IN AUGUST 1998, an 83-year-old man in Brawley, California, went out to mow
his lawn. He had been a bee-keeper, and the bee boxes still stood in his
garden鈥攅mpty, he thought. But unknown to him, a new colony of bees had
moved in. They didn鈥檛 like the noisy lawnmower, and at its sound hundreds of
guard bees swarmed out of the hive and attacked en masse, stinging the old man
more than a hundred times. After two weeks in a coma, he died.
He is by no means the only victim of 鈥渒iller bees鈥�. In the four decades since
these hybrids of African and commercial European honeybees escaped into the wild
in Brazil, their attacks have killed a thousand people and tens of thousands of
animals. Africanised bees make the same venom as European honeybees: the
difference is that within seconds they can muster hundreds of guards to sting
any unfortunate intruder, and it takes much less disturbance to set them off.
Preceded by their fearsome reputation, these hybrid bees have spread across the
Americas, defeating frantic efforts to stop them. At one point, the US Congress
considered building a 15-metre-high fence along the Mexican border. Now they are
the dominant wild honeybee from Argentina to Arizona. They have colonised Los
Angeles. They are expected soon in Florida and the Central Valley of California,
where they will certainly flourish on a heady diet of crop pollen.
Yet they have their fans, too. A growing number of bee scientists think we
should actively encourage Africanised bees, and perhaps even actively
cross-breed them with standard honeybees throughout North America, and even in
Europe. A kinder, gentler killer bee, they say, could hold the solution to a
plague that is ravaging hives on every continent but Australia and threatens
crop pollination vital for $10 billion worth of food per year in the US
alone. 鈥淭hese bees will be the salvation of the bee industry,鈥� predicts Steve
Thoenes, a former bee researcher who now runs a bee removal company in Tucson,
Arizona.
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The killer bee problem began in 1956, when Warwick Kerr, a geneticist in
S茫o Paulo, Brazil, imported 47 queen bees of an African subspecies from
near Pretoria, South Africa. Kerr hoped the bees would produce more honey than
the standard European variety, which performs poorly in the tropics. They
thrived, and soon swarms of hybrid bees escaped from the hives and began to
spread rapidly. By 1986 their descendants stretched from Argentina to Mexico.
Everywhere they went, Africanised drones outcompeted European rivals in
fertilising queens during mating flights, and spread African genes through the
local honeybee population. The Americans tried to keep out the invaders massing
in Mexico by flooding the border with European swarms. They failed. Killer bees
reached Arizona in 1991 and flourished there. The Tucson area now has about
thirty times as many wild bee colonies as before the Africans arrived. Last year
they reached the California coast. This year they got as far north as Las Vegas.
Today, commercial European bees are only hanging on in Africanised areas because
bee-keepers keep importing new European queens. 鈥淲e should just admit that the
Africanised bees are here, and work with them instead,鈥� says Thoenes.
That is what Africans have always done. Mike Allsopp of South Africa鈥檚 Plant
Protection Research Institute in Stellenbosch insists that on their own turf,
the African ancestors of the pesky hybrid bees are quite manageable. 鈥淲e just
don鈥檛 understand this `killer bee鈥� label,鈥� he says. 鈥淵ou only need to know how
to manage them.鈥� That means shunning dark colours and strong scents, avoiding
noises, moving calmly. His students can even lie in front of the hives while the
insects walk across their foreheads.
It鈥檚 the same in Latin America, where the bees have had time to settle in.
鈥淭he first wave of invaders seems to be really aggressive, then they calm down,鈥�
says Susan Cobey of Ohio State University. Bee-keepers from Brazil to Mexico say
their charges are manageable, if a little touchy. Brazil鈥檚 honey production is
now 10 times what it was before the Africans arrived.
Even in Arizona, Africanised bees are proving much less aggressive today than
when they arrived nine years ago, says Thoenes. 鈥淭here are far fewer attacks,鈥�
he says, 鈥渁nd when someone calls me to clear out a nest, most of the bees just
aren鈥檛 that irritable.鈥� Thoenes鈥檚 theory is that a run of dry years has favoured
bees that store honey well, and since European honeybees do this better than
Africans the Tucson bees now tend to carry more European genes鈥攁nd that鈥檚
made them gentler.
Even so, bees with African genes remain more belligerent than their European
kin. 鈥淎t the right time of year, when they are well fed and have a lot of brood
to protect, they won鈥檛 just attack, they will try to kill you,鈥� says Allsopp.
They get upset easily, and stay that way. In Mexico, for example, bee attacks
now kill 30 people a year, compared with three or four in the years before the
Africans arrived, says Ernesto Guzm谩n-Novoa of INIFAP, the national
agricultural research institute near Mexico City.
