First known case of adult female dolphin adopting whale calf documented

written by Oceanographic Staff

New research documents a case of a wild bottlenose dolphin off the coast of French Polynesia caring for a melon-headed whale.

In 2014, researchers spotted a female bottlenose dolphin caring for both what was presumed to be her own baby and an unusual-looking male calf, with a short and blunt beak. After some time, they identified it as a melon-headed male.

Study lead author Pamela Carzon, scientific leader of the Groupe d’Étude des Mammifères Marins (GEMM) de Polynésie, and her team continued to study the dual-species family as a part of their long-term study of this particular community of bottlenose dolphins, which began in 2009.

“We were really excited to be able to witness such a rare phenomenon,” said Carzon, who reported her observations in Ethology in June. “The melon-headed whale was behaving exactly the same way as bottlenose dolphins.”

Adoption in the wild is extremely uncommon but when it does occur, it’s usually between members of the same species. In this case, the mother committed herself to the orphan to a great extent – the two were spotted travelling together for almost three years, a union that continued long after her biological calf disappeared for unknown reasons when it was around 18 months old. The mother was even seen nursing the adopted whale calf on two occasions.

While female bottlenose dolphins have been known to ‘steal’ babies of other species during brief spells of conflict, the dedication shown by both mother and calf rule this out as a potential explanation. The young whale went to great lengths to integrate himself with the pod of around 30 bottlenose dolphins. He demonstrated determination to join and act like the other dolphins. He was even seen socialising with other younger members of the group and joining in their game of surfing and leaping into waves.

Photograph courtesy of  Pamela Carzon / GEMM.

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