Donkeys were brought to Australia from 1866 for use as pack and haulage animals.Up until that point, the Australians had been using the horse as their main mode of transportation. However, problems arose when the horses used in transportation began to become sickened by some of the native poisonous plants. When donkeys proved to be invulnerable to the plants that were making the horses sick, more donkeys were brought in. Escape was common because of the lack of fences, and there were reported herds of donkeys by the 1920s. In western Australia in 1949, there were enough donkeys for them to officially be declared a pest. There were almost 5 million feral donkeys in Australia in 2005.