Sequential ovulation and fertility of polyoestrus in American black bears (Ursus americanus)

摘要: *American black bears (Ursus americanus) are seasonally polyoestrous and exhibit delayed implantation, which may allow equal independent fertility of recurrent oestruses a mating season. We postulated that the luteal inactivity during implantation allows to have sequential ovulation season such each oestrus female will equivalent fertility, pregnancy would not preclude subsequent superfetation. Controlled experiments were conducted on semi-free-ranging American three seasons, wherein females bred by different male cohorts in oestrus. Behavioural observation, vulva score ranking, genetic paternity analysis, gross morphology ovaries microscopic diapaused embryos used evaluate females. Oestrus duration, number successful mounts median scores similar between first Polyoestrus occurred 81.3% oestrous females, with 9.7 ± 5.5 day (mean SD) inter-oestrous interval. Sequential was documented including one possessed both corpus haemorrhagicum developed luteum. Among dams, four nine conceived five second These results indicate is capable even if already pregnant from prior Although superfetation directly observed present study, our strongly suggest potential bear provide novel insight into complex behavioural physiological breeding mechanisms bears. Given most endangered species share reproductive traits bears, captive programmes could take advantage males at order increase diversity