Macropods, feral goats, sheep and cattle. 2. Equivalency in what and where they eat.
The extent to which sheep, cattle, feral goats, red kangaroos, western grey kangaroos, euros and eastern grey kangaroos are equivalent in their use of the Australian southern rangelands is partly dependent on the extent to which their diets and foraging areas overlap. These herbivores all eat large amounts of green annual grasses, ephemeral forbs and the green leaf of perennial grasses when they are available. Overlap in use of these forages by all seven herbivores is concurrent and high. As the abundance of these preferred forages declines, sheep, cattle and feral goats consume increasing amounts of mature perennial grasses and chenopod and non-chenopod perennial forbs. Red kangaroos and western grey kangaroos continue to graze mature perennial grasses longer than sheep, cattle and feral goats, and only switch to perennial forbs when the quantity and quality of perennial grasses are poor. Consequently, overlap in use of perennial forbs by sheep, cattle, feral goats, red kangaroos and western grey kangaroos is sequential and moderately high. When palatable perennial forbs are eaten out, the diets of all herbivores except feral goats comprise predominantly dry perennial grass, and overlap is again concurrent and high. In comparison, feral goats have higher preferences for the browse of a wide range of shrubs and trees, and switch to these much earlier than the other herbivores. When perennial grasses and perennial forbs become scarce, sheep, feral goats and cattle browse large shrubs and trees, and overlap is sequential and high. If climatic conditions remain dry, then red and western grey kangaroos will also browse large shrubs and trees, but overlap between them, sheep, cattle and goats is sequential and low. In contrast to the other herbivores, the diets of euros and eastern grey kangaroos are comprised predominantly of perennial grasses, regardless of climatic conditions. As for diet composition, concurrent overlap in foraging distributions of sheep, cattle, feral goats and the four species of macropods is often low. However, over periods of several months to two or three years, as climatic conditions change, overlap in foraging distributions is sequential and high. While equivalency in what and where these herbivores eat is not quantifiable, it appears to be high overall. This is particularly so for perennial grass, which is the dominant forage for herbivores in the southern rangelands.