In my practice, aggression trails only housesoiling as the principal behavior problem cat owners seek help in treating. The seriousness of the problem can vary from a cat that hisses and avoids social interaction to one that attacks people or other animals. To help such cats and the families that own them, veterinarians must rule out medical problems, take a complete history, make a sound diagnosis, and provide sensible advice.
Although medical problems are not common causes of sudden, severe expressions of aggression, it is important to first rule out medical reasons for any aggressive feline behavior by performing physical and neurologic examinations and laboratory tests, such as a complete blood count, a serum chemistry profile, and thyroid function tests. Pain can lower the threshold for aggressive behavior, so any type of physical discomfort should be noted during the examination. Bizarre manifestations of aggressive behavior or unusual neurologic signs may warrant brain-imaging procedures.
BASIC RECOMMENDATIONS TO OWNERS
Keeping an aggressive pet in the home always presents some risk. Never suggest to clients that treatment will eliminate any chance for future injuries. Make sure clients understand that rehoming (depending on the severity of the problem) or euthanizing aggressive cats may be the most prudent choice and that they are not obligated to keep cats that may seriously injure someone. Factors that should be considered when assessing danger include predictability (whether triggers for aggression are known or warning signs are present), bite inhibition (degree of bite pressure, intensity of aggressive behavior), and the family makeup (ages of family members and their cognitive capability, complexity of the home environment).
You can usually help make the situation safer without getting into complicated treatment recommendations by giving owners some simple, common sense guidelines:
SPECIFIC TYPES OF FELINE AGGRESSION
Fear-induced aggression (defensive aggression)
When a cat encounters someone or something it perceives to be a threat and its escape is impeded, the cat may exhibit defensive behavior and attack until escape is possible.1 The less familiar the cat is with the stimulus, the more heightened the cat's fear response is likely to be. Signs of fear-induced aggression include dilated pupils, ears flattened against the head, limbs tucked under the body, low body position, leaning away from the stimulus, batting with the paws, hissing, spitting, and growling. If the cat's aggressive displays drive away the fear-eliciting stimulus, its behavior is negatively reinforced.2
Genetic and environmental influences can contribute to this problem. Some cats are born with timid personalities, and kittens that have not been adequately socialized during the first two or three months of life are also likely to be fearful of people and aggressive when approached or handled.3 Cats that have aversive experiences associated with people or animals may become fearful and may exhibit avoidance and aggressive behaviors.
Treatment. Counterconditioning and desensitization—which involve gradual, controlled exposure to triggering stimuli—can be used to successfully treat cats that are afraid of people or other animals. These techniques involve repeatedly exposing a cat to the fear-eliciting stimulus at a distance from which the cat is aware of the stimulus but is not close enough to show a fear response. The cat is given a highly desirable reinforcer, such as food, whenever it sees the stimulus. Very slowly, over weeks to months, the stimulus is gradually brought closer to the pet.
Food is often used for counterconditioning during training. It can be a powerful tool to overcome fear if special treats are withheld at all times except during exposure training. To create a positive association with the stimulus, the owner should offer highly palatable food when the cat is just far enough from the fear-eliciting stimulus to be relaxed. For example, if the fear-inducing stimulus is a young woman approaching the cat and the threshold for an anxious response is 10 ft, then the woman should approach within 15 ft of the cat. If the cat shows no sign of anxiety, then the owner should give the cat a tasty food treat (e.g. cooked meat, fish, freeze-dried treats, semimoist cat food). Gradually, over the course of many exposures, the young woman should come closer and closer to the cat. Patience is particularly important since the training must proceed slowly.
Some owners begin training by having a visitor extend his or her hand with a food treat toward the pet's face. Since the food reward is initially not strong enough to overcome the proximity of the fearful stimulus, this method usually doesn't work. In fact, it usually makes things worse. But asking visitors to be quiet, move slowly, avoid eye contact, and ignore the cat as they casually toss treats to it is a simple technique that can be successful in most homes.
