A century ago, more than 100,000 tigers roamed across Asia, from the Indian subcontinent to the Russian Far East. Today they are threatened with extinction, only about 4,000 tigers live in the wild. The main threats are habitat loss and degradation, illegal hunting and the decline in their prey.
Thanks to targeted conservation efforts, the tiger numbers have recovered in some parts of their range. In Nepal, for example, the wild tiger population nearly doubled from 121 in 2009 to 235 in 2018. However, a boom in road construction in Asia could reverse this progress.
Land planners and conservationists like me need to know a lot more about how tigers react to roads and railways so we can find ways to protect these animals. We need this information especially for Nepal, one of the least developed countries in the world, but which is working to expand its economy and lift the people out of poverty. Roads and railways quickly spread through the forests and meadows where tigers live.
Neil Carter, CC BY-ND
Expansion of the infrastructure in Nepal
Little research has been done into how transportation networks threaten tigers, but the few studies that exist show strong effects. In Russia, for example, vehicle collisions caused 1 in 12 tiger deaths monitored from 1992 to 2005. In China, tigers were five times more likely to occupy areas 4 kilometers or more from roads than they were near roads.
In India, a study estimated that widening highways along with unplanned development would increase the risk of tiger extinction in protected areas over 100 years by 56%. The growing network of transport infrastructure in Asia could therefore be catastrophic for Tiger.
New development projects in Nepal will lead through large, lowland forests that are home to tigers, rhinos and elephants. Nationwide roads such as the East-West Highway and the Poststrasse are being expanded and expanded from two to four lanes to enable faster traffic.
The planners are designing new electrified elevated railways that run across Nepal, which is roughly the size of Iowa. A “megahighway” is currently being built from Nepal’s capital Kathmandu to Nijgadh, where the Nepalese government has been trying to build a large international airport for more than 20 years.
Highways pose a growing threat to wildlife
Better roads can bring much-needed social and economic benefits to Nepal, but the nation is building them faster than scientists can judge how they affect endangered species like tigers. In Banke National Park, 45 of 67 wildlife deaths – including key tiger prey such as sambar deer – were due to traffic accidents between July 2018 and July 2019.
In recent years, tiger deaths and injuries from vehicle collisions on major roads have increased, although they are still rare. Before 2019, only one vehicle collision with a tiger along the highway in Bardia National Park had been recorded. In the past two years, five tigers have been hit by vehicles in national parks – three in Bardia and two in Parsa National Park.
Vehicle deaths make it difficult for tigers to move from one population to another, reducing their genetic diversity. Further collisions could increase the risk of extinction for the tigers.
Roads also appear to be a hub for conflict between humans and tigers. A tiger in Bardia National Park recently pulled a passenger off a moving motorcycle that was driving through the park. The tiger killed and ate the person. Last year, three tigers killed nine other people in the same area.
Reveal the hidden life of the tiger
To respond to this unprecedented challenge, I am working with colleagues from the Nepalese Ministry of National Parks and Conservation, the National Trust for Nature Conservation and the International Union for the Conservation of Nature in Nepal. We place tiger collars on tigers that live near roads to better understand how transportation infrastructure affects the biology and ecology of tigers. Our initial focus is on the Bardia and Parsa National Parks, where traffic development could significantly hamper the recovery of the tigers.
Nepal has long been a world leader in tiger research and conservation. The Smithsonian-Nepal Tiger Ecology Project, an international collaboration that began nearly 50 years ago, was one of the first to use radio telemetry collars to track tigers for conservation research.
In the past, ecologists took radio receivers into the field to carefully triangulate the tigers’ locations in natural landscapes once or twice a day. Our new research project builds on this work and uses modern tracking technology to gain new insights into tigers in landscapes that are changing human development.
The collars are connected to GPS satellites several times a day and provide detailed information on the tiger locations. This data can show how tigers move around roads before and after crossing them. How much energy do they use near and far from roads? where and how they hunt near roads; how they react to vehicle traffic at different times of the day; and what their behavioral patterns are near streets versus far away from streets. By analyzing hormones in feces deposited by the tiger collars, we can even understand the stress they experience near roads.
We can already see that the east-west highway that bisects Parsa National Park is blocking the movements of the first tiger collar and restricting its territory. With this knowledge, we can predict a number of impacts new transport projects will have on tiger habitats and populations.
Krishna Hengaju, CC BY-ND
Creation of a tiger-friendly infrastructure
Our employee, Hari Bhadra Acharya, former head of the Parsa National Park and current chief ecologist with the Nepalese government, is striving to make the transport infrastructure more tiger-friendly. For example, we can provide advice on the alignment of roads and railways to avoid high priority habitats.
We can also target habitat restoration and prey activities in areas that tigers use frequently or are important for reproduction. Planners can design and locate wildlife crossings to help tigers cross roads and railways. And we can show where roads need to be closed to vehicle traffic at night or enforce speed limits to reduce the risk of tigers being killed in traffic.
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Information from the GPS collars can also help reduce tiger-human conflict and improve law enforcement. For example, we can find out if roads and railways interfere with tiger hunting strategies and cause them to hunt domestic animals or people instead of wild prey. Our data can also help wildlife managers respond more quickly to tiger injuries, disease, or poaching.
I believe that over time this information will provide evidence-based solutions that will ensure roads work for humans while minimizing damage to tigers and other endangered species.