The claim is often repeated as a neat piece of animal trivia: only five species undergo menopause, humans and four whales. It was a defensible summary of part of the literature a few years ago. It is no longer the best account of the evidence.
A 2024 comparative study in Nature, led by Samuel Ellis, treats menopause as having evolved across five toothed whale species: killer whales, short-finned pilot whales, false killer whales, belugas and narwhals. Add humans and the familiar total becomes six. Evidence from one wild chimpanzee community makes even that number less final than it sounds.
The orca part of the story is better supported than the popular shorthand suggests, but also more specific. Long-running studies of fish-eating resident killer whales in the Pacific Northwest have found that older, post-reproductive females disproportionately lead group movement, particularly when salmon are scarce. Separate demographic work found that maternal grandmothers are associated with better survival among their grandoffspring.
Menopause means more than fertility declining with age
Most mammals show reproductive aging. Fertility falls as the body ages, and reproduction generally ends near the end of life. Researchers studying the evolution of menopause use a narrower idea: females stop reproducing and then regularly live through a substantial post-reproductive stage.
That distinction matters. Finding an old female that has not recently reproduced does not establish menopause as a species-level life-history pattern. Scientists need age-specific evidence about survival and ovarian activity, drawn from enough animals to distinguish a prolonged post-reproductive stage from ordinary aging, illness or an unusual individual.
Whales make that work difficult. Researchers cannot follow most of them from birth to death, and much of the comparative evidence comes from deceased animals recovered after strandings or historical hunts. Age can be estimated from tooth growth layers, while persistent structures in the ovaries provide a record of past ovulation. The measurements are informative, but the samples are necessarily uneven.
Why the old total changed
The four-whale version usually names killer whales, short-finned pilot whales, belugas and narwhals. A 2017 study of false killer whales, also led by Ellis, reported morphological and statistical evidence for a post-reproductive phase in a fifth toothed whale. Its specimens came from a 1981 mass stranding in South Africa and a 1979 to 1980 Japanese hunt. In that sample, ovarian activity had ceased in half of the females older than 45 and in all females older than 55.
The 2024 Nature paper then placed those five whale species in a larger comparison. Its team assembled female lifespan estimates for 32 toothed whale species and reproductive-lifespan estimates for 18. After accounting for body size and evolutionary relationships, species with menopause were predicted to live about 40 years longer than similarly sized species without it. Their reproductive lifespans were not correspondingly shorter.
That is an important reversal of the intuitive story. The result does not suggest these whales evolved by stopping reproduction unusually early. It supports a “live long” pathway in which female lifespan extended beyond the reproductive years. This is a comparative model, not a claim that every individual gains exactly four extra decades.
Older orcas lead when knowledge may matter most
A 2015 Current Biology study, led by Lauren Brent, tested whether older females might act as repositories of ecological knowledge. The researchers analyzed observations of 102 resident killer whales moving through salmon foraging grounds. They defined the whale at the front of a traveling group as its leader.
Post-reproductive females were more likely to occupy that position than reproductive-age females, and their leadership was most pronounced in years of low salmon abundance. Sons were also more likely than daughters to follow their mothers.
This does not establish that every orca pod is permanently commanded by a post-menopausal grandmother. Orcas include different populations and ecotypes with different diets and social arrangements. The evidence concerns collective movement among intensively studied resident whales whose lives are closely tied to salmon. “Older females often led group travel, especially in hard feeding years” is accurate. “Grandmothers rule all orca pods” is not.
Grandmothers were linked to grandoffspring survival
Leadership is only one possible benefit. A 2019 study in Proceedings of the National Academy of Sciences, led by Sarah Nattrass, used annual records from northern and southern resident killer whale populations. Those records ran from 1973 or 1976 through 2016. From 726 individuals, the researchers analyzed 378 whales whose maternal grandmothers were known.
The death of a maternal grandmother was associated with a higher risk that her grandoffspring would die during the following two years. The estimated benefit was greater when the grandmother was post-reproductive rather than still reproducing, and it mattered most when salmon abundance was low to moderate.
The design was observational, so it cannot isolate one act of grandmotherly help as the cause. Older females may lead relatives toward food, share salmon, provide social support or confer several advantages at once. Still, decades of individual life histories let the researchers compare a living grandmother with the period immediately after her death in a way that a brief field season could not.
Long life can help kin without adding reproductive conflict
The evolutionary logic combines help and conflict. In stable, kin-structured groups, an older female can increase the survival or reproductive success of relatives who share some of her genes. Her knowledge may become especially valuable when food is difficult to find. At the same time, continuing to reproduce alongside daughters can create competition over food and care.
The 2024 comparison found that females in the five menopausal whale species had more years of overlap with offspring and grandoffspring, but not more reproductive overlap with daughters. That pattern is consistent with a life history that creates time for intergenerational help without simply stacking more simultaneous mothers into the same family group.
It is evidence for a combination of grandmother benefits and reduced reproductive conflict, not a final proof of one universal reason menopause evolved. The five whale species do not all have equally detailed social data, and the comparative analysis inherits uncertainty from carcass sampling, age estimates and incomplete life histories. As with other stories about exceptionally long-lived marine animals, a striking maximum age is only one part of the biology.
Even six should not become permanent trivia
A 2023 Science paper, led by Brian Wood, reported both demographic and hormonal evidence of menopause among wild chimpanzees in the Ngogo community in Uganda. Females reaching adulthood were estimated to spend about one-fifth of adult life post-reproductive, and older females showed hormonal changes resembling the human menopausal transition.
The authors were careful about what follows. Other wild chimpanzee populations have not shown the same substantial post-reproductive stage, and the Ngogo result could represent a population-specific response to unusually favorable conditions rather than a species-typical trait shaped by evolution. The 2024 whale paper likewise described menopause as seeming to occur in some chimpanzee populations.
So the cleanest current summary is not a timeless number. Five toothed whale species are recognized in the recent comparative framework, alongside humans, while the Ngogo chimpanzees show why the boundary remains open to new evidence. Among orcas, the strongest lesson is equally precise: in two well-studied resident populations, life after reproduction is not an empty biological afterword. Older females can hold a consequential place in how families move, find food and survive difficult years.