Medication such as paroxetine, fluoxetine, buspirone, alprazolam, or lorazepam (Table 2) may be helpful in reducing fear and anxiety to a level low enough to allow behavior modification to begin. Diazepam has been used to treat fear-induced aggression in cats,5 but it should be used with caution—if at all—since it has been associated with fatal hepatopathy in rare cases.6
The most common type of aggressive behavior cats exhibit toward family members is play aggression.7 Young cats or kittens are most frequently presented for this problem. Kitten play typically involves elements of predation (stalking, chasing, attacking, catching, biting), exploration, and investigation. Play objects are often swatted, pounced on, and bitten. Sometimes, the cat will arch its back and hop sideways toward the play object. Bites are usually inhibited and swatting tends to be done with retracted claws, but serious injuries can occur during uninhibited play. Unlike other forms of feline aggression, vocalizations during play aggression are rare. The lack of hissing, growling, and screaming usually differentiates this behavior from more serious types of aggression.
Play aggression is likely when a kitten is the only pet in the home and the family is away most of the day. Most kittens engage their peers in rough and tumble play. When feline playmates are not available, kittens are likely to engage people in similar activities. Damage is usually minimal, but injuries may be serious if a family member has fragile skin, is immunocompromised, or takes an anticoagulant or if the play attacks are directed toward the face. Owners often contribute to the problem by playing with kittens in a way that encourages attacks on hands or feet. Although some young male cats can be wild and frightening to family members, play aggression usually has a favorable prognosis.
Treatment. Play aggression is one of the few behavior problems for which a second pet may be recommended. A second cat of the same age and temperament will usually satisfy the first cat's need for active play, and it is important that the cat have an acceptable outlet for this normal behavior.
Tell the owner to stop engaging the cat in rough play. Playing with the cat should involve tossing or dangling toys for the cat to chase and catch—all chase and attack behaviors should be directed away from the owner. Interactive toys that dispense treats or catnip may help.
Owners should avoid punishment such as yelling, thumping, or swatting cats since these may cause pets to either fear the owners or engage in rougher play. A blast of air from a compressed air can directed over a cat's head or a water gun or a sharp noise directed at the cat may discourage problem behaviors. Aversive techniques should always be matched to the individual cat's temperament, and nothing should be used that causes fear or a strong avoidance response.
Problems with other cats in the home occur when the object of play is another cat that is passive, weak, fearful, or old and can't tolerate the young cat's playful behavior. Initially, the cats should be separated unless a family member is supervising. The owner should provide lots of appropriate toys and playtime to help satisfy the young cat's need for play. During the separation period, the young cat should be taught by using food lures to come on command. Just before allowing the young cat into the room with the victim cat, the owner should exercise the young cat vigorously. Whenever the victim moves and the young cat orients toward it, the young cat should be called for a treat. The owner should never yell at the young cat to try to stop it from going after the victim cat because this will further stress the victim cat, which is already anxious. A water gun can be used to discourage the young cat's exuberant play directed toward the victim cat without further stressing the victim cat. Sometimes the victim cat becomes so stressed that it hides, housesoils, or becomes anorectic. In that case, giving medication (paroxetine, fluoxetine, buspirone, alprazolam, lorazepam [Table 2]) to the victim cat may help reduce its fear. Using the synthetic pheromone Feliway (Ceva Santé Animale) in the environment may also help. In time, the cats should be allowed to spend more time together unsupervised.
This type of aggression—probably the most dangerous—can result in frightening, vicious, and damaging attacks. It occurs when a cat is stimulated to an aggressive state of arousal and directs its aggression toward a person or animal that was not the cause of the arousal.8 Intermale, territorial, and fear-induced are the types of aggression that are likely to be redirected.7
The attack usually occurs when a person or animal approaches or touches the aroused cat. Male cats are more likely to show this type of aggression.9 Stimuli for aggressive arousal include the sight, sound, or odor of another animal; unusual noises; or unfamiliar people or environments. The aroused cat may exhibit growling, yowling, nervous pacing, piloerection, tail lashing, dilated pupils, and a fixed gaze directed toward the arousal stimulus. One common scenario is that of a cat sitting in a window and becoming aroused after seeing or hearing another cat. When someone attempts to pet the cat, pick it up, or nudge it away from the window, it attacks. Another scenario involves an indoor cat that escapes to the yard and is frightened by another animal or the unfamiliar environment. If the arousal level is high enough, the cat may bite when the owner tries to pick it up to take it indoors.
