Geneticists weave possum magic to bring a species back from the brink


The critically endangered mountain pygmy-possum. Picture: Andrew Weeks

Victorian scientists are deeply worried that the critically endangered mountain pygmy-possum may join the growing list of Australian casualties of the species extinction crisis now playing out across the planet.

Thought to be extinct until it was rediscovered in 1966, the mountain pygmy-possum is the only marsupial in the world that hibernates, and the only Australian mammal to exclusively inhabit alpine regions. To survive it requires at least a metre of winter snow cover. In a warming world, that makes it deeply vulnerable.

Picture: Australian Alps collection – Parks Australia.

“If that snow disappears – which is what we expect climate change to do – they’ve got nowhere to hibernate,” says Dr Andrew Weeks, an ecological geneticist from the University of Melbourne and leader of a pioneering program to try to rescue Burramys parvus. 

The tiny creature, a handful of fur and limpid eyes, is fighting a war of survival on many fronts: development of ski fields, road construction, feral foxes and cats.

There are also fears that the pygmy-possum may not have enough food this spring due to a collapse in the number of bogong moths migrating to the area.

There are currently thought to be around 2000 adult mountain pygmy-possums in the wild, making the species critically endangered according to the International Union for Conservation of Nature.

Weeks’ work has focused on the southern population of the pygmy-possum, at Mount Buller, where it was rediscovered in 1996 and where within 10 years the population had declined to just 20 adults. Genetic diversity in the small population was suffering. There are only two other populations – at nearby Mount Higginbotham, and Kosciuszko National Park over the border in New South Wales.

Enlisting a world-first technique referred to as “genetic rescue”, whereby individuals from a larger and genetically healthy population are introduced to a smaller inbred colony, Weeks introduced six healthy males from the other pygmy-possum populations to the Mount Buller colony in late 2007. Further translocations were completed in 2011 and 2014.

Currently on Mount Buller there are about 180 adults, and the population’s genetic diversity is now approaching healthy levels, according to Weeks. Genetic rescue is now being looked at as a potential lifeline for other critically endangered species.

The North East Catchment Management Authority has also been working to improve the outlook for the pygmy-possum. With funding from the National Landcare Program under the Department of the Environment and Energy, the authority has a five-year plan to raise pygmy-possum numbers.

The project seeks to tackle immediate threats to the possum by focusing on weed control, habitat restoration, controlling pest animals and population monitoring.

Olivia Kemp, biodiversity officer at the authority, says it’s too early to report back on results from the program but early ecological monitoring of the animal had revealed one unexpected result: “Quite a few of them had … pouch young litter loss.”

Authorities are concerned this could be a result of the decline of bogong moths migrating to the area, according to Kemp.

Every spring huge numbers of bogong moths migrate from farmlands in Victoria, NSW and Queensland to the Australian Alps to escape the summer heat. The moths are the perfect food source arriving at the perfect time, says Weeks.

But in the past two years there has been a catastrophic crash in the number of bogong moths making the annual migration. This is believed to be due to the severe drought occurring across the moth’s breeding areas. The 32-month period from January 2017 to August 2019 has been the driest on record across the Murray-Darling Basin.

Zoos Victoria is leading a ‘Lights off for the Bogong Moths’ campaign, which encourages residents of NSW, the ACT and Victoria to turn off any unnecessary outdoor lighting.

“There are a number of things that are causing the bogong moth to not arrive,” says Gigi Silk, digital communications manager at Zoos Victoria. “One of them may be that lights are luring the moths away from their destination.

“When they fly down from Queensland to Victoria they follow a certain migration route which happens to go over a number of major of towns and cities like Canberra and Wagga Wagga.”

The campaign is also urging those in charge of public buildings, such as Parliament House, to switch off their lights at night.

Public reaction to the campaign has so far been very positive, says Silk. An animated video about the campaign has been watched 87,000 times on Facebook.

Zoos Victoria has also just launched a Moth Tracker app, where people can record their sightings.

Very little is known about the moth so it is hoped that the app will help explain what is happening to them.

“We just don’t know what’s happening to these moths,” says Silk. “If the moths are still hatching, where is it they are getting lost?”

Citizen scientists who download the app are given instructions about how to identify a bogong moth, and zoo staff verify any sightings before the data is recorded.

Both the Lights Off for the Bogong Moths campaign and the app are intended to raise public awareness of the plight of the moth and the pygmy possum. “If you don’t know about a species, it’s really hard to care about it,” comments Silk.

Many scientists believe that Earth is undergoing its sixth mass extinction event, a “biological annihilation” largely blamed on human overpopulation and overconsumption. Australia has one of the worst animal extinction rates in the world, with more than 500 species under threat.

A Senate inquiry into animal extinction currently under way has heard that over the past 200 years 10 per cent of Australian endemic terrestrial land mammal species have become extinct, accounting for half of all global mammal extinctions during that period.

The Senate’s interim report notes that climate change is one of the major factors in species loss. The inquiry has heard that Australian governments have been ineffective in dealing with biodiversity loss and that existing laws designed to protect against loss of biodiversity are not adequately implemented.

In the past decade, three Australian animals have become extinct – the Christmas Island pipistrelle (a bat), the Christmas Island forest skink (a lizard) and the Bramble Cay melomys (a rodent). The little-known Bramble Cay melomys is recognised as the first mammalian extinction in the world caused by climate change.

“We have such amazing wildlife that is found nowhere else in the world,” says Andrew Weeks.

“I think it would be very sad if we did not have these species in the environment.”

This story is part of the University of Melbourne Centre for Advancing Journalism’s contribution, via The Junction, to the Covering Climate Now initiative, a global collaboration of more than 220 news organisations worldwide.