Menopausal chimpanzees deepen the mystery of why women stop reproducing

The females in a group of wild chimpanzees (Pan troglodytes) are the first non-human primates to be documented experiencing menopause. Toothed whales, such as orcas (Orcinus orca), are the only other wild mammals in which females are known to live long beyond their reproductive years. In captive animals, this seems to be more common: females in 6 out of 20 mammalian orders for which there are data experience cessation of ovulation. This includes European badgers (Meles meles), house mice (Mus musculus) and horses (Equus caballus). Why only some animals experience menopause is still a mystery.