The purpose of aggressive behavior in dogs towards humans or another dog is 1) to gain distance from a threat 2) protect a resource or 3) predation- to acquire food. Aggression is not a single behavior but rather a cluster of behaviors that occur across the universe of organisms. When a dog perceives a threat and is trying to gain distance or is protecting a resource such as food or their caregiver, the dog will display a natural cluster of individual behaviors, strung together to warn off the threat . If the warnings are dismissed and the threat moves closer to the dog then it may result in a bite. The antagonistic behavior is not a switch, there are many signals that lead up to the bite. Reading the communication through the dog’s body language and signaling is often where human’s miss the mark. Lack of communication between species is an important factor in dog aggression and bites.
As well, there have been studies on street dogs (fondly referred to as “streeties”) looking at behavior in comparison to captive dogs in pet homes. In general streeties resort less frequently to biting when faced with conflict. It seems likely that dogs that move more “freely” as opposed to being captive in a pet home, have a more intact ritualized aggression language (signaling & body language) are less inclined to escalate to dog fights and biting. This seems plausible as 1) streeties have more agency-less barriers/confinement 2) Their ability to communicate with ritualized aggression (converse) is still intact 3) They are aware of the expense of physical conflict-injury and no human to help them if they are injured. There is a clear difference in behavior when comparing street dogs and the captive pet dog. They are still the same species but are evolving in different ways. When responding to stimuli the captive dog, more frequently, reaches “fight or flight”decisions in a modern environment that both restricts freedom of choice and freedom of movement. The streetie (free dog) does not lead an “ideal” life free of disease with plentiful food, however, they have agency and resort much less frequently to aggressive behavior. Many street dogs “rescued” from many different states and countries frequently have difficulty adjusting to captivity. The idea that we are giving them the “ideal” life through saving them from “dire” lives may not be what they want. It may be what humans want. Many welfare advocates are providing capture and release programs for medical and vaccination. They have created sanctuaries for the elderly and special needs but their goal is not to take free world dogs out of their environments.
As a captive species dogs are highly prone to experiencing frustration as they come face to face with barriers preventing them from being able to meet their biological needs.
Pet/modern dogs often have an “interrupted” language and often lacks of ritualized signaling. Many of the behaviors can be fueled by frustration.Most pet dogs are punished for signals such as barking, growling and showing teeth. Pet dogs as opposed to street dogs lack agency which is known to attribute to many of the frustration behaviors we see in owned dogs. When owned dogs are permitted to interact in designated places such as dog parks and daycare facilities, there seems to be a lost language between them at times. If you’ve ever seen any videos of street dogs interacting compared to a group of dogs at a dog park you’ll see very different energy and signaling. Conflict among dogs in the modern world is possibly more intense than “free” dogs. Owned dogs that live in “captivity”are often experiencing a communication break with humans. Even among their own species the communication often fails. Owned dogs often develop “learned helplessness” and become compliant. Many people miss this reality and mistake the behavior as the dog being calm or easy to handle.