Kiwi is a mum once again

A bottlenose dolphin thought to have lost her calf after becoming stranded in the Kerikeri Inlet five years ago has adopted a baby of another species.

Inter-species adoption among dolphins is not unheard of but is extremely rare, and Bay of Islands dolphin spotters were thrilled by their discovery last week.

Marine mammal expert Jo ('Floppy') Halliday said she believed the bottlenose dolphin, known as Kiwi, had been looking after a common dolphin calf dubbed Pee-wee since January. That was confirmed on Thursday when Pee-wee was seen taking milk from its adopted mother.

A fellow crew member on the Fullers vessel Tangaroa, Lawrence Hamilton, photographed the calf swimming upside-down and suckling from Kiwi off Onewhero Bay.

"It's just so unusual. The crew are ecstatic," Jo said.

It was especially heart-warming because Kiwi had become stranded at Aroha Island, in the Kerikeri Inlet, five years ago. She was refloated but her calf, named Squirt, was never seen again. It was feared Squirt had been eaten by orca while its mother was stuck on the mudbank. As far as Jo knew Kiwi had not had another calf, but she was now producing milk.

"There's so many things these guys are capable of doing. They may be able to switch on lactation on demand," she said.

Common and bottlenose dolphins grew at different rates, she added, so it would be interesting to see whether Pee-wee adapted to the ways of its new hosts or followed its instincts.

The larger bottlenose dolphins relied on their mothers for three or four years, only reaching sexual maturity around the age of six. Common dolphins grew faster and matured earlier.

It was not known why a dolphin would adopt a calf of another species, but Jo put it down to the large-brained, social creatures not wanting an orphaned juvenile to suffer. It was not clear how much the dolphins themselves distinguished between species.

Common dolphins grow to about 2.5 metres and are found worldwide, hence their name. They typically work together to round up schools of pilchards and mackerel. Bottlenose dolphins grow to about three metres, and are more likely to venture into estuaries hunting for flounder, mullet and kahawai.

Pee-wee's gender is not yet known.