Circulating levels of prolactin and progesterone in a wild population of red kangaroos (Macropus rufus) Marsupialia: Macropodidae.

Circulating progesterone and prolactin levels were measured in shot and live-caught wild red kangaroos using radioimmunoassays validated for the red kangaroo. The objective of the study was to correlate hormone profiles with reproductive status and determine if red kangaroos follow the general pattern elucidated for other macropodids. During Phase 2a lactation ( < 70 days) plasma progesterone concentrations were < 189 pg/ml (n = 41). This value increased to > 600 pg/ml (n = 32) during the transition to Phase 3 lactation (181 to 235 days) when the quiescent corpus luteum and embryo were reactivated. Progesterone concentrations then decreased to < 300 pg/ml (n = 29) during dual lactation when females were suckling a neonate and a young at foot. Concentrations of prolactin during Phase 2a were < 6 ng/ml (n = 17). Coincident with the period of reactivation of the diapausing blastocyst (181 to 235 days), plasma prolactin concentrations increased to 15 ng/ml (n = 32), then decreased and remained low through the subsequent stage of dual lactation. These results indicate that progesterone and prolactin profiles in wild red kangaroos follow patterns found previously in other macropodid species, the tammar and Bennett's wallabies.