Reproductive timing and aseasonality in the sun bear (Helarctos malayanus)

摘要: Most species of bears exhibit a reproductive strategy that includes highly defined breeding season, delayed implantation, pseudopregnancy, and no postpartum estrus. Sun (Helarctos malayanus), tropical lowland species, represent potential departure from the typical ursid pattern. We studied timing in captive sun by examining fecal hormones behavior 13 female 5 male bears, entire North American population H. m. euryspilus at time study. Fecal estrogens progestins females did not vary season or month, nor androgens males. Estrus occurred 11 12 months; births year-round. However, birth rates were lower spring higher fall winter. Our study documented 1 complete pregnancy, which implantation occur; delay between estrus progesterone rise (i.e., implantation) pregnant bear was similar to seen nonpregnant bears. All whether pregnant, exhibited prolonged period high after estrus, indicating obligate pseudopregnancy. Studbook records show can occur within 6 months parturition; these cases typically associated with loss previous cub. findings suggest are unique among ursids, being polyestrous, nonseasonal breeders do appear capable initiating event early