Numbers ebb and flow but mountain pygmy possums are having a good year

I have spent my life believing the giant moths that come out after a big rain were Bogongs. Turns out these are, coincidentally, called rain moths.

Bogong moths are only the size of a 50 cent coin and are largely unremarkable. They fly up into the Australian alpine region when it starts to warm up, and provide an important food source for a range of animals including the endangered mountain pygmy possums.

Every year researchers head into the mountains to monitor the numbers of these possums as they emerge from their winter hibernation and begin to breed. The Bogong moths congregate in boulder fields in the mountains, where the possums also live.

It is in these boulder fields or on a mountainside among the thick heath, where you might find wildlife biologist Dean Heinze.

And on this sunny day, he also had my camera and I for company.

Dean is checking his traps for mountain pygmy possums.

Sometimes the foul smell of urine is the precursor to the disappointing news the next trap is occupied by a native bush rat, however after a quick release it's onto the next one.

Once a pygmy possum is captured, it is transferred to a bag and expertly caught by the tail.

When pulled out, the possum latches onto the ecologist's vest. Dean says the animals seem more relaxed when he uses this method.

The ear tag number is recorded or a tag placed if it is unmarked, sex is determined and if it's a female, milk ducts inspected. It's then released back into the environment.

Mountain pygmy possums live in the shrubby heath land and boulder field areas of the Australian Alps. There are three main populations of the possum based around Mount Hotham/Falls Creek, Mount Buller and Mount Kosciuszko.

The migration of Bogong moths to the alpine region is crucial to the survival of the possums. The moths represent a large source of food arriving in the high mountains and their bodies provide a vital source of energy.

With higher than average Bogong moths observed in the alps last year, initial evidence indicates strong numbers within the possum population this year.

Dean has noticed the female possums have a good milk supply this year, following a decline in successful joeys seen in previous years. This further demonstrates the strong relationship between the two species.

In 2017 very few moths turned up, for reasons largely still unknown, resulting in the pygmy possums having poor condition and being unable to produce enough milk for their young. This caused a large number of pouch young to be lost that year.

Another significant issue the pygmy possums face is habitat fragmentation, caused by roads, ski runs and resort developments. This is particularly a problem for the species because the males and females live in different areas until it is time to produce young.

To resolve this, the original "tunnel of love" was constructed in the 1980s. It is a tunnel under the Great Alpine Road in the Mount Hotham resort that plays an integral role in relinking habitats.

Building tunnels under roads allows possums to travel with plenty of cover. Recently more tunnels have been installed under the road at Mount Little Higginbotham.

Dean is buoyed by the good signs this year.

"We are in a new era where the number of Bogong moths aren't as consistent as they once were," he said.

"Some years might be lean whereas some years we could get a big flush of Bogong moths."