Drew Weigner, DVM, hospital director of The Cat Doctor feline specialty clinic in Atlanta, offers tips for managing aggressive cat behavior.
Face facts. "Play aggression is common and not necessarily a bad thing, especially for kittens," says Weigner. "What's not normal is injuring others." Look at your cat's face to see if they are playing or being aggressive. A cat with turned-back ears and whiskers and dilated eyes that's crouching down and hissing is telling you to beware.
Play around. "Many cats cross the line from play to aggression because they're bored," says Weigner. Play with your cat for 30 minutes twice a day.
Hands off. Using your hands as toys encourages cats to treat them as prey and leaves you open to cat bites, which always require a trip to the doctor, Weigner says. Instead, get in the habit of using kitty teasers, such as toys that look like fishing poles or laser pointers.
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Katherine Miller, PhD, CAAB, CPDT, director of anti-cruelty behavior research, ASPCA's Anti-Cruelty Behavior team, New York, N.Y.
Drew Weigner, DVM, ABVP hospital director, The Cat Doctor, Atlanta.
Dominance aggression is the most common type of aggression in dogs and approximately 60% of aggressive dogs exhibit dominance aggression.  Dominance aggression occurs when a dog battles familiar people or other dogs for higher hierarchical position.  An owner plays a significant role in dominance aggression because 40% of dominance aggression circumstances are related to dog owners who spoil their dogs and provide poor levels of obedience training.  The actions of an owner and the relationship between a dog and its owner influence dominance aggression in dogs.  For instance, the punishments endured by the dog, the obedience training received by the dog, the quality time spent with the dog and how spoiled a dog is contribute to dominance aggressive behavior.  Contradicting research suggests several opposite conclusions, however: 1) Punishing dogs has been associated with a strong likelihood of new or increased aggression and other behavior problems 2) dominance in pet dogs is not a character trait of a dog but rather a power agreement between dogs regarding who has best access to particular resources and 3) the behavior of dogs controlling access to resources is fluid, not static, depending on context. There is also data suggesting that the concept of spoiling a dog is often a misnomer, that this perceived spoiling is often a matter of meeting the dog's emotional and physical needs, as outlined in the Five Freedoms & Five Dominions for companion animals.   
Defensive aggression, also known as fear aggression or avoidance-motivated aggression, occurs when an individual approaches and interacts with a human-avoidant dog. The dog might first try to flee, but may resort to aggressive behavior if cornered, as a means to try to defend itself from a real or perceived threat. The dog displays aggressive behavior in an attempt to avoid a real or perceived negative consequence, such as to avoid pain. Dogs may display a multitude of behaviors leading up to an attack including fear and stress signals, defensive posturing, facial expressions, or no signals at all. Signals are generally different for self-defensive dogs versus those who are truly aggressive, as in competitive aggression. 
Tortora in 1983 experimented with a shock therapy to retrain avoidance-motivated aggressive dogs to condition them with safety cues, a process which he called Safety Training. He wrote that this therapy, when successful, had long-term benefit for the dog and its owners. 
Predatory aggression is usually seen as part of the prey drive sequence starting with a visual or auditory trigger followed by chase, capture and kill.  Predatory aggression is impacted by anxious influences, which results in the expression of affective aggression.  This type of aggression is caused by sympathetic system activation and is non-affective.  Based on a study that examines the predatory aggression in German shepherd dogs, this type of aggression is rarely displayed by dogs.  However, if it does occur, it is usually directed towards unfamiliar dogs.  Furthermore, predatory behavior activates reward centers in the central nervous system.  According to Gonzalo and colleagues, this type of behavior is rewarding and therefore difficult to change.  Predatory aggression is displayed by mature and intact males and this type of aggression results in serious damage to others.  It includes actions such as chasing, biting, catching and may involve death or injury. 
