Male killer whales remain dependent on their mothers for life and this threatens their species

Even in killer whales the mental burden is borne by the females. A study conducted over several decades reveals that males remain dependent on their mothers throughout their lives and rely on them for nourishment. This discovery would almost make you smile if this behavior weren’t such as to compromise the survival of a species already threatened with extinction. Entirely devoted to their male offspring, females would no longer have the time or energy to give birth to more young. However, it would be a strategy to ensure the perpetration of the species, unfortunately not very effective.

The behavior of killer whales studied for 40 years

Killer whales, better known as killer whales, are marine mammals that inhabit many parts of the globe. To better understand their familial mechanisms, Professor Darren P. Croft, a researcher specializing in animal behavior within the Center for Whale Research studied between 1982 and 2021 a pod of 70 evolving orcas off Vancouver. By more specifically following the quarantine of females and their young, the scientists found that intrafamilial relationships played a role in the fecundity of killer whales.

In some species (including lions, African elephants, and some primates), infants remain with their parents long after weaning, and sometimes even for life. Until then it had never been possible to establish whether these dependencies influenced in one way or another the fertility rate of females who were already mothers, or if, on the contrary, they were useful for the survival of the individuals:

In several species, the presence of the mother has a positive impact on the survival of her offspring well beyond weaning and sometimes even for life (…) We have difficulty understanding whether this [ce comportement] whether or not it involves a particular reproductive sacrifice [de la part de la mère], as impacts on female reproduction rates are rarely quantified. In primates, including humans, it is generally believed that mother-child bonds ultimately lead to mutual benefits (…) such as improved maternal survival (…) and that of younger siblings.

Excerpts from the study Expensive maternal lifetime investment in killer whales

In killer whales, however, the study allows us to suppose that this dependence is of no advantage either for the species in general or for individuals in particular.

Caring for one’s children at the expense of one’s life and the species

This research revealed that male killer whales depended on their mothers for their entire lives, including relying on her to provide them with sufficient amounts of food. Conversely, their sisters leave the group to reproduce once they become adults. This omnipresence of male offspring with their mothers negatively affects the reproductive capacities of the latter, who mobilize all their energies to find resources to meet the needs of their children, and this, until the end of their lives. To explain this phenomenon, researchers have advanced the theory that males are the object of long-term investment. By making sure they have enough food, their mothers can hope to raise males who will become powerful as adults, and then be able to reproduce effectively in turn.

This important finding allows similar patterns to be predicted in other species over the long term. Unfortunately, this reproductive strategy does not seem to bear fruit for orcas. Already threatened by ecological disasters, this behavior compromises the birth rate and continuity of the species.