Following the killer whale attack on a SeaWorld trainer in San Diego this week, many people are wondering whether the attack was malicious, or if the whale was just playing around.
But experts say that animal behavior simply can't be predicted and that the result can often be terrifying.
Kasatka the killer whale was back on center stage Thursday at San Diego's SeaWorld, but her trainers did not venture into the water.
On Wednesday, she turned on one of them in front of a horrified crowd.
Ken Peters, the trainer, is still hospitalized in fair condition after the whale tore into his foot.
Just two years ago, a Texas crowd witnessed a frightening display as an Orca whale repeatedly slammed itself against its trainer.
Experts say this kind of aggressive behavior by wild animals is not unusual.
"We can't predict human nature, much less animal nature," said Jack Hanna, director emeritus of Columbus Zoo. "Wild animals are like a loaded gun. They can go off at any time."
Chimpanzees can become violent too.
One man was attacked by a group of them when he visited a chimp he had raised for years.
Miraculously, the man survived the attack but required major reconstructive surgery to his face and limbs.
"Wild animals should not be construed as pets," said Larry Killmar, deputy director of collections at the San Diego Zoo. "They should be looked at as wild animals and leave it at that."
Celebrity trainer Roy Horn nearly died when a 400-pound tiger attacked him and dragged him off stage by his neck.
The tigers, professionally trained for years, were still not able to suppress their instincts.
Still, some humans believe they can safely live among the beasts.
The documentary "Grizzly Man" tells the true story of Tim Treadwell and his girlfriend.
Treadwell lived alongside the most ferocious bears in Alaska, spending every waking moment with them and capturing it all on tape.
"I've now proven myself as able to hold my ground and therefore earning their respect," Treadwell says in the film.
In the end the risks were too great. The couple was killed by a bear.
"They're born with instincts, and we can only modify with training," Killmar said. "We always consider them wild."