CB BureauForest corridors that allowed India’s tigers to breed with one another are vital for their conservation, according to research that has just been published in the Proceedings of the Royal Society B. Using historical data and genetic analyses, Sandeep Sharma of the Smithsonian Conservation Biology Institute in Washington, D.C., and his colleagues studied the extent of genetic intermingling between tiger populations in five tiger reserves (two of which are directly connected) in the states of Madhya Pradesh and Maharashtra.
The team surveyed around 9,000 miles of forests and trails, including within the reserves and in the forest corridors linking the reserves. They collected anything they found that the tigers left behind, including faeces, hair and claws. In all, they analysed the DNA extracted from nearly 1,500 samples. Using genetic clues, the team identified 273 individual tigers.
The tigers, the team found, had continued to mate and exchange genes with those from different reserves even though some of the protected regions were separated by 70 to 230 miles. The better preserved the forest corridor, the higher the rate of gene flow between populations.
With rapidly increasing infringement in the form of roads, crop fields, factories, mining operations and railroads, India’s tiger population has been forced into smaller, distinct groups restricted (on paper) to manmade tiger reserves. In reality, though, the cats still prowl through strips of forest that connect these far-flung populations, the study has found. These corridors enable the tigers to intermingle and stay genetically strong.
Currently, these forest corridors have no legal protection in India. A mining company has just applied for a lease that would sever one corridor in the study. Such a split could be devastating for the tiger population, warns Sharma. If the isolated group is small, what can eventually happen is a genetic bottleneck, or a reduced amount of genetic variability. In drastic circumstances (climate change, natural disasters, etc.), the lack of genetic diversity may lessen the population’s ability to adapt to external pressures.
The team concludes: These corridors play an important role in maintaining genetic variation and persistence of tigers in this landscape. Reconnecting broken corridors and maintaining existing ones in a politically sensitive and logistically feasible way is a big challenge for conservation biologists and policymakers.
India is home to over half of the world’s tigers, and an official assessment carried out in 2010 estimated that there were about 1,700 of these animals in 39 tiger reserves.