Numbat

(Myrmecobiidae)

Class Mammalia

Order Dasyuomorphia

Family Myrmecobiidae

Thumbnail description
Medium-sized reddish brown specialized termite-feeder with five to six striking white stripes across lower back, and a very long tail with long, erect hairs; long, thin tongue can protrude well beyond end of snout

Size
7.9–10.8 in (200–274 mm); 0.66–1.5 lb (0.3–0.7 kg)

Number of genera, species
1 genus; 1 species

Habitat
Forest, woodland, and spinifex

Conservation status
Vulnerable

Distribution
Extreme southwestern Australia; formerly broad band across western, southern half of Australia

Evolution and systematics

The evolutionary history of this family is poorly known. There is only one known species, the living numbat (Myrmecobius fasciatus), which is represented in a few Pleistocene cave deposits in Western Australia and western New South Wales. Myrmecobiids appear to be a sister group of a combined thylacinid-dasyurid group within the Dasyuromorphia.

The taxonomy for this species is Myrmecobius fasciatus (Waterhouse, 1836), Mt. Kokeby, Western Australia, Australia.

Physical characteristics

Numbats are one of the more beautiful and strikingly marked Australian mammals. Morphologically similar to the dasyurids, they are quadrupedal, place the heel of the hind foot on the ground when standing, and the snout is elongated and sharply pointed. Unique features of numbats include a very long tail, almost equal to the head and body length, and ears that are furred, erect, and quite narrow. Numbats also have more teeth than dasyurids; with five structurally simple molar teeth lacking defined cusps. Males and females are a similar size (1–1.1 lb; 0.45–0.5 kg). The medium-length soft fur is reddish brown in color, darker towards the rump and paler below, with five to six transverse white stripes across the lower back and a white-bordered black stripe running from the snout to the base of the ear. Tail hairs are long and often erect. The female has four teats surrounded by crimped hair on the lower abdomen but there is no visible pouch. The very long, thin tongue can protrude several inches/centimeters beyond the end of the snout when feeding.

Distribution

At the time of European settlement (late eighteenth century to early nineteenth century), numbats were distributed in a broad band across the southern half of central and Western Australia, the eastern and northern limits of their range represented by western New South Wales and southwestern Northern Territory, respectively. By 1985, numbats had disappeared from all but two small locations in the southwest of Western Australia. A program of feral red fox (Vulpes vulpes) control, reintroduction, and translocations has resulted in nine wild and two free-ranging fenced populations.

Habitat

The key to numbat presence is an abundance of termites, their primary food. The second prerequisite seems to be adequate ground-level cover, in the form of thickets of dense vegetation or hollow logs, which provides a refuge from predators. Primary predators would have been diurnal raptors, but foxes are now the major force driving extinction of populations. Hollow logs, which provide complete protection from larger predators, are probably more important in the presence of foxes. Numbats formerly occupied a variety of vegetation types, from open forest to woodland to hummock grasslands in the arid zone, although most sites had eucalypt trees.

Behavior

The numbat stands out among Australian mammals in being exclusively diurnal, probably as a consequence of their termite diet. Seasonal patterns in daily activity correspond closely to the abundance of termites in galleries close to the surface. Numbats are active in the warmer parts of the day, from midmorning until late afternoon, except in the hottest part of summer, when they divide their activity into two periods: dawn until midday and then late afternoon. When not active, numbats sleep in hollow logs or trees, or underground burrows that they have dug themselves. They make a nest in a den with grass or shredded bark, and they regularly use more than one den. Numbats are solitary except when females are rearing young and occupy home ranges from which other individuals of the same sex are excluded. Young disperse in December and have been recorded moving in excess of 9 mi (15 km).

