Julia Creek dunnart
Copyright: Greg Mifsud
Common name: Julia Creek dunnart
Scientific name: Sminthopsis douglasi
(sminthopsis = mouse-like; douglasi = named after A.M. Douglas, Western Australian naturalist and collector for the Western Australia Museum)
Animal group: Marsupial carnivores
Conservation status: This species is listed as Endangered both in Queensland (Nature Conservation Act 1992) and nationally (Environment Protection and Biodiversity Conservation Act 1999). It is ranked as a critical priority under the Department of Environment and Heritage Protection Back on Track species prioritisation framework.
Description: The Julia Creek dunnart is the largest of the 19 species of the Genus Sminthopsis found in Australia. They have a body length of 13-13.5 cm, a tail length of 12-13 cm, and weight ranges of 40-60 g for females and 50-70 g for males. They are sandy brown in colour, speckled with grey above and buffy white below. Its face has rufous hair on the cheeks and at the base of the ears and dark hairs towards the tip of its long tapering tail. A darker face stripe runs from behind the nose to the top of the head and there is also a fine ring of darker hair around the eyes. It has large eyes, narrow feet and a pointed snout.
It can also store food in its tail as fat, and individuals will have a swollen base to their tail when food is abundant.
Habitat and distribution
Cracking clay soils Photo: EHP
The predator fence around Julia Creek aerodrome Photo: EHP
The Julia Creek dunnart lives on the Mitchell Grass Downs, and some areas of the Desert Uplands in north-western Queensland. It shelters in the cracking clay soils during the dry season or among the low grass and shrubs following summer rain. Habitat selection appears to be based on the density of holes and cracks in the soil, rather than vegetation cover which is dependent on season and unpredictable rainfall events and not a reliable source of shelter. In the absence of ground cover individuals may be more susceptible to predation when alternative refuge sites (e.g. soil cracks) are unavailable.
Prior to 1992 S. douglasi was known only from four specimens collected in a limited area between Richmond and Julia Creek. Surveys conducted during the 1990s extended the species geographic range considerably within both the Mitchell Grass Downs and Desert Uplands Bioregions, although sightings were patchy and abundances low. The number of known localities increased from three to 11 using indirect survey methods.
Julia Creek dunnarts have been found in Bladensburg National Park and Moorrinya National Park. These are the only protected areas on which they are known to occur.
One live S. douglasi specimen was discovered in Mitchell Grass habitat adjacent to the Julia Creek aerodrome. As the 250 ha area of Mitchell grassland surrounding the aerodrome is relatively undisturbed, McKinlay Shire Council has worked with the Department of Environment and Heritage Protection to protect and manage this habitat for the Julia Creek dunnart. To assist with its protection, a vermin proof fence encompassing the entire aerodrome was installed in January 2008.
Life history and behaviour
The Julia Creek dunnart is nocturnal, emerging from its shelter in the cracked soil to feed on arthropods such as crickets, cockroaches, silverfish and slaters, as well as spiders and small reptiles.
The species appears to be highly mobile occupying stable home ranges that range from 0.25 ha to 7.12 ha in size.
From studies of captive individuals it appears that the Julia Creek dunnart may be polyoestrous (i.e. undergoes oestrus more than once each year). Females are able to breed from between 17 and 27 weeks of age and males between 28 and 31 weeks. This later maturity in males may be a way of limiting inbreeding within small populations. Females can have up to eight young after a gestation period of only 13 days. This life history trait is typical of small species inhabiting semi-arid and arid environments where food supply is unpredictable. Sminthopsis species are considered a ‘boom or bust’ species, being subjected to periodical fluctuations in population associated with seasonal changes. Generally they are short lived, with a lifespan of two to three years.
Before 1990, this species was only known from four skins held in the Queensland and Australian museums and was believed to be extinct.
In 1990 a new survey program began with the help of local landowners and revealed a number of new specimens from owl pellets (i.e. the indigestible remains of an owl's prey that are disgorged as pellets) and domestic cat kills. In 1991 and 1992 the first live specimens were caught (including one rescued from a cat).
Threats to the Julia Creek dunnart include predation from introduced predators (such as cats and foxes), inappropriate grazing regimes that can destroy habitat, and the invasion of prickly acacia that degrades the habitat. Inappropriate fire regimes and extreme climatic events may also impact the species.
Feral cats are significant predators of Julia Creek dunnarts and predation can be high within a local area. Examination of the stomach contents of cats and foxes collected by shooting and trapping on Toorak Research Station revealed that foxes also prey on Julia Creek dunnarts. Foxes are considered less of a threat, but are common throughout the species' range.
Prickly acacia (Acacia nilotica), mesquite (Prosopis spp.) and parkinsonia (Parkinsoniaaculeata) are a major threat to the biodiversity in the Mitchell Grass Downs. Prickly acacia shades out understorey plants, and its extensive root system inhibits the cracking of clay soils (that is an important dunnart habitat).
An experimental burn at Bladensburg National Park in 2001 found that Julia Creek dunnarts can survive the direct effects if there is suitable habitat (i.e. soil cracks and ground cover) to provide protection from predators. The impact of fire on the species depends upon the timing and severity of the burn and the amount of remaining ground cover.
Unpredictable climatic events such as heavy, prolonged rainfall which can cause severe flooding could have the potential to cause high mortality of juvenile Julia Creek dunnarts if the young are not sufficiently mobile to escape rising floodwaters. Similarly, females carrying pouch young may be at risk form drowning because of the increased weight being carried, preventing them from swimming or climbing onto vegetation.
A Julia Creek dunnart at the Julia Creek aerodrome Photo: EHP
The recovery plan for the Julia Creek dunnart suggests that maintaining areas which support suitable habitat has the greatest potential for conserving wild populations.
- Fauna surveys in 2000 and 2001 indicated that population numbers on Bladensburg National Park were reasonably health and high. Appropriate management of suitable habitat, including predator control, will assist in retaining healthy numbers.
- Surveys continue to be conducted to clarify the abundance of this species, and to learn more about its habitat requirements and ecology.
- Private landholders are being encouraged to manage their properties in ways that contribute to the conservation of this species.
- In June 2007, 20 captive-bred sub-adult dunnarts were released into the Julia Creek aerodrome for a pilot reintroduction program. In December 2008, a further 22 captive-bred dunnarts were released to increase numbers in the aerodrome sanctuary as part of the finalisation of the captive breeding program.
National recovery plan for the Julia Creek dunnart (Sminthopsis douglasi). 2009. Report to the Department of the Environment, Water, Heritage and the Arts, Canberra.