Rat poison can kill many other types of small mammals in addition to rats and mice. It is a rodenticide that can be toxic to other animals such as porcupines, squirrels, woodchucks, chipmunks and beavers. It is also dangerous to cats, dogs and birds.
Many types of rat poison are categorized as anticoagulants, meaning they prevent the blood from clotting when ingested. Because the bodies of mammals are biologically similar, the poison has a similar effect. Rat poison is particularly dangerous to wildlife, such as hawks or owls that prey on rats and mice that have ingested the poison. These animals suffer even greater toxicity that builds up over time that is known as secondary poisoning.