Animal instinct seems to have won over human intervention in one particular case as a pair of tigers detached the radio-collar fastened onto a tigress less than two weeks ago by officials of the State's forest department as part of the ongoing tiger census.

The abandoned, fully functional radio-collar was found in fairly good condition in the Pirakhali forest area of the reserve on Thursday.

“For the last three days we had stopped receiving the satellite signal from the tigress so we went into the forest area to investigate. By tracing the collar via an antenna we found that it had had fallen off,” said Subrat Mukherjee, field director of the Sunderban Tiger Reserve (STR).

The collar will be fastened to another animal after the nuts and bolts have been changed, Mr. Mukherjee added.

So far, radio collars have been fastened to two tigresses as a part of the tiger census.

The project, for which the reserve paid Rs. 35 lakh to the Wildlife Institute of India (WII), involves the tagging of 8 tigers within the reserve that will be monitored for about a year by experts of the institute and officials of the forest department.

While the instance of a radio collar falling off is not uncommon (there have been 17 such incidents all over the country), concerns have been raised about the success of the initiative in the Sunderbans.

In December 2007, a tigress was fitted with a radio collar which stopped functioning in just over three months, after the animal had roamed an area of 35 sq km. Although the cause of the malfunction could not be ascertained, it is speculated that a “saline water shock” could be responsible.