Europe’s bats may offer solution to white nose
Montpelier, Vt. - A scientist studying the mysterious fungal ailment killing millions of bats across Pennsylvania, New York and other states said the experiences of European bats that have been infected with a similar fungus that they've survived could provide lessons in the best way to control white nose fungus.
Most scientists believe the fungus that causes white-nose syndrome in North America was brought from Europe where it was first introduced into caves in New York state. From there it spread into the Keystone State. Definitive proof that the fungus is an invasive species has not yet been shown, though a study that could make that link is nearing completion.
"We have done an experiment and are analyzing the data," said Craig Willis, a biology professor at the University of Winnipeg in Canada, who has been studying the issue with money from the U.S. Fish & Wildlife Service and other sources. "If we find evidence of the invasive species hypothesis, then it makes very good sense on focusing our efforts on European bats in hopes that we might come up with some approach for managing the disease in North America."
While definitive proof is lacking, many scientists studying white nose are convinced the fungus that causes the white patch that gives the disease its name came from Europe, making the fungus another in a long line of invasive species.
Among those that have reached Pennsylvania are the invasive algae known as didymo, or rock snot, that can overwhelm cold-water streams; zebra mussels, that have taken over the shallow reaches of Lake Erie, Asian long-horned beetle, which threatens maple trees; the emerald ash borer, which can devastate ash trees; and, of course, gypsy moths, which have been here for more than a century and strip vast sections of forest most every year.
Bats infected with white nose wake from their winter hibernation and die when they fly into the winter landscape where they can't find food. The fungus was first detected in New York's Adirondack Mountains in 2006 and is spreading across North America. It's believed to have killed at least a million bats, though precise numbers are impossible to determine.
"If you were pondering a perfect storm on cave bats, the nastiest catalysts would be organisms that could exist and strike in the dark, cold and wet environments where bats hibernate," explained Greg Turner, Pennsylvania Game Commission biologist. "Their vulnerability then is unparalleled, because their immune system is shut down to conserve energy. Geomyces destrutans has found this opening. Now it's up to bats to find a defense."
In Pennsylvania, bats spend six months annually in hibernation, riding out winter and living off a finite supply of energy generated from consuming massive quantities of flying insects. Geomyces destrutans irritates the deep-sleeping bats, forcing them out of their hibernation stupor, which requires increased energy consumption from a reserve that barely sustains them through winter. Death often follows, Turner pointed out, regardless of whether the bat stays put or flies out over the winter landscape looking for food that isn't there.
"It would meet the definition of an exotic invasive organism," said Scott Darling, a biologist with the Vermont Department of Fish and Wildlife who has led the state's work on white nose since the mysterious death of thousands of bats in the state was first noticed. "For some of us, the invasive species battle has been focused on reptiles, amphibians or mammals as well as plants. Now we're dealing with microbes - and that's a whole other battle."
In Wisconsin, where white nose has yet to be found, the fungus has been listed as an invasive species. The listing helps officials get the word out about the threat and look for the fungus early on. It also allows the Department of Natural Resources to work with property owners to determine the best management for its site, which could include installing gates on caves and hanging bat closure signs, said Erin Crain, an endangered resources section chief for the department.
Those measures have already been taken at a number of Pennsylvania sites.
The fungus that causes white nose, Geomyces destructans, is almost identical to the fungus found on bats in Europe, but it does not appear to have the mortality in Europe that it does in North America, studies have shown.
Willis said there are two basic theories that could explain why white nose is so destructive in North America, but not in Europe.
One is that the North American fungus existed here but went unnoticed until it mutated and became more deadly. The second is that the European fungus was brought to North America where bats are unable to fight off the infection.
If it is proven to be an invasive species - and the study Willis is leading is expected to be published in three to four months - an important next step would be to try to determine why European bats survive exposure to the fungus and most North American bats do not.
It could be the environment in the caves the European bats live could be different, which would slow the growth of the fungus. If so, steps could be taken to protect certain caves in an effort to ensure the bats are living in a better environment. Or it could be there are biological mechanisms that make European bats less susceptible to white nose
The environment in European caves is different, that would offer a concrete way to protect some of the bats.
"Adjusting the environment of a bat hibernacula is risky and likely impractical, but if we do find that the environment plays a major role in how the disease works, it's something to think about," Willis said.