Fear, aggression and other behavioral problems in dogs often arise from maltreatment, lack of socialization and other issues. But science is showing that genetics also play a part.
Behavior problems are among the top reasons dogs are surrendered to shelters. In fact, a study of 12 animal shelters across the US found that 40% of people relinquishing their dogs cited behavioral problems as one of the reasons, with aggression as the most frequently-reported issue. Although abuse, neglect and poor socialization clearly contribute to fear, aggression and other behavioral problems in dogs, scientists are finding that genetics also play a role.
ARE SOME BREEDS MORE AGGRESSIVE THAN OTHERS?
Most of what is known about breed differences as related to aggression comes from reports based on bite statistics, behavior clinic caseloads, and opinions from experts. However, information on breed-specific aggression derived from these sources can be misleading because of the reported disproportionate risk of injury attributed to larger and/or more physically powerful breeds, and the existence of society’s entrenched breed stereotypes.
Other potentially misleading statistics and beliefs come from the fact that most dog bites go unreported unless the victims seek medical attention. Also, the prevalence of a particular breed in a community is largely unknown, and the breed type of the dog is rarely verified.
The genetic study mentioned in the sidebar revealed some interesting data regarding
breed-related aggression in dogs.
1.Compared to other canines, pit bull-type dogs were not shown to be more aggressive, although they were strongly associated with pulling on the leash. Using severity-threshold models, pit bull-type dogs showed a significantly reduced risk of owner-directed aggression and an increased risk of dog-directed fear. Fear and aggression traits directed at other dogs and unfamiliar humans clustered together, with non-social fear.
2.A large dataset study of personality traits in Labrador retrievers, the most popular dog breed in North America, revealed substantial genetic variance for several traits, including fetching tendency and fear of loud noises.
A guardian-evaluated behavioral questionnaire was used along with individualdemographic factors. The results confirmed that these questionnaires were a valuable tool for detecting genetic variance in the everyday behaviors of dogs across different lifestyles. Further genomic analyses indicated that these traits were mainly polygenic (involving many genes), and suggested specific chromosomal associations for six of the traits. The polygenic nature of these traits was consistent with previous behavioral genetics studies in other species, and confirmed the need for analyzing large datasets to quantify the genetic variance and identify the individual genes involved.
3. Eight breeds were studied for aggression toward strangers, dogs, and dog parents. 
Similar aggression rankings were seen for the dachshund, English springer spaniel, golden retriever, Labrador retriever, poodle, Rottweiler, Shetland sheepdog and Siberian husky. Some breeds, like the Chihuahua and dachshund, scored higher than average for aggression directed toward both humans and dogs, while other breeds like the Akita and pit bull terrier scored high only for specific dog-directed aggression. In summary, aggression was most severe when directed toward other dogs, followed by unfamiliar people and then household members.
4. Breeds with the greatest number of dogs exhibiting serious aggression (bites or bite attempts) toward humans included:
- Dachshund, Chihuahua and Jack Russell terrier — toward strangers and guardians
- Australian cattle dog — toward strangers
- American cocker spaniel and beagle — towards guardians
- More than 20% of Akitas, Jack Russell terriers and pit bull terriers were reported as displaying serious aggression toward unfamiliar dogs.
- Golden retrievers, Labrador retrievers, Bernese mountain dogs, Brittany spaniels, greyhounds and whippets were the least aggressive toward both humans and dogs.
- Among English springer spaniels, conformation-bred dogs were more aggressive to humans and dogs than field-bred dogs, suggesting a genetic influence on this behavior.
- The opposite pattern was observed for guardian-directed aggression among Labrador retrievers, indicating that higher levels of aggression are not attributable to breeding for conformation shows.
CAN DOGS INHERIT FEARFULNESS?
Fearfulness of unfamiliar people and other dogs is a prevalent behavioral problem. A large dataset of 6,000 dogs was collected through a behavioral survey filled out by dog guardians. Several factors were associated with fearful behavior, including urban environment, poor socialization during puppyhood, infrequent participation in training and other activities, small body size, female sex, neutering — and several breed differences that suggested a genetic contribution to social fearfulness.
Despite the fact that fear is a major welfare problem in dogs, it is a normal and fundamental emotion that helps with survival in threatening situations. However, while fearfulness is only a moderately heritable personality trait, if it becomes excessive, prolonged, or generalized, it becomes a behavioral problem that causes high levels of distress or anxiety to the dog and guardian.
More research is needed to determine how the link between genetics and canine behavior can be interpreted and applied. In the meantime, while there isn’t much you can do about your dog’s genetics, knowing more about how they might influence his behavior will help you understand him better, while allowing you to take steps to help prevent possible unwanted behaviors from manifesting.
Dr. Jean Dodds received her veterinary degree in 1964 from the Ontario Veterinary College. In 1986, she established Hemopet, the first non-profit national blood bank program for animals. Today, Hemopet also runs Hemolife, an international veterinary specialty diagnostics service. Dr. Dodds has been a member of many committees on hematology, animal models of human disease and veterinary medicine. She received the Holistic Veterinarian of the Year Award from the AHVMA in 1994, has served two terms on the AHVMA’s Board of Directors, chairs their Communications Committee, and currently serves on the Board of the AHVMF, as well as its Research Grant and Editorial Committees.
