AN UPDATE ON CANINE HUMAN DIRECTED AGGRESSION Debra Horwitz, DVM, DACVB

Transcription

1 AN UPDATE ON CANINE HUMAN DIRECTED AGGRESSION Debra Horwitz, DVM, DACVB BEHAVIOR Aggression is the most serious and dangerous behavior problem that dog owners may need to deal with. Since there are many different types of aggression, making a diagnosis, determining the prognosis (the chances of safe and effective control and/or improvement), and developing an appropriate treatment plan are usually best handled by a veterinary or applied animal behaviorist. Many factors can contribute to aggressive behaviors in dogs. Naturally, genetic factors can influence the behavior in any animal. Certain breeds of dogs have been specifically bred for guarding or territorial behavior, and this naturally will influence how they respond to certain stimuli. Biological factors of age and hormonal status can also influence aggression. Many environmental variables may influence the aggressive behavior of a dog. Some occur in development; others are the result of learning. In some cases medical conditions can contribute to aggression; therefore before a behavior consultation it is essential that a dog have a complete physical examination and a set of blood tests (minimally a CBC, Chem Screen, T4, and TSH) to rule out organ dysfunction. Classification of Aggression Aggression is usually defined as threat or harmful action directed to one or more individuals. 1 The behavior can consist of vocalizations, facial expressions, body postures, inhibited attacks, and physically injurious attacks. There are many different methods to classify and categorize aggression in animals. The victim or target, the location where the aggression occurs, or the type of aggression such as offensive or defensive can be used to classify aggressive behavior. In veterinary behavioral medicine, diagnostic categories have been used to classify aggression in companion animals. Those commonly cited include dominance/conflict aggression, fear, possessive, protective and territorial, parental, play, predatory, redirected, pain induced or irritable, pathophysiological or medical, and learned. 2, 3, 4 In many cases more than one form of aggression may be exhibited in any one animal since aggressive responses tend to be multi-factorial. Demographics of Aggression When looking at caseloads of behavior referral practices, younger dogs are more often seen for aggressive behaviors when compared to older animals. In dog bite reports filed with various agencies, mixed breeds are more common than purebred dogs. Interestingly, 85% of bites to people were from dogs that were owned, not stray. Larger dogs seem to be responsible for more reported bites than smaller ones, most likely due to the size of the dog and the related damage to the individual bitten. 5 Between 1979 and 1996 there were more than 300 human dog-bite-related fatalities in the United States. 6 Sacks et al (2000) looked at fatal dog bite reports over a 20-year period and found that 24% of the deaths involved unrestrained dogs off the owner s property, 58% involved unrestrained dogs on the owner s property, 17% involved restrained dogs on the owner s property, and < 1% involved restrained dogs off the owner s property. Their research also found that while recent fatal dog bite reports seemed to show an increase in fatal bites by rottweilers and pit bulls, data from previous years show a different distribution. From 1979 to 1980 great danes caused the most reported fatal dog bites. Since 1975 more than 30 breeds of dogs have been cited in fatal dog bite reports. This does not even attempt to look at mixed breed dogs, whose breed identification is difficult to determine. Guy (2001) looked at the demographic and aggressive characteristics of dogs in a general veterinary caseload. 7 Biting behavior was reported for 15.6% of all dogs, with the highest frequency of biting reported in dogs less than one year of age. Neutered male dogs were the most likely to be reported as having bitten in this study. Other studies have noted a positive association between neutering and aggression, but when dogs that were neutered specifically because they were aggressive were removed from the analysis this association went away. 8 Guy (2001) also found that whether or not a dog was purebred did not significantly affect the reported frequency of biting. Guy further investigated risk factors for dog bites to owners and compared 227 biting and 126 non-biting dogs. 9 She found that significant risk factors for an outcome of biting were the dog being female (particularly if small), the presence of one or more teenage children in the home, a history of a pruritic or malodorous skin disorder which had received veterinary treatment, aggression over food in the first 2 months of ownership, the dog having slept on someone s bed in the first 2 months of ownership, and the dog having been given a significantly higher ranking for excitability based on its behavior in the first 2 months of ownership. Small dogs were determined to be a higher risk of having bitten than large dogs, and biting dogs were more likely to have exhibited fear of children, men, and strangers. 33

