October 29, 2024 - The fungus that causes white-nose syndrome in bats has been detected in several counties across California this year, although bats with visible signs of the disease have yet to be observed in the state.
White-nose syndrome has killed millions of bats across North America and decimated entire colonies. Hibernating bats like little brown myotis, Yuma myotis, and cave myotis are especially vulnerable. While 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 the skin cells of bats, resulting in damage to delicate wing membranes. The infection typically appears as white fuzz on the faces of infected bats, giving the syndrome its name. Bats with white-nose syndrome often end winter hibernation early, when water and insect prey resources are scarce, causing them to deplete their fat reserves and become dehydrated. As a result, infected bats often perish.
In 2023, the California Department of Fish and Wildlife (CDFW) first confirmed definitive presence of the fungus in a bat roost in Humboldt County. In 2024, the fungus was also confirmed 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 around the state. The fungus has been detected on several bat species in California, including the little brown myotis, Yuma myotis, long-legged myotis, big brown bat, Mexican free-tailed bat, and Western red bat.
This is the first time a Western red bat has been reported with presence of the fungus. The positive sample was returned 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 differentiate, so CDFW used genetic sequencing to confirm this individual as Western red bat (Lasiurus frantzii, previously recognized as L. blossevillii).
While white-nose syndrome has not yet been observed in any bat in California, the presence of the fungal pathogen suggests the disease could manifest in California’s bats within the next few years. Such progression has been observed in other states, as the fungus and disease have been spreading across North America since discovery in 2006. The fungus was first detected on the West Coast in 2016 when it was discovered on a bat in King County, Wash.
While the fungus is primarily spread from contact between bats, humans can unintentionally spread it as well. People can carry fungal spores on clothing, shoes or recreation equipment that has come into contact with the fungus at bat roosts. To learn more about limiting the spread of white-nose syndrome, see the National White-nose Syndrome Decontamination Protocol (updated March 2024).
Biologists with CDFW, the National Park Service and U.S. Fish and Wildlife Service have been sampling California’s bats for the presence of the fungus and clinical signs of white-nose syndrome since 2016 in support of national surveillance efforts led by the U.S. 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 fungus. 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 critical to understanding and managing this devastating disease. CDFW and its partners will continue conducting white-nose syndrome surveillance and bat population monitoring across the state to assess potential impacts of the disease and inform research and management actions. The U.S. Fish and Wildlife Service leads the collaborative national response effort for white-nose syndrome through which scientists are continuing 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 each night. California’s bats keep insect populations in check, benefiting rural, suburban and urban communities as well as a wide variety of natural landscapes that range from forests to deserts to grasslands. The pest control services that bats provide also protect crops and benefit California’s agricultural economy – the largest in the nation. Across the country, bats contribute approximately $3.7 billion worth of insect pest control for farmers each year and their guano can be used as fertilizer to improve soil health. Robust bat populations are vital to a healthy environment and economy.
CDFW urges people to not handle wildlife, especially dead wildlife or individuals that appear sick. If you find sick or dead bats, or notice bats acting strangely, please report your sighting. Bats flying or roosting outside during the winter is an example of noteworthy behavior that can sometimes, but not always, be associated with white-nose syndrome.
You can help watch for 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/.
Source: CDFW
