"For a long time, there has been this underlying hypothesis that the reason that sperm-whale females live as a family is the need to communally defend and raise a calf. But there's never really been good evidence, scientifically speaking, of something that would count as cooperation, where there's a cost involved between non-kin that are living together."
"What the footage showed is that, for the first three hours of the newborn's life, the members of Unit A took turns keeping it afloat. At times, they nestled so close to the baby that they formed a sort of raft beneath it."
Newborn sperm-whale calves are born weighing about a ton and are negatively buoyant, making them unable to swim. For the first three hours, members of Unit A take turns keeping the calf afloat, forming a raft or carrying it on their heads. The effort involves both kin and non-kin, including the calf's mother and her half-sister, Aurora. This behavior supports the hypothesis that sperm-whale females live in family groups to cooperatively raise calves, demonstrating costly cooperation among non-kin during critical birth events.
Read at The New Yorker
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