Monday, January 28, 2013

Sperm whales adopt deformed dolphin

Toronto-born behavioural ecologist Alexander Wilson has discovered an unlikely friendship in the North Atlantic. A group of sperm whales have apparently adopted a bottlenose dolphin with a spine deformity, swimming alongside him and at times nuzzling and rubbing up against him, at least temporarily. Wilson and partner Jens Krause of the Leibniz-Institute of Freshwater Ecology and Inland Fisheries in Berlin made the discovery while observing sperm whales about 15 to 20 kilometres off the island of Pico in the Azores. For one week, they captured stunning photographs of the rare sight, which is the first discovery of its kind for sperm whales. The squid-hunting creatures are not known for their gregariousness.

“Sperm whales have never been observed to interact with another species in a non-agonistic way; basically, that means in a friendly way,” said Wilson. “Dolphins, on the other hand, are the exact opposite. They are extremely gregarious. They’re very, very social.” The researchers were so surprised that at first they weren’t sure what they were witnessing. However, they noticed enough physical gestures initiated by both species to determine it was a social interaction. “The touching of flutes and nuzzling with the rostrum, these are all extremely friendly, social gestures for cetaceans to do to one another,” he said. 

A number of explanations for the unusual alliance have been floated – that the dolphin was seeking protection from predators, or the whales were using him to help forage for food – but these don’t add up, according to Wilson. “In the Azores, there are very few predators that can feed on an adult dolphin, and (the whales) for the most part were not behaving in a protective way, so it seems that is not the most likely explanation,” he said. “Foraging’s also unlikely, because sperm whales feed on squid 800 metres below the surface, whereas dolphins tend to feed on fish near the surface.” The most likely explanation, in his scientific opinion? They’re friends. “Really, it seems that, somehow, either one or both parties derive some social benefit, whether it be social play, or just some way to relax and interact with another cetacean.”

YouTube link.

Wilson also pointed out that the dolphin’s malformed spine, similar to scoliosis, suggests he was bullied or harassed by other dolphins and sought social refuge in the group of whales. “In dolphin groups, there are strong hierarchies, with dominant individuals and less dominant individuals. They tend to be very fast,” he said. “It just might be that this dolphin with scoliosis wasn’t as fast or was lower on the pecking order.” He added that sperm whales may be misunderstood – perhaps they’ve just never been given a fair shot at inter-species mingling. “It may not that sperm whales don’t normally do this type of behaviour, it may be that sperm whales don’t necessarily often encounter another species that would desire such a relationship.”

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