Fecal sexual estradiol (E(2)) and progesterone (P(4)) analyses were conducted on three adult female Formosan black bears in order to establish non-invasive enzyme-linked immunosorbent assays (ELISA) for describing the endocrine profile in a simulated natural breeding environment. Moreover, we investigated whether the Formosan black bear living in subtropical habitats in Taiwan is a seasonal breeder with delayed embryo implantation, ovulation pattern, and maternal perinatal fasting. Our results indicate that mating behavior occurred both before and after the fecal E(2) peak of March June. Fecal P(4) concentrations initially increased after mating, then decreased to lower levels, and finally increased again, which is indicative of a delayed embryo-implantation. Fecal P(4) levels decreased postpartum. Peaks of fecal P(4) levels were also observed in unmated female bears housed with male bears without coitus: their annual fecal P(4) levels were higher from winter to spring, similar to the pregnant female bear: Interestingly, only pregnant female bears displayed a physiological state of fasting before and after parturition. These results suggest that Formosan black bears' breeding is seasonal and takes place from spring to early summer. Delayed implantation, maternal perinatal fasting and induced ovulation from male stimulation independent of coital stimulation alone are typical for the species
