Indian rhinos have skewed sex ratio


Photos by Rajibaksha Rakshit

THE ONE-HORNED rhino has defecated its way to a worrisome revelation – its sex ratio is more skewed than that of humans in India.

The first ever rhino census through genetic analysis of dung samples collected from Gorumara National Park in West Bengal in April 2011 put the number of the armour-plated herbivore at 43. More importantly, it confirmed what error-prone conventional animal census methods said earlier this year – rhinos have a male-female sex ratio of 4:1.

The census was carried out by Assam-based NGO Aaranyak, which developed the technique of DNA fingerprinting by analysing dung over a year. The NGO has also provided technical support to genetic population estimation of Javan and Sumatran rhinos, the other two species of Asian rhinos.

“Dung provides the source of DNA sample of every individual and find out its sex. Besides being error-free,this method negates catching of animals which is easier said than done,” UdayanBorthakur, Aaranyak’s dung analysis expert said. “The only thing we cannot estimate is the animal’s age.”

The conventional method – headcount by field workers – applied by the West Bengal forest department at Gorumara almost matched with the genetic method. It revealed the park had one female for 3.5 males.

“The conventional method is suspect because it is not easy to ascertain the sex of rhinos in the field, particularly the sub-adults whose genitals are difficult to notice,” Borthakur said.

According to Assam chief wildlife warden Suresh Chand, the skewed sex ratio is a matter of concern since it could impact the animal’s reproduction. “The dung route to DNA fingerprinting will be taken for rhino habitats in Assam too,” he said.

Assam has 55% of the world’s one-horned rhinos, the bulk of them in Kaziranga National Park followed by Orang National Park and Pobitora Wildlife Sanctuary. These three habitats together have 2,483 rhinos.

“We hope the rhino population in these preserves do not turn out to be as skewed as in Gorumara,”Aaranyak secretary Bibhab K Talukdar said.

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About rahconteur

A mid-career journalist who's worked horizontally across India - from Arunachal Pradesh to Gujarat
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