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The Whale Menopause


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Killer whales and humans are almost unique in the animal kingdom. The females of both species go through the menopause in their 40s or 50s, and then live for decades without producing any more offspring themselves. It's an extremely rare phenomenon. No other mammal does this, including other apes, monkeys and elephants, with the exception of another species of toothed whale. There are good grounds for thinking the menopause evolved for a reason, but why? BBC science reporter Victoria Gill takes to the sea off the northwest coast of the USA with scientists who believe the killer whales in this part of the world can explain why the menopause evolved in both orca and our own species. Victoria encounters 'Granny', the world's oldest known orca - a matriarch killer whale who is estimated to be somewhere between 80 and 105 years old. 'Granny' has not had a calf for at least 40 years and is still very much the leader of her family group. Granny is more properly known as L2 - her individual designation in the longest running and most detailed study of a population of whales in the world. In 1976, the Center for Whale Research took up the task of identifying and counting every member of the resident population of killer whales which inhabit the Salish Sea region between the USA and Canada. The project arose from fears that too many of members of this population were being captured for the entertainment industry and taken to zoos and commercial 'dolphinariums'. The survey's findings led to a ban on the removal and rendition of orca from the Salish but the Center's work has continued. There is now forty years of data on births, deaths, family ties and health status of all the individual whales among the Southern Residents,. The data has become of huge interest to evolutionary biologists Darren Croft of the University of Exeter and Daniel Franks of the University of York who are analysing it to explore why killer whale females live for decades after they've stopped reproducing themselves. They've discovered that these



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