An animal rescue group or animal rescue organization is a group dedicated to pet adoption. These groups take unwanted, abandoned, abused, or stray pets and attempt to find suitable homes for them. Many rescue groups are created by and run by volunteers, who take animals into their homes and care for them — including training, playing, handling medical issues, and solving behaviour problems — until a suitable permanent home can be found. Rescue groups exist for most pet types (reptile rescue, rabbit rescue or bird rescue), but are most common for dogs and cats. For animals with many breeds, rescue groups may specialize in specific breeds or groups of breeds. For example, there might be local Labrador Retriever rescue groups, hunting dog rescue groups, large-dog rescue groups, as well as general dog rescue groups. Animal rescue organizations have also been created to rescue and rehabilitate wild animals, such as lions, tigers, and cheetahs; a job which is normally shared or backed by zoos and other conservation charities. These animals are normally released back into the wild where possible, otherwise they will remain in captivity and may be used in breeding for an endangered species. Widely recognized as an umbrella organization for animal rescue groups, Petfinder.org is an online, searchable database of more than 13,000 shelters and adoption agencies across the United States, Canada and Mexico. The American Kennel Club maintains a list of contacts, primarily within breed clubs, with information on breed rescue groups for purebred dogs in the United States. Animal shelters often work closely with rescue groups, because shelters that have difficulty placing otherwise healthy and pet-worthy animals would usually rather have the animal placed in a home than euthanized; while shelters might run out of room, rescue groups can often find volunteers with space in their homes for temporary placement. Some organizations (such as Old Dog Haven) work with older animals whose age would likely cause them to be euthanized in county pounds. Each year, approximately 3-4 million cats and dogs are euthanized in shelters due to overcrowding and a shortage of foster homes. In the United Kingdom, both shelter and rescue organisations are described using the blanket term rescue, whether they have their own premises, buy in accommodation from commercial kennels, or operate a network of foster homes, where volunteers keep the animals in their homes until adoption. Kennels that have a council contract to take