he effect of male competition on female choice in the Brandt’s vole (Lasiopodomys brandti) was studied in the laboratory. Using a two-way choice test, we showed that when males did not compete, estrous females preferred and mated with the dominant males, but non-estrous females preferred subordinate males. However, when males competed, all dominant males gained the priority to mate, and the amicable behaviour between males, regardless of their dominant status, and between non-estrous females increased, compared with the behaviour between males and the estrous females. These results showed that interactions among Brandt’s voles were not only influenced by male competition but also by reproductive status of female voles.
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.