They're fatter and turning up more frequently in scientific surveys, but Kosciuszko National Park's critically endangered mountain pygmy possums may face leaner times in spring.
NSW Office of Heritage and Environment ecologist Linda Broome says recent rains have affected seed production of mountain plum-pine (Podocarpus lawrencei), a richer food source for the palm-sized possums than fat-rich Bogong moths.
''They're wind-pollinated plants, and with all the wet weather we've had, there appears to be a low seed set this autumn. We're seeing a similar problem with wind-pollinated grasses … So, although possum numbers are up in most areas we surveyed, I'm a bit concerned about the next breeding season.''
Dr Broome, who has been monitoring possum populations in the park for the past 26 years, explains that the plum-pine seeds allow possums to stay under cover in the boulder fields, where they are less exposed to predators, such as cats and foxes.
She has just finished analysing the results of a summer trapping survey, in which the possums were weighed, tagged and released. ''We trapped more mountain pygmy possums at our monitoring sites at the southern end of the park this season - more than we've caught previously. And they're in top condition too, some of the fattest I've seen.''
Dr Broome said populations declined by 43 per cent between 1999 and 2009 because higher temperatures reduced winter snow cover and caused earlier snow melts, making the possums easy pickings for hungry predators.
''The most severe declines occurred in areas around the ski resorts, probably due to a high concentration of feral predators.''
Next week, Dr Broome sets off for a final field trip to the park's remote granite boulder fields before the winter snows set in. The easy part will be using her laptop to program about 80 data loggers to record temperatures and snow duration. But some of areas of boulder field possum habitat are so remote it will take Dr Broome and a research assistant a day to walk in, set up the loggers, and walk out again.
Dr Broome is waiting for the results of DNA analysis of possum populations to see if there are genetic differences between the park's northern and southern populations. The tests will also identify any genetic bottlenecks.
''It's possible we'll see strong genetic differences, but it's unlikely we'll see a sub-species,'' she said.
Genetic diversity will also mean greater resilience to threats such as climate change. ''It's great that numbers are on the rise, but what we do know from the data we've collected over the past 26 years is the possums are affected by hot, dry conditions. And future climate scenarios indicate those conditions will return, so while I'm happy the numbers are up, I'm still concerned about their long-term survival.''