Most generalized animal shelters and dog rescues have plenty of terrier mixes, since they are some of the most common dogs found in the United States. In some areas 80 to 90 percent of the shelter population consists of mixed breed dogs, though not all of these are descended from terriers.
The terrier group of purebred dogs, according to the American Kennel Club, is a lively and active working group, originally bred to hunt vermin such as rats, mice and squirrels in England and Ireland. They are known for their feisty personalities and wiry coats, and often require firm, active owners.
Cross-breeding a terrier, intentionally or unintentionally, can work to mellow or mitigate the stronger aspects of the breed's personality while retaining the friendly and loyal nature for which terriers are valued. It can also exacerbate the problematic aspects while adding new ones from nonterrier breeds, such as the poodle's neurotic nature.
People seeking a terrier mix should contact local humane societies and animal shelters to see what they have available for adoption. They also might consider contacting local rescues, even breed-specific ones, as rescues sometimes end up with mixed-breed dogs or dogs that do not fit their core breed. Rescues specifically aimed at "mutts," or nonpurebred dogs also exist, such as Mutt Love Rescue in Fairfax, Virginia.