The fungus that causes white-nose syndrome in bats has been detected in several California counties this year, although bats with visible signs of the disease have not yet been observed in the state.

White-nose syndrome has killed millions of bats in North America and decimated entire colonies. Hibernating bats such as the little brown bat, Yuma myotis and cave bats are particularly vulnerable. Although white-nose syndrome is often fatal to hibernating bats, it does not infect humans, pets, livestock, or other wildlife.

White-nose syndrome develops when the fungus Pseudogymnoascus destructans invades bats’ skin cells, leading to damage to the delicate wing membranes. The infection usually appears as white fuzz on the faces of infected bats, hence the name. Bats with white-nose syndrome often end their winter hibernation early, when water and insect resources are scarce, causing them to deplete their fat stores and become dehydrated. As a result, infected bats often perish.

In 2023, the California Department of Fish and Wildlife (CDFW) confirmed for the first time the definitive presence of the fungus in a bat roost in Humboldt County. As of 2024, the fungus has also been confirmed to be present in Sutter, Placer, Amador and Inyo counties. Inconclusive laboratory 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 for several other counties across the state. The fungus has been detected on several species of bats in California, including the little brown bat, Yuma myotis, the long-legged bat, the big brown bat, the Mexican free-tailed bat and the western red bat.

This is the first time a western red bat has been reported in the presence of the fungus. The positive sample came from a female bat captured on May 9, 2024, in Sutter County. Both western and eastern red bats occur in California and can be difficult to tell apart. So CDFW used genetic sequencing to confirm that it was indeed the western red bat (Lasiurus frantzii, previously recognized as L. blossevilii).

Although white-nose syndrome has not yet been observed in any bats in California, the presence of the fungal pathogen suggests that the disease could show up in California bats in the coming years. Such progression has been seen in other states as the fungus and disease has spread across North America since its discovery in 2006. The fungus was first detected on the West Coast in 2016 when It was discovered on a bat in King County, Washington.

Although the fungus is spread primarily through contact between bats, humans can also spread it unintentionally. People can carry fungal spores on clothing, shoes, or recreational equipment that has come into contact with the fungus in bat roosts. To learn more about how to limit the spread of white-nose syndrome, visit 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 sampling California bats for the presence of the fungus and clinical signs of white-nose syndrome since 2016, in support of national monitoring efforts conducted by the US Geological Survey National Wildlife Health. Center. When bats at monitoring sites emerge from hibernation each spring, biologists swab their faces and wings to test for the presence of the fungus. The swabs are analyzed by the USGS National Wildlife Health Center and the Pathogen and Microbiome Institute at Northern Arizona University.

Sustained efforts to monitor bat populations will be essential to understanding and managing this devastating disease. CDFW and its partners will continue to provide white-nose syndrome surveillance and monitoring of bat populations across the state to assess potential impacts of the disease and inform research and management actions . The United States Fish and Wildlife Service is leading the national collaborative white-nose syndrome response effort through which scientists continue to develop and test innovative tools to manage the disease.

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

The CDFW urges people not to handle wildlife, especially dead wildlife or individuals that appear sick. If you find sick or dead bats, or notice strange behavior, please report your sighting. Bats flying or roosting outside during the winter are an example of a notable behavior that can sometimes, 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

For more information about white nose syndrome, visit https://www.whitenosesyndrome.org/