Feral goats are herbivores. That means that they only eat plants. Goats, like Camels, will eat any plants and just about any part of the plant too, but feral goats tend to go for the most nourishing plants, therefore leaving the plants that other animals won’t eat. An example of this is the fact that goats and rabbits have eaten the Phillip Island Hibiscus (Hibiscus insutaris) to virtual extinction. Only 2 clumps of this plant now remain. This type of Hibiscus was found only on Phillip Island, which is just off the coast near Melbourne, Victoria. In the future, cases like this could happen as a result of overgrazing. Feral goats have a massive contribution to overgrazing.
Goats are normally found in areas that also inhabit other grazing animals, including wallabies, kangaroos, and domesticated livestock. The rare Yellow-footed Rock-wallaby was nearly extinct due to the massive overlap of the diet and habitat with the feral goats. Since feral goat numbers have been heavily culled in the areas that the Yellow-footed Rock-wallaby inhabits, these marsupials have made a comeback.
If the event that exotic disease would reach the Australian shores, feral goats would be prime carriers and act as disease reservoirs for many diseases, for example bovine foot-and-mouth disease, which devastated livestock in Great Britain and Europe around the turn of the last century costing billions of dollars; rabies, which can effect humans and most animals; blue tongue; rinderpest; and scrapie.
Other diseases already in Australia that feral goats could pass onto domesticated cattle and ultimately cost the Australian Economy billions of dollars is leptospirosis, hydatids, Q Fever, brucella melitensis, tetanus, blackleg, pulpy kidney and several types of parasitic worms that dwell within the gastro-intestinal area.