Killer whale grandmothers keep grandcalves alive

Researchers at the University of Exeter and the University of York studied decades of photo-identification records of killer whales, intelligent marine animals that live in tight family groups along the Pacific coast.

The team compared the survival of grandcalves whose grandmother was still alive, whether reproductive or postreproductive, against grandcalves who had lost her. Postreproductive grandmothers raised their grandoffspring's survival chances significantly more than reproductive grandmothers did, and the benefit was strongest in years when salmon, the whales' main food source, was scarce.

By stopping her own reproduction, a grandmother avoids competing with her daughter for food and calving space while still leading the group to feeding grounds using accumulated knowledge. The pattern offers rare direct evidence of a grandmother effect outside humans, in a species that, like people, can live for decades after its last calf. The record relies on tracking of two specific whale populations, not a wider sample.

Grandmothers who stop breeding still save lives.