Naturally a mother bat is happy to welcome into the world a bouncing baby whatever, as long as it has all its fingers and toe-claws. But she also wants her little one to have every advantage she can give it. So when spring comes early, big brown bats prefer to keep their female embryos. Unwanted males are reabsorbed into their mothers' bodies as if they never existed.
University of Calgary biologist Robert Barclay learned the bats' secret by spying on three colonies living in the charmingly named city of Medicine Hat, Alberta. The bats roost in the attics of elementary-school buildings. Over the course of 15 years, Barclay snagged the bats in nets at night or plucked them from their roosts among the attic beams to examine them.
Since females return to their birth colony every year to breed, while males disperse, these colonies mainly held mothers and babies. Barclay ...
