The kangaroo lives in groups of up to 15. The males compete for females during the breeding season. During these "boxing" contests, they would lock arms and try to push each other over. Usually, only the dominant male in the group mates. The gestation period is 30-31 days, after which, the baby Joey attaches to the teat in the pouch for 130-150 days.
There the matter rested for over 100 years, and it was not until 1917 that researchers realised that the "Forester Kangaroo" of Tasmania was in fact Macropus giganteus, the same Eastern Grey Kangaroo that was, and still is, widespread in the more fertile south-eastern part of the mainland. By 1971, it was understood that the Kangaroo Island species was the same as the kangaroos of southern Western Australia, and that this population extended through much of the eastern part of the continent as well. For a time, three subspecies were described, two on the mainland and one on Kangaroo Island. Finally, by the early 1990s, the current understanding emerged.
There are two subspecies of the Western Grey: Macropus fuliginosus fuliginosus of Kangaroo Island, and Macropus fuliginosus melanops, which has a range of different forms that intergrade clinally from west to east.
The Western Grey is not found in the tropical north or the fertile south-east of Australia, and the Eastern Grey does not extend beyond the NSW-South Australia border, but the two species are both common in the Murray-Darling Basin area. They never interbreed in the wild, although it has proved possible to produce hybrids between Eastern Grey females and Western Grey males in captivity.
The Western Grey Kangaroo is also referred to as a Black-faced Kangaroo, Mallee Kangaroo or Sooty Kangaroo.