"Killer Bees" are Creeping North through California

September 18, 2015 | Sarah Tse

The Africanized honey bee (top) is barely distinguishable from its milder European cousin.
Photo credit: USDA Forest Service

These “killer” hybrid bees are expanding their range throughout California, thanks to global warming’s mitigation of winter temperatures. But their invasion may also bring relief to ailing hives that pollinate our crops.

Even California’s crippling drought can’t thwart the Africanized honey bee’s northward advance. These volatile hybrid bees already dominate much of the southern US, and global warming will likely lower winter temperatures enough that they can move further north.

A study conducted at the University of California San Diego collected bees throughout the state to find out how far north Africanized honeybees have migrated since their introduction to California in 1994. The researchers searched for markers of Africanization among the genes of 256 bees from 91 sites, and discovered that over 60 percent of worker bees in San Diego County possess Africanized genes. These hybrid bees can even be found as far north as the delta region near Sacramento, and instead of infiltrating managed honeybee hives, most of them belong to feral colonies.

SEE ALSO: Global Warming Particularly Tough on Bees

The Africanized honeybee originated from a Brazilian biologist’s misguided attempt in 1956 to strengthen European honey bees so they could thrive in a tropical climate. He introduced a subspecies from southern Africa with genes for larger size, higher reproductive rate, and resistance to many diseases. But like most other invasive species, the bees escaped and went rampaging throughout the wilderness, hybridizing with local populations. These dominant African genes overpower those of the European honeybee, resulting in hybrids with genomes that are 70-80 percent African.

In the last half century, Africanized bees have spread throughout the Western hemisphere both north and south of their origin site. They reached Mexico in 1985, Texas in 1990, and they have since spread north through California and as far east as Florida. In addition to their increased hardiness, the hybrids are much more aggressive and have earned the nickname “killer bees.”

While regular European bees only attack in relatively small groups up to 20 feet away from their hives, Africanized bees are hyper-protective of a turf as wide as 40 yards in each direction from their hives. They can rain down 100 times as many stings as their European cousins and may remain hostile for hours once they are disturbed. They’ll even chase down intruders for half a mile. While their venom is no more lethal than the European variety, the volume delivered by hundreds of stings can seriously weaken and even kill anyone unfortunate enough to incur a colony’s wrath.

But it’s not all bad news. While their northward expansion will force more people to exercise caution to avoid disturbing a hive, Africanized bees may hold the key to saving our dwindling native populations.* A 2010 study showed that they may be more resistant to a species of parasitic mite that’s been plaguing normal European colonies. While Africanized bees are too unruly for beekeepers to manage, geneticists might be able to isolate the genes that grant this protection. They could then reinvigorate the European subspecies, perhaps finally fulfilling the dreams of the biologist who started it all. A more controlled hybridization between the subspecies may avert the impending crisis produced by colony collapse disorder.

Even if we figure out how to harness the strengths of Africanized bees, the feral colonies still pose a threat to people, pets, and wildlife. Global warming will only make it easier for these “killerbees” to push north.

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