Numbat

The numbat (Myrmecobius fasciatus), also known as the banded anteater, or walpurti, is a marsupial found in Western Australia. Its diet consists almost exclusively of termites. Once widespread across southern Australia, the range is now restricted to several small colonies and it is listed as an endangered species. The numbat is an emblem of Western Australia and protected by conservation programs.

Classification

The numbat genus Myrmecobius is the sole member of the family Myrmecobiidae; one of the three families that make up the order Dasyuromorphia, the Australian marsupial carnivores^[1].

The species is not closely related to other extant marsupials; the current arrangement in the dasyuromorphia order places its monotypic family with the diverse and carnivorous species of Dasyuridae. A closer affinity with the extinct thylacine, contained in the same order, has been proposed. 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.^[3]

There are two recognised subspecies. However, one of these, the rusty numbat (M. f. rufus), has been extinct since at least the 1960s, and only the nominate subspecies (M. f. fasciatus) remains alive today. As its name implies, the rusty numbat was said to have a more reddish coat than the surviving subspecies.^[4] Only a very small number of fossil specimens are known, the oldest dating back to the Pleistocene, and no fossils belonging to other species from the same family have yet been discovered.^[4]

Description

The numbat is a small, colourful creature between 35 and 45 centimetres (14 and 18 in) long, including the tail, with a finely pointed muzzle and a prominent, bushy tail about the same length as its body. 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 eyes to the bases of the small, round-tipped ears. There are between four and eleven white stripes across the animal's hindquarters, which gradually become fainter towards the mid-back. The underside is cream or light grey, while the tail is covered with long grey hair flecked with white. Weight varies between 280 and 700 grams (9.9 and 25 oz).^[5][4]

Unlike most other 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 a very long, thin, sticky tongue for penetrating termite colonies, and powerful forelimbs with heavy claws.^[6] There are five toes on the forefeet, and four on the hindfeet^[4]. Like other mammals that eat termites or ants, the numbat has a degenerate jaw with up to 50 very small non-functional teeth, and although it able to chew^[4], rarely does so, because of the soft nature of its diet. Uniquely among terrestrial mammals, there is an additional cheek tooth between the premolars and molars; it is unclear whether this represents a supernumary molar tooth or a deciduous tooth retained into adult life. As a result, although not individuals have the same dental formula, in general, it follows the unique pattern: ^[4]

Like many ant-eating animals, the numbat has an unusually long, 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 that they can be swallowed. The digestive system is relatively simple, and lacks many of the adaptations found in other entomophagous 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 diet, since their kidneys lack the usual specialisations for retaining water found in other animals living in their arid environment.^[7] Numbats also possess a sternal scent gland, which may be used for marking its territory.^[4]

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.^[4] Numbats regularly enter a state of torpor, which may last up to fifteen hours a day during the winter months.^[8]

Distribution and habitat

Numbats were formerly found across southern Australia from Western Australia across as far as northwestern New South Wales. However, the range has declined significantly since the arrival of Europeans, and the species has survived only in two small patches of land in the Dryandra Woodland and the Perup Nature Reserve, both in Western Australia. In recent years, it has, however, been successfully reintroduced into a few fenced reserves, including some in South Australia and New South Wales.^[2]

Today, numbats are found only in areas of eucalypt forest, but they were once more widespread in other types of semi-arid woodland, Spinifex grassland, and even in terrain dominated by sand dunes.^[4]

Ecology and behaviour

Numbats are insectivores and eat an exclusive diet of termites. An adult numbat requires up to 20,000 termites each day. The only marsupial that is fully active by day, the numbat spends most of its time searching for termites. It digs up termites from loose earth with its front claws and captures them with its long sticky tongue. ^[9] Despite its banded anteater name, although the remains of ants have occasionally been found in numbat dung, these belong to species that themselves prey on termites, and so were presumably eaten accidentally, along with the main food. Known predators on numbats include carpet pythons, introduced red foxes, and various falcons, hawks, and eagles.^[4]

Adult numbats are solitary and territorial; an individual male or female establishes a territory of up to 1.5 square kilometres (370 acres)^[6] early in life, and defends it from others of the same sex. The animal generally remains within that territory from that time on; male and female territories overlap, and in the breeding season males will venture outside their normal home range to find mates.

