Zookeepers were left needing counselling after a silverback sent to Australia from Howletts in Canterbury attacked and killed another gorilla in front of primary school pupils.

Otana, 14, was moved down under from the Bekesbourne animal park two years ago because he was too old to remain in his family group.

But last Saturday he displayed “unexpected and unprecedented” aggression towards a female gorilla called Julia, who had been at Melbourne Zoo for 15 years.

The 33-year-old was attacked and subsequently died from her injuries, leaving keepers shocked and devastated.

Although Otana had previously shown some aggression towards female gorillas, zoo staff say the social dynamic between the gorillas had appeared to be working well.

Judith Henke, a zoo spokeswoman, said: “Staff monitoring the group as usual throughout Friday observed Otana displaying an unexpected level of aggression towards Julia.

“Silverbacks assert their dominance as a normal part of behaviour. In this instance, the results were unprecedented.”

“Staff did not realise Otana had severely injured Julia, but noticed she appeared listless and unwell on Saturday.

"This type of incident is extremely rare and is, most likely, a result of Otana’s inexperience as he learns how to manage his group..." - Howletts spokesman

“It was decided to move her to the zoo’s veterinary hospital for examination where she was found to have extensive injuries and later died.”

Reacting to the news, Howletts described Otana as "sweet natured" and said attacks like this are "extremely rare".

A spokesman said: "Keepers from Melbourne Zoo visited Otana at Howletts and spent time with the gorilla team at the wild animal park before Otana’s transfer to Australia and a keeper from Howletts travelled and stayed in Melbourne, to assist whilst Otana settled into his new home.

"Otana is a sweet natured young silverback and as an inexperienced juvenile, away from his natal group and learning to lead his own group, is under a certain amount of pressure.

"This type of incident is extremely rare and is, most likely, a result of Otana’s inexperience as he learns how to manage his group."

The park's animal director, Neil Spooner, has spoken to the team in Melbourne and commended the way they handled the incident.

But PETA Australia’s campaign co-ordinator Claire Fryer claims the zoo could have done more to prevent the attack.

She said: “Humans share 98% of our DNA with gorillas, so it should never be a surprise when a gorilla who has been locked up and put on display in a zoo reacts just as we would — with boredom, frustration, anger, and even psychosis.”

“The only surprise is that incidents like this one don’t happen in the public eye more often.

“PETA holds the Melbourne Zoo responsible for keeping gorillas in conditions that simply cannot come close to their natural environment.

Otana was given to Melbourne Zoo by Howletts in 2013.

At the time, director Kevin Tanner said: “‘After the sad loss recently of our male gorilla, Rigo, it was very important for us to bring in another male to become the new group leader.

“The natural social structure of gorilla groups is a male with several females and their young.

“We were fortunate that Otana had recently reached the age when he was ready for a group of his own right at the same time that we needed to locate a new male for our females.”