‘Killer bees’ found in the Bay Area for the first time

An Africanized breed of honeybees — sometimes known as “killer bees” because of their swarming, aggressive and deadly nature when a colony is threatened — has found its way to the Bay Area for the first time, researchers say.

The bees were found in a Lafayette subdivision called Reliez Valley, near the southeast side of Briones Regional Park, by UC San Diego researchers who have been tracking the bees’ movement throughout the state. Until now, the bees had been detected only as far north as Mariposa County in California’s more inland Central Valley, but they were probably attracted by the Bay Area’s warming temperatures.

Joshua Kohn, a professor of biology at UC San Diego, said it is hard to tell at this point how many of the bees are in the area.

“The sampling is a little sparse up north,” he said from his office at the university. But there is most likely more than one colony, he said.

“Normally honeybees forage within about a mile of their hive, though they can go up to about 5 miles,” Kohn said. “There is no way we found a member of the only Africanized bee colony in that region.”

While the bees can pose a threat of danger to humans, Kohn said, people should not be too concerned.

“An Africanized honeybee out foraging on flowers is no more aggressive than your average European honeybee. Nor is the sting of an individual any different,” he said. “It’s only when a hive is disturbed that the level of aggression from Africanized bees is elevated.”

Then the aggression usually involves more bees and more persistent bees, at that, he said.

Bees spotted last year

Kohn said the bees’ presence was determined from samples taken in spring 2014 and then analyzed in the lab. His report appears in the September issue of the journal Plos One.

In an interview, Kohn said he has no way of knowing whether Africanized bees are in Lafayette permanently. But if they do stay, he said, there could be some benefits. He said the bees could represent a more stable species to replace the rapidly dying European varieties.

“The Africanized bees are more resistant to one of the diseases related to colony collapse disorder in agriculture,” Kohn said.

Steve Schutz, an entomologist for the Contra Costa Mosquito & Vector Control District, said he wasn’t too surprised to hear about the bees’ presence.

“There are so many ways the bees could be moved here,” he said. “It doesn’t seem to have had an impact so far. ... If people do spot the bee colonies, they probably want to have a professional beekeeper come deal with it.”

The Africanized honeybee is a hybrid of the European bee and the African bee, originally brought west to Brazil to improve honey production. The breed eventually escaped and spread through South America, Central America and ultimately the U.S. It entered California in 1994 and has gradually spread north since, primarily circulating in the state’s warmer, southern regions.

More likely to attack

The hybrids are much more defensive than the European breed and more likely to attack a perceived threat to their hive, and do so much more relentlessly and in larger numbers. Their venom is the same as the European breed, but it is delivered in higher amounts since the Africanized bees are more likely to sting than their European counterparts. Africanized bees have been known to pursue a perceived threat for distances well over 500 yards.

The bees have been known to build their hives in trees, under rocks, within caves and under edges of man-made objects such as sheds or chimneys.

Carolyn Jones, spokeswoman for the East Bay Regional Park District, said no one had reported seeing the bees in Briones Park.

“We don’t think this is a threat to the public in any way,” Jones said. “But with climate change, anything is possible in the future.”

However, Brian Johnson, a honeybee researcher at UC Davis, said it’s important to remember that the bees do pose danger wherever they are present.

“Africanized bees are a public health threat,” he said. “People should be educated on what to do if they encounter them.”

Experts say bees overall kill about 40 people a year in the U.S. No statistics are kept for Africanized bees, but people and animals are the most at risk if they don’t have a way to escape an attack, Kohn said. The Africanized bees have killed animals on chains and in fenced enclosures in Southern California and Texas.

Last month, a swarm of Africanized bees killed a construction worker and injured two others in Riverside as the workers graded land for a parking lot unaware that an underground vault housed a hive.

Little risk seen for S.F.

More evidence of the bees’ aggressive nature is that they have replaced European bees in the wild almost anywhere they have settled. But Randy Oliver, a popular California beekeeper, said he doesn’t foresee Africanized bees flourishing this far north and close to the coast.

“I doubt there will be too much of an impact on beekeeping here,” Oliver said. “These bees tend to live in warmer, dryer habitats, but we will see how it all plays out.”

Paul Koski, a member of the board of directors for the San Francisco Beekeepers Association who manages several bee hives around the city, said he doesn’t believe that the Africanized breed will ever establish itself in the city because of its cool climate.

For the study, Kohn and his research student, Yoshiaki Kono, drove across California, stopping every 30 miles to net feral bees hovering over patches of flowers. They then took the bees back to the lab for genetic analysis.

Kohn said genetic testing is the only way to identify bees with certainty.

The majority of sampling in the UC San Diego study focused on the Africanized bees’ population growth in the southern part of California, where they found that more than 60 percent of foraging honeybees in San Diego County are now Africanized.

The news of the spread isn’t all bad buzz. The researchers said the northward spread of the killer bees in California has slowed considerably — potentially due to the bees reaching their northernmost temperature limits. And they may have made it this far only because of the recent onslaught of warmer temperatures.

Kevin Schultz is a San Francisco Chronicle staff writer. E-mail: kschultz@sfchronicle.com Twitter: @KevinEdSchultz

How to get away from attacking bees

Although Africanized bees are slightly smaller than European bees, there is no accurate way for the casual observer to distinguish between them.

Africanized bees out foraging will usually not attack.

If you get close to a hive, you should move away quickly.

If you sense that bees are approaching, run away as quickly as possible, at least 100 yards. Africanized bees have been known to swarm perceived threats relentlessly and in high numbers.

Do not swat away or crush Africanized bees. That will only further antagonize other members of the hive.

If you can get away from enough of them to run inside, do it. You can deal with the ones who made it in with you. Brush them off your clothes. Then remove the stingers by scraping them with a credit card or similar object. Don’t use tweezers (that will inject more venom).

Don’t jump in a swimming pool or bodies of water to get away. They have been known to wait for people to surface.

When in a safe location, call a local bee professional and emergency personnel.