Maternal behavior of rats is affected by hormonal condition of pups.

Previous research has found that maternal rats discriminate male from female offspring and provide more anogenital licking to males. Two experiments were performed to determine whether this discrimination is based on hormonal condition of young. It was found that 500 micrograms of testosterone, estradiol, or dihydrotestosterone injected on the day of birth into female pups led to their receiving an equivalent amount of maternal anogenital licking as males and significantly more than either oil or untreated females. The different steroids had similar effects. Maternal nonanogenital licking was not affected by sex or hormonal condition of pups, but it was significantly increased by injection per se. Effects on maternal behavior of hormonal condition or neonatal injection of young were apparent 1 and 9 days after injection.