2 Identifying Indicators of Aggression Canids have evolved a series of facial expressions and body postures designed to indicate their intention in encounters with other canids, and they use these same signals in their encounters with humans. It is often the misunderstanding of these signals that results in biting episodes. In dogs, staring, snarling (lifting the lip), growling, snapping, and biting are all indicators of aggression. In addition, the positions of the ears, tail, and hair are also used to indicate what the animal will do and the underlying emotional state, such as fear, anxiety, etc. A good understanding of aggressive indicators can help avoid injury. Not all dogs will go through the different signals in order, or slowly. The type of intruder, the distance to the dog, the speed of approach, and prior encounters will all influence the dog s response. If a dog has learned that an aggressive response results in what the dog considers a beneficial outcome, the aggressive response is likely to be repeated. It is important to remember that aggression is just a symptom of the behavior that the dog performs. Without a complete behavioral history it may not be possible to say more than that the dog threatened and/or bit someone. A behavioral history should help establish motivation for the behavior and possibly a diagnostic category. A good understanding of aggressive body postures and facial expressions is necessary to identify types of aggression. Naturally other information such as victim, location of the aggressive episode, location, number and severity of bite wounds, previous aggressive episodes, and other behaviors that the dog does are also needed to make a diagnosis. These cases can be difficult, and the risk and danger to the people who live and interact with the dog may be high. Assessing risk and helping to formulate a prognosis is a useful first step. Certain factors have been shown to affect risk and prognosis in aggressive dogs. These include Willingness of those in contact with the pet to live with risk of further aggression Family composition: young children, elderly individuals, health issues Ability to provide safety for people who come in contact with the pet Size of pet Predictability of behavior Context Choices the pet made Severity of aggression Severity of injuries sustained Ongoing medical disease An essential first step is the safety needs of the humans and other animals that may have to come in contact with the dog while it is undergoing treatment. Factors to consider include the level of aggression to date, the type of bites, the composition of the household, predictability of aggressive behaviors, and owner control of the pet and circumstance. For some owners, creating a safe environment may not be possible either due to their constraints, pet constraints, or both. Safety recommendations should include identifying all aggressive episodes and their stimuli and then avoiding them (such as keeping children separate from the pet, feeding in a separate room, keeping away from visitors) and secure confinement must be created (crates, a room with a locked door, in the yard with a locked gate) if the pet s behavior cannot be predicted or controlled. Punishment is always contraindicated because it can escalate rather than diminish aggression by causing pain, fear, or anxiety. In fact, in many cases underlying anxiety is what has induced the aggressive responses. Owners must be told to stop all punitive measures, including alpha rolls and other attempts to dominate. Owners must be aware of potential liability and the pet be kept away from visitors, strangers, and neighbors. If outdoors the dog must be supervised by an adult while on a leash that is being held by an adult. If possible and practical, muzzle training can begin. Often owners will bring up the discussion of new homes for aggressive dogs. This is very difficult to assess. Owners may make excuses for their pet s behavior and assume that in another environment the dog will not engage in the aggressive responses. This is often not the case. When an aggressive dog is given to another home or shelter without full disclosure of the aggressive tendencies, others can and will be injured. Therefore, another role for the veterinarian is to help the client understand what a danger the pet may represent to others. This needs to be done realistically and empathetically, because despite the behavior most owners love their pet. 34

3 Aggression Directed Toward Familiar People One of the most common types of aggression seen by veterinary behaviorists is aggression directed toward familiar people, usually family members. In the past this has all been labeled dominance-related aggression, yet veterinary behaviorists believe that this is an overused and oversimplified explanation and diagnosis. 2 Practitioners of applied animal behavior interpret dominance hierarchies, ranking, and how they interact in the human dog relationship many different ways and may use varying criteria to define dominance. 10, 11, 12 The concept of dominant and subordinate relationships between animals was developed from observation of animals (wolves, baboons, chickens) living in social groups. 13 Social hierarchies arranged around dominant and subordinate relationships decrease the conflict associated with the allocation of critical resources, i.e., food, shelter, mates, and territory. 