Can killer whales help solve the mystery of menopause?
10 August 2016 Last updated at 00:11 BST
Scientists from Exeter and York University are studying the evolution of the menopause, and have found clues to its origin in killer whales.
Humans and orca are two of only three species that evolved to stop having babies half-way through their lives - something even great apes and long-lived elephants do not do. While some have suggested that menopause is a side-effect of our own greater longevity, researchers say that orcas could hold the key to what's been a long-standing evolutionary mystery.
BBC science reporter Victoria Gill joined the scientists on an unusual whale-watching trip of the North Pacific Coast.
Filmed and edited by David Cheeseman and Victoria Gill
Hear more on this story and the BBC's encounter with the Southern Resident orca on The Whale Menopause, BBC Radio 4, Wednesday at 2100 BST