Fungus Linked to Deadly Bat Disease Detected in California

The fungus responsible for white-nose syndrome, which has decimated bat populations across North America, has been identified in several counties throughout California this year. However, bats exhibiting visible signs of the disease have not yet been observed in the state.

White-nose syndrome, caused by the fungus Pseudogymnoascus destructans, severely threatens hibernating bat species, including little brown myotis, Yuma myotis, and cave myotis.

The infection manifests as white fuzz on the faces of affected bats, leading to damage to their wing membranes. This condition forces infected bats to emerge from hibernation prematurely, depleting their fat reserves and increasing the risk of dehydration, which often proves fatal.

The California Department of Fish and Wildlife (CDFW) confirmed the presence of the fungus in 2023 at a bat roost in Humboldt County. Subsequent confirmations in 2024 included Sutter, Placer, Amador, and Inyo counties, with inconclusive results suggesting possible presence in additional counties such as Trinity, Siskiyou, and San Diego.

Notably, this marks the first time a Western red bat has tested positive for the fungus, detected from a female bat in Sutter County earlier this year.

While white-nose syndrome has yet to be documented in California bats, detecting the fungus raises concerns about potential future outbreaks. Since its discovery in 2006, the fungus has spread rapidly across North America, reaching the West Coast in 2016.

Bats play a crucial ecological role, consuming thousands of insects each night and helping to control pest populations. This natural pest control benefits various communities and supports California’s significant agricultural sector, valued at nearly $3.7 billion annually.

The CDFW, in collaboration with the National Park Service and U.S. Fish and Wildlife Service, has been monitoring bat populations for signs of the fungus since 2016. As part of ongoing surveillance efforts, biologists collect swabs from bats emerging from hibernation each spring for testing.

The public is encouraged to assist in monitoring bat populations by reporting any sightings of sick or dead bats to CDFW:

Report a Sick or Dead Bat
Report a Bat Colony

For more information on white-nose syndrome and how to prevent its spread, visit www.whitenosesyndrome.org.