Roads leading to a large national park in Nepal’s southern plains could increase road accident rates, which could reduce the adult tiger population by nearly two-fifths over two decades, a new study has found.
The study estimated that 46 Bengal tigers (Panthera tigris) could die on the roads near Chitwan National Park, reducing the adult population from 133 to 81 in 20 years. Another 30 tigers could be killed in the same period if a proposed railway line in the area is built, said the study, which modelled its projections using tiger movement data collected in Chitwan since the 1970s.
“The mortality associated with increased traffic volumes and expansions of the roads and railway would have cascading negative consequences on population viability in the long term,” study lead author Neil Carter, from the University of Michigan, told Mongabay.
Since the tiger population in Chitwan is relatively small compared to other habitats in the Indian subcontinent, this 39% decline could put them at greater risk of disease or non-breeding, Carter said. This will increase the risk of their local extinction.
A century ago, around 100,000 wild tigers roamed the grasslands of Asia. But by the early 2000s, their numbers had dropped by 95% due to hunting and habitat loss and fragmentation. During this time, three subspecies have disappeared, the Javanese, Balinese and Caspian tigers.
In 2010, Tiger class countries pledged to double their population by 2022, the year of the Tiger in the Chinese zodiac. Since then, the Bengal tiger population has recovered, and Nepal and India have made progress towards achieving the goal. On July 29, International Tiger Day, Nepal is set to announce its goal of doubling the population in at least some of its protected areas.
Studies have suggested that even the death of one or two tigers, especially females, could lead to a drastic reduction in the overall population. Co-author Narendra Man Babu Pradhan, from the Nepal office of the World Conservation Authority IUCN, explains that tigers not only give birth to their young but also raise and protect them until they can survive on their own.
This means knowing how or when mitigation measures can be put in place, such as animal crossings and underpasses, one or two fatalities can be devastating to the general health of the population.