Scientists in Finland researched aggression in dogs by breed. Of the 22 breeds that were included, one was picked as the most aggressive, based on a large sample. The name of the study was “Aggressive behaviour is affected by demographic, environmental and behavioural factors in purebred dogs.” The rough collie was the most aggressive breed.
“Aggressive” was defined in a spectrum from “biting people and other pets,” which can cause “medical or even lethal consequences for the victim” to “more common growling and barking.” The researchers pointed out that aggressive behavior among some breeds has caused them to be banned in certain countries. The study looked at over 9,270 dogs based on their reactions to humans. This was taken from a larger sample of data on 13,715 dogs. The data for the larger sample was gathered online. Only purebred dogs were included.
From the sample, 1,791 dogs ended up in the “high aggressive behavior” group and 7,479 in the “low aggressive behavior” category. The mean age of the dogs was 4.6 years, out of a range of two months to 17 years. More than half (53%) of the dogs were female.
Among the common characteristics of aggressive dogs, beyond breed, were male dogs and older dogs. The number of dogs in a family and body size were other variables. Additionally, “The dog’s body size was also associated with aggressive behaviour; small dogs had a higher odds of aggressive behaviour than medium-sized and large dogs, but there was no difference between medium-sized and large dogs.” “Fearfulness” also was listed as a reason for aggressive behavior.
The most aggressive breeds after the rough collie were the miniature poodle (toy, miniature and medium-sized) and miniature schnauzer. The breeds with the least percentage likelihood of aggressive behavior were the Labrador retriever, golden retriever and Lapponian herder.
We included the popularity of each breed where available from the American Kennel Club (AKC). For the breeds that do not have a profile in the AKC database, we included the rank for the closest breed with a note.