WASHINGTON, August 5 (UPI) -- Studying whales' equivalencientists said Monday they have at last figured out some of the kinship patterns in the groups of sperm whales once called harems.
"The beautiful thing about whales is that they are constantly sloughing skin," said Jonathan Wright from Dalhousie University in Halifax, Nova Scotia.
When a whale dives, it leaves behind its version of dandruff, flecks of dark old skin, some pieces no bigger than a human fingernail, some more the size of the palm of a hand. Collecting bits of shed skin gives scientists tissue samples for genetic analysis without invasive sampling like shooting darts into the animals.
Wright, Hal Whitehead and other colleagues used sloughed skin for the most ambitious genetic analysis yet of kinship in the clusters of older female and young sperm whales that swim together in the warmer latitudes. The study, published in the Proceedings of National Academy of Sciences, focused on so-called pods of 10 to 30 sperm whales, which scientists "used to think of harems," Wright said. However, he dismissed the term as an imprecise leftover from an era when almost all biologists were male.
The modern view of the sperm whale lifestyle recognizes that females spend their lives swimming in tropical or near tropical waters in pods with young of both sexes. Males eventually peel away from the pod, sometimes joining bachelor groups for a while. They mature into solitary adults, cruising farther and farther north toward the Arctic and Antarctic. A male journeys back to the tropics to mate every five or six years, according to the current estimate.
Researchers now have evidence about what happens next, thanks to the new genetic analysis. A visiting male seems to mate with several of the females in a particular pod before moving on to another pod. The new analysis also confirmed that the youngsters in a pod are related to the adult females, as if several moms and their kids started swimming together for a while. And for the first time, researchers have genetic evidence about when the males leave, which seems to be at age five or six.
This information of kinship may help the biologists who study so-called altruism in animals, Wright said. Whales indeed do things that would be called altruistic in a human, including suckling the baby of another female as well as babysitting and defending other female whales' offspring. These acts of "kindness" might make sense if the helpful whale had some genetic connection with the animals that benefit, Wright said.
The new evidence for tight kinship in a pod of sperm whales fits well with what scientists know about family values in other whale species, said Cathy Schaeff, whale biologist and professor at American University in Washington. "Whales are very social," she said.
In orcas, for example, "the moms are responsible for the mates of their sons," she said. Young whales trail along with their mothers, finding mates when the mothers visit another group of orcas. Recognizing just how sperm whales find their mates and how families stick together will help conservationists figure out how to preserve genetic diversity in the population, Schaeff said.