Victims of redirected aggression do not necessarily need to make contact with the cat. For example, an aroused cat may charge and attack a person who is across the room and paying no attention to it. Such attacks are often intense, sudden, and uninhibited. Multiple bites and severe injuries are common. Attacks may seem unprovoked because the arousing stimulus was present when the owner was not around, and the pet remained in a high state of arousal. Families are often unsettled about the apparent unpredictability of the aggression, thinking that their cats have "gone mad."
Diagnosing redirected aggression requires identifying the arousal stimulus associated with aggressive displays. A good history is key to identifying this stimulus. Get a detailed description of the problem and of other incidents of aggression or extreme fear in the pet's past. Since cats may stay in a high state of arousal for long periods after stimulus exposure, the owner may not know what stimulus caused the attacks. A history of aggressive incidents may lead to a list of likely stimuli. It is reasonable to suspect redirected aggression when two cats that have always gotten along suddenly begin fighting for no apparent reason.
Treatment. Treatment involves removing the cat's access to the stimulus or modifying its response to the stimulus. If the cat becomes highly aroused when it goes outdoors, keep the cat indoors. If it becomes aroused watching outdoor cats through the windows, remove the cat's access to the windows. Intact male cats may pay less attention to cats visiting their territories after they are castrated. Medication (fluoxetine, paroxetine [Table 2]) may help reduce an animal's response to stimuli. Desensitization and counterconditioning may be helpful as well. This approach is more successful when the stimulus is a nonsocial, environmental noise rather than an unfamiliar cat in the territory.
Unfortunately, owners often respond to the aggression with behaviors that make things worse (e.g. screaming, hitting the cat), causing the cat to be fearful. Fearful behavior can be treated with systematic desensitization and counterconditioning, as well as with the medications mentioned (see "Fear-induced aggression").
When the aggression is directed toward another pet in the home, the cats should be separated until the level of arousal diminishes, which could be several hours to a week or more. The cats should be gradually reintroduced as if they were new pets in the home. Medication (fluoxetine, paroxetine [Table 2]) for the aggressive cat or in some cases for both cats may be beneficial, and Feliway can also help the cats relax.
It's important that owners understand what causes the aggression, how to recognize the arousal signs, how to prevent situations that lead to aggressive arousal, and how to handle an aroused cat. When a cat is in a high state of arousal, the ideal way to respond is to leave it in a darkened room, avoid contact, and close the door. If the cat must be handled, thick leather gloves, a fish net, or a large towel may be used for protection.
The decision whether to keep the cat should be based on the frequency and severity of the attacks and on family members' ability to recognize and control the arousing stimuli and to recognize and avoid the aroused cat. If some people in the household cannot avoid the aroused cat, serious consideration should be given to removing the pet from the home or euthanizing it, especially those cats that charge their victims or bite uninhibitedly.
Some cats that are not fearful, in pain, or exhibiting any of the other emotional states described in this article bite while being petted. This problem can be disconcerting for the family. Such cats often seek attention, crawl into laps, or rub against legs and seem to enjoy the initial physical contact. But after a certain amount of petting occurs, the cats suddenly bite and run off. It seems that these cats have a threshold for how much physical interaction they can tolerate and cannot communicate that they have had enough in an acceptable manner. However, an observant owner knows when a cat is about to bite since the cat usually shows signs, including fidgeting, tail twitching, tenseness, leaning away, flattened ears, horizontal retraction of the lips, and hissing.
Treatment. Instruct the family to never absentmindedly pet the cat. Desensitization and counterconditioning should be attempted only when the cat voluntarily approaches. The threshold for the bite behavior must be determined, and petting should stop well before the threshold is reached. For example, if a cat always tolerates five seconds of petting but may bite after that time, then petting sessions should initially be three or four seconds. If the cat shows no sign of anxiety or aggression, it should be offered a tasty food treat. The owner should consistently say "good kitty" or some similar phrase every time the cat takes the treat. To encourage the cat's participation in the petting sessions, the sessions should be held just before feeding time and food treats should be withheld except during training. If the sessions take place on an owner's lap, the cat should not be restrained and should be allowed or encouraged to jump down (a treat can be tossed to the floor if necessary) as soon as each session is complete.
