Wombats

(Vombatidae)

Class Mammalia

Order Diprotodontia

Suborder Vombatiformes

Family Vombatidae

Thumbnail description
Wombats are large burrowing herbivores, stocky with a broad massive head and short powerful limbs; the ears are small and the tail insignificant.

Size
39.4 in (1.0 m); 55–88 lb (25–40 kg)

Number of genera, species
2 genera; 3 species

Habitat
Woodlands

Conservation status
Critically Endangered: 1 species

Distribution
Southeastern Australia

Evolution and systematics

There are only three living species of wombats, but the family was more diverse in the Pleistocene (between about two million years ago [mya] and 10,000 years ago), when it was represented by a total of six genera and nine species. Some of the extinct species were much larger than the living species. Phascalonus gigas, for example, had a skull 16 in (40 cm) in length and may have stood about 39.4 in (1 m) high and weighed 441 lb (200 kg).

Whether these giant wombats dug burrows is unknown; they do not seem to have been as well-adapted for burrowing as their living relatives, and may only have dug short burrows for resting. The earliest fossil wombats are of early Miocene age. Wombats arose from the same stock that produced the kangaroos and possums, and their closest living relative is the koala.

Physical characteristics

The three living species of wombats are similar in size, and all have the same stocky body form. The two hairy-nosed wombats (Lasiorhinus) differ from the common wombat (Vombatus ursinus) in having a hairy covering over the rhinarium. They also have longer pointed ears and finer fur. The hairy-nosed wombats are silver-gray, but the common wombat varies in color from pale gray to rich brown. Males and females are similar in appearance.

The skeletal characters of wombats are well-suited for digging. In particular, the pectoral girdle is heavy and strong and the humerus is broad and massive. This makes the fore-arms very powerful, and the forepaws are broad and have strong claws.

Distribution

Wombats occur in southeastern Australia, and are reasonably widespread in New South Wales, Victoria, Tasmania, and South Australia. The northern hairy-nosed wombat (L. krefftii) is found just to the north of the tropic of Capricorn, and the southern hairy-nosed wombat (L. latifrons) has isolated populations in Western Australia.

Habitat

The two species of hairy-nosed wombats live in open woodlands, shrublands, and grasslands in semi-arid habitats, and the southern hairy-nosed wombat extends into arid regions on the Nullarbor Plain. The common wombat lives in forests and woodlands in areas of higher rainfall.

Behavior

Wombats dig by scratching with the forepaws and flinging soil behind them; the piled-up soil is then bulldozed clear of the burrow as the animal backs out of the entrance. Wombat burrows can be huge. They may consist of 98 ft (30 m) or more of tunnel length, and have several entrances as well as side tunnels and resting chambers. Warrens of the southern hairy-nosed wombat are particularly complex, and probably the same warren is used and expanded by many generations of wombats. The tunnels are wide enough to accommodate a lightly built adult human (no reasonable person would ever risk crawling down a wombat burrow, but a 15 year old boy explored many burrows of the common wombat

in 1960 and wrote up his observations in a now-famous article in his school magazine).

Individuals usually feed alone, but in the southern hairy-nosed wombat many animals may share the same warren. Similarly, in the northern hairy-nosed wombat burrows occur in clusters, and a group of up to 12 wombats makes common use of each cluster of burrows. However, even when two individuals use the same burrow it seems that they occupy different sections of it. There is good evidence indicating that both the female northern hairy-nosed wombat and the female common wombat are more likely to disperse from their home burrow at some stage of their lives, while the males are more philopatric. This is unusual—in most mammals dispersal is male-biased. This suggests that the groups of individuals that occupy burrow clusters in the northern hairy-nosed wombat are composed of related males and unrelated females. It is still not known at what age females disperse in the common wombat, but in the northern hairy-nosed wombat dispersal has been observed by breeding adult females.

Feeding ecology and diet

Wombats are specialized grazers. They have open-rooted teeth that grow throughout life, compensating for tooth wear caused by eating abrasive grasses. The jaws are massive, and deliver powerful, short chewing strokes that reduce their fibrous food to small particles. Gut capacity is large, and the colon is expanded to house cellulose-digesting microorganisms. Food is held in the gut for long periods (70 hours or so) to maximize the breakdown of fiber.

Wombats feed mainly at night, and rest deep in their burrows during the day. Their burrows provide them with refuge from such predators as dingoes and also with protection from extreme temperatures and dry conditions. Wombats have low basal metabolic rates; this, together with the slow rate of passage of food through the gut and the efficiency with which they digest their food, means that they spend less time feeding than other grazers of their body size and they can afford to spend most of their time in their burrows. Their home ranges are small for a herbivore of their body size, typically less than 49 acres (20 ha).

Reproductive biology

The single young is born after a gestation of about 22 days, and stays in the pouch for six to nine months. It remains dependent on its mother for at least a year after leaving the pouch. Wombats have backward-opening pouches. There is no evidence of pair-bonding and there is presumably competition among males for the opportunity to mate with females, but no details of this are known.

Conservation status

The common wombat and southern hairy-nosed wombat are secure, although the ranges of both species have contracted and fragmented since European settlement. The northern hairy-nosed wombat is extremely rare. It has only been recorded in historic times from three localities, and is

extinct from two of these as of the early twentieth century. Probably, the major cause of its decline was competition for pasture from sheep and cattle. The remaining population is protected within Epping Forest National Park in central Queensland. In 2000 the size of this last population was estimated to be 116 individuals. This species is classed as endangered under Queensland State legislation and Australian Federal legislation.

