The vast majority of animals die shortly after the end of their reproductive years. Life after menopause occurs in only three known species. Humans are one such species and the other two are killer whales and pilot whales.

Researchers have long wondered what biological role this anomaly serves and killer whales appear to have provided an answer. The whales are generally fertile between the ages of 12 and 40 but can live well into their 90s.

According to a new study published in the journal Current Biology, the female whales serve as an important repository of information necessary to survival in difficult times.

The older females lead groups when they move into salmon foraging grounds. The researchers found that this leadership becomes more prominent during years when there are fewer salmon.

Salmon shortages are a major cause of death in killer whale populations so, the researchers argue, the accumulated knowledge of where to find food in difficult years could be critical to the survival of whale groups.

“Our results show for the first time that one way post reproductive females may boost the survival of their kin is through the transfer of ecological knowledge. The value gained from the wisdom of elders can help explain why female killer whales and humans continue to live long after they have stopped reproducing,” said Lauren Brent of the University of Exeter in a statement.

In humans the development of writing as a means to pass on information is a very recent development. For most of human history, older, more experienced people would have held important knowledge including where to find food in lean years and other important survival information.

Testing this idea in modern humans would be very difficult. Our civilization now has many ways to store and retain knowledge. In most human societies there are also built in safeguards to protect populations in lean years.

Being non-literate, highly social animals, killer whales can provide insight into the role of menopause.

“In humans, it has been suggested that menopause is simply an artefact of modern medicine and improved living conditions. However, mounting evidence suggests that menopause in humans is adaptive. In hunter-gatherers, one way that menopausal women help their relatives, and thus increase the transmission of their own genes, is by sharing food. Menopausal women may have also shared another key commodity – information,” said Professor Darren Croft of the University of Exeter.

One of the things the researchers found was that during times of shortage, female killer whales were more likely to lead their sons than their daughters.

“Killer whale mothers direct more help toward sons than daughters because sons offer greater potential benefits for her to pass on her genes. Sons have higher reproductive potential and they mate outside the group, thus their offspring are born into another group and do not compete for resources within the mother’s matriline. Consistent with this, we find that males follow their mothers more closely than daughters,” said Dr Daniel Franks of the University of York.

The team combined 35 years of collected information on a total of 102 individual whales to draw their conclusions.