The fat-tailed dunnart (Sminthopsis crassicaudata ) is a species of mouse-like marsupial of the Dasyuridae, the family that includes the little red kaluta, quolls, and the Tasmanian devil. It has an average body length of 60–90 millimeters (2.4–3.5 in) with a tail of 45–70 millimeters (1.8–2.8 in). Ear length is 14–16 millimeters (0.55–0.63 in). One of the smallest carnivorous marsupials, its weight varies between 10–20 grams (0.35–0.71 oz). The tail becomes fat a few mm from the proximal end and remains so right up to the tip. They have trichromat vision, similar to some other marsupials as well as primates but unlike most mammals which have dichromat vision. They are eaten by many things, including invasive foxes and cats, as well as other feral animals that live among its environment.
Fat-tailed dunnarts are small, mouse-like marsupials, closely related to quolls and Tasmanian devils. Their eyes and ears are large, the snout is pointed and the tail is thick. During periods of abundant food, they store fat in their tails for a short time, due to which their tails become swollen, becoming thinner during the winter. These fat stores allow dunnarts to survive food shortages.
Fat-tailed dunnart is an Australian marsupial, found west of the Great Dividing Range and south of the Tropic of Capricorn. This animal inhabits a wide variety of environments from the southern coast to the arid inland regions, occurring in open woodlands, shrublands and grass-lands.
Fat-tailed dunnarts are nocturnal and solitary animals, but sometimes they forms small groups. They spend their daytime hours sleeping in dark, secluded places. During the cooler seasons, they nest and sleep in groups to conserve heat. They can also nest with other animals, including the common house mouse. Each individual has its own home range. They have large territories, which overlap and can change during the year. Females of this species are known for their highly territorial behavior, fiercely defending the territory, surrounding their nesting site as they have older young. However, males do not appear to be territorial. In order to save energy, fat-tailed dunnarts can undergo winter torpor, which is similar to hibernation and can last from just a few hours to several days. When dunnarts awake from the torpid state, they use a lot of energy in order to raise their body temperature. During these periods, they typically spend their time sunbathing.
This marsupial are mainly insectivores. Their diet consists of various insects such as beetles or spider larvae, with addition of amphibians and small reptiles.
Fat-tailed dunnarts may exhibit either polygynous or polygynandrous (promiscuous) mating systems, having multiple partners over their short lifetime. Reproduction depends on weather conditions: if there are suitable conditions, females can breed and give births without breaks for up to 6 months. Fat-tailed dunnarts breed from July to February. Gestation period lasts for 13 - 16 days, yielding a litter of 6 - 8 young, sometimes up to 10. Females of this species are usually solitary nesters. They build their nesting sites from dried vegetation under logs, rocks or in deep ground hollows. Newborn babies remain in the pouch of their mother, before they leave it permanently at 60 days old. After that, the female can leave her young in the nest while she forages. Complete weaning occurs at about 70 days old. Sexual maturity is reached at 4 - 5 months old. Females first breed during the first year of their lives.
Fat-tailed dunnarts generally suffer from the same threats as most small mammals in Australia. They are threatened by loss of their natural habitat. Fat-tailed dunnarts compete with pest animals of their range. They are predated by cats, foxes and other feral species. And finally, these marsupials may be mistaken for mice and as a result, trapped.
According to IUCN, the Fat-tailed dunnart is common and widespread throughout its range but no overall population estimate is available. However, today this species’ numbers are stable, and it’s currently classified as Least Concern (LC) on the IUCN Red List.