Aggression in Dogs: Causes, Symptoms, and Solutions

Aggression in Dogs – An Overview

Action taken by one dog directed against a person or another animal, with the result of harming, limiting, or depriving that person or animal; aggression may be offensive or defensive
Offensive aggression—unprovoked response directed toward a person or another animal in order to control access to some resource (such as food or toys) at the expense of that person or animal; includes social status/dominance aggression, possessive aggression; intermale (that is, between two males) aggression and interfemale (that is, between two females) aggression, and predatory aggression; common targets are familiar people or animals
Defensive aggression—aggression is directed toward a person or another animal perceived as an instigator or threat; includes fear-motivated, territorial, protective, irritable (pain-associated or frustration-related), and maternal aggression; common targets are unfamiliar people or animals
Probability of overt aggression may be influenced by motivation, arousal, and anxiety; specific incidents of aggression may involve both offensive and defensive aggression
In all cases, medical explanations (including pain) as the cause or contributing factor to aggression must be considered
Aggression in dogs is the most common reason dogs are presented to veterinary behaviorists in the United States
According to a 2009 report by the Center for Disease Control and Prevention (CDC), about 4.7 million people are bitten by dogs each year in the United States and approximately 900,000 require medical attention for bite-related injuries

Genetics

Some breed-specific aggressive tendencies and bite styles have been selected for in breeding programs, although this cannot predict behavior of individual dogs
One study linked aggressive English springer spaniels to one breeding sire, suggesting a possible inherited form of aggression

Signalment/Description of Pet

Species

Dogs

Breed Predilections

Any breed may show aggression
Pit bull types and rottweilers are the most common breed types implicated in fatal dog bites in the United States, although comparative rates of aggression based on breed occurrence are not available
Selective breeding for certain behavioral traits may increase the likelihood that dogs will have specific types of aggression; for example, dogs of breeds bred for fighting may be aggressive toward other dogs
English springer spaniels appear at risk for impulsive (“rage”) aggression

Mean Age and Range

Any age puppy or dog may show aggression
Aggression commonly becomes more problematic at social maturity (1–2 years of age)

Predominant Sex

Any sex of dog may show aggression
Males—intact or castrated most commonly are implicated in dog bites

Signs/Observed Changes in the Pet

Behavioral warning signs include being motionless (immobility), growling, snarling, or snapping at air
Offensive aggression warning signs—head up, tail up with stiff wag, direct stare, face-on immobility
Defensive aggression warning signs—head lowered, tail down, body withdrawn, paw of front leg lifted
Physical examination usually unremarkable
Dominance-related aggression, fear-related aggression, or irritable aggression may be evident during the examination
Nervous system examination—abnormalities may suggest a disease process (such as rabies) as the cause of aggression
Signs vary, according to the situation and the type of aggression

Offensive Aggression

Often directed toward familiar household members
Signs include head up; tail up with stiff wag; direct staring; face-on immobility
People-directed triggers (situations or things to which the dog reacts, leading to aggressive behaviors)—reaching for pet; patting on head; approaching or displacing when on elevated resting sites; approaching food, toys, or stolen objects

Defensive Aggression

Often directed to unfamiliar people or dogs that approach, stand over, or reach for the dog
Certain familiar people may be exempt
Signs include head lowered, tail down, body withdrawn, paw of front leg lifted
May be location-specific, as when strangers approach the dog’s home, yard, or car
Aggression may increase if the dog is restrained
As distance from trigger (situation or thing to which the dog reacts, leading to aggressive behaviors) decreases, response may escalate to agitation, barking, lunging, baring teeth
Approach/avoidance behavior is common; “approach/avoidance” behavior consists of the dog approaching the stranger and then moving back away from the stranger
Maternal aggression is directed toward individuals approaching the whelping box/area or puppies

Causes of Aggression in Canine

Part of the normal range of dog behavior; strongly influenced by breed, sex, early socialization, handling, and individual temperament
May be caused by a medical condition—possible but rare; medical causes of aggression should be considered in all cases

