Petre died on Monday at age 32 after suffering a cerebral haemorrhage.

A CT scan identified multiple sites of bleeding on her brain.

Melbourne Zoo's Wild Seas manager Marcia Salverson said there was no prospect of a recovery for the mother of four and she was euthanised.

"Petre was the sweetest animal, so gentle-natured, she was just lovely," she said.

"We loved her and we miss her."

Ms Salverson said Petre was considered to be an older hippo, with anything over 20 years regarded as old for the species.

The Adelaide Zoo-born pygmy hippopotamus had been part of the endangered species breeding program at Taronga Zoo in Sydney and in Melbourne.

Petre's youngest calf, Obi, was much celebrated after becoming the first pygmy hippo to be born at the zoo in 33 years in May last year.

Pygmy hippos are an endangered species native to the rainforests of west Africa.

Researchers believe fewer than 3000 survive in the wild, with deforestation and poaching for meat their major threats.

The death comes weeks after the zoo's baby elephant Willow was also euthanised after battle with an infection.