Unfortunately the African queens escaped from their cages and bred unchecked with the indigenous bees. The result was disastrous. The new strain of honeybee turned out to be far more aggressive than the original African one, to the extent that potential predators would be viciously attacked, even at some distance from the colony. These "killer bees" soon gained a reputation for killing tethered livestock and even humans. Since 1956 the killer bees have extended their range inexorably northwards at the rate of 100km per year. Having killed an estimated 1,000 people in the 50 years since their introduction, they reached Texas in 1990 and are now established in New Mexico, Nevada, Arizona and southern California.