Meet the musky rat-kangaroo, our smallest kangaroo

By Andrew Dennis 30 August 2017
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On top of being the smallest kangaroo in existence, the musky rat-kangaroo has survived in Australian forests for more than 20 million years.

IF YOU STROLL quietly along a rainforest track in Tropical North Queensland in the early morning or evening, make sure you watch for movement on the forest floor— you may just be rewarded with a glimpse of the world’s smallest kangaroo, the musky rat-kangaroo (Hypsiprymnodon moschatus).

If you’re lucky enough to see one, you’ll be witnessing a scene similar to Australian forests 20 million years ago. This tiny kangaroo (620g) once had four similar-looking, related species wandering Miocene rainforests.

Today, the musky rat-kangaroo is the only survivor and it’s managed to retain the ancient characters of its extinct relatives, from their opposable thumbs on their hind feet, used for climbing, to their prehensile tail, unspecialised teeth, digestive tract, diet and the habit of birthing twins or triplets.

Modern kangaroos have lost all these traits, though the bettongs and potoroos— relatives of the musky rat-kangaroo, have also retained their prehensile tails.

The musky rat-kangaroo is restricted to tropical rainforests but can occur from sea-level to 1200m. Larger population exists where rainforest plants are most productive, which is generally on rich basalt soils in the wettest areas. In these areas, the trees shrubs and vines produce abundant fruit, which is the mainstay of the Musky Rat-kangaroos diet.

While fruit is abundant and highly sought, invertebrates are always a welcome addition to the rat-kangaroos diet. In many areas, fruit production declines in the late wet season but fungi produces an array of soft fruit, which musky rat-kangaroos consume with gusto. They are particularly fond of the small white or grey mushrooms that sprout out of rotting logs.

Forest trees often only produce their fruits for short periods of time, so musky rat-kangaroos hide individual fruits and seeds in scattered locations to ensure they get their share. Often, they hide more than they need, burying these food hauls into the soil, carefully covering them with leaves and twigs so that the location is invisible to anyone else. Many of their hidden fruits remain buried. This protects the seeds from being eaten and killed by forest rats and improves the chances of seed germination.

For some species, only seeds that are buried in this way reach germination, meaning musky rat-kangaroos are importan rainforest gardeners, along with the southern cassowary (Casuarius casuarius) and Spectacled Flying-fox (Pteropus conspicilatus), responsible for the continuing regeneration of many rainforest plants.