which passes through Nagarahole Tiger Reserve seven years ago. Camera traps kept on two consecutive sections of the same highway – one closed to vehicular traffic and the other open to vehicles only during the day – the team found that spotted deer, Indian gaur and elephants frequented the segment with higher vehicular traffic density far less, suggesting that they avoid busy highways.

Rituals and roadkills

Scientists found some years ago that religious tourism, which is concentrated across a few months of the year, also killed 56 species on roads passing through the Kalakkad Mundanthurai Tiger Reserve; they recorded a 299% increase in roadkills and a 648% increase in deaths of nocturnal species during this period over the baseline. Conservationists also write about how poachers in south India confessed to illegally hunting deer – including tiger prey like spotted deer – in Bandipur, Bhadra and Biligirirangaswamy Tiger Reserves by driving on roads at night.

In 2008, night traffic was stopped on a 27-km stretch of the Mysore-Mananthavady Highway within Nagarhole National Park; in a first for India, authorities also re-aligned the highway out of the protected area, and invested in repairing the alternative route in 2012. Now, Tamil Nadu’s Mudumalai Tiger Reserve and Gujarat’s Gir National Park and Velavadar Wildlife Sanctuary have also either diverted roads or implemented night closure.

“Closing roads at night will certainly ensure lower casualties,” says Mr. Gubbi. However, options for emergency commuters have to be provided, he adds. “Some compromises are necessary, along with science, outreach and logic.”


Roads and widening projects in wild habitats exacerbate what scientists call ‘edge effects’: this alters plant communities (such as aiding the spread of invasive exotic species like Lantana camara ) due to the disturbance along road edges. It can also change animal behaviour.

Wherever possible, it is crucial to ensure alternative roads outside ecologically important areas, says Gubbi, who continues to study the impacts of roads on wildlife in Karnataka. “If there is no other option, impact has to be to minimised. Mitigation measures are very region - and species - specific and these should be taken into account.”

In Tamil Nadu’s Valparai, the endangered Lion-tailed macaque was a frequent victim of roadkills on the narrow hill roads weaving through coffee and tea states, till 2011. Today, they cross the roads overhead, using seven canopy bridges installed by the Nature Conservation Foundation and the Forest Department in the Puduthotham and Varattuparai estates. Speed breakers also slow down speeding vehicles.

States like Maharashtra, where Bajirao was killed, need other remedial measures: NH-6 and NH-7 intersect at least six tiger corridors in the Vidarbha region alone. In 2016, WII charted out guidelines for mitigation — such as creating underpasses and planting vegetation — to be followed while implementing new road projects. The National Tiger Conservation Authority (NTCA) has already prescribed the implementation of some of these on NH-6 and NH-7 to the NHAI, says Debabrata Swain, Director, NTCA.

“On NH-7, flyovers for traffic to facilitate underpasses for wildlife are already under construction and will be ready soon,” he says. “Measures on NH-6 are is also being implemented.”

However, these will not be offer relief on existing roads; they can be added only to new roads or those that are widened, says Maharashtra Forest Department’s Chief Wildlife Warden A.K. Mishra.

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