To date, only five species on Earth are known to go through menopause. Humans, of course, Short-finned Pilot whales, Beluga whales, Narwhals, and Orcas. Menopause is the post-reproductive part of female life, where the value of knowledge to pass down outweighs the value of possible continued reproduction. So what is the correlation between humans and orcas being two of the most advanced creatures on the planet, and both species experiencing menopause?
Menopause is believed to have evolved similarly in whales and humans, by females increasing their lifespan without increasing their reproductive window, which causes greater overlap with their grandchildren’s lives and decreases competition with their daughters (Nature). This then allows the grandmothers to spend their energy on passing knowledge on to the young, which also decreases the energy the pod mothers must spend, benefiting multiple generations. Grandmothers play an especially essential role in orca pods because hunting methods, prey groups, and geography vary from pod to pod. This means that, like humans, older orcas have knowledge of specific regional practices not used by other orcas. They have, in a sense, traditions. Another similarity to humans is that family deaths affect the whole pod. A study done in 2020 by PNAS on Southern Resident killer whales showed that when grandmothers passed, the survival likelihood for young grandoffspring decreased. These particular whales rely heavily on the chinook salmon population, which has been suffering recently. In years of medium to low salmon abundance, the death of a grandmother was shown to have the most negative impact. This shows the crucial role grandmothers play in passing on hunting techniques and skill acquired by age, which younger mothers lack.

There is an argument to be made that maximum evolutionary efficiency could be reached if grandmothers continued to reproduce as well as teach, but that is not the case. Since orcas are matricarchical, a grandmother continuing to mate may decrease her own offspring’s chance to mate, and since they are younger, they have greater potential for more viable pregnancies. In the end, continued reproduction could actually decrease the number of births in the pod. It could also cause mortality, losing both the individual and her knowledge in the process. Findings suggest that breeding grandmothers can’t offer the same level of education and support to young that non-reproducing grandmothers can (PNAS).
Overall, the adaptation of menopause greatly benefits Killer whale populations, and plays a role in establishing hierarchy and advancing pod success. Orcas and humans alike benefit from the longevity that menopause provides females, both in a familial way and in society as a whole.

Citations

Nattrass, S., & Croft, D. P. (2019, December 9). Postreproductive killer whale grandmothers improve the survival of their grandoffspring | PNAS. Postreproductive killer whale grandmothers improve the survival of their grandoffspring. https://www.pnas.org/doi/10.1073/pnas.1903844116

Ellis, S., Franks, D. W., Nielsen, M. L. K., Weiss, M. N., & Croft, D. P. (2024, March 13). The evolution of menopause in Toothed Whales. Nature News. https://www.nature.com/articles/s41586-024-07159-9

Reilly, P. (2024, March 6). 60-year-old grandmother Orca kills great white shark in incredibly rare moment: Video. New York Post. https://nypost.com/2024/03/05/world-news/60-year-old-orca-kills-great-white-shark-in-incredibly-rare-footage/