Newspaper article The Canadian Press

Killer Whale 'Grannies' Coddle Their Baby Boys Well into Adulthood: Study

Newspaper article The Canadian Press

Killer Whale 'Grannies' Coddle Their Baby Boys Well into Adulthood: Study

Article excerpt

Orca 'grannies' spoil the boys: study

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VANCOUVER - Like some of their human counterparts, killer whale mothers continue to dote on their sons well into adulthood, says a new study based on two pods of resident killer whales off the coast of British Columbia.

That coddling appears to help the male orcas to mate and reproduce.

The study released Thursday by the University of Exeter, in the United Kingdom, looked at more than three decades of research by Fisheries and Oceans Canada in B.C. and the Center for Whale Research in Washington state, and found that orca females live many years after they are no longer capable of reproducing.

"This long period of post-reproduction is not very common in mammals, outside of humans," said Dr. John Ford, a research scientist at federal fisheries' Pacific Biological Station.

A female killer whale typically stops bearing offspring in her 40s and lives, on average, another decade. Ford said whale researchers believe they can live as much as another 50 years.

Using the census data collected off the Pacific coast since 1974, researchers at the University of Exeter were able to model the lifespans of the 300-plus members of the northern and southern pods of resident killer whales and found that these whale grannies have little effect on their adult daughters but a profound effect on the survival of sons.

"We have discovered that female killer whales have evolved the longest menopause of any non-human species so they can care for their adult sons," Emma Foster, the lead author of the paper, said in an email interview.

By looking at the Canadian and American whale census data, Foster and her colleagues found that for a male orca over 30, the death of his mother results in an almost 14-fold increase in his own death within the next year. The effect on female offspring's reproductive success was negligible.

Why that is remains something of a mystery, Foster said, because whales are difficult to observe under water where they spend the majority of their lives.

"However, we have a few ideas about what could be going on here we can speculate that they may provide help with foraging, or support during encounters with other whales," she said. …

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