African Clawed Frogs Invade California Waters

Just when you thought it was safe to enter California waters, yet another killer rears its ugly head. But instead of a fishy Hollywood star crushing through anglers' boats and patrolling popular beaches with a taste for human, the African clawed frog is a real threat that lurks in freshwater streams, rivers, and ponds killing off local wildlife.

Native to the Cape region of South Africa, this largest of the clawed frogs was imported to the United States in the aquarium trade as well as for scientific study. Xenopus laevis is the primary amphibian subject for scientific experimentation for good reason: it's a hardy species with strong resistance to disease. Although a freshwater organism, X. laevis can tolerate water nearly half as salty as seawater, and can live in a wide range of pH and temperatures.

Unfortunately, these same qualities make the frog a menace as it spreads to new frontiers. Escaping from laboratories and let loose by pet owners with a change of heart, X. laevis takes over local waterways, eating native amphibians and out-competing others for invertebrates, small fishes, and other prey. California has one of the worst African clawed frog infestations, second only to Santiago, Chile, where the clawed killer inhabits nearly every body of water.

 

African Clawed Frog, Xenopus laevis.
Photo: John H. Tasjian, CAS Special Collections

The name African Clawed Frog comes from the fact that the toes of the front feet are not connected by webbing.
Photo: John H. Tasjian, CAS Special Collections