Common or hill wallaroo (Macropus robustus)
The common wallaroo or hill kangaroo is one of the largest and heaviest kangaroos. The body mass varies from 6.75-35.75 kg. The head to tail length is 1138-1986 mm for males and 1107-1508 mm for females. The tail is about 551-901 mm for males and 534-749 mm for females.
This stocky kangaroo has coarse, shaggy fur, a hairless muzzle, relatively short, thick tail and an upright hopping style. The robust body shape, with shorter limbs than other kangaroos, may be an adaptation to leap around on rocks; the roughened soles of the short, broad hind feet give extra grip. The mature male is up to twice as heavy as the female and has particularly thick-set shoulders and forearms. Coat colour varies from reddish-brown to very dark blue-grey, almost black, and is generally lighter on the underparts, being pale to nearly white. The medium length fur is directed downwards and less dense than that of red and grey kangaroos and includes thin and sparse underfur. The muzzle has a bare black rhinarium and a slight lateral inflation. The nasal region and the back of the ears are black, while the lips, the inside and base of the ears are white or pale. The legs and tail have a very dark brown color that bleeds into a black tint near the tips of both extremeties.
The teeth have vertically placed roots in the second and third incisors. The second incisor has enamel covering about the height and length of the crown. The outer face of the tooth has an indistinct groove. The third incisor is long, equalling the combined length of the first and second incisors and has an external notch near the front edge. The third premolar is about 7 mm long and the fourth premolar is large and powerful. The molars have well developed transverse ledges with connecting ridges that are small and sometimes absent. The stance is distinctive: the shoulders are thrown back, elbows tucked into the sides and wrists raised.
The wallaroo inhabits most regions of Australia, including Central Australia, Cape York Penninsula of Queen Island in Northeastern Australia, the rocky areas of Hodgson in Northern Australia and the Victoria region, but not Tasmania. The patchy distribution is due to the discontinuous nature of the habitat. The species is found in various habitats in many regions of Australia, such as desert or dune and scrub forest. It prefers mountainous habitats with steep escarpments, rocky hills, overhangs and caves that provide shelter and shade during periods of high temperature and as refuges from predation. It also shelters in dense shrub around streams. It may also use stony rises, grasslands and plains. It can survive where the temperatures rises to 120 F and where the average rainfall is below 380 mm/year.
The wallaroo is often solitary and nocturnal, occupying a relatively small, stable home range near a rocky outcrop or water and moving out of rough country to graze on nearby grasses and shrubs. Small groups sometimes form around favoured resources, but are usually transient. The wallaroo can survive harsh conditions by using caves and rocky outcrops for shelter and protection from predators. It makes a loud hissing noise.
The wallaroo drinks less often than most species in the family and seems able to go for two to three months without drinking, surviving on water contained in food plants. The very efficient excretory system recycles nitrogen and urea to make a very concentrated urine. The wallaroo mainly feeds on spinifex, soft grasses, shrubs, herbs and grass low in protein and/or fibre. In spring it grazes on grass inflourescences and forbs.
The wallaroo is an opportunistic breeder with no regular seasonal pattern of reproduction. A male may mate with several females. Under good breeding conditions, nearly all females have one running offspring and one attached to a teat in the pouch. Under poor breeding conditions, such as prolonged droughts, breeding may cease and females may experience embryonic diapause, so they can become pregnant again soon after giving birth. The new embryo stays dormant until the first young is ready to leave the pouch or is lost, when the embryo resumes development and is born when the pouch is vacant. This means the female can quickly replace young lost to predators or drought and can have embryos ready to develop as soon as conditions become favourable.
One tiny young is born after a gestation period is about 30-38 days and weighs 0.7 g. It climbs, unaided, through the female's fur and into the pouch, where it attaches to a teat and begins to suckle. Most development occurs in the pouch; the young emerges after around 231-270 days. The young is suckled for at least 12-14 months. Males reach sexual maturity at around 18-20 months in captivity and females at 14-24 months. The average lifespan is 18.5 years in the wild and 19.6 years in captivity. The maximum longevity is 22 years in captivity and perhaps 24 years in the wild.
The Red List Category was assessed as Least Concern (LC) in 2008. This is due to the wallaroo's wide distribution, large population, occurrence in several protected areas, lack of major threats, and as it is unlikely to be declining at nearly the rate required to qualify for listing in a threatened category. The species is widespread and relatively common in appropriate habitats. The steep, rocky areas it favours help to protect it to some degree The population is stable. In Victoria, the wallaroo is rare and in urgent need of protection. Due to its isolation, it is vulnerable to predation and human land development. The wallaroo is sparse in the wheatbelt of New South Wales. In Queensland, it is common in some agricultural areas with removal of M. giganteus. It is subject to commercial take under nationally approved management plans. The wallaroo may have benefitted from artificial water holes provided for livestock, as well as a reduction in dingo numbers and the presence of sheep, creating favourable grazing conditions. It is legally culled in some areas for food and skins, as well as alleged damage to pastures and crops; this makes up only about 3% of the overall commercial kangaroo quota.
The four subspecies are based mainly on colour, size, and genetic differences:
1. Eastern wallaroo (M.r. robustus): It occupies the eastern slopes of the Great Dividing Range, from southern New South Wales to Queensland. Males have dark grey fur, but females are lighter, being almost sandy in colour.
2. Inland wallaroo or 'euro' (M.r. erubescens): It is mostly brownish or rufous in colour and occurs over much of the drier areas of the continent, from western New South Wales and Queensland, west to the Indian Ocean coast,
3. Northern wallaroo (M.r. woodwardi): It is the palest subspecies and occurs across northwestern Australia, including the Kimberley region of Western Australia and a band running across the Northern Territory.
4. Barrow Island wallaroo (M.r. isabellinus). This small, stocky, uniformly reddish-brown subspecies reaches only half the size of the other forms. There are about 1,800 individuals on Barrow Island, off the Pilbara coast of Western Australia (1,4,7) and the subspecies is classified as vulnerable. It may suffer from anaemia and poor condition, due related to nutritional stress. This subspecies may be more vulnerable than the mainland subspecies, particularly due to its small, isolated population. It is listed as Vulnerable under the Environmental Protection and Biodiversity Conservation Act 1999 (EPBC), with threats including inappropriate fire regimes, introduced species, road fatalities and habitat degradation associated with the development of oilfields. Conservation priorities include determining the extent of nutritional stress in the population, continuing with long-term population monitoring and determining if oil field management can be modified to improve the wallaroo population. It will also be important to prevent introductions of non-native species, to monitor and improve traffic management to reduce road fatalities, to develop an appropriate fire management strategy and to restore land impacted by the oil field.
In some areas, M.r. robustus and M.r. erubescens overlap and are thought to hybridise (4).