Antechinus

They are also sometimes called 'broad-footed marsupial mice', 'pouched mice', or 'Antechinus shrews'. However, the majority of those common names are considered either regional or archaic; the modern common name for the animal is antechinus. ==Description==

Antechinus have short fur and are generally greyish or brownish in colour, varying with species. The fur is dense and generally soft. Their tails are thin and tapering and range from slightly shorter to slightly longer than body length. Their heads are conical in shape and ears are small to medium in size. Some species have a relatively long, narrow snout that gives them a shrew-like appearance. Species vary from in length and weigh when fully grown. A. agilis is the smallest known species, and A. swainsonii the largest. Sexual dimorphism occurs in most species for both weight and skeletal measurements, with males being typically larger and heavier. Most species nest communally in tree-hollows. They primarily inhabit all forests, woodlands and rainforest as well as heaths and grasslands in some species. The majority of Antechinus species are located on the eastern coast of Australia along the Great Dividing Range. There is a population of A. flavipes in south west Western Australia. A. bellus lives in northern Australia around the Gulf of Carpentaria. ==Taxonomy==

There are currently 15 recognised species of Antechinus with a number of subspecies. A few species of New Guinean Antechinus were recognised, but they have been reclassified into the genus Murexia. The interspecific relations of the genus Antechinus are still under review. Generally, the clades are formed by species with similar geographic distributions. • A. minimus (swamp antechinus) • A. swainsonii (Tasmanian dusky antechinus) • A. vandycki (Tasman Peninsula dusky antechinus) • A. adustus (rusty antechinus) • A. bellus (fawn antechinus) • A. flavipes (yellow-footed antechinus) • A. leo (cinnamon antechinus) • A. mysticus (buff-footed antechinus) == Diet ==

, showing an unknown species of Antechinus Antechinus are mainly insectivorous, but the exact composition of their diet can vary by species and habitat. Antechinus mainly eat beetles, insect larvae and spiders. Amphipods, millipedes and centipedes are also quite common in their diets. It has been reported that Antechinus also eat vertebrates, mainly small reptiles, such as skinks, or mammals, such as feathertail gliders. This is likely to occur most commonly when the Antechinus are food stressed. They are also classified as opportunists because they feed on most of the prey available to them However, they do show preference for some prey, i.e. beetles, spiders and larvae, especially when they are not food stressed. The larger species of Antechinus, such as A. swainsonii, are completely ground dwelling and forage in the leaf litter. The efficiency of Antechinus hunting increases with their age as they learn which prey are the best to eat. Antechinus have been observed scraping slugs on rocks and other objects to remove the mucus and make them more palatable. ==Reproduction==

Antechinus have an extremely unusual reproductive system. The females are synchronously monoestrous with mating occurring over a short three-week period. The males experience mass mortality after mating, with male survival only observed in very rare cases. The gestation period varies by species between 25 and 35 days. The breeding season is in winter or early spring of the Southern Hemisphere, from July to September. The timing of the breeding season changes very little at the same location between different years. This reproductive isolation may have led to sympatric speciation. Males have been selected to be ready before the females to ensure the maximum amount of time for mating. Reproductive anatomy Antechinus do not have a complete pouch, as in other marsupials, but simply a flap of skin covering the teats. The males mate with a number of females and the litters have a number of fathers. An increase in free corticosteroids is thought to allow males to utilise their reserve energy and maximise their reproductive effort, even though the increase usually proves fatal. If there were no male die-off, there would still only be a small likelihood of males surviving to the next mating period. Thus, it is far better for the males to invest heavily in one breeding season than attempt to survive to the next one. There are a few possible evolutionary advantages to the evolution of synchronous mating. It may ensure that as many matings as possible occur during the mating period. It also ensures that males can focus all their effort into one short breeding season. Another possible advantage of synchronous mating is to overwhelm predators with large numbers of offspring after weaning. == Torpor ==

Torpor is periodic lowering of body temperature and metabolic rate to reduce energy consumption. Many marsupials undergo torpor as well as some birds and placental mammals. Unlike hibernation, daily torpor is not simply reliant on ambient air temperatures. Antechinus can move into torpor on summer days with temperatures in the range of . Going into torpor allows them to greatly reduce metabolic rates, sometimes up to 80% However, going into torpor during the night is not uncommon. Increasing body temperature after torpor is energetically costly and reduces some of the metabolic savings. However, animals have been observed basking to help increase their body temperature without increasing their food intake. Females that have survived to a second year go into torpor much more frequently than females that are in their first year, even though second-year females are larger. It is thought that this is because first-year females are still growing and thus need more food which requires more time spent foraging. Older females are also more experienced at foraging and may meet their energy requirements more efficiently. == Threats ==

A. arktos and A. argentus are currently listed as endangered. The main threats to those species, indeed all species of Antechinus, are habitat destruction and introduced animals. Deforestation and habitat destruction removes the complex understorey habitat which Antechinus require for protection from predators and for food. Antechinus also nest in tree hollows, which only form in senescent trees. Introduced predators, especially foxes and cats, threaten Antechinus populations by predating on them. Pigs, cattle and horses trample Antechinus habitats. Changed fire regimes since European colonisation have resulted in more intense bushfires, which can adversely affect Antechinus populations by destroying understorey vegetation and removing their preferred food. Climate change threatens several high altitude species, especially those in northern Queensland. == References ==