Doting orca grandmas help raise young killer whales
- Researchers study first non-human example of the ‘grandmother effect’, where post-reproductive females assist other members of species with their offspring
- Calves whose maternal grandmother died within last two years had mortality rate 4.5 times higher than those with living grandmother
Caring killer whale grandmothers help their grand calves survive, particularly in times of food scarcity, scientists reported on Monday in a paper that sheds new light on the evolutionary role of menopause.
Orca females stop reproducing in their 30s or 40s but can continue to live for decades more, a phenomenon known only to exist in humans and four marine mammal species. While known as “killer whales”, Orcas are actually the largest member of the dolphin family.
It has been suggested that the trait evolved because it allowed post-reproductive females to help their wider kin – referred to as the “grandmother effect” in people, but the theory had not been tested in orcas until now.
“This is the first non-human example of the grandmother effect in a menopausal species,” senior author Daniel Franks from the University of York said.
“It has also been shown in elephants, but they are able to reproduce until the end of their lives. We currently know of only five species that go through menopause: the others are short-finned pilot whales, narwhals and beluga.”