Numbat
The numbat, also known as the noombat or walpurti, is an insectivorous marsupial. It is diurnal and its diet consists almost exclusively of termites.
The species was once widespread across southern Australia, but is now restricted to several small colonies in Western Australia. It is therefore considered an endangered species and protected by conservation programs. Numbats were recently re-introduced to fenced reserves in South Australia and New South Wales. The numbat is the faunal emblem of Western Australia.
Taxonomy
The numbat genus Myrmecobius is the sole member of the family Myrmecobiidae, one of four families that make up the order Dasyuromorphia, the Australian marsupial carnivores.The species is not closely related to other extant marsupials; the current arrangement in the order Dasyuromorphia places its monotypic family with the diverse and carnivorous species of Dasyuridae. Genetic studies have shown that the ancestors of the numbat diverged from other marsupials between 32 and 42 million years ago, during the late Eocene.
Two subspecies have been described, but one of these—the rusty coloured Myrmecobius fasciatus rufus Finlayson, 1933,—has been extinct since at least the 1960s, and only the nominate subspecies is extant. The population described by Finlayson occurred in the arid central regions of South Australia, and he thought they had once extended to the coast. The separation into subspecies was not recognised in the national census of Australian mammals, following W. D. L. Ride and others. As its name implies, M. fasciatus rufus had a more reddish coat than the surviving population. Only a very small number of fossil specimens are known, the oldest dating back to the Pleistocene, and no other species from the same family have been identified.
The following is a phylogenetic tree based on mitochondrial genome sequences:
Placement of the family within the order of dasyuromorphs may be summarised as
- Order Dasyuromorphia
- * Family Thylacinidae
- * Family Dasyuridae
- * Family Myrmecobiidae
- ** Genus Myrmecobius
- *** Species Myrmecobius fasciatus
- * Family †Malleodectidae
Other names include banded anteater and marsupial anteater.
Description
The numbat is a small, distinctively-striped animal between long, including the tail, with a finely pointed muzzle and a prominent, bushy tail about the same length as its body. They have five toes on the fore feet, and four on the hind feet. Colour varies considerably, from soft grey to reddish-brown, often with an area of brick red on the upper back, and always with a conspicuous black stripe running from the tip of the muzzle through the eye to the base of the small, round-tipped ear. Between four and eleven white stripes cross the animal's hindquarters, which gradually become fainter towards the midback. The underside is cream or light grey, while the tail is covered with long, grey hair flecked with white. Weight varies between. Numbats also possess a sternal scent gland, which may be used for marking their territories.Unlike most other small marsupials, the numbat is diurnal, largely because of the constraints of having a specialised diet without having the usual physical equipment for it; most ecosystems with a generous supply of termites have a fairly large creature with powerful forelimbs bearing heavy claws, such as anteaters, aardvarks, and pangolins. Like other mammals that eat termites or ants, the numbat has a "degenerate" jaw with up to 50 tiny, nonfunctional teeth, and although it is able to chew, rarely does so because of the soft nature of its diet. Uniquely among terrestrial mammals, an additional cheek tooth is located between the premolars and molars; whether this represents a supernumerary molar tooth or a deciduous tooth retained into adult life is unclear. As a result, although not all individuals have the same dental formula, in general, it follows the unique pattern:
Akin to other myrmecophages, the numbat has a long and narrow tongue coated with sticky saliva produced by large submandibular glands. A further adaptation to the diet is the presence of numerous ridges along the soft palate, which apparently help to scrape termites off the tongue so they can be swallowed. The digestive system is relatively simple and lacks many of the adaptations found in other insectivorous animals, presumably because termites are easier to digest than ants, having a softer exoskeleton. Numbats are apparently able to gain a considerable amount of water from their diets, since their kidneys lack the usual specialisations for retaining water found in other animals living in their arid environment. Although the numbat finds termite mounds primarily using scent, it has the highest visual acuity of any marsupial, and, unusually for marsupials, has a high proportion of cone cells in the retina. These are both likely adaptations for its diurnal habits, and vision does appear to be the primary sense used to detect potential predators.
