Quinestrol is an effective sterilant of rodents,but we have little knowledge about its effect on social behavior.In this study,we investigated responses in terms of social behavior in male Brandts voles (Lasiopodomys brandtii) after quinestrol treatment.Over 7 successive days,consumption of food containing quinestrol (0,0.001%,0.003%,and 0.006%) was monitored for male voles (8 groups,10 animals per group) .Reproductive parameters were observed and collected at 2 and 4 weeks after the treatment period.Dyadic social encounters and female preferences were recorded at Week 2 for the control males (no quinestrol) and for the group receiving 0.006%quinestrol.Our results revealed that quinestrol reduced the relative weight of testes,epididymides,seminal vesicles,and serum testosterone levels,female pregnancy rates and litter sizes,especially for the highest dose group at 2 weeks.Effects were not as great at 4 weeks.Behavioral responses assessed at 2 weeks post treatment showed that both frequency and duration of female preference were unbiased between control and treated males.In social conflict tests,control pairs (CC) ,treated pairs (TT) and pairs of one control and one treated male (CT) ,there was no difference in patterns of mutual attack and agonistic behavior.In CT pairs,sterile males had the same winning rate and agonistic behavior as control males.Our data indicates that quinestrol has few behavioral side effects on male Brandts voles.