The sandhill dunnart (Sminthopsis psammophila) is a species of carnivorous Australian marsupial of the family Dasyuridae. 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.
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". 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. 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). 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. 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 suggest that it is basal to its genus. 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. The maximum speed recorded for S. psammophila is 3 km/h (1.9 mph).
Ecology
Diet The species prefers to eat invertebrate prey, such as ants, beetles, spiders, grasshoppers, termites, wasps and centipedes. 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). However, dunnarts are thought to be a generalist feeders and extremely opportunistic. Other recorded prey species are gastropods, geckos, skinks and mice. Food intake remains high in all seasons, varying only slightly in proportion.
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. 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.
Reproduction Sandhill dunnarts typically begin breeding in September, with offspring born from September to October. Pouch young, dependent young and weaned juveniles are present in October. However, juveniles have been trapped between October and April. 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. Sexual maturity for both the male and female dunnart is reached by one year of age. The age at which dunnarts are no longer able to reproduce is undetermined. In captivity, males can breed at five years and females at three years. In the wild, S. psammophila typically survives for one breeding season but this can extend to two seasons in favourable conditions.
Behaviour Sandhill dunarts are typically solitary and nocturnal, emerging shortly after dusk and foraging almost continuously until dawn. During the day, they typically shelter from the climatic extremes of the desert within burrows. Populations have naturally low densities but can increase significantly following major rainfall events. Individuals exhibit both "resident" or highly mobile "transient" behaviour to locate resource patches when they become available.
Distribution The sandhill dunnart currently inhabits sandy, semi-arid regions dominated by spinifex (Triodia) grasslands in South Australia and Western Australia. However, the type specimen was caught "with a thrown boot" during the Horn Expedition in 1894 in the Northern Territory. Subsequently, it was recorded in owl pellets only in Uluru's caves. Shortly after, the sandhill dunnart was mistakenly presumed extinct. In 1969, the sandhill dunnart was detected on Eyre Peninsula in South Australia. Eyre Peninsula is a well-studied stronghold. Records have been radiocarbon dated to approximately 2-3 thousand years ago. From the 1990s, the Yellabinna Regional Reserve in South Australia was confirmed as a second stronghold. From 2017, several S. psammophila records were confirmed between the Eyre Peninsula and Yellabinna populations. The third stronghold is the Western Australian Great Victoria Desert. Individuals were detected near Mulga Rockhole in 1985 and later in/near Queen Victoria Spring Nature Reserve and near Tropicana Gold Mine. In 2018, another population was detected 150 km north of the known range. Ancient sandhill dunnart bones have been recorded by Dr Alex Baynes near Yalgoo and Lake Barlee (400-600 km west of the current population), indicating that the sandhill dunnart was once more widespread in Western Australia. Each stronghold is genetically differentiated, based on the frequency of microsatellite alleles and CR haplotypes, and should be considered as distinct Management Units for conservation. Yellabinna and Western Australian populations share a mtDNA haplotype, indicating historical connectivity across the southern Great Victoria Desert. No significant genetic structure or sex-biased dispersal was detected locally, suggesting that both sexes are highly mobile. Individuals can therefore relocate to neighbouring resource patches when available. Although previously more widespread, the sandhill dunnart has experienced a significant range contraction. The sandhill dunnart may continue to contract south in the future because of the effects of climate change. Due to the cessation of suitable spinifex habitats in the south, the Great Victoria Desert populations are at risk of extinction by 2070.
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