Maternal aggression is displayed by mothers when they are approached and particularly when their offspring are young. This type of aggression is linked to pain such as in cases of mastitis.  Oxytocin plays an important role in the early bonding between the mother and her offspring.  Dogs with maternal aggressiveness are protective of their offspring and nest.  The change in hormone is linked to lactation, and the mothers can change the dogs' perception and assessment .  Maternal aggression may lead to bites or other attacks.  Maternal aggressiveness affects the growth and socialization of puppies.  Furthermore, this type of aggression may stem from unstable social environments.  Maternal dogs are very protective of their puppies and their aggressive tendencies decreases as their offspring grow up and they are able to defend themselves. 
The gut microbiome is linked to numerous health problems such as diarrhea and bowel disease, which results in pain and can possibly lead to aggression.  The gut microbiome affects the affective disorders such as anxiety, which contribute to canine aggression.  Based on a study carried out by Kirchoff and colleagues, the composition of gut microbiome differs on the basis of aggressive and non-aggressive assessments.  In this study, the researchers tested rescued dogs that possessed aggressive and non aggressive behavior.  The dogs were tested in the same environment, ate the same diet, and were consistent breed type, but variation was still present in the gut microbiome.  The results of this study show the difference and abundance in lineages in aggressive and non-aggressive groups, indicating that an aggressive dog displays physiological conditions in their gut, which affects the composition of the gut microbiome.  It also shows that the gut microbiome is associated with aggressive behavior.  Lactobacillus are present in the guts of dogs that exhibit aggressive behavior, even though strains of Lactobacillus rhamnosus reduce stress and anxiety in mice.  However, Fusobacterium is present in the stool sample of dogs that display non-aggressive behavior, even though it is known to evoke pro-inflammatory effects of gut microbiome. 
Some aggression stems from generalized anxiety. The dog cannot determine the difference between a legitimate threats and false threats. Some signs of anxiety include dilated pupils, constant yawning and lip licking, ears pulled back, trembling, tail tucked and lowered body or head. An anxious dog may pace or be unable to relax even when there is no threat present. 
Anxiety screening was used in behavioral evaluation of children-directed aggressive behavior in dogs and according to Reisner and colleagues, 77% of animals displayed abnormalities.  Aggressive behavior in dogs is often associated with fear, the separation from their owner, or noise sensitivity, all of which may result in or contribute to anxiety disorder. 
In a study that examines the prevalence, comorbidity, and behavioral variation in canine anxiety, owners of fearful dogs reported that their dogs demonstrate behaviors they consider aggressive, such as barking and growling, to strangers and other dogs.  The owners of 673 dogs noted that their dogs express fear by barking, and growling. The presence of aggression in dogs is associated with defense mechanism.  Based on this study, there was an increase in bites towards strangers and familiar people when the self-defense response was not heeded, such as by cornering an avoidant dog.  However, Abrantes points out that aggressive behavior in dogs is behavior that causes pain or injury,  and HSUS explains that barking and growling are normal communicative behaviors for dogs not necessarily indicative of aggression. 
It is important to recognize that aggression is displayed more in certain breeds, which indicates the influence of genetic background on aggression in dogs.  According to Roll and Unshelm, German Shepherd dogs and Bull Terriers are more likely to display violent behavior to others.  Voith and Borchelt found that higher incidences of aggressive behavior were displayed in purebred dogs when compared with mixed breed dogs.  Often, aggression in adult dogs is usually a result of little to no contact in early life.  In other words, as a result of missed early socialization, a dog will not know how to interact with others, how to follow rules or how to adapt to new environments.  Aggressive behavior is more prominent in intact males when compared with neutered males and in sterilized females than intact females.  According to Hoerlein, the removal of a male's testicles has significant impact on aggressive and dominant males.  Neoplasia of the central nervous system, infectious diseases, developmental and metabolic disorders may impact aggression in dogs.  Many of these illnesses can cause aggressive and violent behavior, especially when located in the frontal cortex, the hypothalamus, the thalamus, the amygdaloid body, the medial mammillary, the nucleus, the habenular nuclei, the hippocampus and the caudate nucleus. 
