The mysterious possum of the Kimberley

The scaly-tailed possum is one of Australia’s least known and most mysterious mammals. New research reveals little difference between the supposedly isolated east and west Kimberley populations. This suggests there are (or recently were) undetected populations in between! Resolving this dilemma will be vital for managing the species.

During her time as the Chadwick Biodiversity Fellow at the Australian Museum, Dr Sally Potter studied a unique Australian marsupial the scaly-tailed possum (Wyulda squamicaudata).

The scaly-tailed possum is odd. It has no close relatives but is distantly related to the familiar brush-tailed possums of Australia and the cuscuses of New Guinea. Unlike its distant cousins, scaly-tailed possums are dependent on rocky outcrops in which they shelter during the day, emerging at night to feed in the surrounding forest. The possums have a curiously flattened head and their prehensile tail is largely furless.

Scaly-tailed possums are only known from the remote Kimberley region of northwestern Australia and are rarely encountered. As a consequence, little is known about them. They were first described by western science in 1919, making them amongst the last medium-sized mammal discovered in Australia.

Although the first scaly-tailed possum specimens were said to come from the east Kimberley, all subsequent specimens and sightings were from high rainfall areas of the coastal west Kimberley. This caused many to wonder whether those first specimens really had come from the east Kimberley. Then in 2012, scaly-tailed possums were rediscovered in a remote gorge in the east Kimberley some 300 km east of any currently known population.

Gathering together all known scaly-tailed possum samples, a relatively meagre 23 individuals, Dr Potter, colleagues from the Australian National University and I used genetic analysis to determine just how different the newly found, isolated east Kimberley population was from those far to the west.

Surprisingly, we found little difference between the east and west Kimberley populations despite their geographic separation. In addition, using spatial models of the environment they currently inhabit we modelled where similar environments occurred in the past. Our results showed that suitable habitat for the scaly-tailed possum has shifted dramatically through space and time across the Kimberley over the last 40,000 years. The models also showed that the eastern and western populations were adapted to slightly different local environments.

Our studies indicate that populations of scaly-tailed possums have recently existed between the two currently known populations, even though no individuals have ever been detected. These ‘missing’ populations are either now extinct, or are still out there, perhaps hiding in small moist areas of suitable habitat such as deep and narrow river gorges.

With large–scale declines in many mammal species occurring across northern Australia, we only have limited time to discover the truth.

Dr Mark Eldridge
Senior Research Scientist

Dr Sally Potter
Research Associate

More information:
Potter, S., Rosauer, D., Doody, S., Webb, M.J. and Eldridge, M.D.B. (2014). Persistence of a potentially rare mammalian genus (Wyulda) provides evidence for areas of evolutionary refugia within the Kimberley, Australia. Conservation Genetics.

Doody J.S., Rhind D., Castellano C.M., Bass M. (2012). Rediscovery of the scaly-tailed possum (Wyulda squamicaudata) in the eastern Kimberley. Australian Mammalogy 34: 260-262.