General information

Kangaroos are marsupials and belong to the Family Macropodidae (i.e. big feet) that is grouped with the Potoroidae (potoroos, bettongs, rat-kangaroos) and Hypsiprymnodontidae (musky rat-kangaroo) in the Super-Family, Macropodoidea. This comprises around 50 species in Australia and a dozen or more in New Guinea.  Some of the smaller species, such as Yellow-footed Rock-Wallabies, Burrowing Bettongs, accompanied Pig-footed and Golden Bandicoots, Bilbies and possibly Hairy-nosed Wombats into extinction with the advent of pastoralism. However, the largest species remain in much of their original range with the grey kangaroos expanding inland as grazing habitat increased and coastal habitat was lost in clearance for agriculture. The defining feature of the kangaroo family is that they are the largest vertebrates to hop (both currently and from what we know from palaeontology).

The Bettongs, Potoroos and Musky Rat-Kangaroo are collectively known as the Rat-kangaroos. In fact, they form two families, the Potoroidae, which includes all the potoroos and bettongs, and, the Hypsiprimnodontidae, whose sole living representative is the Musky Rat-kangaroo. They are observationally distinguished from the kangaroos and wallabies by their diminutive body size but the largest species, the Rufous Bettong, eclipses the smallest Rock-wallabies, the Monjon and Narbelek. In general, they retain more 'primitive' ancestral characteristics with a partly prehensile tail to entrap grasses and sticks for nesting and a simpler stomach (and consequently richer diet). The forelimbs and hindlimbs are more similar in size than the gross differences in the kangaroos and wallabies, and so bounding as well as hopping is a mode of progress. Perhaps possum-kangaroo is more accurate but the first European observers were more familiar with rats than possums.

If you find an intact skull on your exploration of rat-kangaroo habitat then the dentition is clearly distinguishable from the kangaroos. They are more buck-toothed with the second and third incisors smaller than the first and more lateral in the upper jaw. The upper canines are well-developed whereas they are lost in the Macropdodidae. The premolar is large and blade-like and the molars are retained rather than lost anteriorly through wear and progress along the tooth row.

The rat-kangaroos have fared very poorly with the advent of agriculture and pastoralism compounded by the introduction of competitors (European rabbits and hares) and predators (Red foxes and domestic cats). The Potoroids generally have much reduced ranges relative to the first settlement of Australia by Europeans and two of the 10 species are extinct. The most dramatic of the declines is the Boodie (Burrowing Bettong) which was widespread across the rangelands of Australia and ended up marooned on a few offshore islands in Western Australia. Reintroductions are in progress and this species is on the first hops to making a comeback on the mainland. Like the Potoroids, the Musky Rat-kangaroo has lost much of its habitat in the highly prized real-estate of the tropics.

Species

Boodie (Burrowing Bettong)

Bettongia lesueur ('Lesueur's bettong')

Best place to see

There is no place to realistically see this once extremely widespread species in the 'wild'. After extinction on mainland Australia, Boodies have persisted on off-shore Islands including Dorre and Bernier Islands in the Shark Bay region of WA and Barrow Island in the Pilbara region. There is no public access to Dorre Island, and Bernier Island can only be visited by boat during the day and the Boodie is largely nocturnal. Barrow Island also has restricted access that is enforced to protect petroleum and gas industry assets. Boodies have been introduced to Faure Island in Shark Bay and Boodie Island in the Pilbara but the fate of these populations is unknown. They were introduced to Francoise Peron National Park as part of Project Eden but these introductions along with those of Woylies, Mala and Banded Hare-wallabies have largely failed (Woylies may still persist) due to a high susceptibility to feral cat predation and possible additional effects from Wedge-tailed Eagles.

Thus Boodies can only be seen in reserves where they have been introduced for captive breeding or to re-establish historical populations. The reserve with the least restrictions is Dryandra Woodland, Western Australia, where there is a captive breeding program (see the fact sheet for the Woylie) for more information. Introductions have been made to the Arid Recovery reserve at Roxby Downs in South Australia where tours/stays and options for volunteering are provided. Boodies have also been introduced into Australian Wildlife Conservancy properties at Scotia in New South Wales and Yookamura in South Australia. These sanctuaries also have Woylies and Mala but access is only through volunteering programs.

