A sperm whale calf that scientists named Hope rests in a sargassum patch. It has been suckling from an adult called Canopener, but that doesn’t necessarily mean she’s Hope’s mother. Each sperm whale social unit may nurse differently. In some, aunts or grandmothers also provide milk to offspring. Or a single female may nurse two calves at once, even if neither is hers.

A sperm whale calf scientists named Hope rests in a sargassum patch. It has been suckling from an adult called Canopener, but that doesn’t necessarily mean she’s Hope’s mother. Each sperm whale social unit may nurse differently. In some, aunts or grandmothers also provide milk to offspring. Or a single female may nurse two calves at once, even if neither is hers. (Photo by Brian Skerry)