In Australiarabbits are a serious mammalian pest and invasive species. They were introduced in the 18th century with the First Fleet, and became widespread after an outbreak caused by an 1859 release. Rabbits cause millions of dollars of damage to crops. Various methods in the 20th century have been attempted to control the population. Conventional methods include shooting and destruction of warrens, but these had only limited success. In 1907, a rabbit-proof fence was built in western Australia in an attempt to contain the rabbits. The Myxoma virus, which causes myxomatosis, was introduced into the rabbit population in the 1950s, and had the effect of severely reducing the rabbit population.