An animal born singly, rather than one of a multiple birth.

Animals that are no longer being raised with their siblings can also be considered singletons. Often they can be split for any of the following reasons:

• Old enough to go into separate foster homes.
• Animal was too ill to be placed in a foster home and is placed separately after healing.
• Siblings were too ill and did not make it.
• Litter is old enough that rest of siblings were already adopted.