Using genetic information and simulations to predict the future of wild tigers in Central India

© Prasenjeet Yadav

Aditi Patil

Human activities haveaccelerated the decline and extinction of several animal species in recent times. The frequency with which we are losing biodiversity is higher than ever before. Habitat loss is a major threat to animals across the globe. Forests, grasslands, deserts, and other natural habitats are being replaced by human settlements, roads and industries. Most mammals have lost over half of their historical ranges over time. This has led to a decline in animal populations, placing them at a higher risk of extinction. Fragmenting large tracts of natural habitat is forcing animals to live in increasingly smaller and isolated areas. These small populations may not be able to survive on their own. If isolated animal populations can remain connected to each other through a network of structural and functional corridors that can be used by wildlife, their long-term survival can be secured. Animals will be able to migrate between populations with minimal human disturbance. Maintaining connectivity between animal populations will reduce the chances of local and global extinctions of species.

Large carnivores in particular are highly vulnerable to habitat loss because they are long-ranging and need large enough space to thrive. The tiger (Panthera tigris) has lost over 93 percent of its historical range and is now confined to increasingly fragmented habitats. It is globally listed as an endangered species. Four subspecies of tigers have already become extinct. Currently, most conservation efforts for wild tigers in India are concentrated in protected areas like tiger reserves and national parks. While this is important, it should be noted that about 35 percent of India’s tigers are estimated to live outside protected areas. These tigers, residing outside protected areas, likely play an important role in maintaining connectivity among protected areas. With a constant increase in human population and development, landscapes outside protected areas are changing rapidly. Understanding the impacts of changing landscapes on tiger connectivity is crucial to understand potential threats and risks to survival of tiger populations into the future.

A Bengal tiger in Kanha National Park, Madhya Pradesh (Dey.sandip, CC BY-SA 3.0, via Wikimedia Commons)

Research study

A recent study published in Biological Conservation looked at current tiger connectivity in Central India and how it is likely to change in the face of future development. It examined genes of tigers living in protected areas, as well as those residing outside protected areas. By analysing this genetic information, the scientists were able to understand how various features of a landscape influenced tiger movement and connectivity. With this knowledge, the scientists then performed several computer simulations. They predicted how tiger survival will be affected under different future development scenarios.

The results of this study show that while tigers can navigate through farmlands and small villages, dense human settlements and high traffic roads are detrimental for tiger movement. Both, urban areas and road traffic are set to increase in the future. The simulation results establish that unrestricted development will result in extinction of several populations and decrease genetic variation. Protecting corridors would be critical to preserve genetic variation and minimize extinction risk. Certain other measures need to be taken as well. Along with an overall increase in tiger numbers, small intermediate populations should be maintained between protected areas. These populations will act as stepping stone groups between larger populations, thus helping in maintaining a network of tiger connectivity. A buffer area should be maintained, especially outside the boundaries of protected areas, to accommodate more tigers and reduce the strain of direct human-wildlife interaction. Careful planning and assessment will help to map and identify locations that can be earmarked for development with minimum effect on tiger habitats and connectivity.

Future implications

India, a stronghold of the tiger, is witnessing an unprecedented rate of human growth and development. Cities are expanding. Newer roads are being built every day. Existing roads are being widened to accommodate more traffic. More land is being used for agriculture. The landscape of our country is changing rapidly, and it is becoming increasingly important to balance development and environmental protection most assiduously. This study is an example of science that can inform policy and planned development. Informed conservation efforts are needed to ensure long-term survival of tigers.

Original paper: Thatte, Prachi, et al. “Maintaining tiger connectivity and minimizing extinction into the next century: Insights from landscape genetics and spatially-explicit simulations.” Biological Conservation 218 (2018): 181-191.