A ghost lives in the Daintree Rainforest in northeastern Queensland, Australia. There, on a single mountain range located 1,100 meters above sea level, scientists have recently found what may be the last few white lemuroid ringtail possums (Hemibelideus lemuroides), a species that was all but wiped out by a heat wave in 2005.
They may not be there much longer. Like many mountain species, such as the American pika, these possums can only survive within a very narrow temperature range. In fact, exposure to temperatures above 30 degrees Celsius for just a few hours will invariably kill the arboreal marsupials. Professor Bill Laurance of James Cook University (J.C.U.) in Queensland warns that current climate change models predict that high temperatures on the possum's mountain habitat (called Mount Carbine Tableland) will rise above that threshold, pushing the species into extinction.
Professor Stephen Williams, also from J.C.U., recently predicted that the possums could disappear during the next severe heat wave, either from high temperatures or a potential forest fire. Climate change, he says, is creating unusually dry wet seasons, which could exacerbate any future fires in the rainforest.
Of course, this isn't the first extinction prediction for the rare white possums. They were previously declared possibly extinct after the 2005 heat wave, but three of them were spotted again in 2009. That was it for a few years, though. None were seen until this past July, when scientists observed four or five possums over the course of 10 surveys. "This is best survey in nine years since the 2005 heat wave," Williams says, adding that this may be evidence that the species is actually recovering from the near-extinction event, but the threat of future heat waves remains.
Laurance says there may be more than five possums left, as the Daintree's high elevations and levels of vegetation make it a hard place to survey. "They're easy to spot, though," he says. Pointing a spotlight in the right place easily reveals their white fur and reflective eyes. "If they're there, you see them." He worries that the few animals they observed may be a little pocket population that survived the heat wave.
It hasn’t been easy to garner support for the white lemuroid ringtail possums because the white possums may or may not be simple color variants of regular lemuroid ringtail possums, which have brown fur. Laurance says brown possums also live in the rainforest, although they have a larger habitat range and appear to have a wider survivable temperature range. Meanwhile there is another population of the brown possums 100 kilometers to the south, where they live at elevations of about 600 meters. This population also has a few white possums—about one in every 400, Laurance says.
There have been no genetic studies to determine if the white possums on Mount Carbine are a separate species. Laurance says that doesn't matter. "It's moot to call them a distinctive species," he says. "They're a unique evolutionary unit and therefore worthy of conservation." Whether that will be possible in the face of climate change remains to be seen.
Photo courtesy of James Cook University