NO SEX DIFFERENCE OCCURS IN HIPPOCAMPUS, FOOD-STORING, OR MEMORY FOR FOOD CACHES IN BLACK-CAPPED CHICKADEES

A number of recent studies have described sex differences in the relat ive size of the hippocampus that are associated with sex differences i n the use of space. Voles, kangaroo rats, and cowbirds all exhibit a s ex difference in relative size of the hippocampal formation that is co rrelated with a sex difference in spatial behaviour. We wished to dete rmine whether sex differences in the size of the hippocampus occur in the absence of a difference in the use of space, and whether the previ ously described correlations could be adventitious. Relative hippocamp al size was determined in wild-caught black-capped chickadees (Parus a tricapillus) following behavioural observations of food caching and sp atial memory for cache sites. There was no indication of a sex differe nce in either relative size of the hippocampus or in food-caching beha viour and memory for cache sites. These results show that sex differen ces in relative size of the hippocampus do not occur as a matter of co urse, and are consistent with the hypothesis that sex differences in s patial behaviour and spatial ability are predictive of sex differences in the relative size of the hippocampus.