14 However, one s dominance is within the context of a relationship with another individual, not of the individual himself, and neither is dominance synonymous with aggression. An individual could be dominant in one relationship and not in another. When living in social groups, wild canids will establish hierarchies that may dictate access to certain resources such as food, resting places, favored possessions, territory, and mates but may or may not involve aggression, 15 but domestic feral dogs apparently have looser social arrangements. Some speculate that these social relationships can be extended to the human members of the household; 16 however, this is likely not true. Often situations involving aggression between owners and their dog are a result of miscommunication, anxiety, uncertainty, and learning. Between humans and dogs, a controlling outcome for the dog is reinforced by deferring to the dog s demands. This may allow the dog to learn that he can influence the outcome, and each interaction that ends with a beneficial outcome for the dog reinforces that assumption. This has also been called resource holding potential, which can affect the outcome of encounters between individuals. Resource holding potential has been defined as an index of competitive ability which allows the prediction of the outcome of interactions between competitors. It is determined by both physical attributes such as size, weight, age and the outcomes of previous encounters between familiar individuals. 17 This would lead one to speculate that the issue is not one of dominance as much as control of the outcome. The animal has learned that certain behaviors result in certain favorable outcomes. In addition, often a behavior occurs because it can; in other words, the owners do not prevent the dog from engaging in a certain behavior, and that can be reinforcing and lead to repetition of the behavior. Some dogs may control because they can but yet are anxious about the outcome. When a dog develops a position of control in a relationship with a family member (or other dog), any challenge to that dog s control may lead to aggressive responses in an effort to influence the outcome of the encounter toward one that is beneficial to the dog and for no other reason. Therefore, a dog may be in control but uncertain about the outcome or anxious, and the aggression is not about dominance at all. Therefore, it is essential that the body posture of the dog during the aggressive episode be consistent with an assertive dog. Many dogs that are aggressive to family members are fearful or anxious and exhibit conflict behavior. 18 Their behavior arises from uncertainty about their role or place within the social group or the response to their actions, both assertive and deferential. Their future behavior is often determined by the responses to their threats, yet owners can be very inconsistent, allowing behaviors at some times and punishing them at other times. Caution should be exercised to avoid labeling all aggression toward family members as dominance-motivated aggression since this may be simplistic. Whenever you are dealing with an aggressive dog, confrontations should be avoided; these will likely increase rather than decrease aggression since they increase anxiety, fear, and defensive responses. Fear aggression arises when a dog is exposed to people or other animals that the dog is unfamiliar with or to those that have been previously associated with an unpleasant or fearful experience. Although some dogs may retreat when fearful, those on their own territory and those that are prevented from retreating because they are cornered or restrained are more likely to respond with aggressive behaviors. If the person or animal retreats or acts overly fearful, or the pet is harmed or further frightened in any way (e.g., a fight, punishment), the fear is likely to be further aggravated. Fear aggression toward family members might arise out of punishment or some other unpleasant experience associated with the owners. Many cases of fear aggression are seen as combinations or complicating factors of other forms of aggression (dominance, maternal, possessive, etc.). Fearful body postures in conjunction with aggression are diagnostic of fear-related aggression. In some situations, as the dog learns that aggression prevents unwanted outcomes, fearful body postures will be replaced with more confident ones. Therefore, it is important when taking a behavioral history to have the owner relate several episodes including the most recent ones and the early first ones that may show differing patterns and responses. 35

