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We examined the potential influences of existing social housing arrangements on captive sun bear female reproductive cycling. Three social conditions were studied: 1.2, 1.1, and 0.2. Fecal hormone metabolites of total estrogens, progestins and glucocorticoids were compared between the three social conditions and were analyzed along with vaginal cytology data in individuals that experienced a change in social condition. Behavioral data were collected on females in each of the social conditions and summarized into agonistic, affiliative and sexual categories. Results indicated that sun bears are spontaneous ovulators, but that the presence of a male does influence hormone metabolite concentrations and cytological profiles. Male presence was also associated with a greater proportion of females cycling. In most female pairs, only one female cycled, typically the younger, subordinate female. The presence of a second female appeared to have a suppressive influence on both cycling and mating behavior. Agonistic behavior and associated stress may be a mechanism for lowering progesterone. In contrast, high estrogen levels were associated with low levels of agonistic interactions; thus, reproductive cycle monitoring could facilitate social introductions with either sex. Females in 1.2 social groupings had significantly higher GC metabolite concentrations and agonistic behavior, suggesting that 1.2 social groupings may not be advisable for captive breeding programs. Data from the North American historical captive population indicate that at most 32% of all sun bear pairs and only 18.5% of females have successfully reproduced. Implications of these social and reproductive patterns for captive management are discussed. Zoo Biol. 32:581-591, 2013. © 2013 Wiley Periodicals Inc. [ABSTRACT FROM AUTHOR]

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