Seasonal variation of plasma testosterone in a wild population of male Eastern quoll, Dasyurus viverrinus (Marsupialia: Dasyuridae), from Tasmania.

In the wild, male Eastern quoll, Dasyurus viverrinus, exhibit a synchronized sequence of increase and decrease in plasma testosterone concentration, body weight, and scrotal size in response to the breeding season. Basal concentrations of peripheral testosterone between 0.5 and 0.7 ng/ml circulate during the nonbreeding period. By April, 2 months prior to breeding, testosterone concentrations increased to around 1.6 ng/ml. This increase may reflect a resurgence in testicular activity, as scrotal size is maximal at this time. A synchronized testosterone peak of 5.0 ng/ml was observed during the mating period in early June. With the cessation of breeding, testosterone concentrations in resident males returned to basal levels by July; however, transient males maintained elevated levels for slightly longer. The timing of breeding and the short duration of the testosterone breeding peak enable the quoll to intensify its reproductive effort.