Introduced Species
Affecting the California Red-Legged Frog

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Introduction of exotic predators was another cause for the 70 percent reduction in the California Red-Legged Frog population. Since the early 1900’s many different species have been introduced for various reasons, but some of the reasons, particularly the complex interconnections are unknown. Two of their major predators are the mosquitofish and the bullfrogs.         Introduced exotics of importance were aquatic vertebrates and invertebrates with a high probability of being efficient predators on one or more of the life stages of the California Red-Legged Frogs, namely; bullfrogs, red swamp crayfish, signal crayfish, and various species of fishes but especially basses, catfishes, sunfishes and mosquitofish (Jennings, Hayes and Holland 1992). Mosquitofish         With the introduction of these species it caused a massive decline in the California Red-Legged Frog population because they preyed on the frog. Unfortunately, most came from the East Coast of the United States and once introduced to California, did not have any known predators to keep their populations from expanding. Therefore, their interaction in the California Red-Legged Frog habitat was negative because each species found the frog to be palatable and an easy catch.