Extinction For Bats in New Jersey?

Fear of Extinction Grows As Numbers of Little Brown Bats Dwindle in N.J.

By: James M O'Neill | The Record

New Jersey’s little brown bat population, once as high as 30,000 at the state’s largest hibernation site, hit a new low of only 600 in a recent count, as the population continues its deep spiral caused by a fungal disease sweeping through Eastern states.

The recent count showed that little brown bats at Hibernia Mine had dropped another 20 percent over the past year, down from an already alarming low of 750, state officials said.

The population began to plummet in 2009 as the bats contracted a fungus that caused tens of thousands to die. The population stabilized for a few years before declining again over the winter, according to state researchers who finished the late season hibernation count a few weeks ago.

“We were disappointed this year, because the numbers had stabilized the past few years,” said Mick Valent, principal zoologist with the state Department of Environmental Protection. “We had been hoping to see at least the same number of bats, if not more.”

In addition to the state’s principal bat hibernation sites — Hibernia and Mount Hope Mine — Valent also visited a dozen smaller sites that previously had groups of 100 or so hibernating bats. He found that only a third of the sites had any bats, and in some cases there were “just a few remaining.”

The bats are being infected with a fungus that causes them to develop a whitish powder on their muzzles, ears and wing membranes, a condition called white nose syndrome. The fungus causes the bats to exhibit unusual behavior, moving around during hibernation, which burns up their stored body fat. As a result, they die of hunger.

A blow to humans

The loss of bats can have repercussions for humans, since bats eat huge quantities of insects that damage crops or carry West Nile virus and other potentially fatal diseases. Bats can also play an important role in agricultural pollination.

Federal officials conservatively estimate the disease has killed nearly 7 million bats since it was first detected seven years ago in a cave near Albany, N.Y.

The disease has spread to 22 states and five Canadian provinces, mainly along the Appalachian range, where hibernation sites are plentiful. Already this year, federal and state officials have confirmed the presence of the disease for the first time in South Carolina, Georgia and Illinois, as well as at Mammoth Cave in Kentucky, Cumberland Gap National Historic Park in Virginia and on Prince Edward Island in Canada.

And earlier this month the U.S. Fish and Wildlife Service confirmed the presence of white nose syndrome at Fern Cave National Wildlife Refuge in Alabama, which contains the largest documented wintering colony of gray bats, which are already on the federal endangered species list. The disease has also hit the Indiana bat, another endangered species.

“The writing is on the wall that certain bat species are in jeopardy of going extinct from the disease,” said Jeremy Coleman, the U.S. Fish and Wildlife Service’s national white nose syndrome coordinator. “We’re continuing to see die-offs in the most affected states.”

Officials are now weighing whether to add three bat species to the federal endangered list because they have been hit so hard — the Eastern small-footed, Northern long-eared, and little brown bat, which had been the most abundant bat until recently. “Yes, there’s a real extinction risk,” Coleman said.

In New Jersey, the little brown bat used to be so ubiquitous that researchers rarely bothered to count the population. Now little brown bats have been so decimated that it appears some endangered species have become more prevalent. For instance, in 2004, before the disease struck, researchers had counted 15,000 little brown bats and 500 Indiana bats hibernating at Mount Hope Mine in Morris County. This past winter, there were still about 500 Indiana bats, but fewer than 100 little browns, Valent said.

Though Indiana bats — already on the federal endangered species list — were clearly infected with the disease, “They appear to have held their own compared with the little brown bats,” Valent said. “It’s puzzling. Why are they surviving? Is it behavioral? Is it where they move to in the mine?”

Another species — big brown bats — do not appear to have been affected by the disease and their numbers are actually increasing at summer colonies. “We suspect they hibernate in houses and buildings and therefore may not be exposed to the fungus,” Valent said.

Bat species that migrate south for the winter and return to New Jersey in summer, such as tree bats, also have not been affected.

The good news, Coleman said, was that the remaining little brown bat populations in other affected states such as New York and Vermont have leveled off even though they are returning to the same infected sites each winter.

“The critical question is, why are these bats surviving?” he said. “We’d like to know if it’s something that is able to be inherited, a genetic trait that can be passed on, or a characteristic of these particular bats such as choosing hibernation sites that might be drier.”

Scientists believe male bats spread the disease in the late fall when they swarm from one hibernation site to another, looking for females to breed with. “The males can travel great distances during this period,” Coleman said. “Apparently the temperature is cold enough at that time for the fungus to persist on the males as they travel. Clearly the bats are carrying the fungus and spreading it.”

Researchers believe the fungus is a strain new to North America. A European strain exists, but European bats evolved genetically to resist it. Researchers think the European strain may have been introduced inadvertently to North America within the past decade by spelunkers who had been in a European cave and then visited an American cave without decontaminating their equipment. North American bats had not been exposed to the fungus before, and had no immunity to it.

Fighting the disease

To make sure humans don’t spread the disease, many caves in the United States have been closed to spelunkers, and officials are urging cave explorers to decontaminate their equipment between cave visits. The disease does not appear to affect humans.

Fighting the disease remains perplexing. Researchers have come up with anti-fungal agents that could work, but applying it to hibernating bats would be impractical.

New Jersey researchers, meanwhile, have found that some infected bats are able to fight the disease under certain circumstances.

As a test, state researchers took some infected bats out of their hibernation sites and provided them with food and other care, but no medication. Since the bats were taken out of their hibernation pattern, their bodies — including their immune systems — were working as if it were summer. “After three or four weeks they were able to clear their body of the fungus — their immune system was able to kick in and fight it,” Valent said. But when infected bats are in hibernation, their immune system shuts down and they can’t fight the fungus.

The fungus sometimes leaves large scars on wing membranes of bats, and they can even lose portions of wing, Valent said. In some of the bats the state researchers cared for, wing holes that were the size of a nickel or even larger healed.

Officials are hoping that pregnant female bats now emerging from hibernation in New Jersey can give birth successfully and begin restoring the population this summer. “My feeling,” Valent said, “is that eventually the disease will run its course.”

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