In a study published in the journal Science, researchers found that for a male whale over 30, the death of his mother means an almost 14-fold increase in the risk he will also die within the following year. Males whose mothers live well beyond their reproductive years are more likely also to live to older age.
“Male killer whales appear to be ‘mummy’s boys’ and struggle to survive without their mother’s help,” said Dan Franks of the University of York, who worked on the study. Very few species have a prolonged period of their lifespan when they no longer reproduce, as humans do. But women can look to female killer whales as kindred spirits. They stop reproducing in their 30s and 40s, but can survive into their 90s, like human females.
“Killer whales are extraordinary animals and their social groups are really unusual in that mothers and their sons are lifelong companions,” said Emma Foster, a PhD student at Britain’s University of Exeter who led the study. Foster’s team, found that the presence of a mother killer whale who was not reproducing significantly increased her offspring’s survival.
For males over the age of 30, a mother’s death meant a 14-fold increase in the likelihood of their death within a year. But for daughters of the same age, the difference was just under three-fold. For female killer whales under the age of 30, their mothers death had no effect on survival rates. Ah, the mystery of nature!