Green Guide

Report shows no improvement in cave-dwelling bat population

Posted July 9

— The population of cave-dwelling bats, which began declining dramatically about a decade ago, is showing no signs of improvement in Connecticut, according to a new report.

The Connecticut Council on Environmental Quality warns in its recently updated annual report that the continued absence of bats from the evening air will be a "boon to the nocturnal moths and beetles that continually threaten to infest forests and crops."

"Bats have really become beleaguered," said Karl Wagener, the council's executive director. "Bats are actually very important components of the ecosystems, and they're not doing well."

Cave-dwelling bats in Connecticut and other states have been decimated by a fungal disease known as white-nose syndrome. It has been documented in about 30 states since it first appeared in New York in 2006. The fungus thrives in caves and mines, growing on bats' wing membranes and noses while they hibernate.

Each January and February, biologists from the Connecticut Department of Energy and Environmental Protection trek out to caves to count the bats they see hibernating, clinging to the cave walls and ceilings.

Kate Moran, an environmental department wildlife biologist, said they counted 3,300 at one location in 2007. The next year, they found about 300 bats. The year after that, there were fewer than a dozen.

"I think that site just crashed entirely," she said. "We haven't had any activity there in many years."

This year, Moran said, state biologists checked out about a half-dozen locations and determined the population still has not yet rebounded, despite efforts to reduce the spread of the fungus by restricting human access.

"Thus far, there has been no silver bullet," she said. Biologists in Connecticut, she said, are relying heavily on the small pool of bats that have somehow managed to survive, hoping their offspring might be resistant to the fungus.

There has been some evidence that bats may develop a resistance. A study released in December 2016 by Great Britain's Royal Society determined that little brown bats found at several abandoned mines in upstate New York are surviving at rates higher than populations in Virginia and Illinois, where the animals had been more recently exposed to the fungus.

University of New Hampshire researcher Jeffrey Foster, who co-authored the report, told The Associated Press in January he was hopeful resistance to the fungus will occur in other bat species.

In Connecticut, the state biologists banded little brown bats in 2012 to determine how long they might live in the presence of white-nose syndrome. Bats typically can live 20 to 30 years. Moran said she and her colleagues found some of those banded bats alive five years later when they visited the caves last winter.

It is unclear, she said, whether some kind of immunity or behavioral adaptation may be helping that small population of small brown bats remain alive.

"One has to be hopeful," she said. "But the reality is, there are some species that may not survive."

Meanwhile, the Connecticut Council on Environmental Quality report found the big brown bat is now the only one of Connecticut's eight bat species — a list that includes cave-dwelling and tree-roosting bats — that is not classified by state environmental officials as "endangered" or of "special concern. A ninth species hasn't been recorded in Connecticut in several decades.

Tree-roosting species are being harmed by changes to their habitats, Wagener said.

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