Rare white platypus spotted, but it's not an albino

Researchers hunting for an endangered turtle have discovered something even rarer - a white platypus frolicking in a NSW stream.

Photos and footage of the extraordinary creature have been published in a scientific journal after several encounters over the past two years or so.

University of New England PhD student Lou Streeting was searching a Northern Tablelands stream for endangered western saw-shelled turtles when she first spotted the conspicuous enigma in early 2021.

"It surfaced literally a few metres away from us and we were like 'Wow, did we just see a white platypus?'" Ms Streeting says.

"I was glad I caught it on video because I didn't think anyone would believe me otherwise."

She has seen the platypus a number of times since then, most recently three months ago, showing it is coping with its lack of camouflage.

White platypuses have been documented in the past, but this one has a point of difference.

It's not an albino because only part of its body is affected by an absence of melanin - a pigment that gives colour to fur, skin and eyes.

"It does have some pigmentation. It has a black bill, and it has black feet, and a little bit of colour on its tail. So we've said it's a leucistic platypus."

And it's possibly the first one ever documented.

"Our search of scientific literature, newspapers, and databases yielded 12 individual records of albino or atypically white platypus dating back to the first record in 1835, and our observation likely represents the only known record of a leucistic platypus."

Ms Streeting hopes the intriguing discovery will remind everyone of the need to protect the treasure trove of native species in the nation's waterways.

"These environments are not just home to endangered species like the western saw-shelled turtle, but also to other truly unique and extraordinary creatures like this rare white platypus."

The Australian Conservation Foundation says platypus numbers are in decline, with the duck-billed, egg-laying, milk-producing yet nipple-less peculiarity losing roughly a quarter of its habitat during the past 30 years.

Despite the downward trajectory, there's a lack of good data and only broad estimates of how many are left.

In an effort to plug the gaps, the ACF has partnered with the University of NSW's Centre for Ecosystem Science on a citizen science initiative called the Platy-project.

It encourages Australians to look for them in local creeks and rivers, and share the details of any sightings.

UNSW conservation ecologist Gilad Bino worked on a 2021 national assessment of the conservation status of the platypus and says there's much uncertainty about how many are left.

It could sit anywhere between 50,000 and 300,000.

There's no national or state level monitoring frameworks for the species despite evidence of shrinking populations in places such as greater Melbourne.

"That would be true for all urban areas, but we don't have the data," he tells AAP.

Populations are also in decline in parts of the Murray-Darling river system, and there have been localised extinctions in Brisbane.

"In South Australia, they are pretty much extinct except for an introduced population on Kangaroo Island and even they've been impacted by bushfires and drought," he says.

"I don't think platypuses are going to disappear - and I hope I'm right - in the next several decades. But what I do fear is that for many people across Australia, they're going to see them disappear from their local rivers."