A fierce attempt to keep endangered Virginia big-eared bats alive in captivity has shown just how difficult that noble task may be.
The effort was prompted by the discovery of white nose syndrome, an extremely virulent disease that has killed more than a million bats since 2007, in one of the handful of caves where Virginia big-eared bats live. Of 40 bats moved to the Smithsonian National Zoo last November, only 11 have survived.
“We were not under the illusion that it was going to be easy. It’s certainly not a surprise to us that the bats died. But the number of bats that died is greater than we had hoped,” said Jeremy Coleman, white nose syndrome coordinator at the U.S. Fish and Wildlife Service.
The captive colony project was controversial from the start. With only 15,000 Virginia big-eared bats in existence — up from 3,500 in 1979, but far below historic levels — risking even a few is no small matter. The project also cost $300,000, a big chunk of the $1.9 million allotted by Congress for research on white nose syndrome, or WNS.
In the three years since its original detection in an upstate New York cave, WNS has spread south as far as Tennessee, exterminating bat colony after colony with almost total efficiency. The disease appears to be caused by a fungal infection that rouses bats from hibernation, leaving them weak and unable to find food.
There is no known cure, and scientists say that many cave-dwelling bat species — including the little brown bat, the most common bat in North America — could be extinct in a decade. They call the bat die-off “the most precipitous decline of North American wildlife in recorded history” (.pdf).
Early in 2009, WNS was found in a West Virginia cave where Virginia big-eared bats lived. Though infected bats belonged to other species, the discovery was frightening. The Fish and Wildlife Service decided to found a captive colony.
“There were many scientists who didn’t think it would work at all, and are philosophically opposed to captive bat populations anyway. The other school of thought is that desperate times call for desperate measures,” said Peter Youngbaer, WNS liaison for the National Speleological Society. “If this species was going to get WNS, and if you didn’t start an intervention now, you’d never have a chance.”
Unlike fruit-eating bats, insect-eating bats like the Virginia big-eared are notoriously difficult to raise in captivity. Accustomed to catching insects on the wing, many of the bats refused to eat worms from pans. Stressed from relocation and habituated to cave-specific temperatures and humidity, others developed runaway bacterial infections. Despite constant attention from researchers, 29 of the bats died.
The Fish and Wildlife Service is now preparing a report on lessons from the experience, though these may be uncertain. “I think they have more unanswered questions than lessons now,” said Youngbaer.
And trouble for the remaining wild bats keeps coming. In February, the first cases of WNS were found in West Virginia’s Hellhole Cave, home to populations of Indiana bats, little brown bats and almost half of all Virginia big-eared bats.
There are no plans to add more bats to the colony, but Coleman said captive breeding remains an option for other species threatened by WNS. In the meantime, it remains to be seen whether the 11 captive bats will survive and even breed.
“There are so few members of that species left. With the captive colony, the thought was, let’s see see if we can get this to work. And then we’ll have done what we can to save them,” said Youngbaer. “At least we won’t have regrets for not having tried.”
Image: Healthy Virginia big-eared bat. /USFWS