THE MATING SYSTEM OF FREE-LIVING EMUS

Despite their pivotal role in interpretation of the complex mating sys tems of the ratites, the mating system of free-living emus (Dromaius n ovaehollandiae) has not been characterised. Here we report observation s on an introduced but free-ranging population of emus at Tidbinbilla Nature Reserve in the Australian Capital Territory. Emus combined mono gamy, polyandry and promiscuity. All initially unpaired males paired w ith and incubated a clutch for females whose primary mates were preocc upied with incubation. However, females were also promiscuous, and mos t copulations we observed were extra-pair. Females fight vigorously am ong themselves for access to unpaired males. Coupled with observations on cassowaries, these data suggest that there is no simple correlatio n between habitat (grassland/forest) and the mating system in ratites. Instead, the resolution of the complex conflicts of interest between the sexes appears to determine the predominant mating systems exhibite d by a species.