Species of marsupial
The sandhill dunnart (Sminthopsis psammophila) is a species of carnivorous Australian marsupial of the family Dasyuridae.[3] It is known from four scattered semi-arid areas of Australia: near Lake Amadeus in Northern Territory, the central and eastern Eyre Peninsula in South Australia, the southwestern and western edges of the Great Victoria Desert in Western Australia, and at Yellabinna in South Australia.[4]
Description
The sandhill dunnart is commonly known as a species of "marsupial mouse". The genus name of dunnart was likely derived from the Noongar word “danard".[5] It is the second largest of the 19 dunnart (Sminthopsis) species, with an adult body mass of up to 30 g (1.1 oz) for females and 55 g (1.9 oz) for males.[6] Adults are usually 10 to 16 cm (3.9 to 6.3 in) long. Only the Julia Creek dunnart is larger, weighing 40–70 g (1.4–2.5 oz).[4]
It is identified by its compartively larger size and bicoloured fur patterning (typically grey dorsally and white ventrally). The tail is clearly contrasted (dark ventrally/lighter dorsally) and terminally crested. Its forehead usually has a noticeably dark stripe.[4]
Its thermoneutral body temperature is around 34.4 °C (93.9 °F). While the sandhill dunnart's physiology resembles that of other dunnarts, penile morphology and molecular biology[7] suggest that it is basal to its genus.[8]
The sandhill dunnart usually moves by running smoothly on all four legs, sometimes with sudden short stops, during which they often squat with the forebody slightly elevated.[citation needed] The maximum speed recorded for S. psammophila is 3 km/h (1.9 mph).[9]
Diet
The species prefers to eat invertebrate prey, such as ants, beetles, spiders, grasshoppers, termites, wasps and centipedes.[6] In the Western Great Victoria Desert, the sandhill dunnart has an ant-rich diet, commonly consuming Camponotus spp. (sugar ants) and Iridomyrmex spp. (meat ants).[9] However, dunnarts are thought to be a generalist feeders and extremely opportunistic.[6] Other recorded prey species are gastropods, geckos, skinks and mice.[6][9] Food intake remains high in all seasons, varying only slightly in proportion.[10]
Physiology
In severe conditions when food is scarce, the sandhill dunnart enters short and shallow periods of torpor. The species’ documented states of mental and physical inactivity helps it to conserve water and energy.[10] From an analysis of the sandhill dunnart's metabolic, thermal, and ventilatory physiology, the organism's body temperature ranges, including thermoneutral, thermolability below thermoneutral, and mild hyperthermia temperatures are typical of those seen in small dunnarts and dasyurids.[8]
Reproduction
Sandhill dunnarts typically begin breeding in September, with offspring born from September to October.[6] Pouch young, dependent young and weaned juveniles are present in October.[6] However, juveniles have been trapped between October and April.[6] This information may suggest that with the right conditions in a good season, sandhill dunnarts may be able to produce another litter. There is a sixteen- to nineteen-day interval between mating and birth.[11][12]
Sexual maturity for both the male and female dunnart is reached by one year of age.[11] The age at which dunnarts are no longer able to reproduce is undetermined.[10] In captivity, males can breed at five years and females at three years.[11] In the wild, S. psammophila typically survives for one breeding season but this can extend to two seasons in favourable conditions.[13]
Behaviour
Sandhill dunarts are typically solitary and nocturnal, emerging shortly after dusk and foraging almost continuously until dawn.[9] During the day, they typically shelter from the climatic extremes of the desert within burrows.[14] Populations have naturally low densities but can increase significantly following major rainfall events.[15] Individuals exhibit both “resident” or highly mobile “transient” behaviour to locate resource patches when they become available.[16]
Distribution and habitat
The sandhill dunnart can be found in sandy, arid and semi-arid regions with spinifex grass hummocks in Australia.[17]
Because of the dunnart's distinct and limited habitat needs, spinifex hummocks are an essential part of its environment. It takes shelter from extreme temperatures and humidity within the burrows it digs under larger spinifex hummocks, which range from about 12 to 110 centimeters in length and are up to 46 centimeters deep. Females occasionally dig deeper, creating a chamber typically used for raising their young. Males, however, are known to occupy small burrows dug between spinifex clumps, hollow logs and even burrows dug by other animal species.[18] In the Western Great Victoria Desert, the species was found to prefer burrowing within long unburned (32+ years since a wildfire) spinifex grassland habitats. Dense lower stratum swale, sand plain and dune slope habitats were preferred, whereas habitats lacking spinifex and open dune crest habitats were rarely used. Home ranges in this region were approximately 70 ha in size but showed a large range of variation (6-274 ha). Home range size was influenced by sex and reproductive status.[9]
With the continual decrease of the spinifex hummock, the species’ territory also decreases and is now currently restricted to Eyre Peninsula in South Australia, and Great Victoria Desert covering South and Western Australia.[18] It was first sighted in Northern Territory, but it has not been seen there since the late 19th century.[1]
Threats
Although the exact causes of the decline of the Sandhill Dunnart are not known, it is likely to be under threat from predation by introduced species such as Red foxes and Feral cats, habitat degradation due to livestock grazing, and inappropriate fire regimes.[18] But despite the great damage done to their habitat by the fire regimes, sandhill dunnarts are able to recolonize burnt areas because of their adaptation to mid-successional complexes of vegetation. However, a single fire can wipe out an entire population. As the remnants become increasingly isolated from one another, the lack of connective bush corridors greatly reduces the likelihood of recolonisation.[19] They are a major threat to this species because of its dependence on large spinifex hummocks. In addition, land clearance for agriculture at the Eyre Peninsula has caused a great reduction in viable habitat for the sandhill dunnart, leaving only 43 percent of the area's original vegetation remaining.[18]
Conservation status
The sandhill dunnart is listed as “vulnerable” under the Environment Protection and Biodiversity Conservation Act 1999. It is afforded some protection within reserves, such as the Ironstone Hill Conservation Park and the Yellabinna Wilderness Protection Area in South Australia, and the Queen Victoria Spring Nature Reserve in Western Australia. In 2001, a national recovery plan listing several actions to aid in the recovery of the species was published. These actions included preventing further habitat clearance, conducting surveys in areas likely to support the species, implementing monitoring programs for key populations, and conducting research on captive individuals to increase understanding of this species’ reproductive biology. Experimental burns were also recommended to encourage the growth of suitable spinifex habitat.[18]
It has been suggested that the species was more widespread in the past but has recently contracted to more climatically favourable areas of its geographic range. Climate change may be a potentially catastrophic threat for the sandhill dunnart, as models suggest that suitable habitat may be reduced by 95% in 2050 under the current climate trajectory (RCP 8.5), and a revision of the species' IUCN status to Endangered has consequently been proposed.[20]
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