European bees are more docile than their African counterparts because
bee-keepers made them that way. Bee-keepers have been preserving calm colonies
and destroying difficult ones since Roman times, says Gordon Wardell, another
bee specialist in Tucson. There has been no such selection pressure on African
bees. 鈥淚n fact, some bee-keepers like to have defensive bees around,鈥� says
Allsopp. 鈥淚t stops thieves.鈥�
If breeders have made European bees more docile, then surely they should be
able to do the same for African ones. That鈥檚 exactly what Guzm谩n-Novoa
and his colleagues are trying to do鈥攁nd boost honey output into the
bargain. At a big commercial apiary 150 kilometres southwest of Mexico City, the
team selected Africanised hives that made the most honey. They looked at how
often bees from each of the productive hives stung a standard leather patch when
annoyed, and selected those hives whose residents stung least. From these they
bred the next generation.
After just five generations, the bees produced 56 per cent more honey than
unselected bees and stung less than half as often. When the researchers looked
more closely, they found that they had selected bees that carried a higher
proportion of European genes. Once fewer than half the genes are African,
attacks fall to the level seen with European bees. But because the queens mate
with wild drones that carry a higher frequency of African genes, breeders have
to keep on selecting to maintain the traits, says Guzm谩n-Novoa.
It should be possible, he says, to select some mix of African and European
genes that produces honey, yet doesn鈥檛 kill the neighbours. Yet no matter what
breeders do, 鈥渨e will never get rid of all the defensive behaviour,鈥� he warns.
Bee-keepers will still have to learn how to handle their charges more delicately
and start locating them farther from people and animals. And people must learn
how to live with the bees鈥攔ecognising an imminent attack and moving away,
for example, when the bees issue a warning by repeatedly flying into them,
something European bees almost never do.
Greg Hunt at Purdue University in Indiana takes a more precise approach to
breeding productive, non-aggressive hybrids. He wants to breed bees with
specific genes related to defensiveness and other qualities. Hunt鈥檚 team has
mapped three major genes that correlate strongly with stinging behaviour, and
now they are trying to determine how each gene influences the urge to sting. The
one with the strongest effect seems to help determine whether a bee becomes a
guard or merely a worker. A high proportion of guards is typical of the
Africans.
Good breeding
Understanding the genes involved should make it easier to screen for gentler
bees. 鈥淚鈥檓 sure it is quite possible to select Africanised bees with less
aggressive behaviour,鈥� says Hunt. 鈥淭here may be a number of minor genes
involved, but we could select progeny that have the European versions of these
three major genes. They might be a little more feisty than our bees, but we
could certainly work with them.鈥�
A gentle Africanised bee would be far more than a safer neighbour. It could
be a godsend for the entire bee-keeping industry, because Africanised bees are
resistant to several important pests, including the varroa mite. This tiny
parasite jumped from a Siberian bee species, which tolerates it, to honeybees,
which do not, when honeybees were carried east on the Trans-Siberian Railway
early in the 20th century. It wasn鈥檛 until 1977 that bees carrying varroa
arrived back in western Europe, but when they did many bee-keepers lost all
their hives to the parasite. Now no region of Europe is free of it. In 1987 it
arrived in the US, and in 1996 it killed up to 80 per cent of all hives in the
northeastern states. To make matters worse, the mites are becoming resistant to
the pesticides used to control them.
None of this worries Brazilian bee-keepers, though. They have never lost a
hive to varroa because their Africanised bees resist the pest. And since this
means they don鈥檛 need to spray for the mites, their honey and beeswax are
pesticide-free and command premium prices.
Some researchers are thinking about breeding the Africans鈥� resistance into
bees wherever varroa has spread鈥攖hat is, everywhere but Australia, New
Zealand and central Africa. Whether it will be possible to get pest resistance
without aggression remains to be seen. Varroa resistance seems to be mostly due
to intensive hygiene among African bees. 鈥淭hat seems to be closely coupled to
the defensive behaviour,鈥� says Cobey, who nevertheless wants to breed varroa
resistance into honeybees. Doing that with commercial European bees may prove
hard, because there is so little genetic diversity among them, so new genes
would be welcome. 鈥淚鈥檇 like to look at Africanised bees as a source of breeding
material,鈥� she says. 鈥淏ut the bee industry, which funds a lot of my work, would
be against it.鈥� Prejudice against the invaders is strong.
Thomas Rinderer of the US Department of Agriculture鈥檚 bee lab in Baton Rouge,
Louisiana, favours a different source of resistance genes. Bees from eastern
Russia have faced varroa longest so they might fit the bill, except that so far
they have been poor performers in American hives. But he鈥檚 against using African
bees. 鈥淥verall,鈥� he wrote in a 1998 article, 鈥淎fricanised honeybees have done
more harm than good.鈥�
William Ramirez, a bee-keeper in Costa Rica who gets high honey yields from
Africanised hives, strongly disagrees. He says the Americas need more, not
fewer, African bees鈥攊n particular, queens from calmer stocks in Africa for
breeding. And Lionel Gon莽alves of the University of S茫o Paulo,
Brazil, says that breeders all over the world seeking varroa resistance are
welcome to use the bees that made his country the world鈥檚 fifth largest honey
producer.
So far, however, few are interested in the genetic potential of North
America鈥檚 Africanised swarms. 鈥淚 feel remorse when I destroy swarms,鈥� says
Thoenes, the bee researcher turned bee remover. 鈥淚 know that one will have the
genes we need to solve the problems in the bee industry.鈥