More than 100,000 tigers ranged across Asia a century ago, from the Indian subcontinent to the Russian Far East. Today they are endangered, with only about 4,000 tigers left in the wild. The greatest threats they face are habitat loss and degradation, illegal hunting and declines in their prey.
Thanks to focused conservation efforts, tiger numbers have rebounded in some parts of their range. In Nepal, for example, the wild tiger population has nearly doubled from 121 in 2009 to 235 in 2018. But a road-building boom in Asia could undo this progress.
Land planners and conservation scientists like me need to know much more about how tigers respond to roads and railways so we can find ways to safeguard these animals. We especially need this information for Nepal, which is one of the least-developed countries in the world but is working to expand its economy and raise people out of poverty. Roads and railways are spreading rapidly through the forests and grasslands where tigers live.