The white lemuroid possum has been known to thrive in the cooler temperatures of the higher altitude rainforests of far north Queensland. But James Cook University's Professor Stephen Williams is concerned it has not been seen for three years, unlike the darker coloured members of the species who live at lower altitudes.

Professor Williams, who is the director of the university's Centre for Tropical Biodiversity and Climate Change, fears it may have fallen victim to climate change.

If so, it would be the first Australian mammal to become a casualty. There are already fears some frogs and insects have gone.

Professor Williams says the white lemuroid possum has not been seen since the area experienced a temperature rise of more than 0.5 of a degree.

"We've already had in Australia, I think, it's between 0.6 and 0.8 of a degree of increase in average temperature," he said.

"We do have local temperature data but, as I said, it's not really that average increase that's important, it's the increase in the record temperatures.

Professor Williams says despite an intensive search of several different areas, he failed to find a single possum.

"It was quite depressing going back on the last field trip a couple of weeks ago, going back night after night thinking OK, we'll find one tonight, but no we still didn't find any," he said.

"We tried several different areas. We did quite an intense effort without finding a single individual."

But Professor Williams says he is still "a way off" from proving the animal has become extinct.

"I guess that's the danger in talking to the media, because my original comments essentially were that we were concerned. We had made no claim that it had gone extinct," he said.

"It is sort of irrelevant because it's just as serious if it hasn't gone extinct.

"The fact that it has declined to such a degree that we can't find one suggests a very serious impact regardless of whether it's actually completely gone extinct."

Professor Williams says the situation with the white lemuroid possum is a "sign of things to come".

"It means that all of these much more serious predictions that we've been making could come to pass over the next couple of decades," he said.

"So the original predictions were that if we saw three or four degrees of warming we're looking at more than 50 per cent extinction of all species in the region. That's something that's hardly worth contemplating."

But climate change sceptic William Kininmonth, who is the former head of the National Climate Centre and a consultant to the World Meteorological Organisation, says there is little evidence to support the concerns about the white possum.

"Well, I'd be very surprised if the white possum had become extinct because of climate change," he said.

"Over the last few decades the climate really hasn't changed that much at all. We've had some drought periods and some wet periods and it's got a little bit warmer and there's been some El Niño and so forth.

"But there's been nothing that one could say is a remarkable trend. It's more likely that habitat damage and other things have contributed to the demise of the white possum."

Based on a report by Annie Guest for The World Today on December 3.