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 their guns. 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.