An orca killed a trainer at Sea World on Wednesday. The trainer was the third person whose death was blamed on this particular animal, named Tilikum, which drowned another trainer in 1991 and probably killed a man who sneaked into Sea World in 1999. Can an animal really develop "a taste for human blood"?
Sort of, but that's not what happened at Sea World. A wild carnivore that eats a human victim, usually during a time of scarcity, may very well continue to hunt people when it discovers just how vulnerable they are. A well-fed, captive animal is a very different story, however. Zoo or aquarium animals do attack their keepers from time to time, but they don't eat them. Indeed, there's no evidence that Tilikum devoured any of his three victims. This sort of violence is usually attributed to psychological stress brought on by unpleasant living conditions. That said, there is an assumption that a killer animal might kill again: Most zoos and aquariums isolate the aggressor and limit its contact with humans to necessary veterinary care.
There has never been a confirmed case of an orca killing a human in the wild. Sailors have fallen directly into orca pods and emerged unscathed. Whatever orca attacks do occur seem to be those brought on by the strain of being in captivity. Life in an aquarium tank can be stifling for animals accustomed to migrating across oceans in search of food. (Orcas' voices are capable of carrying more than 10 miles.) Captive orcas that are prone to mental stress and aggression have sometimes lashed out, but very few have repeated the behavior. Tilikum was probably just, by nature, more nervous and combative than his peers.
A few terrestrial carnivores, on the other hand, have become famous for manhunting in the wild. A pair of lions killed at least 35 railway workers in present-day Kenya in 1898. (Contemporary accounts put the number at 135, but recent isotopic analysis of the lions' flesh lowered the total considerably.) As in many cases, the beasts probably resorted to preying on humans out of necessity: They were living under drought conditions, and an abscessed tooth prevented one of the lions from hunting its natural prey. Once they learned just how easy it was to kill a slow-footed, poorly armored human, there was no reason to work so hard for zebra or buffalo. (Taste may have had little to do with it.) Other serial man-eating lions include Zambia's Chiengi Charlie (90 victims in 1909), Tanzania's Osama (50 victims between 2002 and 2004), and an entire human-hunting pride in Njombe (accused of killing more than 1,000 people between 1932 and 1947).
Wildlife managers and African villagers are so certain that human-hunting is addictive that they kill novice man-eaters immediately, sometimes taking advantage of the animal's habits by lying in wait at the same settlement where it made its first kill. One man in Tanzania successfully exacted his revenge, and protected his neighbors, by lacing his dead wife's remains with poison and waiting for her leonine killer to return for seconds.
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Explainer thanks Jonathan Balcombe, author of the forthcoming book Second Nature: The Inner Lives of Animals, Marc Bekoff, author of The Animal Manifesto, Craig Packer of the University of Minnesota, Bruce D. Patterson of the Field Museum of Natural History, and Justin Yeakel of UC-Santa Cruz.