Why would dogs fight with a familiar dog living in the same home?
Dogs are social animals whose evolutionary history makes them willing and able to live in groups. Group living enabled the dog’s ancestors, wolves, to work together to obtain food, raise their young, and defend their territory. Much of a dog’s communication with other members of its species is by subtle, energy-conserving body language and physical displays.
"It would be counter-productive for members of a group to fight with each other and risk injury."
It would be counter-productive for members of a group to fight with each other and risk injury. Generally, most well socialized dogs strive to avoid physical or aggressive confrontation. However, these dogs may be living in close proximity to each other with limited opportunities to avoid confrontations or placed in frequent competitions over desirable resources, resting places or human interactions. Dogs that are not well socialized or have deficits either in their ability to interpret or communicate with other dogs are more predisposed to aggressive confrontations. Like people, not all dogs are natural or skilled communicators with members of their own species.
What is a dominance hierarchy, and does this explain why dogs may fight?
Previously, most familiar dog-dog interactions were described as a dominance hierarchy in which one dog was competing to take over by controlling resources such as food, space, and favored possessions. Current interpretations of canine behavior question these underlying motivations as an accurate interpretation of how dogs contemplate these confrontations. Dogs indeed show a preference gradient and a variable desire for certain resources and their ability to retain or secure these may be predicted based on observation of past experiences and confrontations. These resources include food, resting places, mates, territory and favored possessions. Ability to acquire these resources is generally communicated through facial expressions, body postures, and actions. The more confident, bold, assertive dog may deem his chances good against a meeker, less confident and less successful opponent. Fighting is rare, since as soon as one dog submits or defers, the bolder animal gets its way, he or she gives up the challenge. These displays may appear non-existent in some households while in others, these displays are dramatic and may seem to support a clear hierarchy. The apparent winner of these confrontations may change depending on health, previous experience and relative motivation to get or maintain a resource (i.e., who wants it more). While communication of intention and submission are not in dispute, the premise that a linear hierarchy exists and dogs are intent upon successfully taking over the pack is in great dispute. Observations of wild wolf packs suggest not a hierarchal struggle but that wolves interact as human parents with their children by caring for them, leading when appropriate, teaching when appropriate and then the young leave the pack to start their own families. However, our family dogs are not related and do not have the opportunity to leave a social group that is not socially a good fit for them. This can result in ongoing social stress and misunderstandings and perhaps aggressive encounters between dogs (see Dominance, Alpha, and Pack Leadership – What Does It Really Mean? and Canine Communication – Interpreting Dog Language).
My dogs have lived together for some time and now they are fighting. Why?
Fighting between dogs within a household can have several underlying motivations:
1. Fights may occur when a younger, larger, more agile dog challenges an older, confident dog in an attempt to alter the existing pattern of resource division. This is most likely to arise as the younger dog grows and matures or as the older dog ages or becomes more infirm. If the older dog acquiesces, things will be fine; however, if the older dog does not relinquish resources, fighting can persist. In addition, owners may not want the change and will intervene, which creates anxiety, may exacerbate the fighting and may inadvertently support and encourage the dog that is more suited to a deferential relationship.
2.A change in the household, routine, or family may lead to altered responses between the pets. This may result from underlying anxiety in one or both of the pets or an inability to adapt the change. In addition, once aggression arises between dogs, regardless of cause, the learning that has occurred may then affect further interactions between the dogs.
3.Fighting of a younger dog toward a dog that is aging or ill may be a function of the inability of the older dog to respond with appropriate postures and signaling when interacting with the younger dog. This may lead to a change in their predictable relationship. If a pet's responses, including aggression are due to an underlying disease process, the medical factors will need to first be addressed if a harmonious relationship is to be reestablished. Unfortunately many medical problems, especially those associated with aging, might not be able to be entirely resolved; in these cases, prevention rather than improvement might be all that can be expected. For example, dogs with medical conditions that lead to pain and irritability may become increasingly more aggressive when approached or handled. Dogs with cognitive dysfunction, sensory decline or disorders affecting mobility, might no longer be able to communicate effectively with other dogs both in the display of signals as well is in reading the signaling of others (through facial expressions, body postures and actions). While some dogs are quite tolerant and readily adapt to the changes in the way that the older (or ill) pet responses, many dogs become more anxious and unable to cope with the altered behavior of the older pet (see Senior Pet Behavior Problems and Senior Pet Cognitive Dysfunction).
4. When the social group changes such as the confident, assertive dog leaves or a new dog enters the home, the existing dogs try to restructure and predict their new social relationships. This can also occur between dogs raised together as they reach social maturity and attempt to restructure their relationship.
5.In some cases, aggression between the dogs may be redirected (i.e., when one or both dogs become highly aroused by an event or stimulus unrelated to the other dog, e.g., mail carrier's arrival, owner's departure, owner's homecoming), it may direct its aggression toward the other dog because it is nearby or accessible.
6.Fights can also occur due to underlying anxiety such as separation anxiety or noise sensitivities. If this is the case, unless the underlying disorder is identified and treated fighting may not resolve.