4 Possessive aggression may be directed to humans or other pets that approach the dog when it is in possession of something that is highly desirable, such as a favorite chew toy, food, or treat. While protecting possessions may be necessary if an animal is to survive and thrive in the wild, it is problematic when directed toward people or other pets in a household. What can be confusing for some owners is that it is not always food that brings out the most protective displays. Novel and highly desirable objects such as a tissue that has been stolen from a garbage can, a favored toy, human food, or a piece of rawhide are some of the items that dogs may aggressively protect. Aggression Toward Unfamiliar People Protective aggression may be exhibited toward people or other animals that approach the pet s property (territorial aggression). Generally people and other animals that are least familiar to the dog or most unlike the members of the household are the most likely targets of territorial aggression. While most forms of territorial aggression are likely to occur on the property, some dogs may appear to protect family members regardless of the location. In some cases this behavior may actually be fearfully motivated and is about the dog protecting itself rather than the owner. Prevention and Control of Human-Directed Aggression Aggression that is directed toward family members can be complicated to treat. The first step is avoidance of all encounters known to elicit aggressive responses. Having predictable interactions with the dog and daily activities that fulfill canine needs for exercise, social interaction, and exploration are quite useful. Structuring interactions so that all things are earned and attention is given for calm and quiet behavior makes things more predictable for everyone. In some situations teaching the dog how to be confined can also avoid aggressive encounters. Head collars, leashes, muzzles, and gates all might be utilized to keep victims of aggression separated from the dog. Territorial aggression can be prevented or minimized with early socialization and good control. Young dogs should be taught to sit and receive a reward as each new person comes to the door. Ensuring that a wide variety of visitors come over to visit the puppy while the puppy is young and sociable helps to reduce potential fear and anxiety toward visitors. In time, most dogs will begin to alert the family by barking when strangers come to the home. However, the dog that has been well socialized and under good control can be trained to quickly settle down and relax. For dogs exhibiting territorial aggression, the owner will need to gain enough control to have the dog sit, stay, and when calmed down, take a reward at the front door. Generally a leash and head collar will give the fastest and most effective control. Using desensitization and counter-conditioning program retraining can begin with low levels of stimuli (such as people arriving in a car, walking past the front of the house, or perhaps even a family member knocking on the door or ringing the bell). The idea is that each time someone arrives at the house or rings the bell, the dog will come to expect a favored reward (toy, cheese, hot dog slice, or play session) as soon as it stops barking. Once the dog can be controlled and receives rewards in this environment, gradually more intense stimuli can be used. Sometimes an anti-bark collar, shake can, or air horn can be used to disrupt the initial barking, so that the pet can be directed to perform the appropriate behavior and get its reward. References 1 Beaver, B. V The veterinarian s encyclopedia of animal behavior. Ames: Iowa State University Press, 6. 2 Reisner, I. R An overview of aggression In BSAVA manual of canine and feline behavioural medicine, ed. D. F. Horwitz, D. S. Mills, and S. Heath, Gloucester, UK: BSAVA. 3 Houpt, K. A Domestic animal behavior for veterinarians and animal scientists. Ames: Iowa State University Press, Ames, Landsberg, G., W. Hunthausen, and L. Ackerman Handbook of behavior problems of the dog and cat. Philadelphia: Saunders, Wright, J Canine aggression toward people. Veterinary Clinics of North America: Small Animal Practice 21 (2): Sacks, J. J., L. Sinclair, J. Gilchrist, G. C. Golab, and R. Lockwood Breeds of dogs involved in fatal human attacks in the United States between JAVMA 217 (6): Guy, N. C., U. A. Luescher, S. E. Dohoo, et al Demographic and aggressive characteristics of dogs in a general veterinary caseload. Applied Animal Behaviour Science 74: Podberscek, A. L., and J. A. Serpell The English cocker spaniel: Preliminary findings on aggressive behaviour. Applied Animal Behaviour Science 47: Guy, N. C., U. A. Luescher, S. E. Dohoo, et al Risk factors for dog bites to owners in a general veterinary caseload. Applied Animal Behaviour Science 74: Hallgren, A Mother and pups. Animal Behavior Consultant Newsletter (7) (July): 3. 36

5 11 Trattner, A Letter to the editor. Animal Behavior Consultant Newsletter (7) (October): Schilder, M. B. H., and W. J. Netto Letter to the editor. Animal Behavior Consultant Newsletter 8 (July): Alcock, J Animal behavior: An evolutionary approach. 2nd ed. Sunderland, MA: Sinauer Associates, Inc. 14 Voith, V. L., and P. L. Borchelt Diagnosis and treatment of dominance aggression in dogs. Veterinary Clinics of North America: Small Animal Practice 12 (4): Bradshaw, J. W. S., and H. M. R. Nott Social and communication behaviour of companion dogs. In The domestic dog, ed. J. Serpell, Cambridge: Cambridge University Press. 16 Line, S., and V. L. Voith Dominance aggression of dogs towards people: Behavior profile and response to treatment. Applied Animal Behavior Science 16: Shepherd, K Development of behaviour, social behaviour and communication in dogs. In BSAVA manual of canine and feline behavioural medicine, ed. D. F. Horwitz, D. S. Mills, and S. Heath, Gloucester, UK: BSAVA. 18 Luescher, U. A., and I. R. Reisner Canine aggression toward familiar people: A new look at an old problem Veterinary Clinics of North America: Small Animal Practice 38: