CDFW Biologists on High Alert for Signs of White-Nose Syndrome in Bats

The California Department of Fish and Wildlife (CDFW) is monitoring developments following the recent detection of white-nose syndrome (WNS) in a bat in Washington state. The disease has been responsible for killing millions of America’s bats, and CDFW scientists are enlisting the public to help prevent its spread.

Part of CDFW’s effort to educate the public is the launch of a new WNS webpage ( News of the first WNS case in Washington State, announced in March, prompted CDFW to make this information available as quickly as possible, since many species of bats in California could be affected if the disease spreads south.

Senior Environmental Scientist Scott Osborn is CDFW’s Statewide Coordinator for Small Mammal Conservation. “White-nose syndrome has killed more than six million bats in the eastern U.S. and Canada, in some cases wiping out entire colonies of hibernating bats,” he said. “It had spread gradually over ten years from New York into northeastern states and Canada, south to Mississippi and Arkansas, and as far west as Nebraska and Minnesota.”

Osborn said we don’t know yet how the disease moved more than 1,300 miles to Washington. It may have spread undetected by bat-to-bat contact across the Great Plains and Rocky Mountains. But it is also possible that the fungus was inadvertently carried by a person whose clothing or gear was contaminated, perhaps while exploring caves in eastern states.

The fungus Pseudogymnoascus destructans grows on and in the skin of bats during winter hibernation, in some cases giving them a white, fuzzy appearance on the muzzle, wings and ears. The fungus invades deep skin tissues and causes extensive damage. Affected bats awaken more often than normal during hibernation, causing them to burn up fat reserves needed to sustain them through winter, which leads to starvation and death. Wing damage may also cause problems with physiological processes such as blood circulation and the bat’s ability to regulate its body temperature. Impairment of any of these processes may also lead to death.

“Bats provide tremendous pest control services, eating as much as their own body weight in insects every night,” Osborn said. “The national value of pest control by bats has been conservatively estimated at more than $3 billion per year. No doubt California agriculture benefits greatly from healthy bat populations. Some bat species pollinate plants such as agaves and large cacti. And all bats are important to the ecosystems in which they occur and play a large role in controlling insect populations and converting insects into fertilizer used by plants. Of the 25 bat species in California, two are known to have been killed in other states by WNS and another 12 are likely to be at risk due to their similarity to affected species.”

CDFW asks that the public take several simple precautions to help avoid the potential spread of WNS:

  • Please report any bats you see showing signs consistent with WNS, or if you see bats flying outside during very cold or freezing temperatures. Please refer to the online reporting form for information if you have found a sick or dead bat with signs indicating possible infection with WNS.
  • Avoid entering caves, mines or other areas used by bats, unless absolutely necessary, to avoid disturbing bats and potentially spreading the disease to unaffected areas.
  • If you must enter a cave, mine or bat roost, decontaminate all equipment and clothing immediately after visiting. Do not allow dogs or other pets in caves, as they may act as carriers of the fungus to new sites.
  • Do not handle live bats; they can carry rabies.

For more information on bats and White Nose Syndrome, please see, or Bat Conservation International‘s website.

Signs of WNS include:

  • White or gray powdery fungus seen around the muzzle, ears, wings, limbs or tail of bats;
  • Unusual winter behavior, such as bats on the ground (either inside or outside a hibernation roost), roosting near the entrance to or increased bat activity outside a hibernation roost, or premature return to a summer roost during freezing weather;
  • Thin body condition or dehydrated appearance (wrinkled and flaky appearance of furless areas);
  • Moderate to severe wing damage, including membrane thinning, depigmentation, stickiness, holes, tears or flaky appearance on bats found outside of a hibernation roost or at a summer roost;
  • Bats exhibiting yellow-orange fluorescence on hairless skin under long-wave UV light; and
  • Excessive or unexplained mortality or population decline at a winter hibernation roost.


Media Contacts:
Scott Osborn, Nongame Wildlife Program, (916) 324-3564
Deana Clifford, Wildlife Investigations Lab, (916) 358-2378
Dana Michaels, CDFW Communications, (916) 322-2420