Puppy Farms and Pet-Store Puppies: What the Behaviour Studies Found
Dogs bought from pet stores scored worse on most behaviour measures in a large owner survey. What the studies show, what they can't, and what to ask a seller.
Written by thecanineledger
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In a study of more than 6,000 dogs, those bought as puppies from pet stores “received significantly less favorable scores than did breeder-obtained dogs on 12 of 14 of the behavioral variables measured” (McMillan et al., J Am Vet Med Assoc 2013). The researchers’ conclusion was blunt: “the authors cannot recommend that puppies be obtained from pet stores.”
Pet-store puppies are commonly bred in large commercial operations, called puppy mills in North America and puppy farms in the UK. Whatever the source, the buyer doesn’t see the parents or where the puppy spent its first weeks.
While the studies don’t prove that the source causes the problems, they point the same way, and the warning signs for a buyer are clear. This page sets out what was found and what to look for.
1. What the pet-store study found
The 2013 study compared 413 dogs bought as puppies from pet stores with 5,657 dogs from noncommercial breeders. Owners filled in a standard online behaviour questionnaire.
After allowing for other differences between the groups, the pet-store dogs had “significantly greater aggression toward human family members, unfamiliar people, and other dogs; greater fear of other dogs and nonsocial stimuli; and greater separation-related problems and house soiling.” In no category did they score better.
2. What it can’t tell us
This kind of study has real limits, and they matter.
- It’s a survey of owners who chose to take part. The authors describe it as a “large convenience sample.” Owners who took part may not be typical.
- Behaviour was reported by owners, not observed by researchers.
- It shows an association, not a cause. The study can’t separate the effect of a puppy’s early life from the parents’ genes, the stress of transport, or differences in the people who buy from pet stores.
- It’s American. Pet-store supply chains differ by country.
What it does show is a consistent pattern across many measures, in a large group of dogs.
Our note: We found no later study that compared pet-store and breeder dogs directly. “Commonly bred in large commercial operations” is not from a source we’ve read.
3. What changed during the pandemic
A UK study compared people who bought puppies in 2020 with those who bought in 2019. Pandemic buyers “were less likely to seek out a breeder that performed health testing on their breeding dog(s) or view their puppy in-person, and were more likely to pay a deposit without seeing their puppy” (Packer et al., Animals 2021).
Those puppies were also “more likely to be younger, delivered or collected from outside their breeders’ property, seen without their littermates”. Each of these is a common sign of a puppy farm or dealer: the buyer never sees where or how the puppy was raised.
When the same researchers followed these dogs, “Nearly all owners (96.7%) reported that their dog had exhibited at least one problem behaviour up to 21 months of age” (Brand et al., Animals 2024). That study looked at many risk factors together, including how and where the puppy was bought. Problem behaviour in young dogs has many causes, and these studies can’t single out one.
4. Warning signs when buying a puppy
None of these proves a seller is a puppy farm. Each is a reason to slow down.
- You can’t see the puppy with its mother, where it was raised.
- The seller offers to deliver, or to meet you somewhere else, such as a car park or service station.
- Several breeds are for sale from the same seller.
- You’re asked for a deposit before you have seen the puppy.
- The puppy is very young, or the seller is vague about its age.
- No health testing of the parents can be shown for problems common in the breed.
- Pressure to decide quickly.
Our note: The warning-signs list draws on the purchasing behaviours in Packer 2021 plus general advice.
5. If you already have a puppy from one of these sources
Most of these dogs make good pets. The studies describe average differences across groups, not what will happen to any one dog.
What helps: an early vet check, careful socialisation, and reward-based training from the start. → Socialisation Before Full Vaccination: The Risk Both Ways If your puppy seems very fearful, mention it to your vet early. Fear is easier to work with in a young dog.
Our note: Most of these dogs make good pets. The studies describe group risks, not your dog.
6. What the law says
Rules on selling puppies differ by country, province, state and city. Some places ban pet shops from selling puppies; others require that a buyer sees the puppy with its mother.
Our note: We keep the law to a single line and a link, because it differs by country.
7. What we could not verify
| Commonly said | What we found |
|---|---|
| “Puppy-farm dogs are always unhealthy” | Too strong. The studies show average differences in owner-reported behaviour. We didn’t find a study of health outcomes by source. |
| “Pet-store puppies cause behaviour problems” | Association, not cause. McMillan 2013 is cross-sectional and owner-reported. |
| “Rescue dogs have more behaviour problems” | Not covered here. None of the studies we read answered this. |
| How many puppies come from puppy farms | Not found. We found no reliable figure for Canada, the US or the UK. |
Sources
- McMillan FD, Serpell JA, Duffy DL, Masaoud E, Dohoo IR. Differences in behavioral characteristics between dogs obtained as puppies from pet stores and those obtained from noncommercial breeders (J Am Vet Med Assoc 2013; cross-sectional owner survey; abstract read)
- Packer RMA, Brand CL, Belshaw Z, Pegram CL, Stevens KB, O’Neill DG. Pandemic Puppies: characterising motivations and behaviours of UK owners who purchased puppies during the 2020 COVID-19 pandemic (Animals 2021; abstract read)
- Brand CL, O’Neill DG, Belshaw Z, et al. Impacts of puppy early life experiences, puppy-purchasing practices, and owner characteristics on owner-reported problem behaviours in a UK Pandemic Puppies cohort at 21 months of age (Animals 2024; abstract read)
Always confirm with your vet before acting on anything on this page.