Research done in a recent study may suggest that older orca mother protect their adult sons in fights, after the mothers have gone through menopause. This in itself is a puzzling enough revelation, especially considering that the female children of the killer whale mothers do not receive the same treatment, and why female whales experience menopause in their typically long, 90 year lifespans. However, this study may held shed some light on this.
It has been speculated that the role of an orca matriarch spans much larger than just giving birth, and it can be seen with these recent study. Killer whale males, even in stages of adulthood, remain to a large part dependant on their mothers for food and protection, with mothers even directly hunting salmon to feed to their sons. This may explain the early menopause considering the importance of the role they play after it and by being unable to reproduce may be in a better position to lead the pack.
The study also uncovers the role of orca grandmothers in supporting the sons, showing the importance of familial ties and connections in these marine mammals. This might support the existence of what is called the grandmother effect existing in species other than humans. This phenomenon is an observed boost to raising offspring catered to by grandmothers. Lead author Dan Franks from the University of York says:
“If a grandmother dies, in the years following her death, her grand-offspring are much more likely to die.”
Much like in humans, the grandmother killer whales also fulfil the babysitting job, taking care of the children while a mother dives for food. With this study it can also be seen why the male offspring is much likely to be given this favour.
This is hypothesized to be because of the fact that males can mate with multiple females in a short duration of time which would involve a female’s pregnancy and thus reproductive inefficiency. This means that by protecting their sons, even though they are technically unable to reproduce, these matriarchs are spreading their genes and playing their part in ensuring the survival of their bloodline.