For most mammals, growing up means giving up their mother’s milk. Then there are the sea lions of the Galápagos Islands.
A long-running study has documented a significant number of sea lions in the Galápagos, an archipelago in the Pacific Ocean, that kept suckling from their mothers for years after reaching sexual maturity. Some have reached ages comparable to those of human teenagers, with a few nursing into the equivalent of middle age and beyond.
One animal was spotted nursing at age 16, which, given the life expectancy of sea lions, would be akin to people in their early 60s still breastfeeding from their mothers.
No other animal has been shown to nurse offspring so deep into its reproductive life. “It’s utterly extraordinary,” said Patrick Pomeroy, a marine mammal expert at the University of St. Andrews in Scotland who was not involved in the research. “It goes against all the accepted wisdom.”
And “the fact that this is happening in a species producing such costly, lipid-rich milk as sea lions produce makes it all the more remarkable,” said Sarah Blaffer Hrdy, a retired anthropologist from the University of California, Davis.
Darwinian logic holds that mothers should cease costly milk production for their young once those offspring can feed themselves and reproduce. Yet among Zalophus wollebaeki, the scientific name for the Galápagos sea lion, many mothers continue nursing older young even as they raise new pups.
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