Bristol Zoo male gorilla revealed to be a female Published duration 20 June 2018

image copyright Bristol Zoo Gardens image caption Zookeepers thought Kukena was a male for six years

Zookeepers had a shock when they realised a six-year-old male gorilla was actually a female.

Kukena was born at Bristol Zoo on 27 September 2011 to mum Salome and the troop's silverback Jock.

But recently those caring for the western lowland gorilla noticed surprising changes to her sexual organs and behaviour.

Senior curator of animals at the zoo, John Partridge, said gorillas are known for being difficult to sex.

"We have a strict hands-off policy with our animals," he added.

"As gorillas can be difficult to sex, Kukena had been thought to be a male.

"She is a healthy youngster and there have been no reasons to perform more invasive health checks on her during her lifetime in the zoo."

image copyright PA image caption Kukena was born at Bristol Zoo in September 2011

The zoo said Kukena, nicknamed Kuki, recently had her first oestrus and her genitalia became more pronounced which alerted them to her true gender.

The surprising discovery is positive news for the future of the species, which is critically endangered, as there are currently fewer female gorillas than males in the world's zoos.

It means Kukena's future looks dramatically different as she is now likely to be moved to another zoo to continue the breeding programme.

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The future of the gorilla is due to be discussed with the gorilla co-ordinator at the European Endangered Species Programme.