Harley a pit bull type dog

DNA Study Shows Pit bulls Regularly Misidentified at Shelters

Shelter dogs are often labelled incorrectly as ‘pit bull’ by shelter workers. These mistaken identities could have tragic consequences for the dogs in question. A University of Florida study found as many as 1-in-3 shelter dogs are incorrectly identified as pit bulls by experts. 1

Pit bull is not a breed as such, more a type of dog. Lawfully, pit bull describes any dog that is an American Pit Bull Terrier, American Staffordshire Terrier or Staffordshire Bull Terrier. A mixed-breed dog with obvious characteristics or traits of these breeds can also be described as a pit bull.

The breeding or ownership of pit bulls is unlawful in many US states, and banned in the UK under the Dangerous Dogs Act 1991. Because of this, the consequences of a dog being mistaken for a pit bull could be dire.

“Identification of dogs as pit bulls can trigger an array of negative consequences, from the loss of housing, to being seized by animal control, to the taking of the dog’s life” – Julie Levy, professor of shelter medicine at UF College of Veterinary Medicine

The study shows that when expected to determine the breed of a dog on appearance alone, mistakes are made, even by experts. This practice is frequently the case at shelters and also by veterinarians. The amount of errors made shows that visual identification of pit bulls is unreliable. Visual breed assessment has been shown to be incorrect more often than not. 2

Pit Bull Identification Study

The study, undertaken by the University of Florida attempted to show the inaccuracy of pit bull identification. The study consisted of 12 shelter staff and 4 veterinarians across 4 different shelters. All participants had a minimum of 3 years experience in a shelter environment.

Each participant had to assign a breed to each of the 120 dogs. The decision had to be made on visual assessment alone. They were given no predefined choices or breed lists and had the option of listing a dog as mixed breed if necessary. No conferring between staff, or accessing reference materials was allowed.

Each of the 120 dogs had DNA profiles created for them, generated from blood samples. At the end of the study, the staff assessments were compared to the DNA profiles to determine their accuracy.

Comparing Results to DNA Profiles

The table below summaries the number dogs identified as pit bull or ‘not pit bull type’ by the study participants and whether this matched the DNA results. Of the 95 dogs that were not pit bull types, 36 were identified as pit bulls by at least one of the assessors. One in five dogs with genetic pit bull heritage were missed by all shelter staff at the time of the study.

Table 1. Summary of visual assessment vs. DNA profile.
DNA Profile – ‘Pit Bull’ DNA Profile – Not ‘Pit Bull’
Visual Assessment – ‘Pit bull’ 20 36
Visual Assessment – Not ‘Pit Bull’ 5 59
Total 25 95

The Outcome for Pit Bull Shelter Dogs

A large proportion of dogs in this study were labelled pit bull. Although the number of mislabelled pit bulls in this study was likely greater than the expected average across shelters, it still highlights an alarming trend.

“Essentially we found that the marked lack of agreement observed among shelter staff members in categorizing the breeds of shelter dogs illustrates that reliable inclusion or exclusion of dogs as ‘pit bulls’ is not possible, even by experts.” – Julie Levy

As discussed earlier, the implications of being identified as a pit bull could have drastic consequences for a dog. Are these consequences justified however? Perhaps – for a purebred American Pit Bull Terrier, American Staffordshire Terrier or Staffordshire Bull Terrier. However, mixed breed pit bull types are unlikely to display the aggressive characteristics of their purebred counterparts. There have been no reports correlating the behavior of crossbred dogs with that expected of the parental breeds. 3 The need to define a dog by its breed is in part responsible for the surge in home based dog DNA testing kits.

“A dog’s physical appearance cannot tell observers anything about its behavior. Even dogs of similar appearance and the same breed often have diverse behavioral traits in the same way that human siblings often have very different personalities.” – Julie Levy

The DNA profiles of the 120 dogs used in this study showed 25 had pit bull heritage. None of these 25 were actually purebred and therefore unlikely to show any aggressive behaviour based on their genetics alone. Despite this, these dogs could expect all the same legal consequences as a purebred pit bull terrier.

Breed standards can be found on the Fédération Cynologique Internationale website, click here to search a breed.

Your Thoughts

We’d like to hear your thoughts about this. The number of mislabelled dogs, whether the consequences are acceptable and whether pit bull mixes are as aggressive as their pure bred counterparts.

Featured Image – Thomas Hawk


  1. K.R. Olson, J.K. Levy, B. Norby, M.M. Crandall, J.E. Broadhurst, S. Jacks, R.C. Barton, M.S. Zimmerman. Inconsistent identification of pit bull-type dogs by shelter staff. The Veterinary Journal, 2015; 206 (2): 197 DOI: 10.1016/j.tvjl.2015.07.019
  2. V.L. Voith, R.T. Trevejo, S. Dowling-Guyer, C. Chadik, A. Marder, V. Johnson, K. Irizarry Comparison of visual and DNA breed identification of dogs and inter-observer reliability American Journal of Sociological Research, 3 (2013), pp. 17–29
  3. R.A. Casey, B. Loftus, C. Bolster, G.J. Richards, E.J. Blackwell Inter-dog aggression in a UK owner survey: Prevalence, co-occurrence in different contexts and risk factors Veterinary Record, 172 (2013), pp. 127–18

About James Watts

BSc Bioveterinary Science. Editor of PetSci. When I'm not writing, learning, discussing, or reading about animals, you know it's the weekend! Currently developing PetSci HealthTrak, the fast and easy way to monitor your pet's weight and calorie intake. HealthTrak offers a simple way to track your pet's progress, helping them achieve a healthy weight and a long, happy life.

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