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This clip shows zoologist Dr Andrew Dennis studying the musky rat-kangaroo in a rainforest in far north Queensland. It includes footage of the musky rat-kangaroo, its habitat and nests. The narrator points out that the musky rat-kangaroo’s proficiency at climbing makes it a living link between the modern kangaroo and their tree-dwelling ancestors. Dennis is also shown collecting and identifying samples of the forest fruits eaten by the musky rat-kangaroo for a survey he was conducting on the eating habits of the species. The clip includes voice-over commentary from Dennis.

Educational value points

• The musky rat-kangaroo (’Hypsiprymnodon moschatus'), or hypsi, is the smallest macropod (member of the Macropodoidea superfamily, which includes kangaroos and wallabies). It is a marsupial that measures about 42 cm, weighs about 500 g and has a body that is covered in dense grey-brown fur. Unlike other macropods, its tail is covered with small scales (like a rat’s tail) and its hind legs are only slightly elongated so that it runs on four legs rather than hopping. Its name derives from the musky smell it gives off to attract a mate.

• The musky rat-kangaroo may represent an early step in the evolution of kangaroos. It is the only macropod that retains any of the possum-like features found in its ancestors, including the hallux (opposable thumb) on its hind feet and the gripping grooves on its foot pads, both of which enable it to climb trees and vines. Like the early macropods, the female has a litter of two and sometimes three young.

• The tropical rainforests of north-eastern Australia are home to the musky rat-kangaroo, which is usually found in the dampest areas of the rainforest, particularly near creeks and rivers. It maintains a relatively small home range and the home-range population fluctuates according to the availability of food. The 300-sq-m area where zoologist Dennis conducted his study supports about 40 musky rat-kangaroos. According to Dennis, rainforest clearing is having a damaging effect on the marsupial’s distribution and population.

• The musky rat-kangaroo is active during the day. It sleeps at night in a hollow log, under a rock or in a nest made from dried leaves, lichens and ferns, often built among vines or between the buttresses of a tree up to a metre off the ground. It uses its tail to carry the building materials to the nest site, but first it gathers the materials with its mouth, then uses its front paws to place the material on the ground in front of its hind feet. Finally, it curls its tail down towards its hind feet and kicks the material into the nest.

• Andrew Dennis, who is from the Tropical Forest Research Centre of the Commonwealth Scientific and Industrial Research Organisation (CSIRO), was the first scientist to study the musky rat-kangaroo in its natural environment. It was first described by scientists in 1875 and until Dennis’s study little was known about its ecology or behaviour, which Dennis believes is similar to that of early macropods. Dennis examined the diet of musky rat-kangaroos using a range of methods, including microscopic examination of faecal pellets, direct observation and tracking, as well as examining teeth marks left in fruit on the forest floor.

• Dennis found that the diet of the musky rat-kangaroo, which is a frugivore (mainly fruit-eating), is much more varied than previously thought. It mostly feeds on fruits and seeds from at least 44 species of plants, although it also consumes some insects and worms. Unlike other macropods, the musky rat-kangaroo has a primitive stomach, and Dennis has surmised that this may make digestion of the structural carbohydrates found in the cell walls of plants difficult. Its primitive digestive tract and its low-fibre diet may be similar to those of its ancestors.

• The study revealed that musky rat-kangaroos are 'forest gardeners’ in that they disperse seeds throughout the rainforest. Unlike other macropods, the musky rat-kangaroo 'scatter hoards’, meaning that it buries seeds to retrieve later when food is scarce. This seed dispersal contributes to plant diversity in the rainforest and ensures that plant species do not become localised to a specific area. It also benefits the musky rat-kangaroo, as seeds that germinate and mature into large trees are a future source of food.

An interview with zoologist Dr Andrew Dennis over vision of him conducting his research in the rainforest.
Narrator Andrew’s study area is 300 square metres, currently shared by 40 musky rat kangaroos. But he rarely sees more than two at a time.

Dr Andrew Dennis Musky rat kangaroos are intriguing little animals. They’re very small, very difficult to see and they’re constantly on the move through the forest. So it’s really hard to understand anything about them until you spend a lot of time watching them.

Narrator Throughout the study area, the nests of musky rat kangaroos are tucked into the sturdy buttresses of water gums and figs. Constructed from large soft leaves, they’re held together with mould and fungus. The nests decompose very quickly in the wet, humid conditions of the rainforest, so the Hypsis are constantly having to build new ones.

Dr Andrew Dennis One of the most distinctive things you notice straightaway is the fact that they hop on all four legs instead of just two hind legs, like other kangaroos. They’re also very good at climbing fallen trees and vines, and for this they use an opposable thumb on their hind foot.

Narrator These possum-like characteristics have long since disappeared in other species of kangaroo. It makes the musky rat kangaroo a living link between the modern kangaroos and their tree dwelling ancestors. In December, Andrew walks specially marked paths through the forest collecting fruits. Those eaten by the musky rat kangaroos have distinctive teeth marks. These daily collections reveal surprising information about the diet of the musky rat kangaroo.

Dr Andrew Dennis After collecting fruits for many months, I began to realise that musky rat kangaroos ate the fruits of a large number of rainforest tree species, more than anyone had previously realised. One of the really exciting discoveries that I made was that musky rat kangaroos eat even the largest fruit in the forest, and that they are one of the only animals that can carry the really big seeds.