Bullfrogs are an invasive species in Puerto Rico. Bullfrogs were accidentally introduced starting in the 1900s in Colorado and California. Fishermen went out fishing and took their catchings back home, some had bullfrogs in their nets still alive. They have been introduced by pet owners who no longer wanted them. Some pet owners bought bullfrogs to control pests near their homes. The impact of bullfrogs being introduced has negative outcomes. Because of their diet, they can decrease populations of other frogs. Bullfrogs have been blamed for making the California Red-legged Frog a near-threatened species. They have also been blamed for many other amphibian extinctions in California.