Distribution and habitat
Numbats were formerly widely distributed across southern Australia, from Western Australia to north-western New South Wales. However, their range has significantly decreased since the arrival of Europeans, and the species has survived only in two small patches of land in the Dryandra Woodland and the Tone-Perup Nature Reserve, both in Western Australia.Today, numbats are naturally found only in areas of eucalypt forest, but they were once more widespread in other types of semiarid woodland, spinifex grassland, and in terrain dominated by sand dune. There are estimated to be fewer than 1,000 left in the wild.
After measures aimed at excluding feral cats, the number of numbats trapped during annual population surveys in the Dryandra Woodland had increased to 35 by November 2020, after recording just 10 in 2019 and 5 in 2018. There had not been so many numbats recorded since 36 were recorded in the 1990s.
The species has been successfully reintroduced into three fenced, feral predator-proof reserves in more varied environments; Yookamurra Sanctuary in the mallee of South Australia, Scotia Sanctuary in semi-arid NSW, and Western Australia's Mount Gibson Sanctuary. Reintroduction began at large fenced reserves in Mallee Cliffs National Park in NSW in December 2020, and on South Australia's Eyre Peninsula in 2022.
Attempted reintroductions of the species to fenced reserves in two other areas – one in the South Australian arid zone, near Roxby Downs, and the other in the northernmost part of its former range, at Newhaven Sanctuary in the Northern Territory – both failed.
There are plans to reintroduce the species to a managed and semi-fenced area of the southern Yorke Peninsula in South Australia, as part of the Marna Banggara project.
Ecology and habits
Numbats are insectivores and subsist on a diet of termites. An adult numbat requires up to 20,000 termites each day. The only marsupial fully active by day, the numbat spends most of its time searching for termites. It digs them up from loose earth with its front claws and captures them with its long, sticky tongue. Because termites have a high water content Numbats obtain most of their water needs directly from their food, allowing them to survive in dry Australian habitats. Despite its banded anteater name, it apparently does not intentionally eat ants; although the remains of ants have occasionally been found in numbat excreta, these belong to species that themselves prey on termites, so were presumably eaten accidentally, along with the main food. Known native predators include various reptiles and raptors, such as the carpet python, sand goanna, wedge-tailed eagle, collared sparrowhawk, brown goshawk, and the little eagle. They are also preyed upon by invasive red foxes and feral cats.Adult numbats are solitary and territorial; an individual male or female establishes a territory of up to 1.5 square km early in life, and defends it from others of the same sex. The animal generally remains within that territory from then on; male and female territories overlap, and in the breeding season, males will venture outside their normal home ranges to find mates.
While the numbat has relatively powerful claws for its size, it is not strong enough to get at termites inside their concrete-like mounds, and so must wait until the termites are active. It uses a well-developed sense of smell to locate the shallow and unfortified underground galleries that termites construct between the nest and their feeding sites; these are usually only a short distance below the surface of the soil, and vulnerable to the numbat's digging claws.
The numbat synchronises its day with termite activity, which is temperature dependent: in winter, it feeds from midmorning to midafternoon; in summer, it rises earlier, takes shelter during the heat of the day, and feeds again in the late afternoon. Numbats can enter a state of torpor, which may last up to fifteen hours a day during the winter months.
At night, the numbat retreats to a nest, which can be in a log or tree hollow, or in a burrow, typically a narrow shaft long which terminates in a spherical chamber lined with soft plant material: grass, leaves, flowers, and shredded bark. The numbat is able to block the opening of its nest, with the thick hide of its rump to prevent a predator being able to accessing the burrow.
Numbats have relatively few vocalisations, but have been reported to hiss, growl, or make a repetitive 'tut' sound when disturbed.