Now, new research has revealed the first known case of a wild bottlenose mom adopting a calf of another species.

In 2014, researchers spotted a bottlenose mother caring for an unusual-looking male calf, along with what was presumed to be her biological calf, in coastal waters off French Polynesia.

While bottlenose dolphins have slender beaks, the mysterious one-month-old’s beak was short and blunt. Eventually, the scientists identified the orphan as a melon-headed whale—an entirely different species and genus of dolphin.

“We were really excited to be able to witness such a rare phenomenon,” says study lead author Pamela Carzon, scientific leader of the Groupe d’Étude des Mammifères Marins (GEMM) de Polynésie, based in Tiputa, French Polynesia.

Adoption is uncommon among wild