The fat-tailed dunnart (''Sminthopsis crassicaudata'') is a species of mouse-like

marsupial Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are carried in a po ...

of the

Dasyuridae The Dasyuridae are a family of marsupials native to Australia and New Guinea, including 71 extant species divided into 17 genera. Many are small and mouse-like or shrew-like, giving some of them the name marsupial mice or marsupial shrews, but th ...

, the family that includes the

little red kaluta The little red kaluta (''Dasykaluta rosamondae'') is a small, reddish-brown, shrew-like mammal native to dry grasslands of northwest Australia. It is active at night, feeding on insects and other small animals. The kaluta is a marsupial and is t ...

quoll Quolls (; genus ''Dasyurus'') are carnivorous marsupials native to Australia and New Guinea. They are primarily nocturnal and spend most of the day in a den. Of the six species of quoll, four are found in Australia and two in New Guinea. Anoth ...

s, and the

Tasmanian devil The Tasmanian devil (''Sarcophilus harrisii'') (palawa kani: purinina) is a carnivorous marsupial of the family Dasyuridae. Until recently, it was only found on the island state of Tasmania, but it has been reintroduced to New South Wales in ...

. It has an average body length of with a tail of . Ear length is . One of the smallest carnivorous marsupials, its weight varies between . The tail becomes fat a few mm from the proximal end and remains so right up to the tip. The dunnart has

trichromat Trichromacy or trichromatism is the possessing of three independent channels for conveying color information, derived from the three different types of cone cells in the eye. Organisms with trichromacy are called trichromats. The normal exp ...

vision, similar to some other marsupials as well as

primates Primates are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians (monkeys and apes, the latter including huma ...

but unlike most mammals which have

dichromat Dichromacy (from Greek ''di'', meaning "two" and ''chromo'', meaning "color") is the state of having two types of functioning photoreceptors, called cone cells, in the eyes. Organisms with dichromacy are called dichromats. Dichromats require ...

vision. The dunnart is often eaten by other carnivores, including invasive foxes and cats, as well as other feral animals that live among its environment.

Distribution and habitat

The range of ''S. crassicaudata'' in Australia is in diverse habitats except for the

Kimberley region of Western Australia The Kimberley is the northernmost of the nine regions of Western Australia. It is bordered on the west by the Indian Ocean, on the north by the Timor Sea, on the south by the Great Sandy and Tanami deserts in the region of the Pilbara, an ...

and northern

Northern Territory The Northern Territory (commonly abbreviated as NT; formally the Northern Territory of Australia) is an states and territories of Australia, Australian territory in the central and central northern regions of Australia. The Northern Territory ...

Arnhem Land Arnhem Land is a historical region of the Northern Territory of Australia, with the term still in use. It is located in the north-eastern corner of the territory and is around from the territory capital, Darwin. In 1623, Dutch East India Compan ...

and

Kakadu National Park Kakadu National Park is a protected area in the Northern Territory of Australia, southeast of Darwin. It is a World Heritage Site. Kakadu is also gazetted as a locality, covering the same area as the national park, with 313 people recorded liv ...

, but avoids the Wannon and Mallee scrub habitats in Victoria. In the northeast of Victoria, the species can also be found in

grass Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in lawns an ...

woodland A woodland () is, in the broad sense, land covered with trees, or in a narrow sense, synonymous with wood (or in the U.S., the ''plurale tantum'' woods), a low-density forest forming open habitats with plenty of sunlight and limited shade (see ...

s and

samphire Samphire is a name given to a number of succulent salt-tolerant plants (halophytes) that tend to be associated with water bodies. *Rock samphire, ''Crithmum maritimum'' is a coastal species with white flowers that grows in Ireland, the Unit ...

shrublands. The subspecies ''S. c. crassicaudata'' is in the

Epping Forest National Park Epping Forest is a national park in Queensland, Australia, 855 km northwest of Brisbane. The park is a scientific national park so it is not open to the public. Only scientists, rangers and volunteers may visit the park. The park lies with ...

in Queensland. ''S. c. ferruginea'' is found around

Lake Eyre Lake Eyre ( ), officially known as Kati Thanda–Lake Eyre, is an endorheic lake in east-central Far North South Australia, some north of Adelaide. The shallow lake is the depocentre of the vast endorheic Lake Eyre basin, and contains the ...

