A community in northern California is returning to normal after a weekend attack by suspected ‘killer" bees left several people stung and two dogs dead.
The attacks began when beekeeper Arthur Janke tried to move a hive in his backyard in Concord, about 20 miles northeast of Berkeley. The bees in the hive "went berserk," stinging him through his bee suit. They attacked his parents and spread out into the neighborhood, stinging the man who lives across the street from Janke 16 times, descending on a mail carrier, attacking pedestrians and swirling around cars.
Janke's neighbors returned home that evening to find their two dachshunds in the backyard, covered with stings - at least 50 each, by a veterinarian's count. Both dogs died. (This piece in SFGate includes a number of remarkable first-person accounts of the scene as the bees attacked.)
How Do Killer Bees Kill?
By end of day Sunday, police confirmed that the swarms were no longer present in the community, but Concord police spokesman Corp. Chris Blakely told the East Bay Times, "as it gets warmer, you'll see more and more of the isolated (bees), and there's no doubt, they are very, very aggressive. So while the swarms are gone, it's not something that's going to go away entirely overnight."
The working theory is that the bees were Africanized honey bees - a hybrid of European and African honey bees. African bees were imported into Brazil in 1957 to improve honey production, and have been spreading steadily north since then, entering California for the first time in 1994. Once in the United States, they have mated with domesticated European bees to create ‘Africanized' bees.
While African and European honey bees are physically similar, the former are far more aggressive, and can chase a human or animal for a mile or more, according to this University of Florida fact sheet. That's a behavioral adaptation to an environment in which predators such as honey badgers pose a real threat; in contrast, European honey bees have been selectively bred over generations to be more docile.
California's Killer Bees Are Heading North
It seems likely that a colony of aggressive Africanized bees either mated with or displaced the European honey bees in Janke's hive. Although the San Francisco Chronicle reported officials at the Contra Costa Mosquito and Vector Control District as saying that three dead Concord bees they examined didn't appear to be Africanized, studies have shown that once more than 50 percent of a colony consists of Africanized bees, the entire hive becomes more aggressive. DNA testing is being conducted on a number of the bees to establish their genetic makeup.
The attack came shortly after scientists confirmed through genetic tests that Africanized bees had been present in the Bay Area since at least 2014. However, it doesn't necessarily follow that the region's bees are on an inevitable march toward hyper-aggressiveness: The relatively cool weather in northern California may counter the advantages that African bees enjoy in warmer climes, and there's some indication that with repeated hybridization, Africanized bees become less aggressive over time.