By Emily Benson
It takes a village to raise a whale. Rather than sticking exclusively to their mothers’ side, baby pilot whales in the north Atlantic take turns swimming next to other adults – including both females and males. Pilot whales are social creatures. They are thought to live in multigenerational family units of about two to four dozen individuals, says Joana Augusto at Dalhousie University in Halifax, Canada.
Those units often gather in larger groups that stay together for up to a few weeks, allowing whales to travel, feed, rest and socialize together. And while anecdotal evidence suggests calves sometimes accompany members of the gang that aren’t their mothers, nobody had systematically studied the behavior in pilot whales before, Augusto says.
“People have noticed that the calves didn’t really stay with the same adults,” she says. “We would see the babies just go from one individual to the other and then jump back.”
Summer boat trip - To see if this behavior is common among the population of more than 3000 long-finned pilot whales that spend the summer off Cape Breton Island in Nova Scotia, Canada, Augusto and her colleagues tagged along on a whale-watching boat. From the vessel, the researchers photographed and identified specific whales based on physical marks such as nicks in their dorsal fins, scars and pigmentation patterns. During more than 600 whale encounters over three years, the team spotted 356 identifiable calves, about one fourth of which sometimes stuck close to an adult that wasn’t their mother. One baby took turns swimming beside five grown-up companions. Using a foam-tipped dart and a crossbow, the scientists collected DNA samples from 75 adult whales to determine their sex. Only five of those adults were identified as non-maternal calf companions — and of those, four were male. That was a surprise, Augusto says. It is unclear why a male might let a baby stay by his side, but one possibility is that he is showing off in front of the females.
Advertising for a mate - “It’s a way to advertise that they’re a good mate, basically,” Augusto says. The scientists didn’t notice the adults altering their behavior when they had a young companion. That could enable the calf to observe the complex social conventions of their community, Augusto says. “The calf might be learning from experiences with different individuals of how they should be behaving socially,” she says. Shared parenting is something you would expect in a species with such strong social bonds, says Robin Baird at the Cascadia Research Collective in Olympia, Washington state.
Bottlenose dolphins and killer whales sometimes escort others’ calves, for example, and sperm whales and belugas even nurse others’ babies, strengthening the social ties of the group, or perhaps signaling to other adults that the babysitters are pulling their weight in the community.
It will be interesting to gather more details on the nature of the interactions between pilot whale calves and adults, Baird says, like how long they spend side by side, and the age of the adult male companions. If the males are relatively young, for example, they may be seeking playmates rather than pupils. Still, Baird says, it is highly likely that calves are soaking up social understanding during the encounters. “Calves are gregarious,” he says. “Calves are motivated to interact with other individuals when their mom’s not right around them.”
Journal reference: Marine Mammal Science, DOI: 10.1111/mms.12377