London: It's not only humans, but whales also use babysitters to look after their babies while they go out, a new study has revealed.
An international team, led by Dalhousie University, has carried out the study and found that mother sperm whales use organised babysitting sessions so they can go hunting for food, the 'Behavioural Ecology' journal reported.
According to researchers, whales use the equivalent of a babysitting pool in a bid to ensure mothers can feed without endangering their young.
Lead researcher Shane Gero said that in larger groups the babysitting tended to be reciprocal. "The diving behaviour of a group changes when a calf is present," he was quoted by 'The Daily Telegraph' as saying.
Sperm whales are one of the deepest diving whales on the planet and make dives of more than 2000ft below the ocean's surface lasting up to an hour while they search for the squid they feed on.
Added co-researcher Dr Luke Rendell: "The calves are therefore very vulnerable when left alone on the surface to attack from large marine predators which may include sharks but especially killer whales.
"Sperm whales are slow reproducers, 5 years is pretty good calving interval -- so that means every calf represents a huge investment for the mother."
For their study, the researchers spent two years following 23 sperm whale calves and their families through the Sargasso Sea around Bermuda and the Eastern Caribbean in a 40-foot research vessel.
They found that all of the youngsters were cared forby individuals other than their own mothers at given times. In some cases mothers would even nurse babies belonging to other members of the group.
In small groups, responsibility for babysitting a young calf would often fall to the same trusted female, often a great aunt. In larger groups, a number of females took turns to care for the calves of other members.
"It is not unreasonable to suggest that the need to protect vulnerable offspring could have been an important evolutionary driver of co-operation among sperm whales, just as it may have been in humans," Dr Rendell said.