White Nose Syndrome is decimating populations of North American bats that hibernate in caves. The disease was identified in the winter of 2006-07 in New York by a cave explorer who noticed hibernating bats with a fuzzy white growth on their snouts. Since then the disease has spread west in the U.S. and in Canada. Ed Heske, a mammal ecologist with the Illinois Natural History Survey at the University of Illinois, answered questions about the syndrome in an interview with Jeff Unger, of the U. of I. News Bureau.
What happens to bats afflicted with the syndrome?
Typically, they acquire a white fungal growth on their muzzle, wing membranes, and other body parts during hibernation. By late winter, afflicted bats usually become emaciated and show unusual behaviors such as arousing from hibernation more frequently than normal, flying outside of caves in the daytime when it is still too cold and early in the year for normal emergence, and clustering near the entrances of hibernacula. Most afflicted bats die, apparently from starvation and dehydration.
Do scientists know what causes the syndrome and whether a cure is imminent?
The white growth is a newly described species of fungus, Geomyces destructans. Most biologists assume the fungus is the cause of the disease as well as the most obvious symptom. The fungus is psychrophilic, which means it is cold-loving. It grows best in temperatures around 12 degrees C (about 54 F), and seems unable to grow in temperatures above 20 degrees C (68 F). When a bat is active during the summer, its high body temperature as well as the higher environmental temperatures likely inhibit fungal growth. While a bat is hibernating, ambient temperatures are right for fungal growth, and the bat’s immune system is also suppressed. Related species of fungus occur naturally in many caves in the U.S., and remarkably, this “newly described” species was found in caves in Europe in 2010, but European bats do not seem to be affected. There is no evidence of any health consequences for humans.
There also is no cure on the horizon. Attempts to treat infected bats with topical fungicides have often resulted in mortality of bats; they lick the fungicide off their faces and wings. Fungicides that might be broadcast in caves would likely harm many other species and disrupt fragile cave ecologies.
Some have suggested using heaters to provide local, warm areas where infected bats might go to recover, or at least reduce energy expenditures, but this and many other suggestions have not yet produced promising results.
How serious is this disease? Is it the bat equivalent of Colony Collapse Disorder among the honey bees?
WNS has been called the most devastating wildlife disease epidemic yet recorded. Over a million bats have been estimated to have been lost to the disease, and by the second or third year of infection, 90 to 100 percent of the bats in many long-term hibernacula in the northeastern U.S. have died. Because bats have what is called a “slow” life history and low reproductive rates (most hibernating bats have only a single young per year), recovery of decimated populations will be slow if some way to combat this disease is eventually discovered, or some bats develop resistance. Some models predict that currently common and widespread species, such as the little brown myotis (Myotis lucifugus), may become endangered species within a few years.
There is much about this disease we do not know – more questions than answers at this point. So far, it appears that WNS affects primarily cave-hibernating bats, but those are about half of the 45 species of bats occurring in the U.S.
Has the disease been detected in Illinois? If so, will it have any noticeable effect on insect numbers?
If WNS does not already occur in southern Illinois, where most known bat hibernacula occur in the state, it will likely be there by winter 2011-2012. Monitoring of Illinois bat hibernacula is done or coordinated by the Illinois Department of Natural Resources.
Illinois bats are all insect eaters, although they differ on which kinds of insects they eat. We tend not to notice bats because they are nocturnal and generally unobtrusive. Eight of the 12 species of bats found in Illinois are known or considered to be susceptible to WNS. Four of these are fairly common and widespread, two are federally endangered (thus rare), and two occur only in a few places in southern Illinois but are more widespread further south. The other four are migratory and do not hibernate in caves. Will insect consumption by species of bats that are not impacted by WNS compensate, at least partially, for the species that are? Will farmers apply more pesticides if they notice increases in harmful insects usually consumed by bats? Will other, unanticipated ecological interactions emerge if predation rates on certain species of insects change, or some bat species are extirpated? This is not the way any ecologist would want to go about investigating those questions.
