White-nose Syndrome and Minnesota's Bats

Little brown myotis bats hibernating in a cave Little Brown Myotis bats (sometimes called "little brown bats") showing the white fungus on their muzzles that gives White-nose Syndrome its name.

What is White-nose Syndrome?

White-nose Syndrome (WNS) is a fungal disease (scientific name Pseudogymnoascus destructans) first documented on bats in New York in 2006. Since then, WNS has resulted in severe population declines of cave-hibernating bats, including bats in Minnesota. Researchers first observed the white fungus growing on the noses of hibernating bats in New York, giving WNS its common name. WNS was confirmed Minnesota in 2016, resulting in winter population declines of over 90% for Minnesota’s cave-hibernating bats.

How is WNS transmitted?

Scientists believe that WNS is transmitted primarily from bat to bat. Humans and other animals visiting infected caves and mines may inadvertently carry the fungus spores on clothes or gear to unaffected caves. The fungus thrives in cold, humid conditions characteristic of the caves and mines that bats use to hibernate and can remain in a cave after all the bats have died.

Is WNS dangerous to humans?

No. Cave-hibernating bats appear to be the only animals that are susceptible to this disease due to their unique strategy of hibernating in caves where the fungus thrives.

What species of bats are affected?

Eight bat species reside in Minnesota. WNS affects the four species that hibernate in the state: Little Brown Myotis (Myotis lucifugus), Northern Long-eared Bat (Myotis septentrionalis), Tricolored Bat (Perimyotis subflavus), and Big Brown Bat (Eptesicus fuscus). The other four species of bats found in Minnesota migrate out of the state for the winter and they do not hibernate in caves. As a result, they have not been documented to be affected by WNS.

What are signs of WNS?

Bats appear to die from WNS primarily during winter, largely due to starvation, physiological shock or freezing. During winter months, observable signs of WNS may include:

  • white fungus on the bat's muzzle and other hairless parts of the body, such as wings and tail

  • bats active outside during the day when temperatures are below freezing

  • bats clustered at the entrance of hibernacula

  • dead or dying bats on the ground or on buildings and trees.

Note: The WNS fungus does not grow on bats during the warm weather months when bats are active. Also, other white fungi may grow on dead bats that are not associated with WNS.

What should you do if you find dead or dying bats, or if you observe bats with signs of WNS?

Contact the Minnesota Department of Natural Resources.

Photographs of found bats and details about behavior, how many, where and when it was found are very helpful.

Use caution when handling bats: Never handle live bats without gloves. If a person or pet has been exposed to a bite, scratch, or saliva from a live or dead bat, contact the local public health department for further guidance.

What you can do

  • Prevent the spread of WNS
    • Honor cave closures and gated caves.
    • Avoid caves and mines where bats hibernate. Be familiar with cave advisories (National Speleological Society).
    • Decontaminate clothing and gear according to recommended decontamination protocols.
  • Help bats survive
    • Enhance bat habitat on your property by retaining large trees, protecting wetlands, and constructing homes for bats.
    • Use bat-friendly methods to exclude bats from your home. Never exclude bats when females are raising young (May—August). See Dealing with Unwanted Guests.
    • Learn about bats through participation in Bat Week opens in a new browser tab and Bat Festivals!

More information

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