The platypus, once viewed as so bizarre as to be mythical, could end up merely a legend as habitat destruction and climate threats push the mammal towards the “brink of extinction”.

Researchers say platypus numbers may have halved or more since Europeans arrived in Australia, predicting local extinctions may have occurred across 40 per cent of the species’ range due to dam building, land clearing and other disruptions, according to a study published in the scientific journal Biological Conservation.

Taking present day threats and the climate into account, the researchers predicted platypus numbers would decline between 47 per cent and 66 per cent over 50 years.

When adjusted for projected climate change, the decline of an animal once common in waterways across much of the country would be even steeper, at 51 per cent to 73 per cent out to 2070, the research found.