7. Fights are most likely to occur over access to resources that are considered important to one dog more than the other (resource-holding potential) (see Aggression – Possessive – Objects and Toys and Aggression – Possessive – Food Bowl). These might include food, resting places, territory, favored possessions or social interactions with the owners or another dog in the home. These fights occur most often between dogs of near equal ability and motivation and often, but not always, dogs of the same sex, and seem to be most severe between female dogs. High states of arousal and resources that are particularly appealing or novel may increase the chances of aggression. Fighting would most likely arise if both dogs have a high desire for the same resource, if the desire to retain the resource is stronger in the more subordinate dog (especially if he or she gets to the resource first), or if the owner supports the dog that is being challenged.
8.With age and maturity, some dogs with formerly harmonious relationships begin to display posturing and behavior that is inappropriate in a social context. In some cases it might be that the previously subordinate dog fights back in situations where it previously displayed appeasing and deferential posturing. Conversely, dog A, the more confident dog, may continue to attack, despite appropriate subordinate signaling from its housemate. On the other hand, dog A may not display any preliminary posturing (growl, snarl, stiffening) when challenged but proceeds directly to a full-out attack. In both scenarios, dog A is behaving inappropriately. These cases can be diagnostic dilemmas because allowing the pets to work things out or merely supporting the natural development of their relationship might lead to serious injury. In a free living situation these dogs would not continue to co-habitate, instead they would separate themselves sufficiently to avoid ongoing aggressive confrontation. People are rightly concerned when their dogs do not get along with each other but in reality we should be duly impressed anytime our random selection of canine personalities actually do mesh harmoniously.
9.It is likely and advantageous that dogs in a household would use canine communication and posturing to avoid aggressive interactions so that the fights would be mild and inhibited. Therefore, when there is fighting between dogs in a home, it is more likely to be caused by conflict over resources, fear, pain and irritability, redirected aggression, or sociopathic tendencies (in which one or more of the dogs have underdeveloped or insufficient social communication skills). In some cases, one of the dogs is behaving abnormally and a behavior consultation with a veterinary behaviorist is necessary to determine which dog is behaving most abnormally and the diagnosis, prognosis and whether medication may be needed.
How do I find out why my dogs have been fighting?
Because the aggression could be due to normal learned challenges, medical problems, owner responses, excessive anxiety, poor social communication skills or perhaps a lack of impulse control, a full behavioral workup is advised.
"However, the most important diagnostic tool in any behavioral case is often the history you provide."
This would start with a physical examination including a neurological assessment, diagnostic tests to rule out medical problems, and possibly treatment trials to try to resolve the health issues and control the signs. However, the most important diagnostic tool in any behavioral case is often the history you provide. In addition, to the general information on the family, the household, your schedule and previous training, the specifics of the problem itself from the time it began to the present day is critical. A videotape can also help us to diagnose what is happening between the pets (see Diagnosing a Behavior Problem – Is It Medical or Behavioral? and Aggression – Introduction).
Both my dogs are the same age, and after a third, older dog died, they began to fight. Why?
Conflicts may occur between dogs when the relationship is ambiguous or when they have similar motivations and past experiences of success. After the decline, illness or death of an older dog, fighting may begin in the remaining dogs even when one is clearly the most confident and assertive. This is because the older dog may have helped to maintain a stable relationship among all dogs and now they are trying to establish relationship patterns. In any case, the fighting can be severe and injurious. It is also possible that thechange to the household and relationship dynamics may lead to increased anxiety in the household. Although you should generally attempt to allow dogs to resolve their differences on their own if they are just threatening without fighting, you will need to intervene if there is the potential for injury. Under no circ*mstances should the dogs be allowed to "fight it out." You could be injured due to redirected aggressive attacks, or when you attempt to break up the fight (see below).
Both my dogs are the same age, and after a third, older dog died, they began to fight. Why?
Conflicts may occur between dogs when the dominance status is ambiguous or when they are particularly close in rank. After the decline, illness or death of an older dog, fighting may begin in the remaining dogs even when one is clearly dominant. This is because the older dog may have helped to maintain a stable relationship amongst all dogs and now they are trying to establish new positions. In any case, the fighting can be severe and injurious. It is also possible that the change to the household and pack leads to increased anxiety in the household. Although you should generally attempt to allow dogs to resolve their differences on their own if they are just threatening without fighting, you will need to intervene if there is the potential for injury. Under no circ*mstances should the dogs be allowed to "fight it out". You could be injured due to redirected aggressive attacks, or when you attempt to break up the fight (see below).
My younger dog always deferred to the older dog, but now they fight. Why is this happening?
One scenario that can result in social aggression is when an older, previously bold, confident, and assertive dog, is challenged by a younger, more ambitious dog. This may happen as the older dog ages, or as the younger dog reaches behavioral maturity at 12 to 36 months. This may be an attempt to alter the existing hierarchy. Sometimes the older dog will acquiesce and things are fine, but at other times the owners do not want the change and will intervene. In some situations, the older dog may not be willing to defer even though it cannot physically compete with the younger dog. This can result in severe, injurious fights. Commonly, it would be advisable to support the older dog and discourage the younger dog's challenges. However, if change is inevitable then it may become necessary to stop the support of the older dog, and to discourage attempts to fight back. However, if the young dog does not cease its assertive and distance increasing displays as soon as the older dog shows deference or appeasing postures, then it must be controlled and inhibited. Some younger dogs are bullies and do not recognize deference or give any dogs within the household; these dogs should not be supported as the leader dog. (For treatment see Aggression – Sibling Rivalry – Treatment).
Contributors: Debra Horwitz, DVM, DACVB & Gary Landsberg, DVM, DACVB, DECAWBM
