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Shelter Dogs and Breed Identifications

By Claudia Kawczynska, October 2018, Updated August 2022

For shelter dogs, identification of breed mix and heritage can be a matter of life or death. This is particularly true for the thousands of dogs who—based on appearance—are labeled as “Pit Bulls” by shelter workers. However, in a recent study led by Lisa Gunter in the Department of Psychology at Arizona State University, it was determined that shelters inaccurately represent the breed heritage of three-quarters of dogs sampled.

The study, the largest reporting of breed heritage in sheltering to date, involved 919 dogs in the care of the Arizona Animal Welfare League & SPCA (AAWL) and the San Diego Humane Society (SDHS).

Luckily, as the researchers point out, “advances in canine genomics allowed the advent of commercial genetic breed testing, making possible the identification of component breeds within mixed breed dogs.” In addition to identifying the dogs’ breed heritage, the researchers also wanted to delineate their prevalent breeds and the impact of those breeds on the length of shelter stay. Finally, they wanted to test how well shelter staff could visually assess primary and secondary breeds.

DNA samples were collected from dogs admitted to AAWL and SDSH over a period of nine to twelve months. These samples–919 in all—were then analyzed using the Mars WISDOM PANEL™ test. The Mars DNA database from which the dogs’ breed signatures were identified was developed through the genotyping of more than 13,000 purebred dogs, according to the company. Each WISDOM PANEL DNA test report reveals breed signatures going back three generations.


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The results were illuminating. In the 919 dogs tested:

  • 186 breeds and varieties were identified.
  • 4.9% were identified as purebred (45 dogs, representing 22 breeds).
  • 18.7% were identified by a single breed, two specific breeds (like Labradoodles) or one breed plus “mixed.”
  • 81.3% had at least two identifiable breeds “plus ‘mixed’ in their three-generational breed heritage.”
  • 26.6% of dogs at AAWL and 30.7% of dogs at SDHS had at least one breed classified as “Pit Bull-type” (American Staffordshire Terrier, Staffordshire Bull Terrier).
  • The second most common breed at both shelters was Chihuahua (24% at AAWL,  17.8% at SDHS). Poodle came in third (15.3% at AAWL, 14.6% at SDHS).

Even though “Pit Bull-type” breeds and Chihuahuas are the most widely found in shelters, the WISDOM PANEL test revealed that the amount of these breeds in any given dog was low to moderate.

One of the study’s most important conclusions: “Results suggest that the method of description used in shelters does not accurately represent the breed heritage of three-quarters of dogs sampled. Instead, most dogs comprised on average, three breeds, with some dogs having up to five different breed signatures identified at the great-grandparent level.”

Recognizing the limitations of visual identification and the impact breed has on adoption rates, some shelters have actually removed breed labels from their dogs’ descriptive material (see reporting by Linda Lombardi). But the study’s researchers suggest that perhaps just “acknowledging the inherent breed complexity of homeless dogs in animal shelters” might also be effective.

Not surprisingly, the study also found that Pit Bull-type dogs wait the longest to be adopted. Researchers suggest using genetic testing to more fully represent the variety of breed heritage of today’s shelter dogs, and believe that “using DNA-derived breed heritage could help shelters better infer the influence of breed upon outcomes like adoption, length of stay and even adopter satisfaction.”