They have natural prey-chasing, capturing, and killing instincts. As a result of this and the large numbers of them in Florida, cats and dogs have the potential to severely impact local wildlife populations. In addition to reducing populations of species and limiting the number of prey items for native predators, free-ranging pets can cause other problems. For example, they serve as important reservoirs for human and wildlife diseases like ringworm, toxoplasmosis , leptospirosis , distemper, and rabies. They may be an important factor in introducing these diseases into susceptible wildlife populations.
Dogs kill turtles and other wildlife.
My own Australian silky terrier killed a young blue jay, and several frogs and lizards in my backyard. Exotic snakes and other pet predators can also have local impacts if released into the wild. But the pet that is by far the most devastating on wildlife populations is the furry feline. The instinctive hunting and killing behavior of cats is extensively documented. Unlike wild predators that kill to eat, cats kill impulsively even when they are not hungry.