The platypus : historical, ecological, and behavioural advances to improve the conservation of an elusive species

Platypuses are evolutionarily and morphologically unique, making them one of the world’s most iconic animals. Due to their cryptic, nocturnal nature, they are notoriously difficult to study in the wild, limiting knowledge of their distribution, ecology, and behaviour, hindering effective assessments of decline and status. Recently, studies have suggested declines resulting from a range of threats, but despite their distribution overlapping Australia’s most regulated rivers, the impacts of dams remains relatively unstudied. In my thesis, I aimed to address specific knowledge gaps for platypuses, assessing potential past and present distribution, the impact of dams, and their movement behaviours. Chapter one highlights ongoing species declines and provides insight into the life history of the platypus. In my second chapter, I compiled the most comprehensive database on the distribution and abundance of platypus, which allowed me to identify potential declines in range and number. The inclusion of historical data highlighted how shifting baselines have changed perspectives on platypus abundance, impacting perceptions on the magnitude of decline. For Chapters 3 – 5, I examined impacts of large dams and river regulation by surveying upstream and downstream of dams, and on adjacent unregulated rivers, and tracked movement of platypuses downstream of dams. In Chapter 3 I examined population dynamics, finding populations downstream of dams with significantly altered flow regimes had lower abundances and densities of platypuses than above dams, while the opposite was true for rivers where flow regimes had been improved. In Chapter 4, movement tracking highlighted interactions among individuals in a localised pool and revealed no detrimental impacts of an environmental flow on the Snowy River. Long-term movement analysis on regulated rivers in Chapter 5 suggested platypus have restricted movements, with implications for declining populations, given areas of decline are unlikely to be supplemented by migrating platypuses. My thesis provides critical insight on platypus declines using historical baselines and identifies how dams can be major drivers of declines, while also highlighting the benefits of their improved management. These conclusions, combined with insights into movement behaviour, offer valuable information to guide conservation management of threats for the long-term viability of this iconic species