Opuntia in shallow, loose soils, such as on mountain slopes. "Opuntia" spreads into large clonal colonies, which contribute to its being considered a noxious weed in some places. Animals that eat "Opuntia" include the prickly pear island snail and "Cyclura" rock iguanas. The fruit are relished by many arid land animals, chiefly birds, which thus help distribute the seeds. "Opuntia" pathogens include the sac fungus "Colletotrichum coccodes" and Sammons' Opuntia virus. The ant "Crematogaster opuntiae" and the spider "Theridion opuntia" are named because of their association with prickly pear cacti. Like most true cactus species, prickly pears are native only to
Opuntia dulcis Opuntia dulcis Opuntia dulcis has been described as a variety of, and is confused with, "O. phaeacantha". However, "O. dulcis" is a larger plant with ascending branches, to 2 ft (exceptionally 4 ft). While it is a larger plant, immature specimens of O. dulcis may overlap in size with O. phaeacantha. "Opuntia dulcis" resembles "O. engelmannii" in some ways but does not become as erect or large as that species. Also, the spines of "O. dulcis" are finer than those of "O. engelmannii". "O. dulcis" is found across the deserts of the southwestern United States and northern Mexico. It is