Gonadectomy is used to treat aggressive behavior of dogs. Farhoody and colleagues carried out a study to determine the impact of gonadectomy on the aggressive behavior of dogs using the Canine Behavioral Assessment Research Questionnaire (C-BARQ).  According to the data collected, gonadectomized dogs between the ages of 7 and 12 months were more likely to be aggressive to strangers. 
Furthermore, gonadectomized dogs of all ages do not display violent behavior to familiar people or strangers.  The data does not show that gonadectomy prevent or treat aggressive behavior of dogs.  Perez-Guisado and Munoz-Serrano argued that owner-related factors were the primary cause of aggression in dogs. 
Based on their studies, dogs owned by first time owners and with little training displayed aggressive behavior.  Based on McMillan and colleagues’ research, aggressive behavior was prominent in dogs obtained from pet stores.  Guy and colleagues found that environmental factors directly contributed to aggression in dogs.  For instance, a dog that lives in a home with an adolescent or has a skin disorder is more likely to exhibit aggressive behavior to familiar people and strangers. 
Roll and Unshelm believed that the reason for buying or adopting a dog was a significant factor that correlated with aggression.  They also argued that the relationship between the owner and dog determined whether or not the dog would exhibit aggressive behavior.  For instance, the owner's attitude towards training, or physical mistreatment endured by the dog at the hands of the owner resulted in aggressive behavior towards others.  Many factors impact the aggressive behavior displayed by dogs. 
According to Arata and colleagues, reactivity to stimuli is involved in various types of aggression.  The researchers used a questionnaire survey to assess approximately 5000 dogs of 17 breeds.  In this study, a factor analysis was used to extract five consistent factors in 14 of the 17 breeds.  Using 14 behavioral items, the researchers were able to see the consistent presence of these factors in dogs, indicating that these factors are linked to canine aggression. 
The collected data and the established factor system indicated that the French Bulldog, Cavalier King Charles Spaniel, Golden Retriever, and Labrador Retriever did not display aggressive behavior.  However, the Chihuahua and Miniature Dachshund were more aggressive and more likely to chase others. 
Based on this study, reactivity to stimuli was linked to owner-directed aggressive behavior in 13 different breeds, child-directed aggressive behavior in eight different breeds, stranger-directed aggressive behavior in nine breeds and dog-directed aggressive behavior in five breeds.  In this study, dogs that are highly reactive to stimuli were either uneasy and reacted to all movements or less engaged and overreacted to unexpected stimuli. 
The association between canine aggression and sociability with humans and likeliness to chase were examined.  Sociability with humans was linked to child-, stranger-, and dog-directed aggressive behavior in more than seven breeds.  Moreover, likeliness to chase was primarily linked to dog-directed aggressive behavior in 10 breeds and dogs that were more likely to chase smaller animals displayed aggressive behavior when interacting with other dogs.  Reactivity to stimuli was proven to be an underlying temperamental factor that leads to canine aggression. 
Treatment differs for each circumstance, and treatment plans are based heavily on the type of aggression.  Based on Judith Blackshaw's study, dogs exhibited dominance aggression towards familiar people and therefore suggested obedience training as the proper treatment.  According to a study conducted in 1983 by Tortora, avoidance based aggression was treated by conditioning the dog to a safety tone, this resulted in a complete elimination of the aggressive behavior for the duration of the dogs lives.  It is imperative for an owner to train their dog every day for a minimum of 10 minutes.  More specifically, it is recommended for males to be neutered as this ensures that inherited aggression will not be passed on.  It is suggested to use synthetic progestins with castration to reduce and eliminate aggressive behavior in dogs.  Predatory and intermale aggression is inherent and related to testosterone secretion and as a result restrain, castration and the use of progestins are essential in reducing aggression in dogs. 
Missed early socialization and an absence in obedience training may result in aggression in dogs.  Animal behaviour therapy (ABT) aims to reduce aggressive behaviour in dogs by applying scientific ideologies.  Behaviorists aim to familiarize dogs with trigger stimuli by continuously exposing them to it via classical counterconditioning & desensitization, always from a non-triggering distance.  ABT ranges from relaxing a dog by giving massages to implementing consistent obedience training in the daily life. 
