The grey kangaroo, sometimes known as the great grey, is one of the best-known of all kangaroo species, along with the similar-sized red kangaroo. Its closest relative is the western grey kangaroo (Macropus fuliginosus).
Distribution: Mainly in eastern Australia & Tasmania.
Habitat: Open forest.
Description: Small head, large ears; short, slim forelimbs but long, powerful hindlimbs. Long, strong tail. Colour is mainly grey with whitish underparts.
Size: Length: 1.5m weight: up to 91kg
Life-span: Up to 18 years.
Food: Mainly grass & leaves of shrubs.
The grey kangaroo, sometimes known as the great grey, is one of the best-known of all kangaroo species, along with the similar-sized red kangaroo. Its closest relative is the western grey kangaroo (Macropus fuliginosus). In total there are 55 species of kangaroo, wallaby & wallaroo belonging to the family Macropodidae (from a Greek word meaning 'big feet'). They are all similar animals but differ in size & build, from the large red and grey kangaroos to the rabbit-sized rat kangaroos. In general, a wallaby is simply a small species of kangaroo, having hind-feet measuring less than 25cm.
The grey kangaroo is a sociable animal by nature and lives in a band or mob. An average mob is made up of a mature male, two or three females with young and two or three young males. Many mobs often graze together. They feed mainly late at night and early morning, resting during the heat of the day. Kangaroos often graze alongside sheep and cattle, and, because they have teeth in both upper and lower jaw, unlike sheep which have teeth in only the lower, they can crop grass more closely than sheep. Kangaroos can also survive on poor quality grass and go without water for long periods.
Excellent eyesight, a good sense of smell and large, flexible ears, enable the kangaroo to quickly detect approaching danger. An alarmed kangaroo thumps the ground with its hind legs, rather like a rabbit does, to warn the rest of the mob.
When feeding and moving slowly, kangaroos balance themselves on their small front legs and strong tail, swinging the large hindlegs forward. They then bring their arms and tail up to complete the second stage of the movement.
If necessary, the grey kangaroo can travel fast, bounding along using only the two hindfeet with the tail held almost horizontally for balance. In this way, the kangaroo can leap over obstacles, and the length of a jump can be as much as 13.5 metres!
In the breeding season, usually spring and early summer, rival male kangaroos rear up on their hind legs and box to compete for a female. The joey (baby) is born after a gestation of 29 - 38 days. The grey kangaroo is a marsupial mammal, which means that the baby does not develop attached to a placenta inside the mother's uterus, but is born early and spends most of its development inside a pouch. When ready to give birth, the female leaves her mob, finds somewhere quiet and licks her pouch and birth canal clean. The tiny joey, pink and naked, measuring only 2.5cm in length and weighing 1g, is born headfirst and grasps its mother's fur with the claws on its forefeet. The mother offers no help at all. In about 3 minutes, it has dragged itself up to the pouch, entered it and clamped tightly to one of the four teats, which swells in the mouth.
The joey spends 300 days or more inside the pouch, growing very slowly for the first 3 months. After 15 weeks, faster growth begins when the mother's milk increases its fat and protein content. The joey continues to suckle for another 6 months after leaving the pouch; it can run about and jump easily in and out of the pouch.
Grey Kangaroos and Humans
The dingo, a wild dog introduced into Australia, is the only enemy of the kangaroo, except for humans. A natural predator used to be the Tasmanian wolf, but this has become extinct (although reports of sightings crop up from time to time).
A large kangaroo is well able to fight off several dingoes by rearing up on its tail and lashing out with its powerful hind feet. Full contact with one of these kicks can kill. However, a kangaroo has no defence against humans and his gun. The grey (as well as the red) has become a serious competitor with sheep because of its grass-eating habits, and this has made it unpopular with sheep farmers. The loss of natural enemies, the creation of wide areas of grassland and the ability of the kangaroo to breed throughout most of the year, has caused kangaroo numbers to increase to pest proportions. Farmers have erected thousands of kilometres of fencing to keep kangaroos off their pastures, but this is expensive and kangaroos can leap over or squeeze underneath fences. As a result, huge numbers of kangaroos are shot. Many cause accidents as they bound across roads at night, colliding with cars.
Despite heavy annual culling by farmers, there are more than 1.5 million grey kangaroos and, for the time being at least, there is no danger of extinction.
Image: Kanagroo (Grey) by John Schilling