Faith, Auckland Zoo's 41-year-old hippo, was put down on Tuesday.

Auckland Zoo's last remaining hippo, Faith, has died.

The 41-year-old hippopotamus had been unwell for a few days and was put to sleep on Tuesday, zoo spokeswoman Jane Healy said.

Faith had been exhibiting signs of signs of fatal haemorrhagic respiratory disease, or bleeding in the lung, and a preliminary autopsy confirmed Faith suffered from the disease.

SUPPLIED Faith's son, Fudge, died in March at the age of 28.

A short statement from the zoo said the disease is a terminal condition and euthanasia was the only option.

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Faith also had other age-related issues such as arthritis and dental disease.

Faith was a "dearly loved member" of the zoo family, the statement said.

"Our thoughts go out to all our staff, volunteers and everyone who loved Faith - especially our incredible team of Pridelands keepers who cared for her and enriched every day of her long life."

Faith's death comes just months after that of her 28-year-old son, Fudge. He died in March after a short illness.

Both hippos were born at the zoo - Faith in 1975 and Fudge in 1988. The average life-span of a hippo is 40-50 years.

Healy said zoo staff would not know if the deaths were related until Faith's post-mortem was carried out.

"She was a grand old lady. It's still raw," she said.

The hippo enclosure would remain closed on Wednesday.