One study suggests that 40% of dominance aggression in dogs is a result of owners who provide basic levels of obedience training to their dogs.  A dog is an owner's responsibility and it is necessary for the owner to establish leadership over the dog.  A leash that is also known as a control line is critical in establishing and maintaining control.  However other studies suggest that aversive means of control and training contribute to new and increased aggression rather than reduce it. 
All behaviours happen for a reason and occur as a result of the way the dog is feeling – and aggression is no different. A properly qualified and experienced behaviourist will be able to get to the heart of why your dog feels they need to act in this way, what their triggers are, and how to deal with this.
Aggression in dogs nearly always comes from fear – as the purpose of aggression for a dog is one of perceived self-defence, and nearly always is with the intent of making things the dog regards as frightening or unpleasant stop, make them go away, or prevent them from happening in the first place
These fears can arise due to inadequate early puppy socialisation, past experiences, or the perception that valuable resources are under threat of being taken away. Some dog who have been roughly or inappropriately handled as a puppy or put in scary situations when they are too young to be able to do anything about it can also grow up to be more reactive as adults.
Since fear is the most common cause of aggressive behaviour in dogs, you should never punish your dog for growling or for any other display of aggression. Shouting at a dog for growling at something he is fearful of will simply compound his fear, may escalate the aggression, and quite likely his aggressive response will worsen next time.
Aggression, defined as hostile or violent behavior intended to dominate or intimidate another individual, is a fairly common behavioral problem in cats.
Its causes in cats can be complex, both in terms of triggers and targets, making it challenging to find strategies to eliminate aggressive feline behavior.
The consequences of aggressive behavior in cats can be significant, ranging from injuries to other cats and people to the surrender of aggressive cats to shelters. A recent study reported that 27 percent of cats relinquished to shelters for behavioral reasons were surrendered for aggression. Given these high stakes, it is important that cat owners understand the cause of their pet’s aggressive behavior in order to develop a plan to successfully intervene.
Regardless of their cause, recognizing the signs that a cat is fearful or aggressive can help prevent injury to pets and people. These cues can be separated into two categories: those observed in the face and head and those expressed by body posture.
Signs of aggression include dilated pupils, ears flattened backward on the head, tail held erect with hairs raised, and an arched back. Signs of fear include dilated pupils, ears flattened and held outward, whiskers flattened or pressed downward onto the face, tail closely wrapped or tucked under the body, and head held upward while lying prone ( Figures 1 and 2 ).
There are a number of different types of aggression that cats can display, and in some cases, a cat may display more than one type at a time. Here are some general principles for managing all types of feline aggression:
The first step in managing an aggressive cat is to ensure that there is no medical reason for aggressive behavior. Diseases such as hyperthyroidism, osteoarthritis, dental disease, and central nervous system problems may cause aggression, so consult a veterinarian before attempting to manage aggressive cats through behavioral and/or environmental modification.
Once a veterinarian has ruled out medical problems, identifying the type of aggression is key to understanding its cause and to developing a plan to intervene.
Types of Aggression
Cats can display aggression for a number of reasons. Determining the cause of a cat’s aggressive behavior is important, as different types of aggression may be managed differently. The following are general categories of feline aggression and how they can each be addressed.
Young cats and kittens that were not raised with littermates, or that lack opportunities to play most commonly show play aggression. Learning appropriate play is an important part of a cat’s socialization, and this normally occurs during time spent with littermates. Cats learn that they are biting or scratching too hard when their littermates stop playing or retaliate. Cats raised alone during their early lives may not learn this important lesson.
Cats that are about to engage in play aggression will often thrash their tails back and forth, have their ears pinned to the tip of their head, and have dilated pupils. They may stalk their target, whether animal or human, and will often pounce from a hiding place as the target passes by.
To intervene in play aggression, first determine if there is a pattern to when and where aggressive behavior occurs. If so, preempt the aggression by distracting the cat with play or denying access to places that encourage the behavior, such as under the bed if the cat hides there before pouncing. A bell on a breakaway collar may be helpful in signaling a cat’s whereabouts prior to and during aggressive behavior.
