An ornamental animal is an animal kept for display or curiosity, often in a park. A wide range of mammals, birds and fish have been kept as ornamental animals. Ornamental animals have often formed the basis of introduced populations, sometimes with negative ecological effects, but a history of being kept as ornamental animals has also preserved breeds, types and even species which have become rare or extinct elsewhere. This article does not cover animals kept in zoos, wildfowl collections or aquaria.