Feeding ecology and diet

Numbats are highly specialized with a diet that consists almost entirely of termites, although some ants are taken incidentally. Numbats sniff out underground termite galleries and expose termites by digging small holes and turning over sticks and branches. They have extremely sharp claws that they use for digging but the forelimbs are not especially strong. The long, slender tongue is inserted deep into the winding termite galleries and withdrawn rapidly, insects adhering to saliva on the tongue. Numbats have very large salivary glands to supply the prodigious quantities of saliva required for this mode of feeding. The molar teeth are simple in structure with three almost equal cusps and the number can vary in individuals, and also from side to side in the same individual, suggesting that the molars receive light use. Unlike other mammalian anteaters, numbats show no obvious specializations for termite-eating in the stomach.

Reproductive biology

Breeding is probably promiscuous and is seasonal with most young born in summer, after a 14-day gestation. Males as well as females show an annual cycle of fertility. The female usually carries the full complement of four young that, in the absence

of a pouch, maintain attachment orally and by entwining the forelimbs in the crimped fur of the mammary region. Development is slow and young are carried for six to seven months, after which they are deposited in a nest. At this stage they are furred with visible stripes, but their eyes are not yet open. The young are suckled for another three months, until at least late October. During this time they gradually explore and forage within their mother's home range. The female may move them to another nest, particularly in response to disturbance, and does so by carrying small young on her back.

Conservation status

The decline of the numbat, from its formerly wide distribution at the time of European settlement, is documented. Populations disappeared gradually in an east-west progression, with the expansion in range of introduced foxes. The rate of disappearance accelerated after 1920 when fox populations suddenly exploded. By the 1960s, numbats persisted in only two locations: the Gibson Desert and the southwest of Western Australia. The desert population disappeared first, leaving only two populations to the southwest of Perth by 1985.

An experimental fox control program, initiated in the early 1980s, demonstrated that numbat populations increased when fox populations were suppressed by monthly poison baiting. Fox predation was confirmed as the primary factor in the decline of numbats. Since 1985, there has been a successful recovery program involving translocation of wild individuals, supplemented with the reintroduction of captive-bred numbats to suitable habitat in nature reserves within their former southwestern range. This program, combined with regular fox baiting, has increased wild populations to nine localities. An additional two populations live within large, fenced reserves in South Australia and New South Wales. Rates of increase in translocated populations vary with the levels of predation by (native) raptors, residual levels of foxes and feral cats, dispersal opportunities, and habitat type that are related to food supply. Numbats probably never occurred in high density, even though they were widespread. Populations in which wide dispersal is limited by fencing or surrounding farmland increase more rapidly. In 1994, numbats were upgraded from an Endangered listing to Vulnerable under IUCN Red List criteria.

Significance to humans

Numbat is an aboriginal name from South Australia. Central Australian aboriginal peoples knew the animal as

"walpurti" and hunted it to eat. Individuals were tracked to burrows where they were dug up. No commercial exploitation

of numbats is recorded, but up to 200 have been collected for museum specimens.

Resources

Books

Archer, M., T. Flannery, S. Hand, and J. Long. Prehistoric Mammals of Australia and New Guinea: One Hundred Million Years of Evolution. Sydney: UNSW Press, 2002.

Friend, J. A. "Myrmecobiidae." In Fauna of Australia. Canberra: Australian Government Publishing Service, 1989.

Friend, J. A., and N. D. Thomas. "Conservation of the Numbat (Myrmecobius fasciatus)." In Predators with Pouches: The Biology of Carnivorous Marsupials, edited by M. E. Jones, C. R. Dickman, and M. Archer. Melbourne: CSIRO Publishing, 2003.

Krajewski, C., and M. Westerman. "Molecular Systematics of Dasyuromorphia." In Predators with Pouches: The Biology of Carnivorous Marsupials, edited by M. E. Jones, C. R. Dickman, and M. Archer. Melbourne: CSIRO Publishing, 2003.

Strahan, R. The Mammals of Australia. Sydney: Australian Museum, Reed Books, 1995.

Menna Jones, PhD