WHEN sperm whale mothers dive deep for squid their young cannot follow 鈥� so who looks after the kids?
Shane Gero of Dalhousie University in Halifax, Nova Scotia, Canada, and his colleagues tracked sperm whale populations in the Caribbean and Sargasso seas to see what happened when mothers dived for food. The Sargasso mothers formed a babysitting circle, taking it in turns to watch over and nurse the calves, and to go hunting. The smaller Caribbean population had fewer mothers, so calves were left with a close female relative instead (Behavioral Ecology, ).
It makes evolutionary sense for females to protect their young relatives, and for a mother to babysit in return for its own calf鈥檚 protection. There may be a less obvious reason, too: a group that watches each other鈥檚 infants will grow larger, making it safer for all. 鈥淎mong sperm whales, having extra eyes in a group to look out for killer whales is in everyone鈥檚 interest,鈥� says Richard Connor, an expert in cetacean behaviour at the University of Massachusetts, Dartmouth.
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