In addition to humans, the only other mammals who are known to experience menopause are all cetaceans: killer whales, short-finned pilot whales, narwhals, and beluga whales. Of these four types of whales, the killer whale's behavior is by far the most studied and documented. Scientists are not sure why these whales go through menopause when so many other larger mammals do not. One hypothesis for both humans and whales is known as the Grandmother Effect, where older females care for children and grandchildren beyond their reproductive years.
Killer whales live in matriarchal pods and are typically led by older females. Offspring usually stay with their original pod, with males leaving for short periods of time to reproduce with females from other pods. Female orcas go through menopause in their 30's and 40's but can live well into their 90's, if not longer. It is thought that menopause is therefore the best way to ensure that an individual's genetic offspring survive – when orca daughters begin reproducing their mother will often begin menopause, helping to care for her other children and grandchildren instead of adding additional calves to increase competition for food and resources. This is thought to increase the likelihood of survival for the new calves.
Emma Foster, a PhD student from the University of Exeter working with the Center for Whale Research, went through decades of data and discovered some fascinating statistics. If a male orca's mother died before he was 30, he was 3 times more likely to die within a year. If the male was over 30 years old, he was 8 times more likely to die within a year. If his mother had already gone through menopause, he was 14 times more likely to die. This data clearly shows that older female orcas have a massive impact on the survival of their offspring, especially their sons. In addition to sharing food with their sons and younger calves in their pod, the older matriarchs are also thought to be more likely to know where to look for food and mediate conflicts between members of their pod and other orcas.
While the exact reasons behind it are still not certain, menopause is a fascinating connection between humans and whales. It will be interesting to see further research over the years and if any other species experience this phenomenon.