Vultures in genetic bottleneck
as vulture population declines in south Asia, scientists have warned of a possible risk. The oriental white-backed vulture (Gyps bengalensis), classified critically endangered by the iucn, may soon lose its genetic diversity unless immediate measures are taken.
The bird was numbered tens of millions in India, Nepal and Pakistan until the mid-1990s, when its population began to collapse, primarily because of anti-inflammatory drug diclofenac (see 'What's eating the vulture?' Down To Earth, January 15, 1999). By 2007, only 11,000 oriental white-backed vultures were left in the wild, according to the Bombay Natural History Society (bnhs) census. Scientists from the University of Michigan, The Peregrine Fund and Wildlife Conservation Society recently carried out a study to understand how genetic diversity of the vulture has changed as its population dropped.
Genetic diversity within a population plays an important role in the survival and adaptability of a species. When the diversity dwindles, often because of population collapse, the species becomes vulnerable to extinction.
Jeff A Johnson who was with the Michigan university and his team collected dna samples from the bird's only remaining breeding colony in Pakistan between 2000 and 2007, and compared them with samples from museum specimens collected before the decline began. They used computer simulations to see how fast the bird's genetic diversity has changed and also determined how large a population should be to preserve optimum genetic diversity. To retain 90 per cent of the current genetic diversity for a century at least 300 birds need to be bred in captivity, the scientists said in a report published in Biological Conservation (Vol 141) in September. They suggested collaboration between India and Pakistan for this.
"Though captive breeding is the solution, due to funding problems and difficulty in catching the birds, there are only a few vultures in captivity. We have 75 oriental white-backed vultures at three captive breeding centres in India," said Vibhu Prakash of bnhs. Two vultures hatched at bnhs field station in Pinjore, Haryana, last year. The other captive breeding centres are at Guwahati in Assam and near Buxa in West Bengal. There is also one breeding centre each in Nepal and Pakistan. "But most of the vultures in captivity are juvenile, which means it will take another few years before they start breeding," said Prakash.
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