MONTPELIER, Vt. — Biologists with the Vermont Department of Fish and Wildlife are conducting a second experiment this winter to determine if more bats are passing the winter without waking from hibernation and flying in the frigid air where most die from white nose syndrome.

In recent weeks, biologists have attached radio tags to 1,000 bats captured near the Aeolus cave in Dorset and they installed electronic equipment in the cave that will tell them when the bats fly into the cave and when they leave, said Fish and Wildlife biologist Alyssa Bennett, who is running the experiment.

A similar, but smaller experiment last winter found a promising number of the little brown bats that were tagged survived the winter. But a flaw in last year’s experiment was the result of not turning on the electronic monitoring equipment until after some of the bats had already gone into hibernation.

“We didn’t have data on which bats were picked up going into the cave,” Bennett said. “We’re hoping to get a better idea of the survival rate.”

White nose, which has killed up to 99 percent of some species, is caused by a fungus that prompts bats to wake from their winter hibernation and die when they fly into the winter landscape. It was detected in New York’s Adirondack Mountains in 2006 and continues to spread across North America.

Another thousand bats have been banded as part of another experiment designed to get a population estimate for the Aeolus cave, considered one of the most important bat caves in the region. The last time such a study was done — in the 1960s — the cave held an estimated 250,000 to 300,000 bats, Bennett said.

Bennett said there’s no question the number of little brown bats in parts of New York and Vermont has stabilized, but that good news does not appear to have spread, at least so far, to other areas that were hit by the disease.

Nor does it translate to all affected species. Of the 2,000 bats collected by Bennett and her team, only 13 were northern long-eared bats, a species harder hit by white nose than the more common little brown bats. Northern long-eared bats have been so hard hit by white nose the U.S. Fish and Wildlife Service is considering adding them to the endangered species list.

Last season’s results, even the low survival range would have been encouraging, were the first glimmer of hope since white nose syndrome emerged from a New York cave in 2006 that the crisis might be stabilizing, for a least one species.

Bennett also said the number of bats returning to maternity colonies in the Lake Champlain valley have remained consistent for several years. But even though some maternity colonies are stable in one area they have disappeared from other areas where they were once common.

She said people are also helping bats survive.

“Those colonies that we’ve been watching, for the most a part, are in buildings that belong to somebody, whether it’s a barn or a bat house or an attic,” she said. “Without people looking out for these bats, they don’t stand a chance.”

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