When dogs are in shelters, they are typically assigned breed labels based on their appearance. These labels can greatly influence how long it takes for shelter dogs to be adopted, primarily because of the various behaviors that are associated with different breeds.
Using genetic testing, a team at Arizona State University (ASU) set out to investigate the accuracy of breed labels and how they may affect shelter dogs. The researchers obtained DNA from more than 900 dogs located in two shelters in California and Arizona.
The experts used commercially available canine DNA tests from the Wisdom Panel for genetic testing. These kits include a small brush for collecting cells from the dog’s cheeks and gums, which are sent to a lab to be processed.
The DNA tests revealed that the three most common breeds in both shelters were the same, including the American Staffordshire Terrier, Chihuahua, and Poodle.
“The level of genetic diversity in the shelter dogs exceeded our expectations: we found 125 distinct breeds,” said study co-author Lisa Gunter. “We also found that just 5% of the shelter dogs were purebred, even though it is commonly assumed that up to a quarter of dogs in shelters are purebred.”
The DNA tests provided information about three generations of ancestors for each dog. Most of the dogs had signatures of three different breeds, while some dogs had genetic characteristics of up to five breeds.
“Breed identification has quite an outsize role in people’s perceptions of dogs,” said study co-author Clive Wynne. “’What breed is he?’ is often the first question people ask about a dog, but the answer is often terribly inaccurate.”
With such a high level of genetic diversity among shelter dogs, it can be difficult for shelter staff to assess their breeds. Staff at the San Diego Humane Society (SDHS) used the physical appearance of dogs, as well as descriptions from American Kennel Club breed identification guides, to assign dogs a primary and a secondary breed.
By comparing the genetic information that they obtained from the dogs, the researchers found that the SDHS staff identified either the primary or the secondary breeds with 67-percent accuracy. However, when both breeds were taken into consideration, the staff’s level of accuracy fell to just 10 percent.
Breed labels can have negative consequences for shelter dogs. For example, a study published previously in PLOS ONE found that dogs who were labeled as pit bulls stayed in shelters over three times as long waiting to be adopted. The current study found that this was also the case at the SDHS, where dogs labeled as pit bulls remained for an average of three times longer compared to other breeds.
“The genetics of behavior is so complex that a dog who is a cross of two breeds might not behave much like the typical members of either of its parents’ families,” said Wynne. “Then you have a situation where breed-typing is worse than stereotyping members of our own species. Breed labels would be better dropped altogether.”
“Shelter dogs are interesting and complex genetically,” added Gunter. “They really are individuals, and labeling them with a single breed can minimize their uniqueness.”
The study is published in the journal PLOS ONE.