If the ocean were a cocktail party, your average bottlenose dolphin would be hamming it up near the bar, fetching drinks for other marine mammals and regaling them with funny stories. Your average sperm whale would hover quietly near the pretzel bowl, keeping a low profile and avoiding eye contact with that obnoxious dolphin.

The usual aloofness between the two animals explains why researchers were astonished to stumble upon a most unusual sighting near the Azores in the North Atlantic Ocean: a pod of sperm whales that appeared to have accepted a lone bottlenose dolphin calf into their group.

Over a period of eight days in 2011, researchers saw the dolphin and the sperm whales traveling together, nuzzling and generally having a grand time. The dolphin calf had a rare spinal curvature — a deformity that may have made the animal unable to keep up with its own kind, ScienceNOW reported.

"It really looked like they had accepted the dolphin for whatever reason," said behavioral ecologist Alexander Wilson, who has co-authored an upcoming paper about the rare encounter for the journal Aquatic Mammals. "They were being very sociable."


Sperm whales swim more slowly than dolphins and also tend to be more shy. Wilson and fellow behavioral ecologist Jens Krause of the Leibniz-Institute of Freshwater Ecology and Inland Fisheries in Berlin said that as far they know, sperm whales have never been known to mingle this closely with another species, ScienceNOW reported.

Even if the teaming up was only temporary, it still would be unusual given the relationship that typically exists between sperm whales and bottlenose dolphins. Ecologist Mónica Almeida e Silva told ScienceNOW that the dolphins often chase and harass sperm whales and their calves.

"Why would sperm whales accept this animal in their group?" she said. "It's really puzzling to me."
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