Why Tigers Attack

Over the past 24 hours the San Francisco Zoo has gone from a cheerful tourist attraction to a puzzling crime scene. Investigators are combing the premises for clues, trying to figure out how, on Christmas Day, a 350-pound Siberian tiger named Tatiana escaped from its habitat and attacked three young men, killing one and mauling the others before police shot the animal dead. So far they are turning up little evidence; a tiger overcoming a seemingly solid barrier—a 20-foot-wide moat and an 18-foot-high wall—is baffling to police, zookeepers and visitors alike. "We're not certain why the incident occurred—as result of human action or whether this was an incident where the animal was able to get out of the grotto," San Francisco Police Chief Heather Fong told reporters at a press conference.

The incident is, by any estimate, incredibly rare. "To have an animal escape and kill a visitor is unprecedented," says Ed Hansen, executive director of the American Association of Zookeepers and a 25-year veteran of the industry. But for zookeepers it is not particularly surprising: tigers have naturally aggressive and predatory instincts. So when a flaw in design or human error allows one to escape—two factors likely at play in San Francisco—a death is not altogether shocking. It's the rare but very real consequence of allowing humans to come in close contact with predatory animals.

"The fact is you're keeping a wild animal in the cage that eats things the size of humans, sometimes things larger than humans," says Scott Lope, operations director of Big Cat Rescue, an animal sanctuary in Florida. "That's what they do."

While there is no government agency that tracks tiger attacks, Big Cat Rescues recorded 44 attacks by big cats in 2006, one of which resulted in a fatality. The statistic points to a fact that zookeepers say visitors often overlook: large cats, like tigers and lions, are predators even if they have spent their entire lives in a zoo.

"People have a misconception of animals in a zoo that they are tame animals, they've lost their aggressiveness, think of them as pets," says Hansen. "Nothing could be farther from the truth. These are wild animals who have instinctual behavior."

The tiger involved in the San Francisco attack, for example, had already shown her aggressive nature when she attacked a zookeeper during feeding time in 2006. California's Division of Occupational Safety and Health blamed the zoo for the assault, fining it $18,000. While the zoo was at fault, Diana L. Guerrero, an animal expert who previously worked with another tiger at the San Francisco Zoo, says that attack was not necessarily a warning sign; it did not indicate that this particular tiger was any more aggressive than a zookeeper would expect. "Any animal that is a predator will get very possessive at feeding time," says Guerrero. "They are always wild animals whether or not bred in captivity."