Animal-welfare experts have condemned an entertainment park for teaching a gorilla to do handstands.
Video of Bolingo copying his keeper as she stands on her hands at a US attraction has been shared hundreds of times on social media.
The 12-year-old animal, kept behind glass, experiments and learns to put his feet to the spot where her feet are up.
But claims the footage showed the animal was being provided with “mental stimulation” were disputed.
“It says something about the life of animals in zoos when something like this is deemed useful to keep animals occupied,” he said.
“The environment just isn’t fit for purpose if they have to resort to such artificial means to keep animals appropriately stimulated.
“This has all the hallmarks of circuses. It’s not something we should be celebrating.
“The ability of a gorilla to do a handstand should not surprise us. But this video is totally sensationalist and slightly silly.”
Charity Freedom for Animals (formerly the Captive Animals Protection Society) condemned the footage.
“Releasing a video like this to the public is damaging and completely irresponsible,” said spokeswoman Nicola O’Brien. “This just teaches people that animals can be trained to perform tricks and are here for our entertainment.
“For the zoo to claim this behaviour is ‘good for him’ as some way of justifying this just exposes the fact that they recognise that animals are deprived and restricted in captivity.
“This incredible animal should not be reduced to a life on display behind glass, being trained to perform tricks in some poor attempt to stimulate his mind and body.
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“He should be roaming free in the wild, stimulated by the diverse habitat of the jungle and by his social interactions with his group and other animals.”
The western lowland gorilla – an endangered species – lives at the Busch Gardens park in Tampa Bay, Florida, where he was born. The park is owned by SeaWorld, which has been at the centre of protests for keeping orcas and killer whales in captivity.
Dr Draper said zoos caused animals huge mental trauma. “It’s well known that primates and gorillas in particular are sensitive to large numbers of people crowding around their enclosures. Gorillas interpret people staring at them as a threat.
“You can see stress behaviour in captive gorillas and abnormal social behaviour and even repetitive behaviour such as regurgitation and reingestion as a result of stress.”
Dr Draper also dismissed the pro-zoo arguments, saying they were exploitative rather than entertaining, and that rather than educating children about animals, they taught children that keeping wildlife in captivity was acceptable.
“As for conservation, it’s a complex picture. Some zoos do some good for conservation, but none does enough. Zoos claim to raise money but the amount they raise is a drop in the ocean compared to the cost of running a zoo.”
Dr Draper said it was unlikely that doing handstands in the short term would harm the gorilla, but any animal made to perform the same tricks or stunts repeatedly over a long time could suffer effects.
“I would hope they would vary what they are training him to do,” he said.
A spokeswoman for Busch Gardens said: “This type of enrichment and training enables us to build trusting and positive relationships with the animals that call Busch Gardens Tampa Bay home, in order to provide them with the most mentally and physically stimulating environment possible.
“We provide them with positive environments based on choice where they voluntarily participate in anything we do.
“These animals serve as ambassadors for their wild counterparts across the globe. By building and sharing relationships with these animals, we help inspire guests to care for them and have the opportunity to explain the harsh realities they face in their natural environments.”