THE survival of one of the world's most unusual creatures - the platypus - is under threat due to a sustained lack of care in Queensland, NSW and Victoria.
Scientists have found the places platypuses are found have shrunk by at least 22 per cent or about 200,000km in the past 30 years.
They say the platypus is likely to meet the criteria for listing as a threatened species under national environmental law.
UNSW researchers, the Australian Conservation Foundation, WWF-Australia and Humane Society International Australia, have nominated the platypus to be listed as a threatened species under Commonwealth and NSW processes.
Platypus have been seen or their DNA recorded in Hilliards Creek in the Redlands, at Logan and the Scenic Rim at places like the Albert River and its tributaries, Wolffdene, Cedar Creek, and Tamborine.
Research found the decline in platypus observations was most severe in NSW (32 per cent reduction) and Queensland (27 per cent).
Although Victoria recorded a statewide decline of 7 per cent, there have been reductions of 18 per cent to 65 per cent in some Melbourne catchments since 1995.
Declines in platypus observations were worst in places where natural river systems and water flows have been most heavily modified, like the Murray-Darling Basin.
New dams, the over-extraction of water from rivers, land clearing, attacks by foxes and dogs, pollution and suburban sprawl are the main factors driving decline.
Platypuses also drown in so-called opera house freshwater traps designed to catch yabbies and fish. They are still used in NSW and Queensland despite a high death rate and years of campaigns by scientists and conservationists.
Scientists say the changing climate also presents a threat, with more severe droughts, reduced rainfall and intense fires drying out rivers and vegetation.
"Protecting the platypus and the rivers it relies on must be a national priority for one of the world's most iconic animals," said Professor Richard Kingsford, a lead author of the report and the director of the Centre for Ecosystem Science at UNSW.
"There is a real concern that platypus populations will disappear from some of our rivers without returning, if rivers keep degrading with droughts and dams.
"We have a national and international responsibility to look after this unique animal and the signs are not good."
The platypus is considered one of the most unique and archaic mammal species in the world.
Apart from Australians not looking after their habitat, they have suffered historic damage, with one furrier recording that he had sold 29,000 platypus pelts pre-WWI.
In some areas they had become all but extinct by the 1920s. They have since been hammered by introduced species and widespread clearing of riverbanks and damming of rivers.