The Timing and Synchrony of Seasonal Breeding in the Marsupial, Antechinus stuartii: Interaction of Environmental and Social Cues

Abstract

Antechinus sp. have a short, highly synchronous, annual winter breeding season. Females are sexually receptive for approximately three weeks but ovulations of most females of a population occur within three or four days. In order to investigate the cues used for the timing and synchronization of this seasonal breeding, male and female A. stuartii were kept under two artificial photoperiod conditions and under four social conditions. An artificial long-day photoperiod inhibited reproduction for both males and females but short days did not facilitate breeding for either. Short-day photoperiod reduced and slightly delayed the normal seasonal rise in androgen concentrations of the males. Isolated females in natural photoperiod ovulated asynchronously, whereas isolated females which received pheromonal cues from urine and feces from females housed with other females ovulated in synchrony with them. These social cues mediating the synchrony of ovulation could not control the timing of seasonal breeding in the absence of the proper endogenous and environmental cues. The latter cues, however, did not allow for very precise timing.