Evidence of sex-biased postnatal maternal investment by Mongolian gerbils

Three experiments were undertaken examining the relative costs to female Mongolian gerbils, Meriones unguiculatus, of rearing four male or four female pups from birth to weaning. In experiment 1, it was observed that gerbil dams rearing all-male litters were almost twice as likely as gerbil dams rearing allfemale litters to be found: (1) with all their young in the nest throughout a 20-min observation period; and (2) with one or more pups …