CDFW News | Bat invasive species confirmed in five California counties

Bat invasive species confirmed in five California counties

The fungus that causes white-nose syndrome in bats has been detected in several California counties this year, but no bats have yet been observed in the state showing obvious signs of the disease.

White-nose syndrome has killed millions of bats and wiped out entire colonies across North America. Hibernating bats such as the little brown myotis, Yuma myotis, and cave myotis are especially vulnerable. White-nose syndrome is often fatal to hibernating bats, but it is not contagious to humans, pets, livestock, or other wildlife.

White-nose syndrome occurs when the fungus Pseudogymnoascus destructans invades a bat's skin cells and damages the delicate wing membranes. This infection usually appears as white fluff on the faces of infected bats, giving the syndrome its name. Bats with white-nose syndrome often exit hibernation early due to lack of water and insect prey resources, depleting fat stores and becoming dehydrated. As a result, infected bats often die.

In 2023, the California Department of Fish and Wildlife (CDFW) confirmed the first definitive presence of this fungus in a bat roost in Humboldt County. In 2024, the presence of the bacterium was also confirmed in Sutter, Placer, Amador, and Inyo counties. Inconclusive test results suggest the fungus may also be present in Trinity, Siskiyou, Shasta, Plumas, Alpine, San Diego and San Bernardino counties. Additional results are still pending in several other counties in the state. This fungus has been detected in several bat species in California, including the little brown myotis, Yuma myotis, long-legged myotis, large brown bat, Mexican free-tailed bat, and western long-eared bat.

This is the first time that the presence of this fungus has been reported in Western red bats. The positive sample was returned from a female bat captured in Sutter County on May 9, 2024. Because western and eastern long-eared bats both occur in California and can be difficult to differentiate, CDFW used genetic sequencing to determine whether this individual was a western long-eared bat (Lasiurus frantzii, formerly L. blossevillii). was recognized as ).

Although white-nose syndrome has not yet been observed in bats in California, the presence of this fungal pathogen suggests that the disease may develop in California bats within the next few years. This fungus and disease has spread across North America since its discovery in 2006, and similar progression has been observed in other states. The fungus was first detected on the West Coast in 2016, when it was discovered in bats in King County, Washington.

This fungus is primarily spread through bat-to-bat contact, but humans can also unintentionally spread the fungus. People can carry fungal spores on clothing, shoes, or recreational equipment that has come into contact with the fungus in bat roosts. For more information on how to limit the spread of white-nose syndrome, National White Nose Syndrome Decontamination Protocol (Updated March 2024).

Biologists from CDFW, the National Park Service, and the U.S. Fish and Wildlife Service have been working since 2016 to identify the presence of the fungus and detect white-nose syndrome in support of a national surveillance effort led by the U.S. Geological Survey National Wildlife Health Service. We have been sampling California bats for clinical signs. center. Every spring, when the bats at the monitoring site emerge from hibernation, biologists swab their faces and wings to test for fungi. The swabs will be analyzed by the USGS National Wildlife Health Center and Northern Arizona University's Pathogen and Microbiome Laboratory.

Continued efforts to monitor bat populations are essential to understanding and managing this devastating disease. CDFW and its partners will continue to conduct white-nose syndrome research and monitor bat populations across the state to assess the potential impact of the disease and inform research and management efforts. The U.S. Fish and Wildlife Service is leading the national joint response effort to white-nose syndrome. Scientists continue to develop and test innovative tools to manage disease.

California is home to 25 species of bats. A single bat can eat thousands of insects each night. California bats suppress insect populations, benefiting a variety of natural landscapes from forests to deserts to grasslands, as well as rural, suburban, and urban communities. The pest control services provided by bats protect crops and also benefit California's agricultural economy, the largest in the nation. Nationwide, bats provide farmers with about $3.7 billion worth of pest control each year, and their guano can be used as fertilizer to improve soil health. A healthy bat population is essential to a healthy environment and economy.

CDFW urges people not to handle wild animals, especially those that are dead or appear to be sick. If you find a sick or dead bat, or notice any strange bat behavior, please report the sighting. Bats flying or roosting outdoors in the winter is an example of a notable behavior that may, but not always, be associated with white-nose syndrome.

You can help monitor white-nose syndrome in California by reporting bat sightings to CDFW.

Report a sick or dead bat
Report a bat colony

Click here to learn more about white nose syndrome. https://www.whitenosesyndrome.org/.

Copyright/Photo Credit: Troy Gipps, North American Bat Program Public domain posted on Flickr page.

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Media contact:
Katrina SmithCDFW Wildlife Branch, (916) 207-5573
peter tiraCDFW Communications, (916) 215-3858
sidney giulianoU.S. Fish and Wildlife Public Affairs, (413) 658-4613