Allonursing and cooperative birthing behavior in Yellowstone Bison, Bison bison

Abstract

We document allonursing and cooperative birthing behavior in wild Bison near Yellowstone National Park in the western United States. During spring 2007, two female Bison nursed each other's newborn calves and mutually cleaned both calves and consumed expelled birth material. Intensive cooperative birthing behavior has never been documented in wild Bison before. This observation of allonursing might be explained by kin selection and reciprocal altruism.