in South Australia. ''S. c. centralis'' is found in Killalpannina (as Killalpanima, Lake Eyre East), SA.Fat tailed dunnarts can be found in most deserts in Australia, e.g. the Simpson Desert and Gibson Desert. The habitats in which the species can be found include sparse grasslands, open shrublands and farmlands where there is considerable bare land. The impact of unimproved farming has been positive for this species as the type of habitat created is suitable to this

dunnart Dunnart is a common name for species of the genus ''Sminthopsis'', narrow-footed marsupials the size of a European mouse. They have a largely insectivorous diet. Taxonomy The genus name ''Sminthopsis'' was published by Oldfield Thomas in 18 ...

's requirements, but intensive agriculture is seen as a negative factor for the species.

Social organisation and breeding

This species breeds from July to February, with the young in the pouch from July to April (Morton 1978b). Gestation is for 13 days and the young remain in the pouch for 70 days with litter size on average 7.5 with a 33% infant death rate. They generally have two litters per year with females not breeding for the first year. The average life span of the females is 18 months, and males 15 months.

Diet

The fat-tailed dunnart's diet includes insects such as beetles, spiders, small reptiles, and amphibians. It stores fat reserves in its carrot-shaped tail for times of food shortage.

Survival

The fat-tailed dunnart can survive in extreme, semi-arid environments. This is due to various physiological and behavioral characteristics. First, this

is nocturnal and functions within a 24-hour

circadian rhythm A circadian rhythm (), or circadian cycle, is a natural, internal process that regulates the sleep–wake cycle and repeats roughly every 24 hours. It can refer to any process that originates within an organism (i.e., Endogeny (biology), endogeno ...

. During the nighttime it is protected from high temperatures that cause energy loss. While awake, it spends the majority of its time feeding. Every night it consumes approximately its own body weight of food. During periods of food shortage it decreases its duration of activity while also increasing its intensity of feeding. It uses specialized, sharp teeth to grind its prey into fine pieces. This increases its ability to obtain nutrients from its prey. It has a high rate of digestion and can use fat stored in its tail as an energy source. Another survival technique that it uses is daily torpor. It lowers its body temperature and

metabolic rate Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cell ...

, in order to reduce energy expenditure. Torpor is unaffected by alterations in

photoperiod Photoperiodism is the physiological reaction of organisms to the length of night or a dark period. It occurs in plants and animals. Plant photoperiodism can also be defined as the developmental responses of plants to the relative lengths of light a ...

but is greatly affected by environmental conditions. Two conditions must occur in order for the fat-tailed dunnart to use daily torpor: low ambient temperatures and food shortage. There are seasonal variations in torpidity. They use it more often in the winter because food is scarce and it requires more energy to maintain a high constant body temperature. During torpor, the body temperature can drop as low as 14.6 °C. This species does not use torpor for extended periods of time, thus the heart rate is variable and does not reach a

steady state In systems theory, a system or a Process theory, process is in a steady state if the variables (called state variables) which define the behavior of the system or the process are unchanging in time. In continuous time, this means that for those p ...

, such as seen in long-term torpidators. This species is unique in that it can use torpor during development and reproduction. Even during

lactation Lactation describes the secretion of milk from the mammary glands and the period of time that a mother lactates to feed her young. The process naturally occurs with all sexually mature female mammals, although it may predate mammals. The proces ...

a female is capable of entering daily torpor without affecting the offspring. Coupled with the daily torpor is a process called re-warming. The re-warming process demands a high amount of energy in order to raise the body temperature. After awaking from a torpid state, these marsupials actively seek out areas in which they can bask in the sun to aid in this process. Nesting is also used as a behavioral survival technique. During times of cold temperatures, the fat-tailed dunnart shares nests with rodent species such as the household mouse, ''Mus musculus'', to conserve heat. This is unusual because the fat-tailed dunnart preys upon these mice during less extreme conditions. Group nesting is observed only during times of non-breeding.

References

External links

Fat-tailed dunnart

Australian Biological Resources Study

{{Taxonbar, from=Q194519 Dasyuromorphs Mammals of Western Australia Mammals of South Australia Mammals of the Northern Territory Mammals of New South Wales Mammals of Victoria (Australia) Marsupials of Australia Mammals described in 1844