Mammals’ urine contains chemosignals known to affect the sexual behaviour and reproductive physiology of both male and female recipient. Here we demonstrated that male urine can also elicit physiological changes on sexual maturation rates in the Brandt’s voles. In the first experiment we showed that urine from breeding adult male anticipated the puberty on female voles and at opposite delayed puberty on males. The results from the second and third experiments showed a strong agonistic behaviour between male Brandt’s voles compared to that of females. The introduction into social groups of an adult male, but not an adult female, increased the agonistic responses of the resident male. The results suggest a high rate of competition for mating in the male. Therefore, we conclude that a breeding adult male uses chemosignals to differently affect the sexual maturation of pre-pubertal conspecifics as a tactic for reducing competitive mating pressure. Little or no competitive pressure for copulation was seen in the oestrous female, and its urine had no effect on the maturation rate of young Brandt’s voles.