Deficit in reproduction in polygynously mated females of the monogamous mound-building mouse Mus spicilegus

International audienceIn monogamous mound-building mice Mus spicilegus, facultative polygyny was observed in April, at the beginning of the reproductive season. In order to evaluate the cost of polygyny, we compared under laboratory conditions the reproductive success of trios and pairs composed of sister females mated with unrelated brother males. Females in trios were able to tolerate each other during the reproductive period and to reproduce with the same male under spatial constraints. Polygyny had, nevertheless, a strong negative effect on the reproductive success of females. The average number of young per litter was smaller in trio females than in paired females, whereas the interval between two successive litters was higher. As a result, the number of litter and the number of young per time unit was smaller in each of the trio females than in paired females. Agonistic behaviour being absent in trios, our results strongly suggested that living in trio led to pheromonal productions affecting female physiological state and reproduction. Males of trios did not obtain a better reproductive success than males in pairs