Pair of BettongsThe Tasmanian bettong is a small kangaroo. Though its range once extended over much of the coastal areas of south-eastern Australia, it is now found only in Tasmania. It survival in Tasmania can be attributed to the absence of the introduced European fox which is widespread on mainland Australia and the greater availability of undisturbed habitat.
Late in the 19th century, John Gould the famous naturalist and artist described the bettong as "perhaps Tasmania's most ubiquitous animal". This is certainly not the case today and the bettong is vulnerable to forestry operations and other changes in land use.
Bettongs are found in the warmer, eastern half of Tasmania. They generally occur at low altitudes but their range can extend to 1000 m above sea-level, areas that would be frost or snow covered during winter. They sleep in a thick grassy nest made in a slight depression in the ground; the whole nest being about the size of a football. Bettongs are unusual kangaroos as their long tails are prehensile and are used to carry nest material some distance. Bettongs are able to recolonize areas some time after fire has destroyed much of the ground cover because they are able to bring their own 'mobile home' with them (nest material from unburnt areas) and their food remains underground untouched by the fire.
Bettongs feed mainly on subterranean fungi that exist in a symbiotic relationship with the roots of Eucalyptus and Acacia trees. The bettong is probably an important vector of the spores of the fungi. Passage through the bettong's digestive system may increase the germination ability of the fungal spores.
Baby Bettongs bred in captivityProfessor T.T. Flynn in 1930 published a paper on the reproduction of the Tasmanian bettong that summarized much of his work over the previous 10-15 year period. His infamous son, the film-star Errol Flynn, often assisted his father in capturing bettongs and, I believe, was paid one shilling (= 10¢) per animal. No further scientific work was carried out for the nearly 50 years or so until I started my studies in the late 1970s.
The bettong, as are other rat-kangaroos, is a continuous breeder, able to produce young in all months of the year, though more occur in the winter months. It is unusual to capture an adult female without a young in her pouch.
Pregnancy is the bettong is the shortest of all kangaroos at only 21 days. At birth, the single young weighs only 0.3 grams and has to climb to the mother's pouch. At birth the young is naked and only the fore limbs are well developed, the hind limbs being merely buds with little form. The baby remains in the pouch for 15 weeks although for the last 2 weeks or so it does make forays into the outside environment. On the night that the young leaves the pouch 'for good', a precise series of co-ordinated, behavioural and physiological events take place. Firstly the pouch contracts markedly, preventing the large furred young from returning - so tightly is the pouch closed, that the teat must protrude through the small opening or the older young would be unable to feed!. The mother then produces a new young and shortly thereafter mates. In other words there is never a day in the year really when the pouch is empty
The Habitat, Distribution and Conservation Status of the Tasmanian Bettong, Bettongia-Gaimardi (Desmarest)
The Tasmanian bettong, Bettongia gaimardi, appears to be the most common member of its genus. Though formerly distributed on the Australian mainland, B. gaimardi is now found only in the open forest habitats of eastern Tasmania, the vast majority of which are susceptible to forestry operations, such as clearfelling, burning and the laying of 1080 poison. Unless carefully managed, all of these practices in the long term are likely to reduce bettong populations. This and the fact that only 5% of bettong habitat lies within National Parks, leads to the conclusion that the conservation status of this species should be regarded as 'vulnerable'