Memory retention of male offspring to their parental urine odors was studied on Chaidamu Root Voles(Microtus limnophylus).Male offspring weaned at 10 days in age.Experiments were conducted in 0,10,20,30,and 40 days after weaning,male offspring were exposed to their parental urine and to unrelated adult male's urine.The results showed that:(1)male offspring approached to paternal odor more frequency than to strange one when they were not separate from their parents.The time difference in visiting their paternal and strange male's odor was significant in 10 d after weaning.There was a significant difference in duration of latency,visiting time and self-grooming frequency in 20 d after weaning between they approach to their paternal odor than to strange one;(2)no difference in behavioral responses to paternal and strange odor was found when subjects were separated 20 to 30 d with their paternal;(3)no difference was recorded in behavioral responses to the odor of their maternal and strange adults when subjects were not weaned;(4)male offspring performed different behavioral patterns to maternal odor than to strange female's odor in 10 d after weaning,while no difference in behavior was recorded when they were weaned in 20 d after weaning.In conclusions,the memory of male offspring to their paternal odor could last 20-30 d after weaning,while their memory to their maternal odor only last 10 d after weaning.