Melatonin implants were administered to 6 female bandicoots during the months of May and July. These animals, together with 6 control bandicoots were housed in large outside enclosures with mature males. Births were observed in the 6 control animals from 26 July to 2 September, but no births were observed in the 6 bandicoots with melatonin implants. These results would suggest that photoperiod, which is known to influence melatonin concentrations, may be a factor in the initiation of births in the bandicoot. However, the gradual build-up of births would suggest that other factors such as temperature and rainfall may also have some influence.