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Survey: White-nose syndrome decimates N.H. bat population

A cluster of little brown bats infected with white-nose syndrome were found in a New Hampshire mine during a survey in 2009. That was the year the disease was first documented in the state. Courtesy: NH Fish and Game.

A cluster of little brown bats infected with white-nose syndrome were found in a New Hampshire mine during a survey in 2009. That was the year the disease was first documented in the state. Courtesy: NH Fish and Game.

The two-person team maneuvered over a sheet of ice before sliding into the dark dampness of a Grafton County mine. Amid the icy stalagmites and stalactites, the group’s headlamps illuminated a single, reddish bat clinging to the rocky ceiling. In the soft glow, it was clear the animal was infected – a white fungus covered his muzzle and wing. By the time the team reached the end of the cave, the situation was far darker.

“There were no other bats,” said Emily Preston, a wildlife biologist with New Hampshire Fish and Game. “You go in very hopeful, and the further you go, the hope starts to fade away.”

During the winter hibernation, that mine once housed 948 bats. But that was in 2009, before a fungal disease known as white-nose syndrome decimated the state’s bat population.

In early March this year, New Hampshire biologists surveyed three mines across the state, out of the eight that they know bats call home for the winter. In all, the researchers counted 28 bats – down from more than 2,900 in 2008.

It’s the first time the state has done a comprehensive survey since 2011, when bat numbers were so low researchers didn’t want to risk disturbing the population. The teams returned to the sites this year with tepid hope, but found disheartening results. At the state’s largest bat hibernation site, in Coos County, which held roughly 1,800 bats in 2008, researchers counted 27.

Missing entirely from the count were the little brown bat and the northern long-eared bat, two formerly very common species in New Hampshire. Across the entire Northeast, more than 90 percent of those two species have died from the disease.

“It’s awful. You feel like you are watching an extinction happen,” Preston said.

White-nose syndrome was first documented in bats hibernating in New York in 2006. The disease was discovered in New Hampshire bats during winter 2009, at the height of the state’s wintering population.

The fungus thrives in the same conditions that bats seek out for hibernation: high humidity and 40 to 50 degree temperatures. The white fuzz grows into the bats’ skin, damaging their wings. It also causes the bats to wake up more frequently during hibernation, which depletes their stored body fat more quickly.

“What appeared to be killing bats is starvation and dehydration,” Preston said. “In desperation, they will fly, and if they are flying in February, in New Hampshire, they are doomed.”

The state will still have bats come summer because most of the New Hampshire bats hibernate next door in Vermont or in New York, said Scott Reynolds a bat biologist from Concord’s St. Paul’s School who has surveyed the state’s bat populations. But, there will likely be lower numbers because white-nose syndrome has affected the entire region, and Vermont has also seen severe declines.

“Every winter we are basically increasing the number of states, as (the spread of white-nose) marches west and southwest,” said Jacques Veilleux, a professor of biology at Franklin Pierce University, who has been working with bats in the state since 2004.

Just last week, researchers announced they found evidence of the disease in bats in Wisconsin and Michigan. “At this point a lot of the focus has to do with are there ways to mitigate the spread,” Veilleux said. “It is one of those situations that is very, very difficult to control.”

Bats infected with the spores can spread the disease when they meet up with summer colonies after coming out of hibernation. It can also be spread by humans who explore caves and carry out the fungus on their gear or clothing.

The spread of the disease and the loss of bats could have a larger effect on local ecosystems. Bats are the biggest predator of night flying insects, Preston said, and when a mother bat is nursing, each day she can eat her weight in bugs.

“We have to anticipate there is going to be a boom . . . to those insect numbers, any agricultural pest, disease carriers, we could end up with issues there,” Veilleux said.

There isn’t a cure for bats who have the disease, but researchers have seen a stabilization in some of the original white-nose sites in New York. In Ontario, some of the populations have stabilized and slightly increased, Reynolds said.

“There seems to be a remnant population that are through the worst of it and are slowly, slowly recovering,” he said. “We’re hopeful this remnant population is a true resistant group . . . (and) those bats, if allowed to, will slowly repopulate and get us back to where we were.”

But it could take at least a century for the population to return to the pre-white-nose numbers, Reynolds said. Bats usually have one pup a year, and those babies have a fairly low survival rate.

“To rebuild the population will take decades. . . . If it can ever happen,” Preston said.

In the meantime, she urges people to take care of every bat left, and for homeowners to consider living with any bats that have taken up residency in their barns or sheds.

“As long as there are still bats on the landscape,” she said, “there is hope.”

(Allie Morris can be reached at 369-3307 or at amorris@cmonitor.com.)

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