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Macropus robustushill wallaroo

Geographic Range

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.

Habitat

Macropus robustus is found in many regions of Australia. They can survive where the temperatures rises to 120 F and where the average rainfall is less than 380 mm/year. They prefer rocky places for shade and can inhabit regions of sparse vegetation. Strahan, 1995; Tyndale-Biscoe, 1973; Nowak, 1991

Physical Description

Macropus robustus is one of the largest and heaviest of the macropodid family, with mature males attaining twice the weight of mature females. Wallaroos are stout and heavy with a head to tail length of 1138-1986 mm (males) and 1107-1508 mm (females). The tails are about 551-901 mm (males) and 534-749 mm (females). The pelage is darker (greyish-black) than most others in the Macropodidae, and it is of medium length and directed downwards. The fur is less dense than that of red and grey kangaroos and includes thin and sparse underfur. The color of the fur is dark grey on the dorsal side and pale to nearly white on the ventral side. 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 that covers about the height and length of the crown. The outer face of the tooth has an indistinct groove. The third incisor is long and equals the combined length of the first and second incisors and also has an external notch near the front edge. The third premolar is about 7 mm in length 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 isdistinctive: the shoulders are thrown back, elbows tucked into the sides and wrists raised. Strahan 1995; Tyndale-Biscoe 1973; Nowak 1991

  • Sexual Dimorphism
  • male larger
  • Range mass
    6.75 to 35.75 kg
    14.87 to 78.74 lb
  • Average basal metabolic rate
    33.056 W
    AnAge

Reproduction

Wallaroos reach sexual maturity before two years of age. They are opportunistic breeders with no regular seasonal pattern of reproduction. Under good breeding conditions, nearly all females have one running offspring and one attached to a teat in the pouch. Under poor breeding conditions, females experience embryonic diapause. The gestation period is about 34 days and the pouch life ranges from 237-269 days. Strahan,1995; Tyndale-Biscoe, 1973; Thomas, 1888; Nowak, 1991

  • Average number of offspring
    1
    AnAge
  • Average gestation period
    32 days
    AnAge
  • Average birth mass
    0.703 g
    0.02 oz
    AnAge
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    547 days
    AnAge
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    670 days
    AnAge

Lifespan / Longevity

Behavior

One of the most unusual characteristics of wallaroos is that their behavior is very well adapted for survival in arid environments. Temperatures in the desert can reach as high as 120 F, yet wallaroos are able to survive. They have several ways in which they thermoregulate their body temperatures. When heat is excessive, they pant to induce evaporative cooling. They also excavate a hole near or under rocks and stunted trees. In the hole, they lie in a upright position, very alert and difficult to approach. They prefer rocky terrain because shade from rocks is the primary source of protection from the desert heat. They rarely forage more than 200 m from a rock shelter. To minimize water loss and reduce energy lost in thermoregulation, they venture from their shelters and forage in the evening. Wallaroos can survive on minimal nutrients and do not need to forage great distances or at great speeds for nutrient rich plants. They lead sedentary and solitary lives. Little is known of territorial or social behavior. However, a most interesting question is whether or not the cave refuges are claimed and defended as territory (Strahan). If an individual feels threatened or disturbed it utters a loud hissing sound, followed with exhalation. It also makes a distinct 'cch-cch' sound. Strahan, 1995; Thomas,1888; Warneke,1995.

Communication and Perception

Food Habits

Wallaroos are herbivores that do not require much water or highly nutritious foods. They drink less frequently than most species in the family and eat foods that have lower nutritional value. They mainly feed on spinifex, soft grasses, shrubs, herbs and low protein/ low fiber grasses. In the spring they graze on grass inflourescences and forbs. Strahan, 1995; Tyndale-Biscoe, 1973.

  • Plant Foods
  • leaves

Economic Importance for Humans

Economic Importance for Humans: Positive

Wallaroos are vwell adapted to arid environments. Aside from their behavioral adaptations, wallaroos are interesting to scientists because of their physiological adaptations. Wallaroos have a very efficient excretory system that recycles nitrogen and urea to make a very concentrated urine. This physiological adaptation can provide scientists with much information about evolution of physiological characteristics. Tyndale-Biscoe, 1973; Warneke, 1995.

  • Positive Impacts
  • research and education

Conservation Status

In Victoria, wallaroos are in urgent need of protection. Due to their isolation, they are vulnerable to factors such as predation and human land development. In Victoria they are classified as rare. In all other areas that are known to contain wallaroos, however, the populations are abundant. Warneke, R.M. 1995. Mammals of Victoria: Distribution, Ecology and Conservation. Oxford University Press, Australia. 189.

Other Comments

Macropus robustus was described by Gould in 1839. One interesting aspect of wallaroos is what they choose as more important: water or shelter. In an experiment, scientists placed water tanks near rocky terrain and in open flat areas. They observed that hardly any visited the water tanks placed in the open flat areas, but they did frequent tanks near the rocky shelter. Another interesting result was that the water tank near the shelter attracted only 72% of wallaroos in that area; these were predominantly lactating females. This study showed that wallaroos placed shelter over free water and even when given the opportunity to obtain free water, they did not do so unless necessary. Strahan, 1995

Glossary

Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

diurnal
  1. active during the day, 2. lasting for one day.
endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

folivore

an animal that mainly eats leaves.

herbivore

An animal that eats mainly plants or parts of plants.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

saltatorial

specialized for leaping or bounding locomotion; jumps or hops.

scrub forest

scrub forests develop in areas that experience dry seasons.

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

year-round breeding

breeding takes place throughout the year

References

Dixon, Joan and Huxley, Linda. 1985. Mammals and Fishes of Northern Australia. Thomas Nelson, Australia. 272.

Nowak, Ronald. 1991. Walker's Mammals of the World (vol. 1). Johns Hopkins University Press, Baltimore, MD. 489.

Strahan, Ronald. 1995. Mammals of Australia. Chatswood, N.S.W.: Reed Books 347-9.

Thomas, Oldfield. 1888. Catalogue of the Marsupial and Monotremata in the collection of the British Museum (Natural History). Order of Trustees, London, England. 22.

Tyndale-Biscoe, H. 1973. Life of Mammals. American Elsevier Publishing Company, Inc., New York, NY. 340.

Warneke, R.M. 1995. Mammals of Victoria: Distribution, Ecology and Conservation. Oxford University Press, Australia. 189.

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