Estrous Cycle Based on the Plasma Progesterone Changes and its Seasonality of Brazilian Tapirs (Tapirus terrestris) in Captivity

Abstract

Plasma samples were collected from two female Brazilian tapirs (Tapirus terrestris) in captivity once a week. Changes in plasma progesterone concentrations (P₄) were determined by enzyme immunoassays (EIAs). As the result of cyclic change in P₄, it was assumed that the estrous cycle length was approximately four weeks. Birth month of Brazilian tapirs in Japanese zoos during the years of 1960-2001 were surveyed. Although their births had occurred throughout the year, high incidence of birth was observed in March to June. From the P₄ profiles, it was suggested that there was no obvious reproductive seasonality and Brazilian tapir could be an annual breeder. However, the incidence of birth throughout the year was biased, it was supposed the breeding may be influenced by climate factors.