Grandmother Orcas Help Orca Calves' Survive

The survival chances of young orca whales are boosted by the presence of their grandmothers, especially in times of food scarcity, according to new research that offers a clue as to the evolutionary purpose of menopause.

While female orcas normally stop reproducing in their 30s and 40s, they can live for many decades following menopause, said the study, published in the Proceedings of the National Academy of Sciences on Monday.

Scientists analyzed 36 years of data from the Center for Whale Research on killer whales in Canada and the United States. They found that post-reproductive whales were especially important because they were the most knowledgeable when it came to hunting.

"The death of a post-menopausal grandmother can have important repercussions for her family group," said Dan Franks, senior author of the study and a professor of biology at the University of York.

He added that breeding grandmothers were less capable of providing the same level of support to baby calves, as they were busy taking care of their own offspring.