Preferences of pre- and post-weanling Long-Evans rats for nest odors

Three experiments were conducted on the preferences of infant rats for nest odors. Pre-weanling rats preferred their own nest odor to nests of strange litters and showed low preferences for the nest odors of virgin females. Nest odors of unmated males were investigated less than the pup's own nest odor but more than the odors of virgin females. Male and female rats did not differ in odor preferences. Rats reared with both their dam and sire did not differ in their odor preferences from rats reared with their dam alone when tested at 16-20 days of age, but when tested at 33-38 days of age they showed a greater preference for male odors. Post-weanling rats did not show a preference for the nest odors of lactating females and began to show sex differences in their preferences.