While the numbat has relatively powerful claws for its size,^[6] it is not strong enough to get at termites inside their concrete-like mound, 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 mid-morning to mid-afternoon; in summer, it rises earlier, takes shelter during the heat of the day, and feeds again in the late afternoon.

At night, the numbat retreats to a nest, which can be in a hollow log or tree, or in a burrow, typically a narrow shaft 1-2 metres 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 access the burrow.^[10] Numbats have relatively few vocalisations, but have been reported to hiss, growl, or make a repetitive 'tut' sound when disturbed.^[4]

Reproduction

Numbats breed in February and March, normally producing one litter a year, although they can produce a second if the first is lost.^[11] Gestation lasts 15 days, and results in the birth of four young. Unusually among marsupials, female numbats have no pouch, although the four teats are protected by a patch of crimped, golden hair and by the swelling of the surrounding abdomen and thighs during lactation.^[4]

The young are 2 centimetres (0.79 in) long at birth, and crawl to the teats, and remain attached until late July or early August, by which time they have grown to 7.5 centimetres (3.0 in). They first develop fur at 3 centimetres (1.2 in), and the adult coat pattern begins to appear once they reach 5.5 centimetres (2.2 in). After weaning, the young are initially left in a nest, or carried about on the mother's back, and they are fully independent by November. Females are sexually mature by the following summer, but males do not reach maturity for another year.^[4]

Conservation status

Until European colonisation, the numbat was found across most of the area from the New South Wales and Victorian borders west to the Indian Ocean, and as far north as the southwest corner of the Northern Territory. It was at home in a wide range of woodland and semi-arid habitats. The deliberate release of the European red fox in the 19th century, however, wiped out the entire numbat population in Victoria, NSW, South Australia and the Northern Territory, and almost all numbats in Western Australia as well. By the late 1970s, the population was well under 1,000 individuals, concentrated in two small areas not far from Perth, Dryandra and Perup.

The first record of the species described it as beautiful;^[12] its appeal saw it selected as the faunal emblem of the state of Western Australia and initiated efforts to conserve it from extinction.^[10]

It appears that the reason the two small Western Australia populations were able to survive is that both areas have many hollow logs that may serve as refuge from predators. Being diurnal, the numbat is much more vulnerable to predation than most other marsupials of a similar size: its natural predators include the Little Eagle, Brown Goshawk, Collared Sparrowhawk and Carpet Python. When the Western Australia government instituted an experimental program of fox baiting at Dryandra (one of the two remaining sites), numbat sightings increased by a factor of 40.

An intensive research and conservation program since 1980 has succeeded in increasing the numbat population substantially, and reintroductions to fox-free areas have begun. Perth Zoo is very closely involved in breeding this native species in captivity for release into the wild. Despite the encouraging degree of success so far, the Numbat remains at considerable risk of extinction and is classified as an endangered species.^[2]

Discovery

The numbat first became known to Europeans in 1831. It was discovered by an exploration party who were exploring the Avon Valley under the leadership of Robert Dale. George Fletcher Moore, who was a member of the expedition, recounted the discovery thus:

"Saw a beautiful animal; but, as it escaped into the hollow of a tree, could not ascertain whether it was a species of squirrel, weasel, or wild cat..."

and the following day

"chased another little animal, such as had escaped from us yesterday, into a hollow tree, where we captured it; from the length of its tongue, and other circumstances, we conjecture that it is an ant-eater—its colour yellowish, barred with black and white streaks across the hinder part of the back; its length about twelve inches."^[12]

The first classification of specimens was published by George Robert Waterhouse, describing the species in 1836 and the family in 1841. Myrmecobius fasciatus was included in the first part of John Gould's The Mammals of Australia, issued in 1845, with a plate by H. C. Richter illustrating the species.

References

External links

• ARKive - images and movies of the numbat (Myrmecobius fasciatus)
• Numbat Western Australia's Department of Environment and Conservation (DEC) WebPage.