Nature
Killer whales are one of only five species known to go through menopause
Female orcas stop reproducing around age 40 but can live into their 80s or 90s, spending decades as post-reproductive grandmothers. Long-term study of resident killer whale pods found a grandmother's presence measurably boosts her grandoffspring's survival, especially in lean salmon years. Only killer whales, short-finned pilot whales, narwhals, belugas and humans share this trait.