A study of approximately 9,000 dogs conducted at the University of Helsinki found that fear, age, breed, the companionship of other members of the same species, and the owner's previous experience with dogs were associated with aggressive behavior toward humans. The findings may provide tools to understand and prevent aggressive behaviour.
Aggressive behavior in dogs can include growling, barking, snapping and biting. These gestures are part of normal canine communication and also occur in non-aggressive situations, such as while playing. However, aggressive behavior can be excessive, making the dog a threat to the health of both humans and other animals.
“Understanding the factors underlying aggressive behavior is important. In what circumstances does aggressive behavior occur and what is the dog's motive for such behavior? In normal family dogs, aggressive behavior is often undesirable, while some dogs with official duties are expected to be aggressive. At the same time, aggressiveness can be caused by well-being problems, such as chronic pain,” says PhD student Salla Mikkola from the University of Helsinki.
The dog gene research group active at the University of Helsinki examined links between aggressive behavior and various potential risk factors using a dataset that includes more than 9,000 dogs, a sample of a larger dataset from a behavioral study of nearly 14,000 dogs. The study examined aggressiveness towards both dog owners and unfamiliar people. Dogs were classified as aggressive if they often growled and/or had attempted to bite or bite a human, at least occasionally in the situations described in the study.
“Dogs' fear had a strong link with aggressive behavior, where fearful dogs would often behave more aggressively. In addition, older dogs behaved more aggressively than younger ones. One of the possible reasons for this could be pain caused by a disturbance of the senses, which can contribute to making it more difficult to notice people, and dogs' reactions to sudden situations can be aggressive,” added Mikkola.
Small dogs are more likely to behave aggressively than medium and large dogs, but their aggressive behavior is not necessarily considered threatening as that of large dogs. Consequently, their behavior is not addressed. In addition, the study found that male dogs were more aggressive than females. However, sterilization had no effect on aggressive behaviour.
The first dog owners' dogs were more aggressive than dogs whose owners had previous dog experience. The study also indicated that dogs that spend time in the company of other dogs behave less aggressively than dogs that live without other dogs in the household. Although this phenomenon has been observed in previous research, the causality remains unclear.
“In the case of dogs that are initially prone to aggressive behavior, owners don't necessarily have to risk conflict with another dog,” muses Mikkola.
Significant differences in aggressive behavior between races
Differences in the aggressiveness of different dog breeds may indicate a genetic cause.
“In our dataset, the long-haired collie, poodle (toy, miniature and medium) and miniature schnauzer were the most aggressive breeds. Previous studies have shown fear in long-haired collies, while the other two breeds have been shown to be aggressive towards unfamiliar people. As expected, the popular Labrador Retriever and Golden Retriever breeds were at the other extreme. People considering buying a dog should familiarize themselves with the breed's background and needs. As far as breeders are concerned, they should also pay attention to the character of the mother dogs, as both fearfulness and aggressive behavior are inherited,” says Professor Hannes Lohi of the University of Helsinki.
