Very rarely do wild animals adopt young of a different species—although it is not so uncommon for domesticated animals to do so, or for animals to adopt young of their own species.
The first-ever case of a bottlenose dolphin adopting a melon-headed whale calf was documented in the coastal waters of French Polynesia in the South Pacific, and it’s sublime to behold.
Researchers filmed and photographed the mother bottlenose, with her slender beak, and her adoptive 1-month-old baby, with his blunt beak, together over the course of several years starting in 2009.
Orphan began to behave like his adopted family, researchers observed
The melon-headed whale, unlike the name suggests, is not in fact a whale but a type of dolphin—though it is an entirely different species and genus as the bottleneck, making the pair a unique coupling.
“We were really excited to be able to witness such a rare phenomenon,” said Pamela Carzon, head researcher from Groupe d’Étude des Mammifères Marins de Polynésie, based in Tiputa.
“At the time we were really, really astonished.”
Among a community of around 30 dolphins, the mother caught the researchers’ attention because she had two young in tow—bottlenose dolphin moms normally nurse only one baby at a time—one was her biological bottlenose infant daughter, and the other, the melon-headed whale calf.
This is the first known case of a wild bottlenose mom adopting a calf of another species. The melon-headed whale calf even gained acceptance into the community by acting like a bottlenose dolphin.
Remarkably, the melon-headed calf seemed even more bonded to the mother than her daughter was. The pair were often seen swimming together. Twice he was observed nursing from her, and, in a bout of sibling rivalry, he was even spotted jealously shoving his sister away from mom’s abdomen.
Moreover, the baby melon-headed calf stayed with his mother long after his sister had left her side at one-and-a-half years old. Mother bottlenoses care for their young for as long as six years, National Geographic reported. The baby calf eventually left her around April 2018.
The pair’s unusually long bond also underscores the mother’s investment in a species other than her own.
“In mammals, synthesizing milk is very costly—it’s a very precious resource,” said Kirsty MacLeod, a behavioral ecologist at Lund University in Sweden.
The apparent adoption, unusual in and of itself, was made all the more striking by the fact that the bottlenose already had a biological baby; typically, dolphin mothers only care for one calf at a time.
As for why the mother chose to adopt this particular calf, one can only speculate; although it’s possible that the birth of her biological daughter triggered maternal instinct, which served as a catalyst.
“Most likely, it was just a perfect moment for this calf to come along, when [the mother] was at a very receptive period to forming those bonds with her own offspring,” MacLeod said, via National Geographic, “and it led to this slightly wacky situation.”
This mother dolphin, it was also reported, exhibited particularly friendly traits toward local divers, and those traits may have displaced the typical aggression bottlenoses have toward the young of other animals.
Additionally, the young melon-headed calf had little difficulty fitting in with the dolphin pod, and that may have helped facilitate the mother-offspring bond. The melon-headed calf was sometimes seen playing with other young and exhibiting behavior very similar to his bottlenose counterparts. He even took up the same leisure activities as them, surfing and leaping into the waves.
“It shows that young dolphins have striking behavioral flexibility,” Carzon said.
As for other wild mammals adopting young orphans of differing species, there is only one other scientifically documented case that was reported. In 2006, primatologist Patricia Izar from São Paulo University observed a group of capuchins that were taking care of a marmoset.
“At the time, we were really, really astonished,” Izar had said.