The critically-endangered mountain pygmy possum
Photo: Rebecca Gibson, Shutterstock

Mountain pygmy-possums—big-eyed, stupefyingly cute hamster-sized marsupials—aren’t doing so hot. Critically-endangered, the nocturnal fuzzballs found only in boulder-strewn pockets of the high Australian Alps have suffered in the face of habitat loss and introduced predators. Now, new research suggests that climate change may hit the possums right in the gut, restricting access to their favorite, most nutritious foods.

Pygmy-possums (Burramys parvus)  are fairly unique among their pouched cousins. They’re one of just a few Australian mammals that hibernates seasonally and the only one restricted to regions above the winter snowline, Rebecca Gibson, a biologist at the New South Wales Office of Environment and Heritage, told Earther. Hibernating for half the year requires fattening up on high-energy foods, so pygmy-possums make heavy use of the seasonal arrival of bogong moths, which reach the mountains following a mass migration from their pupation sites on the plains. This occurs in the spring, right when the possums are shaking off their hibernation hangovers.

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Since the influx of fluttering calories is seasonal, Gibson and her colleagues wanted to see what pygmy-possums are eating throughout the year, how much season and climate influences key food resources, and how climate change might affect pygmy possum meals.

To find answers the researchers analyzed pygmy-possum scat samples collected over 17 years. They also developed a long-term survey of spring and summer bogong moth numbers in the Alps, and compared patterns in the possum diets and moth numbers with climate and plant growth data both in the mountains and in the moths’ lowland breeding grounds.

The results, published recently in the journal Wildlife Research, reveal that what pygmy-possums eat is largely at the whim of seasonal fluctuations. At lower elevations in the spring, pygmy-possums hork down lots of bogong moths, but eat more of other food sources later in the season when the moths move higher up the mountainside. Overall, bogong moths are a staple, joining other protein and fat-rich foods—like the seeds of the mountain plum-pine, a type of conifer—to make up 70 to 80 percent of the possums’ diet.

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Bogong moths huddle in huge numbers in deep, cold crevices within granite outcrops in the mountains.
Photo: CSIRO

The problem? These same key foods are under threat due to climate change.

Bogong moths are dependent on cool caves and crevices in the mountainside to congregate en masse, chasing these spaces by moving higher in elevation as the warm season progresses. Though direct tests of bogong moth heat tolerance have not yet been conducted, it’s likely that reduced access to cool microhabitats from warming will impact their survival, says Gibson. As for the plum-pine, predicted increases in fire severity in the mountains may reduce the number of seeds available, since plum-pine is particularly apt to burn.

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With fewer moths and plum-pines in the picture, Gibson thinks the pygmy-possums may move from a fat and protein-rich diet to one high in carbohydrates, with untold impacts on pygmy-possum health or hibernation.

Such malnourishment would add to an already long, steadily growing list of hardships inflicted upon alpine ecosystems by climate change. Rising temperatures are pushing some tropical mountain species towards extinction, for example, by sliding their narrow bands of habitat right off summits. Pygmy-possums themselves are already at risk from other varieties of climate change-driven ecological chaos; warmer temperatures are allowing feral cats and foxes to invade former high-elevation sanctuaries.

What can be done to help these alpine bug-gulpers? Part of the puzzle is simply gaining a better understanding of exactly how climate change will impact bogong moths, and if pygmy-possums can actually handle a dietary switch. In the immediate term, Gibson says, continuing possum captive breeding programs can provide a “genetic safety net” for the species. Fire management also needs to be prioritized, for the sake of the plum-pines.

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But addressing the root problem of climate change itself is the most effective route. “Slowing the pace of climate change, and limiting the magnitude of change, will give the mountain pygmy-possum the greatest chance of survival,” Gibson said.

Jake Buehler is a science writer living on Washington’s Olympic Peninsula with an adoration for the Tree of Life’s weird, wild, and unsung—follow him on Twitter or at his blog.