A pet is an animal kept for companionship and enjoyment or a househeld animal, 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 to those who like having animals around. 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.
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.
Over the course of fifty years, Russian scientists also domesticated silver foxes, resulting in the Tame Silver Fox. While the number produced was extremely small, they have been sold as pets, and they prove that domestication of canids other than wolves is possible.
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. 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 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. On 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.
Condominium associations and rental properties often ban animals because of the smells and noise the animals create.
According to a 2007-2008 Pet Owners Survey
Number of U.S. Households that Own a Pet (millions)
Freshwater Fish 14.2
Saltwater Fish .8
Small Animal 6.0
Total Number of Pets Owned in the U.S. (millions)
Freshwater Fish 142.0
Saltwater Fish 9.6
Small Animal 24.3
In Canada the latest survey done by Colin Siren of Ipsos Reid it is estimated that there are 7.9 million cats and 5.9 million dogs in Canada. The survey also shows that 35% of Canadian households have a dog, while 38% have a cat, which is consistent with other surveys conducted around the world.
Animal protection advocates call attention to the pet overpopulation "crisis" in the United States. According to the Humane Society of the United States, 3-4 million dogs and cats are euthanized each year in the country and many more are confined to cages in shelters. This crisis is created by nonneutered animals (spayed/castrated) reproducing and people intentionally breeding animals. A particularly problematic combination of economic hardship combined with a love of animals contributes to this problem in parts of the rural United States. In an average year, a fertile cat can produce three litters of kittens, with up to 4 to 6 kittens in each litter. Based on these numbers, one female cat and her offspring could produce up to 420,000 cats over a seven year period if not spayed or castrated. There are also major overpopulation problems with other pet species, such as birds and rabbits. Local humane societies, SPCAs, and other animal protection organizations urge people to neuter their pets and to adopt animals from animal shelters instead of purchasing them from breeders or pet stores.
Moving with pets takes time and planning. Moving with a cat or a dog is not impossible, but many people still choose to give their animals up to animal shelters instead of taking them to a new home. This is another big reason for pet overpopulation.
Different pets require varying amounts of attention and care; for example, cats have lower maintenance requirements than dogs.