Mukulu packed plenty into his 23 years, including becoming a great, great-grandfather 10 times over.

As an infant, the Rothschild's giraffe gained world-wide attention after he was photographed being kissed on the head by his mother.

On Wednesday Melbourne Zoo confirmed the sad news that Mukulu had died.

Born at Perth Zoo, he moved to Victoria in 1996. He was the oldest male of his subspecies in the Australasian region.

Keepers were forced to make a difficult decision after Mukulu showed a loss of appetite, following weeks of deterioration in his health.

They described him as a calm and gentle creature who would be "dearly missed".

"Veterinarians and the devoted keeper team have done a tremendous job keeping Mukulu active for his 23 years at Melbourne Zoo, and I thank the team for their dedication to Mukulu's welfare and wellbeing," zoo director Kevin Tanner said.

"Mukulu was a wonderful ambassador for his wild cousins who, with only approximately 670 left in the wild, are very much under threat."

The image of Mukulu with his mother, Misha, bending down as she plants her lips on his head, was taken by a photographer from the West Australian newspaper.

Perth Zoo, where the photo was taken, said it helped to raise the profile of the endangered Rothschild's Giraffe.

Mukulu lived with his mate Twiga after she arrived at Melbourne Zoo from Holland in 1997.

They produced four calves and Mukulu was a great, great-grandfather to 10.