Identification

Boodies average 1.25 kg and reach a weight of 1.5 kg. The colour at the back and the head is a grizzled yellow to pale brown-grey. There is a fairly indistinct, pale hip stripe. The ears are moderately haired and are shorter and much more rounded than other Bettongs. The underside is a creamy white to pale grey brown. The upper surface of the tail is black, but the central part is darker towards the tip. The tail tip is usually white and there is no crest. The claws are long slender and curved, but not as long as other species in spite of the fact that the Burrowing Bettong, as its name suggests, digs  burrows.

Habitat

The Boodie was once the most widespread of all the Potoroids. Its range extended right across Western Australia and the Northern Territory, through South Australia into western New South Wales, south-western Queensland and north-western Victoria. Except for reintroductions,  it is extinct on mainland Australia and occurs naturally only on Bernier, Dorre, Barrow and Boodie islands off the West Australian coast. Black rats caused its extinction on Boodie Island but a successful eradication of the rat has enabled the Boodie to be re-introduced to the island bearing one of its common names. The Boodie has been successfully reintroduced into mainland West Australia in the Francois Peron National Park. It is also being reintroduced into fenced fauna reserves in South Australia and New South Wales. Given that the species was once widespread across the rangelands of Australia, it occupied a range of open habitat types. Its current habitat on the islands off the coast of Western Australia is low heath, scrub and hummock (spinifex) grassland. However, introduction show is that it can live in spinifex grasslands, chenopod shrublands and mallee. The species need to burrow and so a rocky substrate obviously precludes its occupation of some areas. The burrows, however, have persisted in some parts of the rangelands and certainly can be found in New South Wales rangelands in national parks such as Kinchega National Park.

Foraging behaviour

The Boodie is the exception amongst the rat-kangaroos as it eats few if any fungal fruit-bodies. Rather it predominately eats roots and tubers along with some bulbs, leaves and stems of plants, seeds. In the island populations, it may eat some carrion scavenging along the sea shores. On the mainland, fruit such a quandong is eaten along with various native yams.

 

The diets of Boodies and European rabbits have been compared at Herrison Prong in Shark Bay (WA). Greatest overlap in diets occurred in summer (56% overlap) when Boodies ate seeds, stems and the foliage of shrubs and rabbits ate roots, stems and browse from some shrubs. Overlap was less in winter (43%) when the boodie diet was more typical of the rat-kangaroos with 19-23% hypogeal fungi, along with fruit and forbs. Rabbits similarly ate forbs but browsed the foliage and stems of shrubs. There is a widespread belief that rabbits were a significant cause of the mainland extinction of Boodies through competition for food and shelter. The Herrison Prong study has cast doubt on both assertions. Boodies better utilised common resources and Boodie and rabbit diets diverged. Boodies maintained populations when rabbits boomed and then busted as they depleted pasture under unfavourable conditions. Boodies typically forage in areas where the canopy cover is above the average for the habitat, and ground cover and height is relatively high. Livestock, particularly sheep, remove such cover and so the introduction of pastoralism, not the rabbits, cats and foxes that followed, is the prime cause of Boodie extinction.

 

The foraging behaviour of Boodies, like other rat-kangaroos, creates diggings and pits that turn over the soil surface. These increase soil permeability and may leach soluble surface nutrients but they also entrap plant detritus and seeds that add to soil humus. Species that modify their environment with effects that may cascade through an ecosystem as known as 'ecosystem engineers'. Boodies and the other rat-kangaroos along with bandicoots are mammalian engineers. Their loss from western NSW has had a significant impact on landscape function and natural controls on invasive native shrubs. The compaction of soils, often attributed to the introduced of ungulates (hard-hoofed livestock), has been compounded by the loss of soil engineers in boodies and bandicoots and the inadequacy of the rabbits that followed their extinction. However, it is unlikely that a rabbit-sized macropod will be welcomed back into the rangelands except by containment in fenced reserves. The first settlers complained about Boodies eating the peas and beans from their garden beds and so containment in a minute portion of their former range seems to be their fate.

