A pet or companion animal is an animal kept for companionship and enjoyment, as opposed to livestock, laboratory animals, working animals or sport animals, which are kept for economic reasons. The most popular pets are noted for their loyal or playful characteristics, for their attractive appearance, or for their song. Pets also generally seem to provide their owners with non-trivial health benefits; keeping pets has been shown to help relieve stress. There is now a medically-approved class of "therapy animals," mostly dogs, who are brought to visit confined humans. Walking a dog can provide both the owner and the dog with exercise, fresh air, and social interaction.

Koko the gorilla is one of few examples of a non-human animal which has had an explicit pet. Using sign language, she requested a cat; her first pet was a kitten named All Ball, to which she was reported to be quite attached and mourned for several days after the cat escaped and was killed by a car.

While in theory any animal might be a pet, in practice only a small number of species of mammals (especially dogs and cats) and other small animals, such as birds, fish, or lizards, are practical. One reason for this is that large animals are not able to fit inside small dwellings.

In general, a pet must either be small enough (or easily controlled) for his or her undesirable behavioral tendencies to be negligible, or the animal must be actually domesticable. Examples of the former are such animals as fish (including carnivorous ones such as piranha), chickens, invertebrates or small mammals.

A few animals are sufficiently capable of adapting to human interaction to be considered domesticable. Dogs ("man's best friend") are considered to be a classic example of domesticated animals normally suited to being pets. Domestic dogs are quite similar to wolves, but their physical form and behavior are characteristically different, more than mere differences in size, coat, or coloring. Behaviorally speaking, characteristic changes in dogs due to domestication include a prolonged infancy, increased playfulness, and increased barking. Wolves are far less playful and vocal.

Many rodents—such as fancy rats, fancy mice, and Syrian hamsters—are commonly kept as household pets.

Such animals as reptiles are typically considered exotic pets. This may change in the future, as 'exotic' pet ownership is increasing rapidly. Some of these animals, such as green iguanas, large monitor lizards, and large birds, do not make suitable pets for the average person, as they require extensive housing and diet. They can also become quite aggressive if not regularly handled. Exotic mammals are also becoming increasingly more popular as pets. For example, the domesticated hedgehog has been selectively bred to the point where its physical characteristics no longer directly match its wild European and African counterparts.[citation needed] Individuals have occasionally run into legal trouble for keeping large exotic pets, both in rural estates and urban apartments. A few years ago, New York Police Department officers arrested a man who had kept large cats and an alligator in a small Manhattan apartment [4] Many animal species are difficult to handle and cannot be pets for the general populace. Raptors, such as eagles and falcons, must be handled very carefully to avoid attacks on their handlers; the sport of falconry is to a large extent ways of avoiding such outcomes, and so they are not really pets in the sense meant here. Large cats cannot become pets, as they do not reliably restrain their impulses (although cheetahs are an exception and have been kept as pets in the past). Nor do the large bears, for similar reasons. Small monkeys can be human companions, but they are notoriously unable to defer their curiosity which leads to much destruction. Raccoons also fit this example. They adapt easily to almost any environment, but resist domestication. One the other hand, several of the ferret and otter varieties can be human companions.

A pet can be acquired from a pet store, animal shelter, a breeder, and from private transactions, typically due to the giving away of extra newborns after the birth of a litter. See also pet adoption. Because of environmental and public safety concerns, some pets are illegal in many areas.

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Author's Bio: 

This definition is part of a series that covers the topic of Pets. The Official Guide to Pets is Lola Michelin. Lola Michelin, owner of the Northwest School of Animal Massage, has been a force in the field of animal massage for over 20 years. For more information about classes at the Northwest School of Animal Massage, visit www.nwsam.com or call toll-free 877.836.3703.

Additional Resources on Pets can be found at:

Website Directory for Pets
Articles on Pets
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Lola Michelin, The Official Guide to Pets