Significance to humans

Wombats do not feature strongly in Aboriginal mythology. The southern hairy-nosed wombat and common wombat are sometimes regarded as pests of agriculture, because of the damage they cause to crops and fences. None of the species has commercial value. By and large, however, wombats are regarded with deep affection in Australia. They feature in many children's stories, beginning with Ruth Park's classic Muddle-Headed Wombat series from the 1960s. There was also a vogue for wombats in Britain in the mid-nineteenth century. The painter Dante Gabriel Rossetti regarded them as "the most beautiful of God's creatures;" when one of his two pet wombats died in 1869 he commemorated it with a touching drawing entitled Self-portrait of the artist weeping at the wombat's tomb.

Species accounts

List of Species

Common wombat

Vombatus ursinus

taxonomy

Didelphis ursina (Shaw, 1800), Tasmania, Australia.

other common names

None known.

physical characteristics

Head and body length 35–45 in (90–115 cm); tail length about 1 in (2.5 cm); height about 14.2 in (36 cm); weight 48.5–86 lb (22–39 kg). Coarse black or brown to gray coat; bare muzzle, short rounded ears.

distribution

Southeastern Australia including Flinders Island and Tasmania.

habitat

Temperate forests and woodlands, heaths, alpine habitats.

behavior

Solitary, and mostly nocturnal. Burrows are dispersed, and usually simple. Each animal uses several burrows within its home range.

feeding ecology and diet

Feeds mainly on grasses, but also sedges, rushes, and the roots of shrubs and trees.

reproductive biology

One offspring may be born at any time of the year. Pouch life is about six months, and the young remains at heel for about another year. Sexual maturity is at two years of age. Mating system is not known.

conservation status

Not threatened. Range has declined by 10–50%, but the species is common throughout large parts of its original range. Vombatus vombatus ursinus has gone extinct from all Bass Strait islands except Flinders Island.

significance to humans

In parts of Victoria, common wombats are considered pests because of the damage they do to rabbit-proof fences, and some local control is carried out.

Southern hairy-nosed wombat

Lasiorhinus latifrons

taxonomy

Phascolomys latifrons (Owen, 1845), South Australia, Australia.

other common names

None known.

physical characteristics

Head and body length 30–37 in (77–94 cm); weight 42–70 lb (19–32 kg); tail and height similar to common wombat. Coat is fine, gray to brown, with lighter patches; hairy muzzle, longer pointed ears.

distribution

Central southern Australia.

habitat

Semi-arid and arid woodlands, grasslands, and shrub steppes.

behavior

Solitary while feeding, but in many areas warrens are large and complex and used by five to ten individuals. Warrens may be connected by well-used trails, which are marked at intervals by urine splashed and dung piles. Usually nocturnal, but animals may often be seen basking outside their burrows on sunny days in winter.

feeding ecology and diet

Feeds on grasses, but also eats forbs and foliage of woody shrubs during drought.

reproductive biology

A single young is born in spring or early summer and remains in the pouch for six to nine months. Weaning occurs at approximately one year, and sexual maturity at three years. Mating system is not known.

conservation status

Not threatened. Range has declined by 10–50%, but the species remains common through much of its original range.

significance to humans

In some areas it damages grain crops and fences and is controlled as a pest.

Northern hairy-nosed wombat

Lasiorhinus krefftii

taxonomy

Phascolomys krefftii (Owen, 1873), Breccia Cavern, Wellington Caves, Australia.

other common names

French: Wombat à nez poilu de Queensland; Spanish: Oso marsupial del Río Moonie.

physical characteristics

Head and body length of males 40 in (102 cm), females 42 in (107 cm); height about 16 in (40 cm); male weight 66 lb (30 kg), female weight 72 lb (32.5 kg). Coat is silky and silver gray, with dark rings around the eyes.

distribution

There is only one surviving population, in Epping Forest National Park near Clermont in central Queensland. Populations near St George in southern Queensland and Deniliquin in southern New South Wales went extinct early in the twentieth century.

habitat

Semi-arid woodland and grassland.

behavior

Burrows are distributed in loose clusters, and up to 12 wombats make common use of the burrows in each cluster. However, individuals usually feed and rest alone, except for mothers and young. Piles of dung and urine splashes are placed outside burrow entrances and along regularly used paths that connect different burrows within a group.

feeding ecology and diet

Feeds on grasses, plus some sedges and forbs.

reproductive biology

Mating associations are transient; the mating system is not known. One young born in spring or summer. Pouch life is about 10 months, weaning age unknown. On average, females breed twice every three years.

conservation status

Critically Endangered; only about 116 individuals remain. Numbers have evidently increased since Epping Forest National Park was declared and cattle were excluded in 1980, when there may have been only 30 individuals in the population. Current threats include occasional predation by dingoes and (possibly) genetic decline due to isolation and inbreeding.

significance to humans

The northern hairy-nosed wombat is one of Australia's rarest species, and its rarest large mammal.

Resources

Books

Long, J., M. Archer, T. Flannery, and S. Hand. Prehistoric Mammals of Australia and New Guinea. Sydney: University of New South Wales Press, 2002.

Wells, R. T., and P. A. Pridmore. Wombats. Sydney: Surrey Beatty & Sons, 1998.

Woodford, J. The Secret Life of Wombats. Melbourne: Text Publishing, 2001.

Periodicals

Banks, S. C., L. F. Skerratt, and A. C. Taylor. "Female dispersal and relatedness structure in common wombats (Vombatus ursinus)." Journal of Zoology 256 (2002): 389–399.

Christopher Johnson, PhD