`Killer bees' from Africa cause havoc in South America

 

Most of us have had the experience of driving along with the family when someone shouts: "There's a bee in the car." This is a sure trigger for instant bedlam. Everyone dreads the prospect of being stung despite the fact that, for the vast majority of people, the only consequence is a mild, short pain.

However, there is a type of honeybee, fortunately not found in Ireland, that is rightly feared because it will attack in great numbers at the slightest provocation and with possibly fatal consequences. This is the African bee, and the Africanised bee found in South America. These bees have been given the chilling nickname of "killer bees".

The honeybee first arose in tropical Asia, the European and African honeybee varieties coming later. There are important differences between the varieties. Everything moves at a faster pace with the tropical bees. They are more high-strung and attack far more viciously and in much greater numbers when they perceive a predator.

No honeybees existed in the "New World" until Europeans settled there, bringing European bees with them. These bees thrived in temperate regions, performed well as honey producers, and established wild populations through southern Canada, the US, Mexico and southern South America. However, they did not thrive in the tropical regions of Latin America where their presence in the wild is negligible and their honey production poor.

In 1956, the noted Brazilian bee geneticist, Warwick Kerr, was asked by his government to import bees better suited to the Amazonian region. Kerr had heard reports of huge honey crops in Africa and this is where he headed for his new bees. He knew that African bees were very aggressive but he planned to interbreed them with temperate-natured European bees to produce a hybrid, a good honey producer with a gentle nature.

Kerr began a testing and breeding programme in Brazil with 35 African queens and found that the hives headed by the new queens were the most productive he had ever seen.

In 1957, 26 of the colonies escaped into the forest near Sao Paulo. The escaped bees started off a wild population that has spread with great speed and density across South and Central America.

Colonies of European bees in this region were taken over and "Africanised" by the newcomers when African drones mated with European queens or when African swarms took over European colonies.

The front of Africanised bees has moved at about 300 miles a year and it is estimated that there are now more than a trillion Africanised bees in Latin America, distributed over 100 million nests. In 1990, the bees reached Texas.

One feature of African bee behaviour that led to success in colonising the Latin American habitat is their high rate of swarming. The function of swarming is to reproduce the colony.

A queen and most of the worker bees leave and establish a new hive, but some workers and another queen are left behind to continue the old hive. This high swarming rate enabled the Africanised bees to spread rapidly, occupy the available ecological niche and to out-compete the resident European bees within that niche.

Why are tropical bees so much more aggressive than bees from temperate climates?

Bees were never domesticated in Africa to the extent that they were in Europe, and honey is frequently stolen from hives by humans. African bees also have a legacy of evolutionary adaptation to millions of years of heightened pressure from a wide array of animal life - army ants, anteaters, honey badgers etc.

The African bee today is far more easily aroused than the European bee and will abandon a nest (abscond) or sting much more easily than the European bee.

There have been many cases in South America of deaths of livestock kept too close to hives of Africanised bees. There have also been occasional deaths of people after receiving huge numbers of stings. For example, in Costa Rica in 1986, a botany student from the University of Miami died after receiving 8,000 stings.

The ferocity with which African bees attack was vividly described by Prof William Hamilton, of Oxford University, in an article in the Times Literary Supplement (September 11th, 1992). He was helping a farmer to do some work on a hive. He wore a veil over his head, a leather glove on one hand, and a sock on the other hand. This protective clothing had been sufficient for previous work with wasps.

The following is part of Hamilton's account of his experience: "Within 30 seconds, everything had clarified beyond doubt; everyone near to the hive was going to have to flee for their lives. My hands, in so far as I could see them through a brown fog of bees, had become boxing gloves; they appeared as large brown moving balls. The bees were very quickly reminding me which hand wore the sock and which the leather glove, while others all over me were reminding me that I was wearing only tropical clothing.

"I rushed to my jeep. A mile up the road, when there were more bees inside my vehicle than outside, I jumped out and ran into the forest, and finally, when there seemed to be more bees inside my veil than outside, I flung that off and ran further. Half an hour later, daring to return and dreading to find what had happened to the farmer, my first ominous encounter was with a pig dashing grunting up the road and trailing behind it a small but still furious brown retinue.

"On the farm, no human or large animal seemed to have been seriously stung. The chickens and ducks, however, had failed to escape and all of them were already laid out dead, under the bushes, where they had crept unavailingly for shelter."

The rise of the African bee disrupted beekeeping all over Latin America. Stinging incidents created panic. The reputation of the African bees as great honey producers didn't pay off, largely because beekeepers were unwilling to carry out minimal colony management due to the aggressive nature of the bees. The honey industry crashed.

Eventually, beekeepers in South America adopted strategies that have led to a slow rebuilding of the beekeeping industry. To minimise stinging incidents, apiaries are now located at least 300 yards from roads, houses and cultivated fields. The number of colonies on each site is restricted to 25. Colonies are on individual stands, yards apart, so that an aroused colony will not stir up its neighbours.

Beekeepers have compensated for high levels of swarming and absconding by setting up empty hive boxes to attract wild swarms. Wild swarms are requeened - mated with European queens to create more manageable colonies. Protective equipment for beekeepers has been greatly improved and a very active public education system on how to manage bees, how to avoid being stung, etc, is in place.

The African bees are already established throughout Mexico and are expected to continue to colonise America throughout the 1990s. However, cold weather conditions should limit their northward spread. The most immediate concern is for human health. At present, some 40 people die each year in the USA from bee and wasp stings (mostly from allergic reactions). This may rise to about 100 per year.

William Reville is a senior lecturer in biochemistry at UCC.