Bay Journal

White-nose syndrome taking bite out of bat populations

  • By Kathy Reshetiloff on October 01, 2011
A healthy colony of Virginia big-eared bats, above, hibernate.  (Craig Stihler / West Virginia Department of Natural Resources) White-nose syndrome has taken hold of this little brown bat, left.  (Marvin Moriarity / U.S. Fish & Wildlife Service)

Bats. Just the word makes some people cringe. Despite what movies, television and literature would have us believe, bats are not terrors of the night. One of the most misunderstood and maligned animals, bats are incredibly important to our ecosystem and economy.

As primary predators of night-flying insects, bats help to control many of our most annoying pests. One bat eats as many as 3,000 flying insects a night during the summer months. Some bats consume crop pests including cucumber beetles, June beetles, leafhoppers, cutworm moths and corn earworm moths.

In the animal world, there's nothing similar to bats. They are our only flying mammal. The fingers in a bat's hand are elongated and connected by skin to form a wing. Like all mammals, bats have hair and their young are born live and feed on milk.

Bats are not blind. Those that hunt in the dark have developed a system to help detect objects. These bats produce sounds at high frequencies. By listening to the echoes of these sounds, bats are able to discern objects. This is known as echolocation. Using the reflected sounds, they form pictures in their brains just as we do when we interpret reflected light with our eyes.

Bats are often associated with rabies. Like all mammals, bats can contract the disease but less than 1 percent of bats carry it. Bats with rabies are not very aggressive and die quickly. Like most wild animals, bats will only try to bite when handled. The infamous vampire bat of Mexico and South America is the only species to feed on blood, but mainly that of cattle or other domestic animals.

While tropical bats are active year-round, those in temperate regions either hibernate or migrate during the winter. Many bats hibernate in caves in winter and move to trees and buildings during summer. Some bats reside in caves all year but have different summer and winter roosts.

During hibernation, a bat's metabolism slows so that it uses very little of its stored fat. Heart rates slow drastically and body temperatures drop to 40–60 degrees Fahrenheit. To control body temperature, bats often roost together in great numbers.

Disturbance by people has been a threat to many bat species. Disturbing a maternity colony can cause mothers to drop their young or move them to a less suitable site. Waking bats during hibernation causes them to burn the precious fat reserves they have stored for the winter.

Bats are also threatened by the loss of feeding or roosting habitat, usually wooded areas near water sources. As traditional roosts in trees and caves have been destroyed, many bats seek shelter in man-made structures. Scientists have studied the roosting requirements of bats in order to provide artificial homes. Some bats use these bat houses quite successfully.

Protecting habitat is crucial to bats. Wooded streamside areas need to be protected for roosting. Preventing people from entering maternity caves and winter hibernation caves is critical. Because bats use these caves seasonally, entry may only have to be restricted during certain months. A cave entrance can be gated or fenced, preventing people from entering while allowing bats to fly in and out.

A new threat to bats has emerged: white-nose syndrome. Named for the white fungus that appears on the muzzle and other body parts of hibernating bats, white-nose syndrome has killed more than 1 million bats in the Northeast and Canada. First documented in New York in the winter of 2006-2007, white-nose syndrome has spread rapidly across the eastern United States and Canada.

Bats with white-nose syndrome exhibit uncharacteristic behavior during cold winter months, including flying outside in the day and clustering near the entrances of hibernacula. Bats have been found sick and dying in unprecedented numbers in and around caves and mines. In some hibernacula, 90-100 percent of the bats have died.

Numerous laboratories and state and federal biologists are investigating the cause of the bat deaths. A newly discovered fungus, Geomyces destructans, is associated with white-nose syndrome. Scientists are investigating the dynamics of fungal infection and transmission, and searching for a way to control it.

Eleven bat species and subspecies are already affected by or are at risk from white-nose syndrome, including: big brown bats (Eptesicus fuscus), eastern small-footed bats (Myotis leibii), little brown bats (Myotis lucifugus), northern long-eared bats (Myotis septentrionalis), tricolored bats (Perimyotis subflavus), and the endangered Indiana bats (Myotis sodalist) gray bats (Myotis grisescens), Virginia big-eared bats (Corynorhinus townsendii virginianus), and Ozark big-eared bats (Corynorhinus townsendii ingens). Indiana bats and Virginia big-eared bats are found in the Chesapeake Bay watershed.

At the end of the 2010-2011 hibernating season, bats with white nose syndrome were confirmed in 16 states including: Connecticut, Indiana, Kentucky, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Tennessee, Vermont; Virginia and West Virginia.

Geomyces destructans has also been confirmed in Delaware, Missouri and Oklahoma.

What can you do? Report unusual bat behavior to your state natural resource agency, including bats flying during the day when they should be hibernating (December through March) and bats roosting in sunlight on the outside of structures. More difficult to discern is unusual behavior when bats are not hibernating (April through September); however, bats roosting in the sunlight or flying in the middle of the day would be unusual. Bats unable to fly or struggling to get off the ground would also be unusual.

For information about white-nose syndrome, go to the U.S. Fish and Wildlife Service Northeast Region's website at www.fws.gov/WhiteNoseSyndrome/index.html.

For information about ways to protect bats, contact Bat Conservation International at www.batcon.org; P.O. Box 162603, Austin, Texas, 78716; or 800-538-2287.

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About Kathy Reshetiloff

Kathryn Reshetiloff is with the U.S. Fish and Wildlife Service’s Chesapeake Bay Field Office in Annapolis.

Read more articles by Kathy Reshetiloff

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