Risk Factors

Unneutered male
Inadequate socialization during critical period (3–14 weeks of age)
Traumatic or negative experiences
Environmental conditions may lead to aggression or may increase the level of aggression—such as associating with other dogs in a pack; barrier frustration or tethering; cruel handling and abuse; and dog baiting and fighting
Previous aggression/bite history (number of incidents, severity of aggression)
Presence of children, elderly people, or other people or animals at high risk living in or visiting household

Treatment for Dog’s Aggression

Health Care

The first tenet of management is to prevent injury to people
Euthanasia—appropriate solution in cases of vicious dogs; may be the only safe solution
Board the dog until an outcome decision or implementation of a safe management plan is made
Use physical barriers, to reduce risk of injury to people, until the owner obtains treatment
Identify specific situations that have led to aggression in the past; use a specific plan to avoid these situations
Improve physical control of the dog using reliable barriers (such as fences, baby gates), muzzles, leashes, and head halters
Calmly and safely remove dog from aggressive-provoking situations
Avoid punishment and confrontation; punishment and confrontation promote defensive (fear) responses and escalate aggression
Management success—combination of environmental control, behavior modification, and medication

Activity

Appropriate and safe exercise regimen should be incorporated into the treatment plan, since frustration and arousal may increase the incidence of aggression

Diet

A reduced-protein diet may be helpful in controlling territorial aggression in dogs

Surgery

Neuter or castrate male dogs

Medications for Aggression in Dogs

Medications presented in this section are intended to provide general information about possible treatment. The treatment for a particular condition may evolve as medical advances are made; therefore, the medications should not be considered as all inclusive:

No medications are approved by the federal Food and Drug Administration (FDA) for the treatment of aggression in dogs; discuss the risks and benefits of using medications with your pet’s veterinarian
No medication will eliminate the probability of aggression
Medication should be used only in conjunction with a safe management plan
Medications that increase serotonin (chemical messenger in the brain that affects mood and behavior) may be helpful to reduce anxiety, arousal, and impulsivity
Treatment duration: minimum, 4 months; maximum lifetime of pet
Medications that have been tried include fluoxetine, paroxetine, sertraline, clomipramine, amitriptyline, and L-tryptophan
Megestrol acetate has been used successfully with dominance-related and intermale aggression; however, it does have side effects that should be considered

Follow-Up Care

Patient Monitoring

Weekly to biweekly contact—recommended in the initial phases
Clients need feedback and assistance with behavior modification plans and medication management

Preventions and Avoidance

Avoid all situations that previously have lead to aggression
Use extreme care when handling aggressive dogs; use safe confinement, gates, halter, collars, leashes, or muzzles and other restraints to prevent injury to people and other animals
Reduce the risk of aggression in young dogs with positive socialization when puppies are 3–14 weeks of age
Avoid intimidation techniques for training and negative and/or fear-inducing situations

Possible Complications

Injury to people and/or other animals
Interdog aggression—” interdog aggression” refers to aggression between two or more dogs; people often seriously injured when interfering with fighting dogs, either by accident or by redirected or irritable aggression; owners should not reach for fighting dogs; pull apart with leashes
Liability to the owner; human injury, bite-related lawsuits, and loss of homeowner’s insurance can result from dog aggression

Expected Course and Prognosis

Aggressive dogs weighing more than 40 pounds (18.5 kg) are at risk for euthanasia due to their inappropriate behavior
Overtly aggressive dogs are never cured; depending on the situation, they may be managed successfully
Prognosis is case-dependent due to risk factors and management of each situation

Key Points

Overtly aggressive dogs are never cured; depending on the situation, they may be managed successfully
Behavioral warning signs include being motionless (immobility), growling, snarling, or snapping at air; offensive aggression warning signs include head up, tail up, direct stare, face-on immobility; defensive aggression warning signs include head lowered, tail down, and body withdrawn
Avoid situations that lead to aggression
Use extreme care when handling aggressive dogs; use muzzles and other restraints to prevent injury to people and other animals
Liability to the owner; human injury, bite-related lawsuits, and loss of homeowner’s insurance can result from dog aggression