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Antechinus stuartiibrown antechinus

By Ross Secord

Geographic Range

Antechinus stuartii are found in eastern and southeastern Australia, including Victoria, New South Wales, and Queensland. (Nowak, 1997; Strahan, 1983)

Habitat

Antechinus stuartii prefers wet sclerophyll forest with dense ground cover and an abundance of fallen trees in which to build nests. They usually stay on the ground, but may adopt a more arboreal lifestyle in drier areas, or where they occur sympatrically with Antechinus swainsonii, which lives on the ground. Population densities range from less than one to eighteen per hectare. Outside the breeding season males and females have their own foraging ranges. The availability of habitat may be influenced by foresters that "ring" trees leaving the trunk and major branches to rot, which provides nesting sites (Cockburn and Lazenby-Cohen, 1992). (Nowak, 1997; Strahan, 1983)

Physical Description

There is sexual dimorphism in size. Weight ranges from 29-71 g in males and 17-36 g in females. Average weight is 35 g for males and 20 g for females. Body length ranges from 150-250 mm in males, and 139-220 mm in females (Strahan, 1983).

Antechinus stuartii have short, dense, and somewhat coarse fur. Their back and sides are a uniform grayish-brown while the underbelly is lighter colored. The overall appearance is similar to placental mice with a long pointed head, elongate, plantigrade hind feet, a pink nose, and a tail length almost as great as body length. The tail is moderately furred, eyes are dark brown, and ears are relatively large. Females lack a pouch, instead they have a variable number of exposed nipples. The number of nipples varies by habitat. Females with 6 nipples live in the wettest areas and those with 10 nipples live in the driest and highest areas. Males are 20 to 100 percent heavier than females. (Strahan, 1983; Nowak, 1997)

  • Range mass
    17 to 71 g
    0.60 to 2.50 oz
  • Average basal metabolic rate
    0.189 W
    AnAge

Reproduction

Antechinus stuartii have a single breeding season restricted to about three months, and produce one litter per year. Gestation lasts for 26-35 days and at least as many young as the number of nipples are usually born. With the absence of a pouch, young cling to the mother's underbelly and are dragged across the ground while she searches for food for about 5 weeks. Births usually occur within a period of about 2 weeks for any given population. Newborns are 4 to 5 mm in length at birth and weigh an average of 0.016 grams. They stay with the mother for about 90 days and reach sexual maturity in 9 to 10 months. The young leave the mother with the onset of winter. (Nowak, 1997; Strahan, 1983)

One of the more striking and unusual things about Antechinus is that all males die shortly after mating in their eleventh or twelfth month of life (McAllan, et al., 1997). This phenomenon occurs at the same time each year in any given population. Increased physiological stress results from aggression and competition between males for females, and heightened activity during breeding season. Increased stress levels apparently cause suppression of the immune system after which the animals die from parasites of the blood and intestine, and from liver infections. In the wild, many females die after rearing their first litter, although some do survive a second year. (Strahan, 1983; Nowak, 1997)

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual
  • Average number of offspring
    7
    AnAge
  • Average gestation period
    30 days
    AnAge
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    285 days
    AnAge
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    285 days
    AnAge

Lifespan/Longevity

Behavior

During warm parts of the year individuals live in solitary nests and occupy their own home ranges. As temperatures drop, however, individuals of both sexes cluster together in nests with up to 18 animals. The nests are not stable and individuals may change nests. 28 females and 24 males were observed using a single nest over one winter (Cockburn and Lazenby-Cohen, 1992). Females typically nest alone to rear young and may split their offspring between nests in different trees. To cope with winter stress individuals may slip into a torpor for a few hours to lower their metabolic requirements. Males leave their foraging ranges when mating season begins and group together in all-male nests during most of the night. Females remain solitary, but make excursions to the male aggregations. During mating season males become vocal, emitting staccato chirps, losing much of their caution, and becoming highly aggressive. (Nowak, 1997; Strahan, 1983)

Communication and Perception

Food Habits

The diet of Antechinus stuartii consists primarily of invertebrates, particularly beetles, spiders, and cockroaches. Their diet also includes smaller amounts of vertebrates, such as placental mice, as well as plant material and flower pollen (Van Tets and Whelan, 1997). A. stuartii are voracious predators and have a high metabolism. During winter they will consume as much as 60 percent of their weight in arthropods each day. They typically hunts at night but may be active during the day, especially during times when food is scarce, such as winter months. (Strahan, 1983; Nowak, 1997)

Economic Importance for Humans: Positive

A. stuartii may be important in the pollination of some Australian flowering plants (Goldingay et al., 1991).

Economic Importance for Humans: Negative

A possible correlation between Antechinus stuartii and the distribution of a pathogenic soil fungus (/Phytophthora cinnamomi/) was reported by Newell and Wilson (1993). P. cinnamomi can have devastating effects on plant communities such as the forests, woodlands, and heathlands of Australia (Newell, 1998).

Conservation Status

Antechinus stuartii is generally not thought to be under any serious threat from humans or others, and is found in abundance in many areas. Some populations have been reduced, however, by predation from domestic cats (Nowak, 1997; Strahan, 1983). IUCN (1999) listed species decline as less than 10 percent and placed it in its "lower risk" and "least concern" categories.

Other Comments

A peculiar behavior of mothers is that they will deny milk to male offspring, preferring to wean females. Mothers also commonly eat their young, at least in captivity (Cockburn, 1994).

Contributors

Ross Secord (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.

scrub forest

scrub forests develop in areas that experience dry seasons.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

References

Cockburn, A. 1994. Adaptive sex allocation by brood reduction in Antechinuses. Behavioral Ecology & Sociobiology, 35(1): 53-62.

Cockburn, A., K. Lazenby-Cohen. 1991. Communal nesting in Antechinus-stuartii marsupialia dasyuridae. Australian Journal of Zoology, 39(3): 273-284.

Cockburn, A., K. Lazenby-Cohen. 1992. Use of nest trees by Antechinus-stuartii a semelparous lekking marsupial. Journal of Zoology (london), 226 (4): 657-680.

Goldingay, R., S. Carthew, R. Whelan. 1991. The importance of non-flying mammals in pollination. Oikos, 61(1): 79-87.

McAllan, M., T. O'Shea, J. Roberts. 1997. Seasonal changes in the reproductive anatomy of male Antechinus stuartii (Marsupialia: Dasyuridae). Journal of Morphology, 231(3): 261-275.

Newell, G. 1998. Characterization of vegetation in an Australian open forest community affected by cinnamon fungus (Phytophthora cinnamomi): Implications for faunal habitat quality. Plant Ecology, 137(1): 55-70.

Newell, G., B. Wilson. 1993. The relationship between cinnamon fungus (Phytophthora cinnamomi) and the abundance of Antechinus stuartii (Dasyuridae: Marsupialia) in the Brisbane Ranges, Victoria. Wildlife Research, 20(2): 251-259.

Nowak, R. 1997. "Walker's Mammals of the World 5.1 Online" (On-line). Accessed Novermber 20, 1999 at http://www.press.jhu.edu/books/walkers_mammals_of_the_world/marsupialia/marsupialia.dasyuridae.antechinus.html.

Strahan, R. 1983. Complete book of Australian mammals: the national photographic index of Australian wildlife. London, Sydney, and Melbourne: Angus and Rorertson.

Van Tets, I., R. Whelan. 1997. Banksia pollen in the diet of Australian mammals. Ecography, 20(5): 499-505.

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