Fat-tailed Dunnart
Encyclopedia
The Fat Tailed Dunnart (Sminthopsis crassicaudata) is a species of mouse-like marsupial
of the Dasyuridae
family, the family includes the Little Red Kaluta
, quoll
s, and the Tasmanian Devil
. It has an average body length of 60–90 mm with a tail of 45–70 mm. Ear length is 14–16 mm. Its weight varies between 10-20 grams, it is one of the smallest carnivorous marsupials. The tail becomes fat a few mm from the anus and right up to the tip of the tail.
and northern Northern Territory
like Arnhem Land
and Kakadu National Park
, but avoids the Wannon and Mallee
scrub habitats in Victoria. In the northeast of Victoria, the species can also be found in grass
y woodland
s and samphire
shrublands. The subspecies S. c. crassicaudata is in the Epping Forest National Park
in Queensland. S. c. ferruginea is found around Lake Eyre
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. Simpson desert, 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
's requirements, but intensive agriculture is seen as a negative factor for the species.
is nocturnal and functions within a 24-hour circadian rhythm
. 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
, in order to reduce energy expenditure. Torpor is unaffected by alterations in photoperiod
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
, such as seen in long-term torpidators
. This species is unique in that it can use torpor during development and reproduction. Even during lactation
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 behavioral, survival technique. During times of cold temperatures, the fat-tailed dunnart shares nests with other 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.
Marsupial
Marsupials are an infraclass of mammals, characterized by giving birth to relatively undeveloped young. Close to 70% of the 334 extant species occur in Australia, New Guinea, and nearby islands, with the remaining 100 found in the Americas, primarily in South America, but with thirteen in Central...
of the Dasyuridae
Dasyuridae
Dasyuridae is a family of marsupials native to Australia and New Guinea, including 61 species divided into 15 genera. Many are small and mouse-like, giving them the misnomer marsupial mice, but the group also includes the cat-sized quolls, as well as the Tasmanian Devil...
family, the family includes the Little Red Kaluta
Little Red Kaluta
The Little Red Kaluta , also known as the Little Red Antechinus, Russet Antechinus, Spinifex Antechinus or simply Kaluta, is a carnivorous nocturnal marsupial. It lives in the dry areas of Western Australia. Individuals are 9-11 cm long and weigh 20-40 grams...
, quoll
Quoll
The quoll, or native cat, is a carnivorous marsupial native to mainland Australia, New Guinea and Tasmania. It is primarily nocturnal and spends most of the day in its den. There are six species of quoll; four are found in Australia and two in New Guinea...
s, and the Tasmanian Devil
Tasmanian Devil
The Tasmanian devil is a carnivorous marsupial of the family Dasyuridae, now found in the wild only on the Australian island state of Tasmania. The size of a small dog, it became the largest carnivorous marsupial in the world following the extinction of the thylacine in 1936...
. It has an average body length of 60–90 mm with a tail of 45–70 mm. Ear length is 14–16 mm. Its weight varies between 10-20 grams, it is one of the smallest carnivorous marsupials. The tail becomes fat a few mm from the anus and right up to the tip of the tail.
Distribution and habitat
The range of S. crassicaudata in Australia is in diverse habitats except for the Kimberley region of Western AustraliaKimberley region of Western Australia
The Kimberley is one of the nine regions of Western Australia. It is located in the northern part of Western Australia, 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, and on the east by the Northern Territory.The region...
and northern Northern Territory
Northern Territory
The Northern Territory is a federal territory of Australia, occupying much of the centre of the mainland continent, as well as the central northern regions...
like Arnhem Land
Arnhem Land
The Arnhem Land Region is one of the five regions of the Northern Territory of Australia. It is located in the north-eastern corner of the territory and is around 500 km from the territory capital Darwin. The region has an area of 97,000 km² which also covers the area of Kakadu National...
and Kakadu National Park
Kakadu National Park
Kakadu National Park is in the Northern Territory of Australia, 171 km southeast of Darwin.Kakadu National Park is located within the Alligator Rivers Region of the Northern Territory of Australia. It covers an area of , extending nearly 200 kilometres from north to south and over 100 kilometres...