Reproductive behaviour

The Boodie like most of the rat-kangaroos has a gestation period just shorter than the oestrous cycle and thus has a post-partum oestrus with mating taking place very soon after the current pouch young vacates the pouch permanently. They show embryonic diapause and breed continuously regardless of season but some bias towards the wetter winter months was noted on Bernier and Dorre Islands. Pouch life is around 4 months and thus they are able to produce more than one young per year but island populations do not reach the theoretical maximum of three young.

 

Body size plays a role in the reproductive success of females. They are sexually mature at 7-8 months and a body weight around 900 g but females heavier than 1000 g are more likely to be lactating (40% < 1000 g vs. 62% > 1000g). The island populations showed a strong male bias especially in the sub-adult.

 

Males compete amongst themselves for access to females and so male-male agonistic interactions, especially chasing, are more frequent than interactions between females. Males and females interact less aggressively but unreceptive females will drive off male mounting attempts by lying on the side and kicking out at the male. In courtship males may utter a 'thk-thk-thk' sound in as they hope behind an attractive female and may stand over her with tail and hindquarters quivering. Mounting is typical of macropods and from the rear with the female drawing aside the tail and placing her forepaws on the grounds. Multiple intromissions occur over a period of 20 min or more.

Social organisation

Home ranges for females have been estimated in an 800-ha and 1400-ha enclosure where Boodies have been reintroduced in northern SA (Arid Recovery Site near Roxbury Downs). Females used an average of 2.7 burrows in three months and had larger home ranges of 35 ha at the higher density of 7.5 bettongs km^-2 than the 29 ha at a density of 2.75 bettongs km^-2.  The low density population had a higher reproductive output and better food quality was suggested for the cause of this and the smaller home range. Nightly movements are relatively short and females rarely ranged more than 300 m from their warren.

 

In a much smaller 4-ha enclosure at Shark Bay in WA, individual bettongs used between 1 and 10 burrows over a 5-month period. Males changed burrows more frequently than females and where individuals had a stable association within a burrow system, these were likely to be close female relatives (e.g. mother-daughter). However, such associations may break down when daughters are older than 10 months. The day ranges of males were larger than those of females but at night individuals used the whole 4-ha enclosure which was much smaller than the home ranges estimated in SA. Some organisation was apparent with males holding exclusive day ranges against other males but overlapping those of 1-5 females.

 

As self-sustaining populations become well-established in large mainland reserves, it is likely that further insights will be gained into the social organisation within burrow complexes of this unique fossorial macropod.

 

Further readings

Claridge AW, Seebeck JH, Rose R (2007) 'Bettongs, Potoroos and the Musky Rat-kangaroo.' (CSIRO Publishing: Melbourne)

Finlayson GR, Moseby KE (2004) Managing confined populations: the influence of density on the home range and habitat use of reintroduced burrowing bettongs (Bettongia lesueur). Wildlife Research 31, 457-463.

Noble JC, Hik DS, Sinclair ARE (2007) Landscape ecology of the burrowing bettong: fire and marsupial biocontrol of shrubs in semi-arid Australia. The Rangeland Journal 29, 107-119.

Pizzuto TA, Finlayson GR, Crowther MS, Dickman CR (2007) Microhabitat use by the brush-tailed bettong (Bettongia penicillata) and burrowing bettong (B. lesueur) in semi-arid New South Wales: implications for reintroduction programs. Wildlife Research 34, 271-279.

Robley AJ, Short J, Bradley S (2001) Dietary overlap between the burrowing bettong (Bettongia lesueur) and the European rabbit (Oryctolagus cuniculus) in semi-arid coastal Western Australia. Wildlife Research 28, 341-349.

Robley AJ, Short J, Bradley S (2002) Do European rabbis (Oryctolagus cuniculus) influence the population ecology of the burrowing bettong (Bettongia lesueur)? Wildlife Research 29, 423-429.

Sander U, Short J, Turner B (1997) Social organisation and warren use of the burrowing bettong, Bettongia lesueur (Macropodoidea: Potoroidae). Wildlife Research 24, 143-157.

Short J, Turner B (1999) Ecology of burrowing bettongs, Betongia lesueur (Marsupialia:Potoroidae), on Dorre and Bernier Islands, Western Australia. Wildlife Research 26, 651-669.