A group of sperm whales appear to have taken in a deformed bottlenose dolphin, marine researchers have discovered.
Behavioral ecologists Alexander Wilson and Jens Krause of Berlin’s Leibniz-Institute of Freshwater Ecology and Inland Fisheries came across the heartwarming scene some 15 to 20 kilometers off the Azores in the North Atlantic, as they observed the dolphin six times while it nuzzled and rubbed members of the group, reports the journal Science.
“It really looked like they had accepted the dolphin for whatever reason. They were being very sociable,” Wilson told the journal.
The dolphin’s unfortunate deformity — a spinal disfigurement, likely a birth defect, which gives its back half an “S” shape — could help explain how it’s come to be taken in by the sperm whale group, explains Science.
“Sometimes some individuals can be picked on. It might be that this individual didn’t fit in, so to speak, with its original group,” Wilson says, speculating that the deformity could have put the animal at a disadvantage among its own kind — perhaps it had a low social status, or just couldn’t keep up with the other dolphins.
Sperm whales swim more slowly than dolphins, notes the journal, and the pod designates one member to “babysit” the calves near the surface while the other adults dive deep.
But what was in it for the sperm whales? There’s no obvious advantage, Wilson tells Science.
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In fact, as cetacean ecologist Mónica Almeida e Silva of the University of the Azores in Portugal tells the journal, sperm whales have good reasons not to like bottlenose dolphins. “Why would sperm whales accept this animal in their group?” she said. “It’s really puzzling to me.”
But maybe we shouldn’t draw too much from this apparent display of affection: as behavioral biologist Luke Rendell of the University of St. Andrews in the U.K. explained to Science, the briefness of the observation, and its rarity, as well as how little is known about these particular whales, makes it hard to interpret. They might simply enjoy the dolphin’s attentions, says Rendell, or “they could just be thinking, ‘Wow, this is a kind of weird calf’.”