Hybrid African clawed frog, Silurana sp. Native to sub-Saharan Africa, clawed frogs were exported worldwide in the 1940s and 1950s for use in human pregnancy tests, and were later sold widely as pets. Feral populations are now established in many countries, including the United States, where they are a threat to native amphibians and fish. Especially large populations exist in California, preying on endangered California red-legged frogs, Rana aurora draytonii, and endangered unarmored threespine sticklebacks, Gasterosteus aculeatus williamson. Recent evidence suggests the chytrid fungus that is currently decimating frog populations around the world originated in Africa and was spread by these frogs.