In animals with polygamous mating systems, in which males' territories overlap the territories of two or more females, males perform spatial tasks with fewer errors than do females. While it has been suggested that these differences persist due to natural selection, this does not explain how they develop. In this study, I investigated the development of sex differences in spatial abilities of montane voles (Microtus montanus), a polygamous species, as influenced by environmental and hormonal factors. Litters were culled to three same-sex pups and raised in clear plastic cages, either small (21x20x23cm = Restricted) or large with objects for exploration (21x38x48cm = Expanded) . The pups were weaned at 21 days of age and remained in their natal environment
