Killer Bees Move North
Back in the 1970s, a journalist friend of mine worked for an editor who thought Mother Nature had two good headlines in her. One was “Killer Bees Move North”--meaning out of Latin America and across our borders. The other was “Sharks Sighted in Mississippi River.” I like to imagine him still lurking on a levee, waiting for that first view of a dorsal fin slicing through the waters outside St. Louis.
Killer bees, though, must have disappointed him. They did cross the border more than 10 years ago and made themselves at home in the American Southwest, and they continue to slowly spread north. But the hyper-headlines didn’t arrive with them. In California, hives of Africanized honeybees--as scientists prefer to call them because they are the product of interbreeding between European bees and a group of more aggressive African bees inadvertently released in Brazil during the 1950s--have now been found beyond Porterville in the San Joaquin Valley. The reporting has been mostly matter-of-fact, the stories lacking the murderous spin--or Page 1 sizzle--of earlier reports.
In fact, headline lovers might consider the invasion of Africanized bees to have been a nonevent. Scientists, on the other hand, see it as a remarkable story. Journalism and science can be an interesting mismatch. On the one hand, you have an event-driven approach, shaped by current interest and intrigue. On the other, you have a process of exploration conducted detail by cautious detail. Too often, good science happens after reporters have lost patience and moved on.
In the case of Africanized bees, reports to be presented at Indiana University during this week’s annual meeting of the Animal Behavior Society confirm that patience can be a virtue. Researchers seeking to understand the bees have also managed to illuminate the shape of a perfect invasion. If you want to know how to overrun a country, look no further than the military strategy of these tough and capable insects. “The animals are just incredibly successful invaders,” says Robert Page, head of the entomology department at UC Davis.
Counter to expectations, being “killer” bees--well-armed and famously aggressive--is not an advantage. Compared with our standard honeybee--imported from Europe centuries ago--the tropical bees are lethal. Africanized bees attack 20 times faster than those sweet-tempered Europeans. A swarm can deliver up to 200 stings a minute. It pursues farther. It stays angry longer. About 30 people are stung to death annually now in Mexico. In the United States, only eight people have died since the bees first appeared in 1990, but some of those deaths have been memorably awful. An unfortunate Arizona man who pushed a lawnmower over a hive suffered almost 1,000 stings.
Vicious behavior, however, tends to identify you rapidly as an enemy. The Africanized bees have been marked as killers since entomologists imported them into Brazil decades ago, hoping to use them as breeding stock. There is now a growing branch of the beekeeping industry dedicated to eliminating them. In Mexico City alone as many as 5,000 hives have been destroyed in a single year. Swift attack undoubtedly served the bees well on the African savanna, where they fended off aggressive predators. Traveling across the human-dense landscape of the Americas, it only served to draw attention and provoke retaliation.
Nevertheless, despite the counterattacks, the bees have thrived here. Why? Well, partly because these are very paranoid bees. Complete suspicion is helpful when overrunning hostile territory. At a hint of threat or disturbance, Africanized bees tend to pack up and move. Beekeepers call this “absconding,” and for people trying to make a living from hives, it poses a serious problem. Ernesto Guzman-Novoa, an entomologist at INIFAP-Mexico, the national agricultural research institute, tells of one beekeeper who brought 9,000 hives with Africanized bees into a region that needed pollination. Seven thousand hives promptly absconded--Africanized bees don’t like to be moved and didn’t trust the territory in question.
And that’s a lot of bees--a small hive can contain 5,000 insects, a large one up to 50,000. Those numbers reveal another component of a successful invasion. Make sure the population odds are overwhelmingly in your favor. Put simply, Africanized bees reproduce so rapidly and prolifically that no one can kill off enough of them to hold them back.
“These fascinating bees,” as Guzman-Novoa calls them, have other talents that weren’t so well appreciated in the initial panic. They can eke out a living from the barest of vegetation. Compared with their softer cousins, they fly faster; they respond faster; their sensory system is more revved--they pick up on fainter odors and signals. This may make them jittery, but it also makes them survivors.
Further, the newest studies show, these bees are extraordinarily skilled at converting the natives to their approach. At the ABS meeting Wednesday, Guzman-Novoa and two researchers at Purdue University, Greg Hunt and Miguel Arechavaleta-Velasco, will detail the surprising ability of the bees to impose their own behavior patterns on others. In particular, they can convince their gentler cousins to fight mean as well.
Entomologists have known for years that the genes that control aggression in the Africanized bee are superbly dominant. If European and Africanized bees are bred together, all the offspring are born fighters. But the entomologists had not realized, until recently, that the bees were so adept at social influence. In hives that contain a mix of the two bee types, if scientists approach with a “threat target”--for instance, a black patch of leather--the Africanized bees boil out of the hive first. The European bees are more hesitant. In the first second, 80% of the stings are from Africanized bees. But within 30 seconds, all the bees are furiously in the attack.
What better way to complete an invasion than to persuade the competition to your side? Entomologists are still trying to figure out this particular talent. Is it peer pressure? Does hanging out with the bad guys eventually turn you into a bad guy yourself? Pragmatically, the scientists suspect that the Africanized bees may release a particularly seductive alarm pheromone. And there seems to be something about watching violence, seeing a companion hurl himself into the fray, that brings out the best--or the worst--in the gentler bees, depending on your point of view.
Certainly from the human perspective, this is a “worst” result. It emphasizes that the invaders are unlikely to become truly domesticated--rather, they are far more likely to prod our safer and sweeter bees into wildness. Most scientists predict continued adjustments in managing bees, beekeeping, honey production and commercial pollination. UC Davis entomologist Page also expects a gradual shift in people’s attitudes toward bees--still appreciating their value and importance but at an increased distance. “These bees need space,” he says. “So that the hive that you used to admire in your backyard may be something you no longer want quite so close.”
Page’s team, among others, tracked the bees into the San Joaquin Valley. He expects them to continue trekking northward. The march has slowed, although no one is sure exactly why. It may be no more than the cooler climate--these are tropical bees, after all--providing a natural limit. In which case, of course, a continued global warming trend could act enormously to their advantage in this elegantly handled invasion, built on numbers, toughness, adaptability and a rare talent for co-opting the homeland population.
So the killer bees have moved north. Instead of stopping them, we are learning to live with them. Perhaps we should take a reluctant moment to admire them as well. Human invasions rarely run so competently and smoothly. It’s good to remember, sometimes, that we aren’t quite the masters of the planet that we like to imagine. But let us also hope that sharks never figure all of this out.
