Lone dolphin with spinal deformity travels among a group of sperm whales.

By Linda Poon – National Geographic News

“In 2011, behavioral ecologists Alexander Wilson and Jens Krause of the Leibniz-Institute of Freshwater Ecology and Inland Fisheries in Germany were surprised to discover that a group of sperm whales (Physeter macrocephalus)—animals not usually known for forging bonds with other species—had taken in an adult bottlenose dolphin (Tursiops truncatus).”

“The researchers observed the group in the ocean surrounding the Azores (map)—about 1,000 miles (1,600 kilometers) off the coast of Lisbon, Portugal—for eight days as 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.

Among terrestrial animals, cross-species interactions are not uncommon. These mostly temporary alliances are forged for foraging benefits and protection against predators, said Wilson.

They could also be satisfying a desire for the company of other animals, added marine biologist John Francis, vice president for research, conservation, and exploration at the National Geographic Society (the Society owns National Geographic News).

Photographs of dogs nursing tiger cubs, stories of a signing gorilla adopting a pet cat, and videos of a leopard caring for a baby baboon have long circulated the Web and caught national attention.

A Rare Alliance

And although dolphins are known for being sociable animals, Wilson called the alliance between sperm whale and bottlenose dolphin rare, as it has never, to his knowledge, been witnessed before.

This association may have started with something called bow riding, a common behavior among dolphins during which they ride the pressure waves generated by the bow of a ship or, in this case, whales, suggested Francis.

“Hanging around slower creatures to catch a ride might have been the first advantage [of such behavior],” he said, adding that this may have also started out as simply a playful encounter.

Wilson suggested that the dolphin’s peculiar spinal shape made it more likely to initiate an interaction with the large and slow-moving whales. “Perhaps it could not keep up with or was picked on by other members of its dolphin group,” he said in an email.

Default

But the “million-dollar question,” as Wilson puts it, is why the whales accepted the lone dolphin. Among several theories presented in an upcoming paper inAquatic Mammals describing the scientists’ observations, they propose that the dolphin may have been regarded as nonthreatening and that it was accepted by default because of the way adult sperm whales “babysit” their calves.

Sperm whales alternate their dives between group members, always leaving one adult near the surface to watch the juveniles. “What is likely is that the presence of the calves—which cannot dive very deep or for very long—allowed the dolphin to maintain contact with the group,” Wilson said.

Wilson doesn’t believe the dolphin approached the sperm whales for help in protecting itself from predators, since there aren’t many dolphin predators in the waters surrounding the Azores.

But Francis was not so quick to discount the idea. “I don’t buy that there is no predator in the lifelong experience of the whales and dolphins frequenting the Azores,” he said.

He suggested that it could be just as possible that the sperm whales accepted the dolphin for added protection against their own predators, like the killer whale(Orcinus orca), while traveling. “They see killer whales off the Azores, and while they may not be around regularly, it does not take a lot of encounters to make [other] whales defensive,” he said.”

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“The gurgles, whistles, and squeaks of humpback whales singing off Hawaii’s island shores can now be heard live, courtesy of underwater microphones placed near Puako, Hawaii by the Jupiter Research Foundation.

Eavesdropping on this underwater soundscape reveals that the enormous marine mammals — which can reach more than 15 meters (50 feet) long — at times sound like cows, coyotes or UFOs.

Male humpbacks can sing for hours, a behavior thought to play a role in attracting mates. Their all-day chorus contains repeating low-frequency notes and melodies that can be heard many kilometers away. Females also vocalize, but they don’t sing.

Humpbacks congregate near Hawaii in late December to breed, and stick around through April. In 2003, the Jupiter Research Foundation dropped its first hydrophone into the islands’ warm coastal waters and they’ve been broadcasting the sounds each year since 2004; this year’s broadcast just went live last week. Deployed along with a heavy anchor, the hydrophones sit at a depth of about 18 meters (60 feet). They connect to solar-powered buoys on the surface that transmit signals to a radio relay station in the Kohala mountains.”

Read the Entire Article by Nadia Drake.

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