The Western grey kangaroo is one of the biggest and most abundant of kangaroos, and can be told apart from its close relative, the Eastern grey kangaroo by the browner fur, darker color of the head, long dark ears which are almost hairless on the backs, and in some of them, a blackish patch at the elbow. The male is much bigger than the female, and has longer and more muscular forearms and shoulders, heavier claws on its forepaws, and thicker skin over its belly, which helps in absorbing the impact of kicks when fighting. The adult male has a strong, curry-like smell, which has given it the common name ‘stinker’.
The Western grey kangaroo inhabits the southern region of Australia including western Victoria, southern Queensland and southern New South Wales. It is also found on Kangaroo Island off Australia's southern coast. They inhabit woodlands, open forests, open grassland areas and coastal heathland. They are sometimes found in areas near cities and on golf courses.
These kangaroos form social groups or "mobs": small family groups where an adult female is the matriarch, with other females in the group, as well as young. Male kangaroos compete for dominance of these groups, with the strongest becoming the leader. During the mating season, young males can form male-only groups that are separate from the mobs. More mature males sometimes have loose associations with other male kangaroos which vary from one year to another. Old male kangaroos are usually solitary. This species, in the east of its range, may mix with mobs of eastern grey kangaroos, although they usually exist separately, as they prefer different habitats. The Western grey is most active from the late afternoon until early morning, and it rests during the day under trees and shrubs.
These kangaroos are polygynous, the males competing during the breeding season for females. During such "boxing" contests, the kangaroos lock forearms and attempt to push one another over. Typically, only the dominant male of the group will mate. These kangaroos can breed year round, but there is a peak in reproductive activity in spring and summer. Gestation lasts for only 30 days, and the tiny newborn climbs up by itself through its mother's fur to the pouch, where it will remain to be nursed. Most of its development takes place in its mother's pouch, and the young emerges after about 9 months, suckling until it is about 17 months of age. Female western greys become sexually mature at about 20 to 36 months, males at about 20 to 72 months.
Western grey kangaroos are still abundant through the majority of its original range, with the population possibly even expanding. However, this species may be threatened by the spread of agriculture, particularly where the land has undergone clearance for cereal crops, and it may also have gone from many areas densely populated by people. Western greys are very numerous in some regions and it is considered as a pest species, seen as a competitor for water pasture with domestic cattle and sheep. The kangaroos are culled under license every year, to prevent damage to pasture and crops. Additionally, regulated commercial hunting is allowed for meat and skins, the skins providing a high-quality, long-lasting leather. There is discussion about whether populations of kangaroo can sustain the present hunting levels, particularly in the face of drought and increased human habitat modification.
According to the Australian Government Department of the Environment, the total population size of the Western grey kangaroo is 2,348,393 individuals. Today western greys’ numbers are increasing and they are classified as least concern (LC) on the IUCN Red List.
Western grey kangaroos control the growth of vegetation by feeding on forbs and grasses.