Sessions with the cat in someone's lap or next to someone on the sofa should be frequent, and, gradually, the length of the petting sessions should be increased. With time, the cat will learn to tolerate longer and longer petting sessions in anticipation of a food reward. Eventually, the treats can be phased out, and the cue words good kitty can be used without food to promote a relaxed state.
Many species engage in territorial aggression to expel or keep out other animals from a discrete, protected area, which helps preserve area resources for the resident or the resident social group. It is a common type of aggression in male and female cats, although it is particularly noticeable in male cats during the breeding season.1 Intrusion into a cat's indoor or outdoor home territory can trigger this type of behavior. Territorial aggression typically does not involve the threat rituals observed in intermale aggression.10
A typical territorial problem occurs when a new cat is brought into the home and the resident cat becomes aggressive toward it. The resident cat focuses intently on the intruder and may take a slow, steady approach as it stalks, or it may immediately attack the new cat. Some cats relentlessly pursue and attack a newcomer. Defensive displays by the new pet may include hissing, growling, yowling, and piloerection. This response often increases the resident cat's arousal and aggression.
Cats may also exhibit territorial or fear aggression toward visitors. Differentiate these two types of aggression by asking the owner about the cat's response to visitors. A territorially aggressive cat is bolder and typically approaches or lunges at a visitor. The lunging may be accompanied by piloerection, growling, and hissing, and batting with forepaws or biting may occur even if the visitor stands still or moves away. A fearful cat generally growls and hisses from a hiding place at a distance and only bites if approached, crowded, or handled. Identifying the aggression type is important because fear-induced aggression has a safer prognosis than territorial aggression does. The arousal caused by territorial aggression accounts for a high percentage of redirected aggression incidents.
False territorial aggression may occur when a cat returns home from a veterinary hospital or groomer. If the cat acts or smells differently than it did when it left the house, another resident cat may show signs of territorial aggression (or fear-induced aggression) until it recognizes its roommate, which may take a few hours to several days or more. The treatment is the same as for territorial aggression related to introducing a new pet.
Treatment. Systematic desensitization and counterconditioning exercises are used to treat territorial aggression.11 For conditioning to begin, the cats need to be able to see each other at a distance yet remain calm. In some cases, administering fluoxetine or paroxetine may reduce the arousal response so that behavior modification can be initiated.12,13 It may take two to four weeks for these medications to become effective. Progestins are rarely recommended because serious side effects are associated with them. Feliway can be helpful in calming some cats.
Behavior modification requires immense patience. Because treating territorial aggression is difficult and potentially dangerous to visitors or another cat, it may be more prudent to confine the cat when people visit and to avoid adopting another cat.
Prevention. In attempting to prevent territorial aggression, it is always wise to have a separation period when introducing a new cat into the household. The family should confine the cats in separate areas of the home where they cannot see each other. The confinement areas can occasionally be switched (without the cats seeing each other) to allow the new pet the opportunity to explore all areas of the home and to help both pets get used to the other's odor.
Confinement should be followed by a slow, progressive introduction of the cats. To begin, the cats should be allowed to see each other during a low-arousal situation, such as while being fed. To control the speed of the introduction, use crates or harnesses and place the cats far enough apart that they show no aggressive displays. They can then slowly be moved closer together each time they are fed. Another approach is to feed the cats in rooms separated by a screen door or a partially opened door. Start the feedings at the far ends of the rooms, and gradually move the food bowls closer to the doorway.
When the cats show no signs of aggression as they are fed in proximity, the owners can allow them to meet. Owners should assign a person with treats to each cat and station them at opposite ends of a large room. A cat can be kept close to each person by intermittently tossing treats on the floor. Gradually, the treats can be tossed toward the middle of the room, thus controlling the cats' slow approach toward each other. Water guns can be used to interrupt aggressive behavior if necessary. Caution the family against holding either of the cats and approaching the other during the initial meeting.
Eventually, the owners can allow the cats to have freedom together in the home, although initially the cats should be supervised. When the cats are finally allowed to roam freely in the home, at least two feeding stations and litter boxes should be placed in relatively open areas so that neither cat will be trapped or surprised when eating or using a litter box.
Aggression between male cats is one of the most common forms of feline aggression.1 As male cats behaviorally and sexually mature, they begin challenging each other. Intermale aggression is particularly common during the breeding season. The aggressive interactions involve posturing, threatening, and fighting. Hissing and growling often occur. Aggressive interactions between male cats may contain elements of intermale and territorial aggression.
