University of Michigan ecologist: 'Our results provide clear evidence that vehicle traffic on major roads impedes tiger movements'

Researchers from the University of Michigan conducted a study in Nepal tracking the movement of two tigers that were tagged with GPS collars during a nationwide COVID-19 lockdown. The study revealed that the tigers were more mobile during lockdown than before.

“Our results provide clear evidence that vehicle traffic on major roads impedes tiger movements, but also that tigers can respond quickly to reductions in human pressures,” Neil Carter, the study's lead author and a conservation ecologist at Michigan's School for Environment and Sustainability, said in a release by the university.

Carter's team found that the tigers were two to three times more likely to cross the highway during the lockdown and exhibited relaxed avoidance behaviors. The study was the first to use GPS collars to assess the impact of traffic on tigers' movement patterns, giving valuable insight into the effects of roads on endangered species. Researchers said the data showed the importance of mitigating road impacts to allow tigers to roam their territories.

The study, published in Global Ecology and Conservation, was the first research on Nepalese tigers using radiotelemetry, or GPS tracking, since the 1980s. Roads pose significant challenges to the conservation of endangered species, especially carnivores. Because large carnivores need large habitats and have low reproductive output and low population densities, animals such as tigers are particularly susceptible to the impacts of roads. The fewer than 4,500 tigers remaining in the wild, most of which live in South Asia and Southeast Asia, face human development pressure as the construction of roads in tiger habitats continues to increase and threaten the species.

The widening of the East-West (Mahendra) Highway in Nepal's southern lowlands, home to all of the country's approximately 250 tigers, poses a major threat to conservation, the study found, as the road cuts through all tiger-bearing parks in Nepal, as well as vital habitat corridors and bottlenecks. The study's authors worry that the lack of mitigation measures will continue to harm the endangered big cats.

The study found that the male tiger's home range expanded significantly, and he crossed the highway more frequently during the lockdown, especially at night. In contrast, the female tiger displayed less sensitivity to the highway, although she crossed easier during the lockdown, and her home range contracted during the first month of the lockdown.

Researchers said the differences were down to variations in traffic patterns, regulations and ecological conditions, as the female living in Bardia National Park lived in an area with tightly controlled traffic speed enforced by armed guards, meaning traffic caused less disturbance. The male inhabited an area in Parsa National Park where speed limits were not enforced. So, the highway created a movement barrier that was removed during lockdown, the study shows.

Carter's team plans to track more Nepalese tigers in the future, and they urged policymakers in Nepal to take proactive measures to mitigate the impact of the highway project on wildlife.