SCIENCE LAB SCENICS : MATERNAL TIES [ 2 ]

IN the Galapagos, - some sea lions can't get enough of mother's milk.

So why has natural selection allowed these animals to keep returning to the milk bar?

'' It's very hard, at the moment, for us to grasp,'' said Oliver Kruger, a behavioral ecologist in Germany, and a leader of the study.

DR. KRUGER leads the Galapagos Sea Lion Project, which since 2003, has monitored a single population of the endangered pinnipeds. This colony lives on the tiny Caamano Islet.

Over the years, the team occasionally glimpsed adult sea lions continuing to nurse. 

But it took a graduate student Alexandra Childs, to join Dr. Kruger's lab and began examining the practice in earnest.

She combed through two decades of field records and began tallying every instance of prolonged nursing she could find.

Most sea lions had been weaned by their third birthdays, around the age of puberty, and were feeding independently, mainly on fish and squid.

But 11 percent of these newly pubscent animals kept returning to their mothers for nourishment. And among these sea lions, about one in five continued well past the point of sexual maturity and reproductive activity.

The researchers called these unusually mom-dependent animals : '' supersucklers.''

This behaviour showed no clear bias towards sons or daughters, the researchers found.

That discovery defied expectations that mothers might preferentially feed males, rather than smaller female offspring.

The World Students Society thanks Elie Dolgin.