The Platypus is restricted to streams and suitable freshwater bodies, including some shallow water storage lakes and ponds (Carrick et al. 2008). Its food is almost exclusively benthic macroinvertebrates and so the species is water-dependent. Platypuses are largely solitary, and when not foraging in water they normally occupy a resting or nesting burrow in earth banks, although some individuals have been found resting in accumulated stream debris or in low dense vegetation. The species is seldom observed moving on land in mainland Australia, but is frequently seen out of the water in Tasmania, where its predator, the fox (Vulpes vulpes), has been introduced only relatively recently (T. Grant, S. Munks, F. Carrick, and M. Serena pers. comm. 2014). The breeding season varies widely depending on location. Females produce one to three eggs annually, but usually two (Carrick et al. 2008). Platypuses are long-lived animals (up to 20 years in the wild).

The Platypus is endemic to Australia, where it is dependent on rivers, streams, and bodies of freshwater. It is present in eastern Queensland and New South Wales, in eastern, central, and south-western Victoria, throughout Tasmania, and on King Island. An introduced population is established at the western end of Kangaroo Island (Carrick et al. 2008). Its occurrence is reasonably continuous within some catchments, but discontinuous in others (e.g., the Bega River catchment in New South Wales; Lunney et al. 2008), and in many catchments its actual distribution is poorly known. In Victoria, fewer than 200 individuals occupy the Wimmera-Avon River basin (distributed over an area of >2,400,000 ha), and the species appears to have recently become extinct in the neighbouring Avoca River basin (Australian Platypus Conservancy, unpublished data) (T. Grant, S. Munks, F. Carrick, and M. Serena pers. comm. 2014). The species now appears to be extinct also from its former range in the Adelaide Hills and Mount Lofty Ranges in South Australia.

Conservation of the Platypus is limited to its listing as a legally protected species in all states in which it occurs and its incidental inclusion in some national parks and reserves. Legislation prohibiting or controlling problematic fishing activities has been enacted in New South Wales and Victoria, but regulations concerning illegal netting and trapping are often poorly enforced. The most widespread field monitoring program for the species is in Victoria (Australian Platypus Conservancy). There are also a few system-specific studies in other states and community-based reporting of anecdotal occurrences of the species to a variety of institutional and private databases. Still more information about population numbers and monitoring are crucial, especially for a long-lived species such as the Platypus where a lack of recruitment can be masked until a dramatic population crash occurs as adults reach the end of their lifespan.

Population studies of fragmented populations should be a research priority, together with studies to help verify the current distribution and baseline population parameters in areas where the species has declined (Grant and Temple-Smith 2003). Once the Platypus becomes extinct in a river system, the likelihood of its re-colonising that system without human intervention is minimal (T. Grant, S. Munks, F. Carrick, and M. Serena pers. comm. 2014). One reintroduction program is underway in a single fire-affected stream in Victoria (Australian Platypus Conservancy).

Some populations of Platypuses have exhibited antibodies to Leptospirosis, probably transmitted via cattle, but no clinical symptoms have been observed. Mortality from an ulcerative dermatitis caused by Mucor fungus, however, has been recorded across many river systems in Tasmania. There is currently limited investigation of this disease, which should be a research priority both in that state and on the mainland where the fungus is also found (T. Grant, S. Munks, F. Carrick, and M. Serena pers. comm. 2014).