Females of most species continue to reproduce for the duration of their lifespans. However, just like humans, orca females undergo menopause. Around half way through their lives, they lose their ability to sexually reproduce. For killer whale females, 95 percent of their own lifetime fecundity has been accomplished by the time they are 39 years old – yet adult females regularly live up to the age of 90.
There are some distinct evolutionary advantages to leaving procreative mating to the next generation. Orcas live in matriarchal groups of mothers and their adult children, male and female. Different matrilineal groups that associate regularly with each other are called pods - and it’s common for pod members to forage, hunt and socialize together.
Language is an incredibly important part of the social lives of orcas, and dialects between pods are usually quite different. These linguistic dialects are kind of like family cultural traditions. Rather than being genetically inherited, they are transmitted socially via the great matriarchs, and can be stable for many generations.
Grandmother orcas also benefit their pods with long-time knowledge of foraging grounds, physical strength and unchallenged leadership. This role is especially important because her adult children remain biologically busy creating the future generations of the pod.
When it comes to reproduction, killer whales exhibit something called exogamy. Both males and females temporarily leave the pod during mating season. They each mate with a member of the opposite sex from another pod before returning home. However, the workload that they bring home is drastically different.
Females return home pregnant and soon after deliver a calf - the newest member of the pod. This results in more work for grandma orcas in terms of what it takes to care for, feed and defend the entire pod - including the moms providing direct care to newborns and juveniles.
After mating, adult males return home on their own. A female in another pod is carrying his baby - and like most male mammals in the animal kingdom – his reproductive work is done. Grandmother orcas are generally more protective over her adult sons. She readily comes to their defense, and makes sure they always have abundant food to eat. In fact, an adult male orca is much more likely to die in the year following his mother's’ death than his sisters are.