Cincinnati Zoo gorilla killing: Animal behaviour experts question shooting of Harambe

Animal behaviour experts have queried the decision to shoot dead a silverback gorilla after a child fell into its enclosure at a US zoo.

Cincinnati Zoo's decision to kill rather than use tranquilisers on rare primate Harambe as he held on to the four-year-old has prompted international outrage.

The zoo said a tranquiliser would have taken too long to take effect, but experts in ethology - the study of animal behaviour - said tranquilisers could be highly effective in disabling a large animal and might have saved both lives.

Melissa Bateson, a professor of ethology at Newcastle University, said gorillas were among some of humans' closest living relatives and, like chimpanzees, were highly complex creatures.

"I think one of the main questions is, why didn't they shoot it with a tranquiliser? I'd have thought they would have," she told The Independent.

"When I've seen animals shot with tranquilisers, they've gone down very, very fast. One issue is the animal could have become confused, so the zoo was probably worried."

They also placed particular responsibility with the zoo for having an enclosure for the gorilla that a child of that age could get inside.

The director of the zoo, which shot Harambe after the boy fell about 3.5 metres into his enclosure, said "some people can get past" any barrier and the zoo was not at fault.

Professor Bateson, who has researched behaviour in chimpanzees in the past, said no human could ever predict how an animal, even one hand-reared by humans, would react in a given situation.

She said animal enclosures always needed to be secure.

"I think it's very unfortunate to have enclosures where children can climb in. I would lay responsibility with the zoo for that," she said.

Gisela Kaplan, an animal behaviour expert at the University of New England, said gorillas were not known for being violent or killing humans.

"The silverback would have understood that it was a defenceless small child," she told the Daily Telegraph in Sydney.

"They would not normally attack, they are not an aggressive species and in the wild I'm certain the boy would not have been killed."

A video of the incident appears to show Harambe both trying to help the child and becoming panicked by screams and pulling him away to a corner.

In defending the decision to kill the 17-year-old gorilla, zoo director Thane Maynard, said: "The barriers are safe. The barriers exceed any required protocols.

"The trouble with barriers is that whatever the barrier some people can get past it... No, the zoo is not negligent."