When do Tasmanian platypuses breed? Anatomical, physiological and behavioural evidence

Understanding the timing of reproduction in wildlife species is important for interpreting individual health data, investigating environmental factors that may affect reproductive success, assessing population health and managing wild populations. It is broadly acknowledged that the breeding season of platypuses occurs later in Tasmania than in any of the mainland states. However, there is a paucity of published information about the timing. The aim of this study was to determine the timing of breeding events in Tasmanian platypuses, using ultrasonography of the reproductive organs, serum reproductive hormone concentrations, and observations of behavioural patterns. Testis volume varied significantly by month of sampling; platypuses sampled in October had larger testis volumes than those sampled in January. Seasonal variation was observed in male serum testosterone concentration and female serum progesterone concentration; concentrations were lowest during autumn and increased through spring. Patterns of behaviour showed strong evidence of breeding behaviour in November and December. The findings of this study suggest that, to avoid disruption of nesting burrows containing breeding females and their young, the current recommendation to avoid disturbing activities, such as earthworks, around water bodies from December to April should be extended to include the month of November.