EFFECTS OF CABERGOLINE ON REPRODUCTION IN 3 FAMILIES OF AUSTRALIAN MARSUPIALS

The effects of the prolactin inhibiting drug, cabergoline, on pregnant and lactating marsupials were investigated in four species from three diverse families: the tammar wallaby, Macropus eugenii, the quokka, S etonix brachyurus, the brushtail possum, Trichosurus vulpecula, and th e fat-tailed dunnart, Sminthopsis cassicaudata. In tammar wallabies, 2 0 mu g cabergoline kg(-1) injected intramuscularly I day before expect ed birth did not alter the timing of parturition but neonates died wit hin a day of birth, suggesting that the onset of lactation was comprom ised. During early lactation in tammars (56-69 days post partum), an i ntramuscular injection transiently retarded growth of the young, altho ugh they subsequently survived. This treatment induced reactivation of the quiescent corpus luteum and the blastocyst from diapause, so a ne w birth occurred 26-27 days later, despite the continued sucking of th e young in the pouch. Intramuscular injection during late lactation (1 66-199 days post partum) apparently suppressed milk secretion since po uch young lost up to 20% of their bodyweight or died within 7 days of treatment. Oral administration of cabergoline had no effect on the gro wth of the young or on the quiescent corpus luteum and diapausing blas tocyst. Quokkas showed similar responses to tammars after treatment in late lactation. Possums and dunnarts were less sensitive to injected cabergoline than the two macropodid species, and possums showed no res ponse to oral administration. The lack of response of these marsupial species to oral cabergoline treatment suggests that accidental ingesti on of baits, containing 20 mu g cabergoline kg(-1), used to control in troduced eutherian pests such as the red fox, Vulpes vulpes, or the fe ral cat, Felis cattus, should not affect the reproduction of native ma rsupials.