Overpopulation in domestic animals
The phenomenon of overpopulation in domestic animals refers to the surplus of domestic animals, such as cats and dogs, and exotic animals. In the United States alone, between 5-7,000,000 animals are brought to shelters each year. 3-4,000,000 of those animals are subsequently euthanized. This is sometimes attributed to the fact that most shelters do not have the resources for the long-term care of these animals. As a result, most humane societies, animal shelters and rescue groups urge animal caregivers to have their animals spayed or neutered to prevent the births of unwanted and accidental litters.
Effects upon animals
Unwanted dogs and cats may have been acquired from any source. Large numbers of animals are placed in shelters by pet owners each year for reasons such as moving, allergies, behavioral problems, and lack of time or money. Another common reason for surrendering a pet is because of milestones, like marriage or the birth of a new baby.
One contributing factor in domestic animal homelessness is the cultural preference for young, purebred, animals. Many people who prefer purebred animals choose to purchase them, often at significant cost, from breeders. One reason some owners choose to purchase a pet through a breeder or store is because people know what size and characteristics the animal will eventually have. This is not often possible with puppies acquired at a shelter. It should be noted, however, that approximately 25% of the dogs who enter animal shelters are purebred.
Recognizing the high demand for purebred animals, some people choose to engage in backyard breeding or operate puppy mills. This practice, where operators breed purebred animals for profit, is often without concern for the health or welfare of the animals involved. These animals may be sold through pet stores or directly from the breeders themselves.
Additionally, individuals seeking purebred animals may not realize that a homeless animal adopted from a shelter can have many advantages: often the shelter will have performed all necessary veterinary procedures, such as spaying or neutering, vaccination, deworming, microchipping, etc. Also, the personality of a kitten or puppy is not always an indicator of how the animal will behave in adulthood. Many shelter animals have reached adulthood and their personalities are apparent, allowing the would-be caregiver to select an animal with a personality that suits them. However, disease issues should be considered with shelter animals. Some shelter animals are transported to Northern states where there is no overpopulation problem. Such animals may be incubating disease or have parasites. Animals without a documented history may also have behavioral issues.
There are several nonprofit organizations that are attempting to solve the problems associated with the overpopulation of animals, like euthanasia and high costs, through spay and neuter services.
- American Society for the Prevention of Cruelty to Animals (ASPCA) 
- American Humane Association 
- Sante D'or Foundation in Southern California 
- Pet Project Rescue in the Twin Cities in Minnesota 
- AnimalKind in North Carolina 
- Project CatSnip in Georgia
Dealing with a population of unwanted domestic animals is a major concern to animal welfare and animal rights groups. Domestic animal overpopulation can also be an ecological concern. It is also a financial problem: capturing, impounding and eventual euthanasia costs taxpayers and private agencies millions of dollars each year. Unwanted pets are also commonly released to the wild, sometimes contributing to severe damage to ecosystems (e.g., the effect of introduction of exotic snakes to Florida's Everglades).
- No-kill shelter: an animal shelter that does not euthanize animals due to overpopulation
- Animal shelter
- Cat colony
- The Humane Society of the United States. "HSUS Pet Overpopulation Estimates : The Humane Society of the United States". Humanesociety.org. Retrieved 2012-07-24.
- "Pet Overpopulation". Americanhumane.org. Retrieved 2012-07-24.
- "Puppy Mills : The Humane Society of the United States". Humanesociety.org. Retrieved 2012-10-16.
- "ASPCA Launches National Relocation Program for Shelter Animals". Prweb.com. 2011-05-12. Retrieved 2012-10-16.
- "The American Society for the Prevention of Cruelty to Animals". ASPCA. Retrieved 2012-07-24.
- "Sante D'Or Foundation - An Atwater Village Animal Rescue —". Santedor.org. 2011-11-16. Retrieved 2012-07-24.
- "Pet Project Rescue". Pet Project Rescue. 2012-05-08. Retrieved 2012-07-24.
- "**". Animalkind.org. Retrieved 2012-07-24.
- "Project Catsnip — Experts in Feline Spay-Neuter". Projectcatsnip.com. Retrieved 2012-10-16.
- "New Research Exposes High Taxpayer Cost For ‘Eradicating’ Free-Roaming Cats". Prweb.com. Retrieved 2012-10-16.
- National Council on Pet Population
- ASPCA Official Website
- Addressing the Problem of Pet Overpopulation: The Experience of New Hanover County Animal Control Services
- American Humane Association on pet overpopulation
- AnimalKind in NC
- Chesley V. Morton v. Georgia Department of Agriculture and Tommy Irvin in his Official Capacity as Commissioner