Brown Antechinus

The brown antechinus is a carnivorous marsupial found predominantly in Australia’s eastern and southeastern parts. It is the world’s smallest semelparous mammal, which means that they breed only once in their lifetime before they die.

James Stuart, an Irish surgeon, first discovered this species in 1837. In 1841, William Sharp Macleay described this species and named it after Stuart. This is why the brown antechinus is known by other names like Macleay’s marsupial mouse and Stuart’s antechinus.

Description

Length: Male –  6 to 10 inches (150 to 250 mm); Female – 5.5 to 8.7 inches  (139 to 220 mm)

Weight: Male – 1 to 2.5 Oz  (29 to 71 g); Female – 0.60 to 1.26 Oz (17 to 36 g)

Body and Coloration: The brown antechinus has short, dense fur that is grayish-brown on its back and sides and lighter on its underbelly and tail. They have long, pointed heads, elongated hind feet, and moderately furred tails almost as long as their body. They also have 4 pairs of sharp incisors. Female antechinuses do not have a pouch like other marsupials but have exposed nipples with a flap around them. They also do not sport an eyering similar to other species of the antechinus. Male antechinuses are significantly heavier than their female counterparts.

Range and Distribution

The brown antechinus inhabits the eastern region of Australia, specifically, the areas east of the Great Dividing Range, stretching from southeastern Queensland to Kioloa in New South Wales and parts of Victoria.

Habitat

They can be found in various environments, such as woodlands, rocky outcrops, heathlands, moist and dry eucalyptus, and mangrove forests. Brown antechinuses build nests on the ground or in vines growing from tree limbs. They often prefer environments that are not prone to wildfires and have many dead trees.

Diet

The carnivorous brown antechinus mainly feeds on invertebrates, such as beetles, spiders, centipedes, and cockroaches. They also eat small reptiles and smaller vertebrates like placental mice. Sometimes, they also feed on plant material and flower pollen.

Known for their voracious appetite and high metabolism, they consume up to 60 percent of their body weight in arthropods daily in winter.

Behavior

• The brown antechinus is primarily nocturnal. Although they are known to hunt primarily at night, they may also be active during the day, particularly when food is limited, such as during winter.
• They are semi-arboreal and usually live in nests found in tree hollows, logs, or crevices on the ground during the daytime.
• When it is warmer, they live alone in their nests. However, as temperatures decrease, they gather in groups of up to 18 individuals in one nest, with the individuals sometimes changing their nests.
• In winter, the brown antechinus may experience stress, and to manage it, they may enter a state of torpor for a brief period. This helps to reduce their metabolic needs.

Lifespan

The male brown antechinus, on average, lives for 1 year. Some females live up to 3 years, but many die after rearing their first litter.

Adaptations

• They can quickly run down tree trunks head-first because their ankle joints rotate backward.
• These creatures are skilled climbers due to their nimble feet, and their sharp incisors allow them to take down large spiders and centipedes.

Mating and Reproduction 

The species has a single breeding season lasting about 3 months, resulting in 1 yearly litter. Males gather in nests consisting of just the males during mating season, becoming vocal and aggressive, emitting staccato chirps. Meanwhile, females remain solitary but may occasionally visit the male aggregations.

Females engage in polygamy and mate with multiple males, resulting in litters with offspring from different fathers. Gestation takes around 28 days, typically producing as many newborns as the number of nipples the females have. Newborns are generally 4-5 mm long and weigh an average of 0.016 grams. As they lack a typical pouch, the young cling to their mother’s underbelly for about 5 weeks and are dragged along the ground while she searches for food. Females often raise their young alone and may move them between different nests. They stay with the mother for roughly 90 days and reach sexual maturity within 9-10 months.

Males die shortly after mating, within the first year of their life. Increased stress levels in males during the breeding season lead to immune system suppression and death from parasites and infections. 

Predators

Brown antechinus is preyed upon by feral cats, foxes, and some owl species.

Conservation Status

Currently, the IUCN has classified the brown antechinus as “Least Concern.”

Although this species faces no significant threats, deterioration of their environment, leading to a loss in habitat, negatively impacts their population.

Interesting Facts

• According to a study, this marsupial significantly pollinates certain flowering plants native to Australia.
• The population of this species that was once locally extinct in Sydney’s North Head Sanctuary in Manly has been successfully reintroduced by the Australian Wildlife Conservancy in April 2022.
• According to a study, after experiencing a prescribed fire in their habitat, the brown antechinus chose to stay in their scorched home despite unburned areas nearby. In this scenario, they significantly increased their use of post-fire torpor to lower their need for foraging and exposure to predators.