Macrotis lagotis (Reid, 1837)

Russell A. Mittermeier & Don E. Wilson, 2015, Thylacomyidae, Handbook of the Mammals of the World – Volume 5 Monotremes and Marsupials, Barcelona: Lynx Edicions, pp. 350-361 : 360-361

Greater Bilby

Macrotis lagotis

French: Grand Bilby / German: Grof 3er Kaninchen-Nasenbeutler / Spanish: Bilbi

Other common names: Bilby, Dalgyte, Greater Rabbit-eared Bandicoot, Pinkie, Rabbit Bandicoot

Taxonomy. Perameles lagotis Reid, 1837 ,

Swan River, Western Australia, Australia.

Over the years, three different generic names have been used forthis species, and at one point, several species were attributed to Macrotis genus. E. L. G. Throughton suppressed Macrotis sagitta , named by O. Thomas in 1905, which was collected east of Lake Eyre, Central Australia, and M. nigripes, named by F. W. Jones in 1923, and collected near Ooldea in South Australia, and considered them as subspecific of M. lagotis . Troughton in 1932 also named three new subspecies: interjecta from Nullarbor Plain, near Rawlinna in Western Australia; grandis from Lake Alexandrina, south-east of Adelaide, South Australia; and cambrica from eastern New South Wales and southern Queensland; he continued to include to the nominate subspecies the type specimen from the Perth region, Western Australia. All but the nominate subspecies are now extinct. Genetic studies have indicated that although there is some divergence between extant populations in Queensland and those in the Northern Territory and Western Australia, the species is a single evolutionary unit. Monotypic.

Distribution. C & W Australia (Western Australia, Northern Territory, and SW Queensland). A population has been successfully translocated to Thistle Island South (Australia) and a reintroduced population at Lorna Glen (Western Australia) persists.

Descriptive notes. Head-body 30-55 cm (males) and 29-39 cm (females), tail 20— 29 cm (males) and 20-27.8 cm (females); weight 1.2-5 kg (males) and females 0-8— 1-2 kg. Fully grown Greater Bilbies of both sexes can be more than twice the size of newly recruited sexually mature individuals, and large males are often twice the size of large females. Adult males have longer, bulkier, and broader heads than females, giving the appearance ofa shorter snout on males. Head length of males is 10-8 cm compared to 9-5 cm for females. Body furis silky and finely textured and a light ashy blue gray. Belly, feet, and neck are white to cream. Hip stripe of light tan to white extends from the mid-thigh to base oftail; another band appears to run just above the hip. Tail is a striking ashy blue-gray with body fur at the base (c.20% of total length), black in mid-section (c.40%), and white terminally (c.40%). Tail possesses a dorsal crest of coarse hairs throughoutits length. A cornified horny spur on tail tip is often evident on older individuals. Ears are large and 60-90% of head length and naked for the most part. On forelimbs, third, fourth, and fifth digits are well developed and terminate with stout claws. First and fifth digits are reduced and clawless. Hindlimbs are long and slender, and feet are macropod-like, with a syndactyl grooming claws. First digit has been lost, and fourth digit larger than fifth, and fifth larger that second and third. When disturbed, Greater Bilbies are capable of bursts of speed with frequent rapid directional changes. During rapid movements, the flashing tail becomes distractive. Dental formula of the Greater Bilbyis15/3,C1/1,P 3/3, M 4/4 (x2) = 48; upper canines are 8-12 mm in males compared to 3-5 mm in females.

Habitat. Remaining populations in three major vegetation types: open chenopod and tussock grassland on uplands and hills, mulga (Acacia aneura) woodland/shrubland growing on ridges and rises, and hummock grassland in plains and alluvial areas. Historically, the Greater Bilby occurred in a much wider variety of soil and vegetation types and landforms. Its distribution extended over a variety of climatic zones, including regions in northern Australia that experienced predominately summer rainfall (e.g. 600 mm/year), low and often highly variable rainfall in central Australia (e.g. 165 mm/year), and temperate areas in the south and west with primarily winter rainfall or evenly distributed rainfall in the east (e.g. 500-600 mm/year). Vegetation types included eucalypt open forest and woodland in the west, south, and east; tall shrublands and open woodlands in semi-arid regions; and open chenopod tussock grasslands or hummock grasslands and mulga woodland/shrubland in arid Australia. Greater Bilbies required soils with a suitable depth and texture to enable burrow construction. These soils included stony loams and red earths with laterite (residual landscapes), deep brown calcareous clays (clayey downs landscapes), siliceous and calcareous loams, and sands (sand plains, dunes, and paleodrainage lines).