Treatment. Intermale aggression is facilitated by postpubertal androgen secretion and is largely prevented or eliminated by castration.14 Neither the fighting experience nor the cat's age seem to affect the success of castration.14
Desensitization and counterconditioning may be helpful but are not successful for most cases when used alone. Drug therapy (see "Territorial aggression") may be necessary. When the medication is withdrawn, the cat may become aggressive again. In cases in which aggression persists after castration, separating the aggressive cats may be the only remedy.
Intense aggressive displays are common when people or animals approach a queen and her litter. This type of aggression is likely related to the hormonal state of females during lactation as well as to the presence of the young.2
Treatment. Because of the relatively short duration of maternal aggression, simply avoiding the queen may be the most prudent solution. Adequate socialization of female cats when they are young may also help prevent problems. Gently handling and hand-feeding a queen throughout her pregnancy and after parturition may also help.
Even the most sociable and docile cat may exhibit aggression with handling that elicits pain or discomfort (e.g. when its hair or tail is pulled, when it is stepped on, or when a painful area of the body is touched).1 Underlying painful conditions such as abscesses, otitis, and arthritis should be ruled out in all cases of aggression.
Although physical punishment can sometimes produce submission and facilitate restraint in social species, it is seldom a satisfactory method for modifying behavior or gaining control, especially in cats.2 In most cases, physical punishment either elicits aggression or intensifies the aggression that is already present, and it usually leads to fear and avoidance behaviors.
Treatment. It is best to avoid handling a cat when it is in pain. However, that is not always practical, especially when medications must be given or physical therapy needs to be performed. Thus, the approach must be to control the cat to reduce danger to the handler but to minimize the cat's discomfort. In some cases, analgesics may be helpful.
Habituation, desensitization, and counterconditioning exercises to increase a cat's tolerance for being handled may be of benefit as a preventive. Handling exercises performed with a kitten may help raise its threshold for pain-elicited aggression. These exercises can be performed at feeding time. To begin, instruct owners to gently handle all parts of the cat's body while it is being hand-fed. As days go by, the owner should increase the intensity and variety of handling; for example, grooming and claw trimming can be done during these exercises. Although the effects of all painful stimuli cannot be anticipated, a cat that is trained to be relaxed during handling that includes claw trimming and teeth brushing will also be more likely to tolerate handling when it is in pain.
OTHER TYPES OF AGGRESSION
Some cats exhibit learned aggression when an aggressive display successfully removes the source of fear, pain, or territorial intrusion, the behavior is reinforced, and the cat learns to use aggression in future encounters.
Another category of aggression is pathophysiologic, which includes aggressive behaviors that are not typical for domestic cats. Neurologic disorders stemming from conditions such as infections, trauma, or parasite infestations can lead to abnormal behaviors. Aggression due to psychomotor seizures is another rare type of pathophysiologic aggression.
Finally, idiopathic aggression is a catchall for aggressive displays that appear to be unpredictable and for which the underlying cause is unknown. However, most cases in this category probably have a legitimate etiology, but the pertinent information has not yet been elucidated. Cases of redirected aggression or fear-related aggression that resulted from circumstances the owner did not observe are likely to end up in this category. Instruct owners to always be cautious around a cat that behaves aggressively because of an unknown stimulus. Unpredictability increases the danger posed by the cat, and euthanasia should be considered for any cat that is unpredictably aggressive, especially when aggressive arousal typically results in attacks and injuries.
PRACTICAL SOLUTIONS FOR REDUCING INJURIES
While initiating long-term treatment, owners can take steps to immediately reduce injuries. These steps include regularly trimming aggressive cats' nails, applying Soft Paws (Soft Paws), or having the aggressor cat wear a belled collar during the treatment period. Remember these measures may help reduce injuries, but they don't alter a cat's motivation.
Wayne L. Hunthausen, DVM
Animal Behavior Consultations
Westwood Animal Hospital
4820 Rainbow Blvd.
Westwood, KS 66205
Dr. Hunthausen lectured on this topic at the 2006 CVC East. His paper originally appeared in the conference proceedings.
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