adorable acrobats with unusual sex lives

Name(s): Agile antechinus (Antechinus agilis), also called the agile marsupial mouse

Group: Dasyurids

Size: Length 80-116mm, including a tail of 75-102mm; weight 16-44g

Diet: Carnivores – mainly insects and spiders with the occasional flowers or fungi

Habitat: Found at lower levels of the Great Dividing Range and into coastal forests of Victoria and southern NSW

Preservation status: Not endangered

Superpower: “Agile” is a very good description. If you hold the agile antechinus at the base of a tree and let it go, it always runs up the trunk – very fast. They are like Cirque de Soleil gymnasts; no gymnastic feat seems beyond them, and they do it with such verve!

Credit: Michael Sale via Wikimedia Commons.

The agile antechinus is an adorable marsupial that resembles a mouse or shrew, but has the personality of a lion. Like many other dasyurids, agile antechinus are carnivores with interesting reproduction, short pregnancies and a long lactation period. These critters live in communal nests in tree hollows. They are mostly nocturnal, but can occasionally be found sunbathing on fallen tree trunks or rocks to warm up in the morning.

Agile antechinus eats mainly insects and spiders. They are also happy to snack on a mouse, some pollens or, like any gourmet, a native truffle in the autumn – a bit gritty but delicious. Those humans living in coastal forest areas know they are co-habiting with an antechinus when they begin to find piles of little bones. Their antechinus houseguests are helping them by eating their pest mice: a true symbiotic relationship.

The agile antechinus have highly synchronized sex lives, getting together during a frantic period of 1-3 weeks in July or August. When the day length starts to increase following the winter solstice in June, a response is triggered in the antechinus to start their breeding season. This synchronization ensures that young agile antechinus are born when there are plenty of insects around to eat. The timing of the breeding season is further fine-tuned by population density: the denser the population, the shorter the season.

Closeup photograph of the face of an agile antechinus in a blanket
Credit: Mel Williams via Wikimedia Commons.

During this breeding season, the females gather where they are visited by the males. Foreplay is long and copulation is long. Not only is this fun, but it keeps the other males away. The females can store sperm for up to 21 days after mating. All the males die after the mating frenzy, in an event known as “the die-off”.

The nearest human equivalents to agile antechinus males may be chief executives of large companies. Like them, agile antechinus live eventful and rich lives, are always active, and have full-on sex lives. They both have high stress levels and develop gastric ulcers, which are often fatal in antechinus. Dasyurids are now known to have their own species of Helicobacter, the bacterium that causes gastric bleeds, or they can be infected by the human version. This highly synchronized life and high stress level leads to the die-off of male antechinus each year. A warning to human CEOs – avoid too much synchrony.

Back to the females – half of the 27 days of pregnancy in agile antechinus are taken up by developmental arrests, which are pauses in fetal development that allow the antechinus to maximize their reproductive performance. Together with the synchronization of breeding, these pauses ensure that no female gives birth until all the males are dead, giving them a stress-free lactation period to look after their young for 70 days. The females have between six and 10 teats, and they usually raise a number of young equal to or slightly less than this number, depending on the season.

Surely you can agree that these tiny marsupials deserve your vote in Australian Mammal of the Year!

We all love birds, but why should our feathered friends get all the fun? This winter, join Cosmos in celebrating the amazing diversity of Australian mammals, from antechinus to yellow-footed rock-wallaby, in our first-ever Australian Mammal of the Year poll.

Keep an eye on the Cosmos website or subscribe to our email list for new articles about awesome Australian mammal species every week. You can even nominate your own favorite Australian mammal using the form below!

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