of the role predation can play in a community involves the introduction of prickly pear cactus to australia in the nineteenth century, by 1925 occupying 12 million hectares of rangeland in an impenetrable morass of spines that made cattle ranching difficult. to control the cactus,a predator from its natural habitat inargentina, the moth CC, was intorduced beginning in 1926. by 1940, cactus populations had been decimationed, and it now generally occurs in small populations.