CONSERVATION STATUS AND THREATS
The cryptic nature of platypuses means there are significant challenges associated with the collection of data on free-ranging individuals. This makes it difficult to accurately assess population size and density, and thus accurately establish the species’ conservation status and the impacts of threatening processes (Grant 2012).
There is, however, evidence of local population reductions since the European colonisation of Australia, although there has been little change in the overall distribution of platypuses in the past two centuries (Macgregor 2015). Given their dependence on healthy river systems for survival, platypuses are inherently vulnerable to environmental degradation, climate change, pollution, and waterway regulation (Macgregor 2015).Platypuses are currently listed as ‘Near Threatened’ on the IUCN Red List, based on observed population declines and local extinctions, particularly in Vic. (Woin- arski and Burbidge 2016). Platypuses are listed as ‘Endangered’ in SA (National Parks and Wildlife Act 1972) and ‘Vulnerable’ in Vic. (Victoria Government Gazette. Authority of Victorian Government Printer (2021)). However, they are not listed as threatened at a federal level and are unlisted at the state level in NSW and Tas. Based on evidence of past and projected declines in platypus populations, it has been recommended that platypuses be downgraded to Vulnerable, both under the IUCN and under Australia’s Environment Protection and Biodiversity Conservation Act 1999 (Hawke et al. 2020).
Platypuses were extensively hunted for the fur trade in the late 19th and early 20th century, until receiving nation-wide protection in 1912. Platypus populations likely never fully recovered from the impacts of hunting, leaving populations more vulnerable to the multiple and synergistic threats they currently face (Bino et al. 2019).
This includes changing land use, such as for agriculture and urbanisation, which has resulted in habitat disturbance, fragmentation or destruction. Furthermore, their range coincides with some of Australia’s most highly regulated and disrupted river systems. Platypuses are also impacted by catastrophic climatic events. Current climate change projections predict an increase in the frequency, severity and duration of droughts, bushfires and floods (Bino et al. 2021). While some evidence suggests that platypuses are inherently resilient to the impact of fires, the combination of increased fire severity and frequency, and reduced water availability, may significantly impact platypus populations (Griffiths et al. 2020). As a result of the projected impact of climate change and other threatening processes, the long-term viability of many platypus populations is under threat, with platypus abundance and metapopulation occupancy predicted to decline significantly within a 50-yr period (Bino et al. 2019; Bino et al. 2020; Bino et al. 2021; Hawke et al. 2021a; Hawke et al. 2021b; Mijangos et al. 2022). This could result in the extinction of local populations across about 40% of the range (Bino et al. 2020).Many studies have reported on anthropogenic threats to platypus populations (Table 28.1). Serena and Williams (2010) reviewed records from the 1980s to 2009 of platypus deaths in Vic. Threats included drowning in nets or traps set to capture fish or freshwater crustaceans; predation by raptors and canids; flooding
Table 28.1. Anthropogenic threats and causes of morbidity and mortality in platypuses
| Threat | Effect |
| Forestry and logging | Changes in water flow, sedimentation, loss and damage to burrowing sites, habitat loss and fragmentation, changes in benthic invertebrate abundance and diversity |
| Mining | Erosion, sedimentation, direct mortality, changes in benthic invertebrate abundance and diversity |
| Land clearing and agriculture | Altered river flow, bank erosion, increased water run off, increased organic matter, inorganic nutrients, sedimentation, changes in benthic invertebrate communities, loss of suitable burrowing sites, damage to burrow sites, exposure to pesticides, trampling of burrow sites by livestock |
| Urban development | Habitat degradation and loss, excavation of burrows, pollution, road-kill, predation (dogs, cats), disturbance |
| Invasive introduced species | High-invasive plant densities clogging rivers resulting in flooding, loss of habitat for platypus and aquatic macro-invertebrates, predation by dogs, cats and foxes |
| Fisheries (including recreational) | By-catch (fish/yabby/eel traps and nets [often illegal], fishhooks), fishing gear entrapment and entanglement; results in drowning or injury |
| Dams and weirs | Barriers to platypus movement, resulting in genetic isolation, changes in communities of benthic invertebrates, increased water depth resulting in reduced access to benthic invertebrates |
| Irrigation pumps and hydropower turbines | Drowning |
| Salinity | Effects on osmoregulation and electrolocation of prey, changes in benthic invertebrate communities in water body |
| Vehicle strike (cars, boats) | Trauma and death |
| Pollution - rubber and plastic rings, discarded fishing gear, agricultural pesticides, heavy metals, sewage, petroleum products, vegetable oils | Entanglement, entrapment, constrictions, toxicity, disease, loss of fur insulating properties |
| Human malice | Trauma and death from bludgeoning or shooting |
| Climate change | Extreme weather-related events (increased frequency, severity and duration of bushfires, drought, floods), resulting in drowning, starvation, dehydration, reduced water availability, habitat loss, morbidity and mortality due to burns |
Booth and Connolly 2008; Ladds 2009; Serena and Williams 2010; Gust and Griffiths 2010; Macgregor 2015; Scheelings 2016; Bino etal. 2019; Bino etal.
2020; Bino etal. 2021; Griffiths etal. 2020; Hawke etal. 2021a; Hawke etal. 2021b; Mijangos etal. 2022and drought; litter and fishing hooks; entrapment in structures such as irrigation gates and pumps; and motor vehicle strikes. A review of the morbidity and mortality of monotremes admitted to the Australian Wildlife Health Centre, Healesville Sanctuary, concluded that anthropogenic factors were a significant cause of morbidity and mortality of platypuses in Vic. (Scheelings 2016). Disease is not considered to be a major threatening process of platypuses. Previously, the fungal disease mucormycosis has been postulated to be a threat to free-ranging populations in Tas., however, case numbers appear to have significantly declined over the last decade.
Urgent conservation action is required to ensure the persistence of viable platypus populations across their range. Effective conservation relies on controlling threatening processes, supported by systematic long-term monitoring of trends in population sizes, demographics, distribution, genetics and health (Bino et al. 2019; Bino et al. 2020). Several of the organisms that infect platypuses are host-specific (including Ixodes ornithorhynchi, Theili- era ornithorhynchi, and Trypanosoma binneyi), and should be considered as high-conservation value in their own right. This has implications for conservation actions such as translocations.
Conservation translocations (CTs) can support platypus conservation by re-establishing viable platypus populations in areas where they have undergone unsustainable decline or local extirpation.
There have been four successful platypus CTs: 19281946 from Tas. and Vic. to Kangaroo Is., an area where they were not historically present (Ellis 2000); 2004-2007 from the Tarago River to Cardinia Creek, Vic. where the population had declined due to bushfires (Serena and Williams 2008); in 2019 the rescue, temporary relocation and return of five platypuses from a drought affected river system Tidbinbilla Nature Reserve, ACT (Hawke et al. 2024); and in 2023 ten platypuses were re-introduced to the Royal National Park NSW, an area from which they had been extirpated (NSW Government press release, May 2023).
Zoos can play an important role in platypus conservation through research, raising public awareness of threats, potentially establishing insurance populations to secure genetic diversity, and providing refuge in emergencies such as drought, bushfires and flood events.
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