Melbourne Zoo has been rocked by the death of a female gorilla.

The gorilla, Julia, died of complications from injuries inflicted by a young male gorilla.

Melbourne Zoo staff said Otana, the silverback – as adult males are called – had been displaying an “unexpected level of aggression” towards Julia.

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“Silverbacks assert their dominance as a normal part of their behaviour,” Zoos Victoria said.

“In this instance, the results of the aggression Otana displayed towards Julia on Friday were unexpected and unprecedented.”

Zoos Victoria said Julia spent Friday evening away from the main group of gorillas, sleeping in a heated cave outside.

“On Saturday morning staff checking on Julia observed that she appeared to be unwell and was not responding as normal, although no wounds were visible,” the zoo said.

“After immediate consultation with the vet team, the decision was made to move Julia to the veterinary hospital for an examination.

“The vet team examining Julia found that she had experienced extensive trauma and significant complications resulting from the aggression on Friday.

“The team worked to stabilise her condition into the early hours of Sunday, but unfortunately she passed away at 3am today.”

Otana has since been separated from the group, Zoos Victoria said, and keepers are helping the primates get through the event, which has changed the social structure of the group.

Julia, a 33-year-old western lowland gorilla, came to the zoo on December 10, 1997 from Jersey Zoo.

She previously bred with silverback Motaba, producing a female offspring Jumano, now living at Taronga Zoo.

Zoos Victoria said staff were devastated by the loss.

“Staff throughout the zoo are devastated and the primate keepers have been offered counselling to help them through this difficult time,” Zoos Victoria said.

Otana the western lowland gorilla, had been showing unexpected levels of aggression.