A Companion Animal is considered to be an effective means of lowering blood pressure, heart-rate, and general feelings of anxiety. The most popular companion animals (or "pets" as they are commonly called) are mammals with soft fur that the owner can stroke. However, any animal that can be caught and caged is fair game to be made into a companion.
Some people prefer non-mammalian pets, such as fish or turtles, which demand less care. Others opt for the rare and exotic.
Companion animals have long been a fixture in the nuclear family unit. While the domesticated dog (Canis lupus familiaris) was once the most common pet, the domesticated cat (Felis catus) has supplanted the dog in many homes. This is probably the result of human overpopulation, and the necessary down-sizing of all aspects of modern life. Plus, you can get away with ignoring a cat for longer periods of time.
Although some companion animals may be found as ingredients in chow mein, chimichanga, or 'game' pie; many are chained (or otherwise imprisoned), kept in steel cages in humane hostels (for up to one week1), allowed to roam wild as free-range pets, or simply ignored.