New horizons in the reproductive biology of Taiwanese pangolin (Manis.p.pentadactyala): Gondal hormonal profile and evidence for delayed implantation

Abstract

Abstract The extant biological reports on pangolins have mainly been established from rescued gravid individuals or a handful of observations done in captivity, thus, generating data discrepancies. The present research characterizes the Taiwanese pangolin's annual seasonal reproductive pattern by measuring immunoreactive estrogens and progestagens in 34 captive females and testosterone in 29 captive males. Our results showed that Taiwanese pangolins are seasonal breeders, with most births (10/13) witnessed during Dec-Jan as field records. Females exhibited spontaneous ovulation and post-partum ovulation. Pregnant females exhibited a higher P4 level for ~ nine months (Jan-Sept) and decreased before parturition (Oct-Dec). The circulating E2 is maintained at the baseline in pregnant females year-round. Contrastingly, in non-pregnant females, P4 is maintained at the baseline apart from slight elevation in January, and E2 demonstrates a sudden hike from November and remains elevated until February, suggesting the onset of ovulation. The serum testosterone concentration in males peaked during October, which is in sync with the female ovulation period. As a result that their major reproductive events, ovulation, mating, and parturition, all transpire from November-March. Evidence also supported that Taiwanese pangolin exhibit the signs of postimplantation (pregnancy) ranging only from 5–6 months (May-October) preceded by facultative delay implantation triggered by lactation. The provided data not only filled in the knowledge gap for this critically endangered species but also can assist in making informed decisions, which can directly affect the successful breeding of this species in captivity.