By Maureen Halsema
White nose syndrome—believed to be caused by a fungus—has already killed about a million bats in the northeastern regions of the U.S. and Canada, and is spreading into Appalachia.
The fungus attacks bats as they hibernate in winter months. Once the fungus starts in a bat cave, 90 to 100 percent of the bats die, and bat carcasses are scattered across the cave floors.
“The biggest concern is that white-nose syndrome [WNS] is moving about 200 kilometers a year,” said Dr. Thomas Kunz, biology professor and director of the Center for Ecology and Conservation Biology at Boston University. “It’s moving at a rate that is typical of an infectious disease.”
Earlier this year, the epidemic hit Virginia and West Virginia, and the Tennessee Wildlife Resources Agency recently confirmed it in that state as well.
Since white-nose syndrome’s discovery in 2006 in a cave near Albany, N.Y., about a million bats have died. A spelunker exploring the cave discovered the disease when he found and photographed several bats with the fungus growing on their faces.
The following winter, January 2007, the New York Department of Environmental Conservation observed and documented the beginning of the white-nose syndrome epidemic.
Thus far, six hibernating bat species in the northeastern U.S. have been affected by WNS, including the big brown bat, tri-colored bat, little brown myotis, eastern-small footed myotis, northern long-eared bat, and the Indiana bat (an endangered species).
Should the disease spread further into Appalachia, there are two other species—both of which are endangered—that may be affected: the Virginia big-eared bat and the grey myotis.
What is the cause of this massive epidemic? The answer is still unknown, but there are several hypotheses.
Many scientists believe that a fungus called Geomyces destructans that thrives in cold and humid conditions is the cause.
The illness is dubbed white-nose syndrome because Geomyces destructans is a fungus that attacks their skin glands and hair follicles and in the later stages grows in white tufts on the muzzle, wings, ears, and tails of many of the infected bats.
Bats affected by the disease display abnormal behaviors, such as moving to the colder sections of the cave and flying during the day and during months of hibernation when their food source is nonexistent and fat stores are vital. These daytime excursions may be desperate attempts to find food, depleting the bats’ remaining energy and fat reserves and effectively starving them to death.
Although this fungus has been observed in Europe’s caves for quite some time, it is new to the scientific world and scientists are not certain if the fungus itself is the cause of death or if it is a secondary symptom.
One hypothesis, the itch-and-scratch hypothesis, suggests that irritation caused by the fungus causes bats to prematurely arouse from hibernation—a side effect of the fungus.
“If they are scratching those itchy places, this is likely to cause higher bouts of arousal and thus they expend energy,” said Dr. Kunz.
To test this hypothesis, studies conducted by Dr. DeeAnn Reeder of the Department of Biology at Bucknell University and Sarah Brownlee, a masters student at Bucknell University, are using infrared motion-sensitive video cameras set up in hibernacula to monitor what bats are doing after they arouse from hibernation.
Another hypothesis proposes that bats are not ingesting sufficient amounts of polyunsaturated fatty acids for their fat reserves to last the duration of hibernation.
To try to combat white nose syndrome, scientists are testing bat immune systems and fungicides to see if they can find a way to combat white nose syndrome before it wipes out North American bat species.
“Another concern is how we could implement a cure if one could be found,” said Rick Reynolds, wildlife diversity biologist for the Virginia Department of Game and Inland Fisheries. “For example, if you found a way to treat white nose syndrome on bats, how do you implement the treatment across the landscape? This would be especially difficult if it is not a one-time-treatment.”
In 2008, the U.S. Forest Service closed down approximately 2,000 caves and mines across the eastern states in an attempt to try to stop the spread of the fungus.
It is possible that unsuspecting spelunkers, who accumulate the fungus on their equipment and reuse that equipment in uninfected caves, are transmitting the disease from cave to cave.
Even if scientists do find a cure, bat populations have already been dealt a severe blow—the majority of bat species are only capable of birthing one pup each year. It would seem unlikely that many populations could recover for many generations. This could have serious implications for the ecosystem, in which bats play a significant role.
“The loss of bat populations at the scale we are looking at right now has economic, ecological and public health implications,” said Dr. Kunz. “Ecologically, bats play an important role in pest control in agriculture and forestry.”
During the warm months of the year, when they are not hibernating, bats can consume up to their body weight each night in insects. With the loss of one of nature’s best pest controls, the use of pesticides to combat insects that attack agriculture and horticulture would likely increase. This would impact public health as well as agricultural economics.
“It’s a pretty dire situation because there is not adequate funding to support the research that needs to be done,” said Dr. Kunz. “We don’t have adequate resources to even go out and monitor some of these colonies. It’s pretty basic biology that we need to understand before we can get to the root causes.”