Relationship between gonadal steroid hormones and vulvar bleeding in southern tamandua, Tamandua tetradactyla

This study aimed at demonstrating the profiles of circulating gonadal steroid hormones during the estrous cycle and pregnancy in a southern tamandua (Tamandua tetradactyla). Additionally, this study clarified the relationship between vulvar bleeding and hormonal changes. The concentrations of serum progesterone (P₄) and estradiol-17β (E₂) were determined by enzyme immunoassays. Serum P₄ and E₂ concentrations changed cyclically and the estrous cycle length (±SD) based on the E₂ cycles was 44.3±4.5 days. Vulvar bleeding started to be seen at the decreasing of P₄. The cycle length for vulvar bleeding was 43.3±4.2 days. Interval from the first day of bleeding to the peak of E₂ concentration was 23.1±3.1 days. Serum P₄ during pregnancy remained high and E₂ increased 8 weeks after conception and remained high until parturition. The female delivered normally after a 165 day-pregnancy period and reared the offspring well. Approximately 3 weeks after parturition, serum E₂ and P₄ cycles resumed. Visual bleeding may be useful as a real-time indicator for understanding the ovarian cycle of southern tamanduas, and estrus could be expected approximately 3 weeks after the first bleeding. Zoo Biol 30:212-217, 2011.