As mothers, we often make sacrifices for our children. But for orca mothers, the devotion to their sons goes beyond the ordinary, to the extreme. A new study published in Current Biology has found that orca mothers are sacrificing their own reproductive prospects to ensure the future success of their sons.
This mama’s boy phenomenon is true for the 73 resident orcas that make up the “southern resident” population, living off the coasts of Washington state and British Columbia. The Center for Whale Research has been studying this population since 1976 and discovered this “bizarre social system” where the mothers continue to hunt for their adult sons.
Orca groups are matrilineal, meaning both sons and daughters stay with their mom’s group for their whole lives. But the sons are more likely to follow their moms around, while the daughters are cut off from prey sharing by their moms once they reach sexual maturity.
So why are mom orcas giving their sons preferential treatment? Researchers think it all comes down to an evolutionary cost/benefit analysis. Males are bigger and need more calories, so they may have less luck catching fish. From the mom’s point of view, there’s a cost to helping the daughter reproduce, while helping the son reproduce has the same benefits without the cost of having another mouth to feed.
Unfortunately, this coddling of males comes at a cost for the mothers. The study found a “strong negative correlation” between females’ caring for their grown sons and their probability of producing a viable calf. Each surviving son cuts a mother’s chances of having a new calf by more than 50% in a given year.
This study highlights the remarkable bond between orca mothers and their sons, and the lengths they will go to ensure the success of their offspring. It’s a reminder of the power of maternal love and the sacrifices we are willing to make for our children.