Behavioral ecologists Alexander Wilson and Jens Krause of the Leibniz-Institute of Freshwater Ecology and Inland Fisheries in Germany have discovered a group of sperm whales (Physeter macrocephalus) living around the Azores that has adopted a deformed adult male bottlenose dolphin (Tursiops truncatus) with a spinal curvature that gives his back half an "S" shape. Over a period of eight days they observed "the dolphin traveled, foraged, and played with both the adult whales and their calves. When the dolphin rubbed its body against the whales, they would sometimes return the gesture." A research paper on these observations is forthcoming in the journal Aquatic Mammals, a media report published by Science Now can be seen here, and another story and a video can be seen here.
Sperm whales are not known for developing bonds with other species and this observation, the first of its kind, shows that "surprising" cross-species relationships and unlikely friendships can and do develop even in the wild (see also). The dolphin was able to hang out with the whales because they swim more slowly and whale calves are left in the care of a "babysitter" near the surface while others dive deeply into the water.
"Wow, this is a kind of weird calf"
While it's possible that the dolphin gained some protection from hanging out with his new friends, it's not clear what the whales got out of it. Dolphins often harass sperm whales so this relationship is puzzling according to cetacean ecologist Mónica Almeida e Silva of the University of the Azores in Portugal who has studied dolphins in the Azores archipelago.
Perhaps the whales welcomed the male because they felt pity for him or because he wasn't a threat to them. Compassion can and does cross species lines. It's clear that nothing was lost by their adopting him.
Luke Rendell of the University of St. Andrews in the United Kingdom notes that, "Interpreting is hard given the observation's briefness and rarity, as well as how little is known about these particular whales. They might simply enjoy the dolphin's attentions, or 'they could just be thinking, 'Wow, this is a kind of weird calf.'"
Whatever the reasons for this rare observation, it shows just how much there is to learn about the fascinating animals with whom we share our magnificent planet. I'm sure we will discover more of these "surprises" as additional research is conducted on species whose living rooms overlap.
The teaser image can be found here.