Whale species go through menopause, say scientists

BELUGA whales and narwhals go through the menopause – taking the total number of species known to experience the “change” to five, according to a study.

Apart from humans, killer whales and short-finned pilot whales had been the only other species known to experience the menopause. Most species retain the ability to reproduce until they die.

But a study by the University of Exeter published in the journal Scientific Reports used data from the dead whales of 16 species and found dormant ovaries in older beluga and narwhal females.

The researchers believe they go through the menopause to prevent resources being taken away from their other children and grandchildren, but stay alive to help protect the younger pod members.

Dr Sam Ellis, the lead author, said: “For menopause to make sense in evolutionary terms, a species needs both a reason to stop reproducing and a reason to live on afterwards.

“In killer whales, the reason to stop comes because both male and female offspring stay with their mothers for life – so as a female ages, its group contains more and more of its children and grandchildren. This increasing relatedness means that, if it keeps having young, they compete with her own direct descendants for food.

“The reason to continue living is that older females are of great benefit to their offspring and grand-offspring. For example, their knowledge of where to find food helps groups survive.”

Research into human ancestors suggests they also lived among more and more relatives as they aged, and may have evolved in a similar way so they could impart their wisdom.

Prof Darren Croft, also of Exeter, added: “It’s hard to study human behaviour in the modern world because it’s so far removed from the conditions our ancestors lived in. Looking at other species like these toothed whales can help us establish how this unusual reproductive strategy has evolved.”

There has been extensive research into the menopause among killer whales, but no detailed observations of live beluga whales and narwhals.