It turns out that raising sons takes a higher toll on southern resident orca mothers, when compared to raising daughters. So much so that the mother’s annual likelihood of successfully breeding is reduced by about half.

This is because the mothers share the fish they catch with their sons even after the latter become adults. The mothers would bite the fish they catch into two, consume one half and give the other half to their sons.

(In the case of their daughters, the mothers also share their food, but stop doing so when the daughters reach reproductive age.)