A bat-killing fungus may have arrived in Southern California

A cold-loving fungus that has killed millions of bats across North America has significantly expanded its presence in California and could potentially spread from the northern to southern tip of the state.

After first being discovered in the Golden State last year, the fungus is now found in five counties: Humboldt, Sutter, Placer, Amador and Inyo, according to state and federal wildlife officials. It may also be the case in at least six other cases.

Pseudogymnoascus destructans – the fungus – causes the deadly white-nose syndrome, so named for the distinctive snowy down that manifests itself on the delicate faces of infected bats.

The fungus invades the skin tissue of hibernating bats, causing them to wake up too often or too early in the winter, depleting their valuable fat reserves when there is little food. The result is often starvation, dehydration and death.

So far, no signs of the disease, which can also eat holes in their delicate wings and cause them to flutter carelessly into the daylight, have been observed in California bats, but wildlife officials expect that to happen soon.

“It wouldn’t surprise me if it showed up next year,” said Bronwyn Hogan, regional white-nose syndrome coordinator for the U.S. Fish and Wildlife Service. “But I wouldn’t be surprised if there were three or four.”

California wildlife officials last year confirmed the presence of the fungus in a bat roost in Humboldt County on the north coast. It was the first definitive detection in California, although officials have documented low levels in the state since the winter of 2018. Test results this year showed it had spread to four additional counties.

Recent testing also found low levels in San Diego and San Bernardino counties in Southern California and in Trinity, Siskiyou, Shasta and Plumas counties in far northern California. Wildlife officials have called these results “inconclusive” because they don't consider them robust enough, but some experts see them as signs on the cave walls.

“These early signals can be helpful in understanding the progression of the fungus and where it ends up,” said Winifred Frick, senior scientist at Bat Conservation International and associate professor of ecology and evolutionary biology at UC Santa Cruz.

Experts reacted to the news with resignation. Hogan said she was “depressed” but the spread of the fungus was not unexpected. Scientists have known for years that the fungus was present in small quantities in several locations across the state. And they have increased their surveillance.

California and state wildlife agencies, along with other partners, are working closely to identify the fungus and disease through sampling and observation. This year, biologists collected samples at nine locations in California and swabbed the noses and forearms of the tiny animals, said Katrina Smith, statewide small mammal conservation coordinator for the California Department of Fish and Wildlife.

The fungus has appeared in a number of California's 25 bat species, including the little brown bat, the Yuma myotis, the long-legged bat, the big brown bat, the Mexican free-tailed bat and, at the time documented so far, a western red bat.

Mexican free-tailed bats fill the sky in San Antonio.

(Bob Dean / Nature Photography Views / Bat Conservation International)

There is an air of science fiction about the origin of white-nose syndrome. When biologists first encountered bats succumbing to the disease in caves near Albany, New York, in 2007, the fungus behind the destruction was unknown to science, according to federal officials. (It has since been found in bats in Europe and Asia, where they appear to be resisting the invader.)

No one knows how the fungus got to North America, but it has quickly spread across the United States and Canada, leaving legions of bat carcasses in its wake on its death march. Many of the victims were the little brown bat.

Scientists tracking the spread were surprised when the disease first appeared on the West Coast in 2016, when a hiker found a dying bat on a trail in Washington state.

“It was a big jump from where it was, kind of in the center of the country,” said Jeremy Coleman, national coordinator for white-nose syndrome at the U.S. Fish and Wildlife Service.

Officials estimate that more than 6 million bats across the U.S. have died from the syndrome by 2012. The number of bats is likely higher now and officials are working on an update. (According to authorities, the fungus is not known to cause disease in humans or other animals.)

California's bats are more elusive than those in the East, which can congregate in the thousands in caves and mines. Golden State bats are thought to hang out in smaller numbers in rock crevices, swaying palm fronds, highway underpasses and other hiding places where they are difficult to find.

The distinctiveness of the West Coast can be a blessing and a curse. On the one hand, the spread of bats across the landscape could slow the progression of white-nose syndrome, which spreads primarily between bats when they groom or touch each other.

However, it makes it difficult to know what is going on with them.

“There is hope that the disease may have a less dramatic impact here, but it may also be more difficult to measure that impact,” Frick said.

In areas where bats congregate in large groups, scientists can simply go to the caves where they are known to frequent and count them to see if they die.

Coleman said the disease typically appears one to two years after the fungus is discovered.

“Unfortunately, since it is now in California and we know from all the other locations where we have seen the fungus spread, disease will occur at some point,” he said.

Bats, the only flying mammals, provide free pest control by eating insects, including those that target crops. Their annual national contribution to farmers is an estimated $3.7 billion. Their guano or dung can also be used as fertilizer.

There is currently discussion in California about the possibility of vaccinating bats. Smith said vaccinations could improve the winged animals' chances of survival during an outbreak of white-nose syndrome, but injecting individual bats would be laborious.

“It just provides a chance for some of the individuals to build their resilience to the disease and hopefully over time some of them will survive and find ways to get through it,” she said.

They are also awaiting results on other possible options, such as probiotic powders that can boost bats' skin microbiome and thus slow fungal growth. Researchers have tested blowing probito-containing dust into bat roosts as they leave them for the night, so that it covers them when they return.

A colony of Mexican free-tailed bats living in the Yolo Bypass Wildlife Area.

(Carolyn Cole/Los Angeles Times)

Some bat boosters take more creative approaches.

Bat Conservation International, a non-profit organization, has launched the Fat Bat Project to help the furry mammals feed before and after the onset of winter.

Because white-nose syndrome causes bats to lose fat during hibernation, Frick says the idea is that stronger bats are better able to withstand the often fatal physiological disorder.

The nonprofit is testing a method that involves installing a UV light to attract insects to bats near hibernacula, the cool-sounding plural for bat sanctuaries.

“We like to call it our insect buffet,” Frick said.

The public is urged to to report Sightings of sick or dead bats – or those behaving unusually, such as B. flying during the day – to California wildlife authorities. However, people should not handle the animals.