When Indian wildlife authorities took three Bengal tigers by helicopter to an empty reserve in Rajasthan last year it was hailed as a groundbreaking experiment to revive the country’s flagging tiger population.

Now, some experts fear that the male and two females relocated to the Sariska reserve could all be siblings — reducing their chances of a successful long-term breeding programme.

The Wildlife Institute of India (WII), which is in charge of the project, began testing DNA samples from the three tigers yesterday to decide if they need to introduce others from different parts of the country. It already had blood samples from the two females but had not taken a sample from the male until it was briefly captured on Monday to have its broken radio collar replaced.

“We’re to blame — we should have done this earlier but everything was done in a hurry,” K. Sankar, a WII tiger expert who is overseeing the project, told The Times. “Now we have the samples, the analysis is under way and after that we will be able to say for sure. We’re keeping our fingers crossed.” Results are expected this weekend, when the Indian Environment Minister is due to visit Sariska.

If the tigers are proven to be siblings it would be the latest in a series of embarrassments for Indian wildlife officials, who were forced to admit in 2005 that all of Sariska’s tigers had been killed.

Sariska used to be India’s most famous tiger sanctuary and was at the centre of the Project Tiger conservation programme launched by Indira Gandhi, the late Prime Minister, in 1973. But the programme has failed to prevent India’s tiger population plummeting to 1,411 as of February last year — down from 3,642 in 2002 — largely as a result of poaching.

Last year’s relocation, the first of its kind, was part of a £93 million emergency plan to revive the tiger population, which was estimated at 40,000 a century ago.

Dr Sankar said that Wildlife Institute experts knew the females were likely to be sisters, or half-sisters, because they were relocated from the same area of the Ranthambore reserve, also in Rajasthan. The male was selected from a different part of Ranthambore and there was no evidence that the females were his siblings, he said.

However, critics say that the institute should have carried out DNA tests to confirm its analysis before airlifting the tigers to Sariska. “It’s a very simple procedure,” said Dharmendra Khandal, a field biologist based in Ranthambore.

He said that the WII’s census data showed that one adult male occupied the entire territory where the three relocated tigers were born. Inbreeding is common in the wild — even between a male and daughter. But it could create problems by perpetuating genetic weaknesses.

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