, but avoids the Wannon and Mallee
Mallee Woodlands and Shrublands
Mallee Woodlands and Shrublands is a Major Vegetation Group which occurs in semi-arid areas of southern Australia. The vegetation is dominated by mallee eucalypts which are rarely over 6 metres high...
scrub habitats in Victoria. In the northeast of Victoria, the species can also be found in grass
Grass
Grasses, or more technically graminoids, are monocotyledonous, usually herbaceous plants with narrow leaves growing from the base. They include the "true grasses", of the Poaceae family, as well as the sedges and the rushes . The true grasses include cereals, bamboo and the grasses of lawns ...
y woodland
Woodland
Ecologically, a woodland is a low-density forest forming open habitats with plenty of sunlight and limited shade. Woodlands may support an understory of shrubs and herbaceous plants including grasses. Woodland may form a transition to shrubland under drier conditions or during early stages of...
s and samphire
Sarcocornia
Sarcocornia is a genus of succulent salt tolerant coastal plants.-Species:*S. alpini*S. blackiana *S. fruticosa*Sarcocornia globosa...
shrublands. The subspecies S. c. crassicaudata is in the Epping Forest National Park
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....
in Queensland. S. c. ferruginea is found around Lake Eyre
Lake Eyre
Lake Eyre is the lowest point in Australia, at approximately below sea level, and, on the rare occasions that it fills, it is the largest lake in Australia and 18th largest in the world...
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. Simpson desert, 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
Dunnarts are furry narrow-footed marsupials the size of a mouse, members of the genus Sminthopsis. They are mainly insectivorous. A male dunnart's Y chromosome has only 4 genes, making it the smallest known mammalian Y chromosome....
'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 2 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, spider larvae, 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 marsupialMarsupial
Marsupials are an infraclass of mammals, characterized by giving birth to relatively undeveloped young. Close to 70% of the 334 extant species occur in Australia, New Guinea, and nearby islands, with the remaining 100 found in the Americas, primarily in South America, but with thirteen in Central...
is nocturnal and functions within a 24-hour circadian rhythm
Circadian rhythm
A circadian rhythm, popularly referred to as body clock, is an endogenously driven , roughly 24-hour cycle in biochemical, physiological, or behavioural processes. Circadian rhythms have been widely observed in plants, animals, fungi and cyanobacteria...
. 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
Basal metabolic rate
Basal Metabolic Rate , and the closely related resting metabolic rate , is the amount of daily energy expended by humans and other animals at rest. Rest is defined as existing in a neutrally temperate environment while in the post-absorptive state...
, in order to reduce energy expenditure. Torpor is unaffected by alterations in photoperiod
Photoperiodism
Photoperiodism is the physiological reaction of organisms to the length of day or night. It occurs in plants and animals.Photoperiodism can also be defined as the developmental responses of plants to the relative lengths of the light and dark periods...
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
Steady state
A system in a steady state has numerous properties that are unchanging in time. This implies that for any property p of the system, the partial derivative with respect to time is zero:...
, such as seen in long-term torpidators
Hibernation
Hibernation is a state of inactivity and metabolic depression in animals, characterized by lower body temperature, slower breathing, and lower metabolic rate. Hibernating animals conserve food, especially during winter when food supplies are limited, tapping energy reserves, body fat, at a slow rate...
. This species is unique in that it can use torpor during development and reproduction. Even during lactation
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 occurs in all female mammals, however it predates mammals. In humans the process of feeding milk is called breastfeeding or nursing...
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 behavioral, survival technique. During times of cold temperatures, the fat-tailed dunnart shares nests with other rodent species such as the household mouse, Mus musculus,
House mouse
The house mouse is a small rodent, a mouse, one of the most numerous species of the genus Mus.As a wild animal the house mouse mainly lives associated with humans, causing damage to crops and stored food....
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.