Release hopes for orphaned bats

The bats were tracked for the battery life of the transmitters

Specially designed transmitter "bat packs" have been used to track orphaned pipistrelle bats released back into the wild, the RSPCA has said.

Two previous techniques to rehabilitate hand-reared bats had failed, using light-weight radio tags and antenna attached with disintegrating glue.

Pipistrelles released under those two methods had to be rescued and taken back into captivity or died.

But the "bat packs" tracked the bats for five to 10 days before falling off.

The successful technique, tested at the RSPCA's Stapeley Grange Wildlife Centre in Nantwich, Cheshire, involved keeping the bats in an outdoor flight cage for 21 days.

It shows hand-reared pipistrelle bats can survive independently, at least in the short term Dr Andrew Kelly, Stapeley Grange Wildlife Centre

Various methods were used to attract the bats' food of insects, including using ultra-violet lights, planting shrubs and putting decomposing fruit and vegetables in the cage.

This was in contrast to the failed techniques, tested by experts at the University of Exeter and the RSPCA.

The first allowed bats to fly for short periods in an enclosed room before being moved to a box near an existing colony, provided with mealworms and then allowed to emerge when they wanted.

The second involved a greater amount of time for the bats in a larger indoor enclosure and then placing them into a known bat roost.

Dr Andrew Kelly, manager of Stapeley Grange, said the "bat pack" trial had proved hand-reared bats could survive in the wild.

"Bats have to be able to do three things to survive - fly, echo-locate and use their echo-location to catch insects.

"If they can't do any one of these things they'll suffer and ultimately they'll die, and that's not good animal welfare.

"This research is particularly important because it shows hand-reared pipistrelle bats can survive independently, at least in the short term, but only if they get the extensive conditioning we've been providing at Stapeley".

'No distress'

Dr Kelly said the transmitters weighed less than 5% of the bats' body weight and caused them no discomfort or distress.

"We consulted widely with the foremost bat experts in the UK," he told BBC News.

"After the transmitters were attached to their fur, we watched them for two days to ensure they showed to signs of discomfort."

He said the packs would fall off after about four weeks, when the glue on the bats' fur became brittle and broke off.