Food and Feeding. The Greater Bilby is a generalist omnivore and eats a variety of plant and animal materials, including grass seeds, bulbs—particularly from Cyperus bulbosus ( Cyperaceae )—and invertebrates, especially termites, but also ants, spiders, beetles, and insect larvae. Food is located above and below ground primarily by smell. Diggings or feeding excavations are generally conspicuous when Greater Bilbies are present. Key invertebrates in the diet included termites, root-dwelling larvae, and burrowing spiders and represent a scarce but persistent food resource during times of drought. In comparison, plants that produce bulbs and seeds can be quick growing annuals that proliferate afterfire or severe drought and good “breaking” rains. Following a pulse of production, seeds are collected and concentrated at nests by harvester ants that later use the eliasome (oil rich body ofseeds attractive to ants) or the endosperm as food. Fecal material of Greater Bilbies can often contain a high seed or bulb content several months after conspicuous evidence of the plants have disappeared from a site. Fecal pellets are distinctive and often voided when individuals are digging for food, which results in the pellet group being covered by excavated soil. It has been suggested that residual and clayey downs landscapes support invertebrate assemblages that allow Greater Bilbies to persist when plant foods are scarce. Key plant foods can flourish on all the occupied substrates but suitable conditions occur infrequently and patchily. An abundance of suitable plant food enables Greater Bilbies to converge and breed. Diminishing availabilities of plant foods forces individuals to become more widely dispersed in the pursuit of invertebrate foods. Hot-season fires are an important driver of production of plant food in the northern parts of the current distribution of the Greater Bilby.

Breeding. Greater Bilbies reach sexual maturity at ¢.6 months of age and continue to grow until c.18 months of age. Mating system is polygynous; females are polyestrous and length of the estrous cycle is c.21 days (12-37 days). Breeding can occur throughout the year but varies depending on seasonal conditions. Gestation is c.14 days (13-16 days), and pouch life is 75-80 days. After offspring exit the pouch, females tend their young in a burrow for another two weeks. Litters comprise 1-3 young, and mean litter size at pouch exit is 1-1-9 young depending on conditions. Sex ratio of emerging pouch young is 1:1. Smaller females aged 7-9 months have about one-half the fecundity of older larger females. Under ideal conditions, a female may produce 4 litters/ year. Females commonly continue to breed past the age of four years. Mortality of young can be high in reintroduced populations and even in captive settings where conditions are crowded. Only 25% of the reintroduced young were known to have reached maturity. Based on weight, most individuals caught in the wild are less than twelve months old.

Activity patterns. Foraging occurs at night. Burrows are used for shelter during daylight hours and intermittently throughout the night for rest and refuge. Burrows may be simple with a single open entrance, or “warren-like” complexes with a number of open entrances and pop-holes covering an area of 10 m in diameter. Burrows provide protection from predators and stable thermal environments, and they can extend to a depth of 2 m. Multiple burrows usually occur within an individual's nightly foraging range. Day-refuge burrows can be used on consecutive nights, and females tended to use the same burrow longer than males. Foraging activity, as evident by the numerous excavations created while searching for subterranean food, often occurs within 200 m of a burrow. Nevertheless, individuals may move over considerably greater (6-7 times) areas than that reflected in the spatial distribution of burrows used during the day. Home ranges of Greater Bilbies in the sandy deserts are usually temporary in location and may suddenly shift, presumably in response to changes in food availability. In more productive areas, individuals are more sedentary.

Movements, Home range and Social organization. Greater Bilbies are polygynous. Captive males form a linear hierarchy, maintained with little actual fighting. Reintroduced large males appeared to shadow each other and were, at times, captured in traps set side by side. Males and females differ in their movements and the number of burrows they consistently occupy within their home ranges. Males may use several burrows in 2-3 weeks, and these can be spaced more than 400 m apart, covering c.15 ha. Over the same period, female often use burrows spaced ¢.200 m apart, covering 3 ha. Freshly disturbed or excavated soil is not always evident at the entrance of occupied burrows. Female—female and female—male sharing of burrows may occasionally occur. Male home ranges and male-female home ranges overlap considerably. Average dispersal distance of females in a reintroduced population was 2-3 km/year.

