In an unusual twist of nature, a bottlenose dolphin has adopted a pilot whale calf in the Bay of Islands.
The phenomenon has been documented in recent weeks by the Far Out Ocean Research Collective based in Paihia.
Marine researcher Jochen Zaeschmar told 1 NEWS bottlenose dolphins are known to adopt the young of other ocean mammals but it's not exactly known why.
"It could be a misguided motherly instinct, or she lost her own calf," he says.
There is also the possibility the dolphin just took a shine to the pilot whale calf and essentially stole it for her own.
The bottlenose dolphin that adopted the calf is "well-known" in the area, according to Zaeschmar, and had recently been spotted in a combined pod of pilot whales, bottlenose dolphins and false killer whales.
Photos taken by the Far Out Ocean Research Collective show the pilot whale calf and bottlenose dolphin have been together for at least five weeks.
"Pilot whales spend seven years with their calves," Zaeschmar explained. "There is a good chance it will eventually join another pod of pilot whales as they often cross paths."
However, he added there isn't much chance of the pilot whale calf being reunited with its original mother if still alive, as "it's a big ocean".
"We are hoping to re-encounter her to monitor this interesting phenomenon," Far Out Ocean Research Collective says.