White-Nose Syndrome: Mystery Bat Killer

Researchers have yet to confirm the cause of white-nose syndrome, an often fatal fungal infestation that has claimed more than a million bats.

| August/September 2010

white-nose syndrome

What we know: White-nose syndrome is detected by the presence of geomyces destructans, a white fungus that appears around the bats’ muzzles.


Researchers are struggling to pinpoint the source of a mysterious bat illness known as “white-nose syndrome.” The illness has been confirmed in 14 states and two Canadian provinces, and has resulted in more than a million bat deaths since 2007.

The name of the illness comes from the presence of a white fungus on bats’ muzzles. White-nose appears to cause emaciation, robbing the mammals of the body fat they need to survive hibernation through the winter months. It has been documented in caves and mines where large numbers of bats hibernate. So far, nine bat species have been affected by the mysterious condition: the little brown, cave myotis, southeastern myotis, northern longeared, tri-colored, small-footed, big brown, and the endangered Indiana and gray bat.

The fungus has been identified as Geomyces destructans, and researchers think it may cause bats to increase their body temperature to initiate an immune response, thus leading to increased metabolism of the stored fat the bats depend on during winter hibernation. Use of the pesticide malathion — which has risen sharply since 1999 to combat West Nile virus — may also interfere with the bats’ metabolic rates, exacerbating the effects of the fungus.

Researchers speculate that the illness may also interrupt hibernation patterns, increasing the periods during which bats are awake and active, further depleting their valuable fat stores (possibly to the point of starvation). Some researchers even suggest that the emaciation effects of white-nose are compounded by global warming, which changes the temperature of the caves and mines, and affects the bats’ ability to decide when to begin and end hibernation.

Bats are an important part of the ecosystems in which they live. They are the primary predators of insects such as flies, gnats, and mosquitoes, and they consume agricultural crop pests such as leafhoppers, cucumber beetles, corn earworm moths, and more. Healthy bat colonies help farmers use fewer pesticides, thereby keeping our air, soil, and water cleaner. That symbiotic relationship, though, is now at great risk. Research on the cause of the white-nose outbreak continues.

How you can help: Provide bat houses and leave dead or dying trees standing to provide much-needed summer roosts. Report any unusual bat behavior or bat deaths to state wildlife agencies. Contact state and federal legislators to urge them to support research on white-nose syndrome. Educate others about the important role bats play in the ecosystem.

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