Status and Conservation. CITES Appendix I. Classified as Vulnerable on The IUCN Red List. The USFish and Wildlife Service lists the Greater Bilby as an internationally endangered species. Total population size may be fewer than 10,000 mature individuals, and it suffers from an ongoing decline estimated to exceed 10% over the last three generations (twelve years), which is likely to continue. Listed as vulnerable in Australia under the Environment Protection and Biodiversity Conservation Act since 16July 2000, with Queensland populations listed as endangered. The wild population in Queensland occurs within the Channel Country and Mitchell Grass Downs bioregion, butits distribution is disjunct with some populations extremely small. The main population of Greater Bilbies is centered on Astrebla Downs National Park and adjacent properties. Astrebla Downs National Park was established primarily to protect Greater Bilbies. In the Northern Territory, the wild population occurs in the southern part of the Sturt Plateau bioregion, the Ord-Victoria plain bioregion, the central and western parts of the Tanami bioregion, and the northern Great Sandy Desert bioregion. In addition to the former three bioregions, Western Australian populations occur in the Dampierland, Pilbara, Central Kimberley, Little Sandy Desert, and Gibson Desert bioregions. In each bioregion, populations are patchily distributed. A number of populations along the southern extent of the Northern Territory distribution are known to have gone extinct since the 1990s. Aerial and ground surveys in western Queensland during the 1990s indicated a significant and ongoing contraction in the species’ distribution in that state. Populations occur in captive breeding facilities and predatorfree, fenced enclosures at several sites in Western Australia, South Australia, Queensland, and New South Wales. The Greater Bilby faces a number of threats throughoutits distribution; however, the relative importance of each threat and interactions among threats are not clearly defined. Predation from invasive predators is considered a major threat particularly from the Red Fox (Vulpes vulpes) and feral cats. The domestic/feral cat (Felis catus) occurs throughout the remaining distribution of the Greater Bilby, and Red Fox presence is negatively correlated with presence of the Greater Bilby. Distribution of the Red Fox is known to have shifted northward in the Northern Territory in recent decades, which is likely to be the case in Queensland and Western Australia. Distribution of the Greater Bilby correlates with a low abundance or absence of the European Rabbit (Oryctolagus cuniculus) and pattern of pastoralism. The European Rabbit competes for food with the Greater Bilby, particularly for Cyperus bulbosus , and can alter composition of vegetation and elevate predator levels. Pastoralism can reduce suitability of habitat from overgrazing by livestock, elevating invasive predator or herbivore levels by providing waterto livestock, or altering offire regimes. Greater Bilbies usually do well in predatorfree enclosures and captive breeding facilities. These facilities provide valuable settings to conduct research and engage and educate the public, but they are costly to maintain and limited in offering realistic, long-term conservation outcome for the Greater Bilby. Similarly, baiting control of predators in remote parts of Australia has proved difficult to sustain and resulted in some perverse outcomes. In some situations, control of Dingo (Canis lupus dingo) and Red Fox has led to an increase in numbers of feral cat. Less intensive management options include implementation of fire management to promote favorable food plants in the northern part of the distribution of the Greater Bilby, protection from pastoral expansion, decommissioning of stock water points, and translocation to offshore islands where invasive predators and herbivores are absent. Continued development of effective, broad-scale control measures for Red Fox, feral cat, and European Rabbit is imperative.

Bibliography. Abbott (2001), Archer & Kirsch (1977), Burbidge et al. (1988), Burrows et al. (2003), Christensen & Burrows (1995), Cockburn (1990), Dickman (2007), Finlayson (1932b, 1935b, 1939, 1961a), Friend, Morris & van Weenen (2008), Gibson (2001), Gibson et al. (2002), Groves & Flannery (1990), Hume (1982), Johnson, C.N. & Johnson (1983), Johnson, K.A. (1989), Kirsch (1977), Krefft (1862), McCracken (1986, 1990), McKenzie et al. (2007), McRae (2004), Meredith, Westerman & Springer (2008a), Moritz et al. (1997), Nilsson et al. (2010), Pavey (2006a), Reid (1837), Rolls (1969), Southgate (1990a, 1990b, 1995), Southgate & Adams (1993), Southgate & Carthew (2006, 2007), Southgate & Possingham (1995), Southgate, Christie & Bellchambers (2000), Southgate, Paltridge, Masters & Carthew (2007), Southgate, Paltridge, Masters & Nano (2005), Spencer & Gillen (1912), Tate (1948), Thomas (1905), Troughton (1932a), Tyndale-Biscoe (2005a), Watts (1969), Westerman, Kear et al. (2012), Westerman, Meredith & Springer (2010), Wood Jones (1923a, 1924).

Figures

Greater Bilby

Distribution. C & W Australia (Western Australia, Northern Territory, and SW Queensland). A population has been successfully translocated to Thistle Island South (Australia) and a reintroduced population at Lorna Glen (Western Australia) persists.