Scientists have discovered that mother killer whales have the longest menopause of any non-human species so they can care for their adult sons.
Female killer whales stop reproducing in their thirties or forties, but can live beyond the age of 90.
A team of scientists analysed 36 years of records from killer whale populations in the North Pacific. For an adult male, the death of his mother increased the likelihood of him dying within a year 14-fold.
Dr Dan Franks, from the University of York, said: "Male killer whales are pretty much mummy's boys and struggle to survive without their mother's help."