Wild Neighbors: Rabid Bats in Berkeley

By Joe Eaton
Thursday July 24, 2008 - 10:20:00 AM

A rabid bat was found on July 15 in the Sonoma-Hopkins Triangle area of North Berkeley. According to Manuel Ramirez of the Environmental Health Division of the city’s Health and Human Services Department, it was identified as a California myotis, a common western bat species. 

Ramirez said his agency gets about one rabid bat report each year. Environmental Health staff have been going door to door in the neighborhood and distributing fliers to residents. 

“We want to make sure the public is aware of the need to take precautions,” he said. “We advise people not to touch or allow children or pets to come in contact with bats or other wild animals. If they see an animal acting in a peculiar way, they should call Animal Control at 981-6600. They should also ensure that their dogs and cats have the required rabies vaccinations.” 

In addition to bats, most carnivorous animals—skunks, ferrets, raccoons, coyotes, foxes, dogs, and cats—are susceptible to the incurable disease. So is the occasional horse. According to Ramirez, most of Berkeley’s rabid-animal incidents involve skunks. Rodents (squirrels, rats, and mice), rabbits, and opossums are unlikely to be carriers. 

Peculiar behavior might include daytime activity by nocturnal creatures like bats and skunks, staggering, or aggressive reactions to humans. Grounded bats should also be considered suspect. A bat with rabies is likely to be passive, although it may bite in self-defense. 

A recent study by the Centers for Disease Control and Prevention (CDC) reported that bats were implicated in almost half of U.S. rabies cases in humans, dogs in just under a third. But the incidence of bat-transmitted rabies is low, with only 48 confirmed cases in the last 55 years. The most recent human fatality in California occurred in September 2003, when a 66-year-old Trinity County man died six weeks after having been bitten by an unidentified bat. 

Rabies researchers consider the California myotis one of the three North American bat species most likely to carry rabies, along with the Mexican free-tailed bat and the big brown bat. It occurs far beyond California’s borders, through most of the American West. One of our smallest bats, the California myotis sometimes roosts in groups of up to 25 but is never as gregarious as the Mexican free-tailed. These bats hide out in crevices in buildings and under the bark of trees. Unlike other, more site-faithful species, they use the nearest available roost after their nightly round of insect-hunting. 

As a precaution, Environmental Health recommends bat-proofing homes and other buildings to prevent incursions, by caulking or screening openings larger than a quarter inch by a half inch, especially at roof level. The CDC suggests the use of chimney caps and draft guards under attic doors, and ensuring that all doors close tightly. Bat exclusion is best done in winter to avoid sealing in flightless young bats. 

Bats have their defenders, including Austin-based Bat Conservation International, the leading bat-advocacy group. On its website, BCI claims that dog attacks kill more humans every year than bat-borne rabies does in a decade, and that bee stings cause far more human fatalities than bats do. Putting up a bat house to attract the creatures is said to be statistically “safer than owning a dog or planting flowers.”  

BCI also points out that bats are the primary predators of insects that spread diseases and ravage crops and forests, to the tune of billions of dollars annually. Many species are declining because of habitat loss, and a mysterious disease called White-Nose Syndrome has been killing off hibernating bats in the Northeast. 

The recent rabid-bat detection is reason for precaution but not for panic. Just keep an eye on your kids and pets, and call the pros if a bat turns up in your house or on your lawn.