The use of noise deterrents within a few seconds of aggressive behavior, such as a blast from a can of compressed air or a person hissing, may be helpful in startling a cat and redirecting his attention. The goal is not to scare the cat, but to distract him and refocus his attention. Never physically punish, or even touch a cat, during these times, as this may cause a cat to become fearful of people or may be interpreted as play, which may inadvertently reward the aggressive behavior. Walking away and ignoring a cat engaged in play aggression may teach him that inappropriately aggressive play results in no play at all.
Any objects used to distract a cat from play aggression should be kept at a distance from your hands so that the cat cannot bite or scratch you while venting his aggression on the toy.
This type of aggression may be seen when a cat encounters unfamiliar stimuli, such as a new person, animal, or noise, or when a cat is exposed to an experience that he associates with unpleasant events, such as a trip to the veterinarian.
Cats demonstrating fear aggression may flatten their ears against their heads, hiss, bare their teeth, or crouch low to the ground with their tail tucked under their body, and their fur may stand on end.
The best way to deal with fear aggression is to identify and avoid situations that produce a fearful response. If a situation cannot be avoided, then you can attempt gradual desensitization by briefly exposing the cat to the stimulus that causes the fear from a distance, and then rewarding non-aggressive behavior with food and praise.
It is very important not to console an aggressive cat, as this may be perceived as approval of aggression. It is also important not to retreat or show fear, as this may reinforce the behavior if your retreat is what the cat wants. Lack of attention is a better way to handle fear aggression.
For reasons that remain unknown, some cats may suddenly become aggressive when being petted. Possible explanations include overstimulation and an attempt by the cat to control when the petting ends. Handling, bathing, grooming, and nail trimming can also cause this type of aggression. In many cases, the cat will demonstrate dilated pupils, tail lashing, and ears moved backward on the head before becoming aggressive.
To manage a cat with petting-induced aggression, owners should avoid uninvited handling or petting, any type of physical punishment or restraint, and attempts to pick up or interact with the cat while he is eating. Rewarding a cat with a food treat for allowing brief, light stroking without signs of aggression may also be helpful. Over time, owners can gradually increase the duration of stroking, but with any sign of aggression, the owner should stop the petting and begin a cooling down period with no physical contact.
It is particularly important to supervise cats that display this type of aggression when they are in the presence of young children, who often want to pet cats but miss the visual cues of impending aggression. Ideally, owners should prevent physical contact between small children and a cat with a history of petting-induced aggression.
When a cat is excited by a stimulus but cannot respond directly, the cat may redirect his aggression toward a human or another cat. Common stimuli that trigger redirected aggression include loud noises, seeing an outdoor or stray cat through a window, or an altercation with another cat in the house. Sometimes, aggression may be redirected toward a human after an aggressive interaction between indoor cats.
The best way to prevent this type of aggression is to remove or avoid the stimuli, for example, by pulling down a window shade, using deterrents to keep stray cats away from the window, or by preventing aggressive interactions among indoor cats.
Cats that are in pain may act aggressively toward people or other pets in an attempt to avoid touch, movement, or certain activities that might worsen the pain. Cats with osteoarthritis, for example, may resent having their joints touched or manipulated, and may hiss, bite, or scratch in response. Rarely, some cats may continue to act aggressively even after once-painful parts of their body have healed, presumably to avoid the pain they experienced previously.
Owners can manage pain-induced aggression by refraining from touching painful parts of a cat’s body and by working with a veterinarian to establish an effective therapeutic plan for pain control.
Cats may occasionally show signs of aggression toward people or other pets when they want to establish social dominance. Cats that block doors with their bodies or swat at other cats as they pass may be demonstrating this type of behavior.
The best way to address status-induced aggression is to ignore an offending cat completely. Attention, including play and food rewards, should be given only when an aggressive cat is relaxed. A relaxed cat is not swatting or hissing, has normal sized pupils, ears held upright, and normal tail posture, with the tail held upward with no flicking, twitching, or hairs on end.
Cats tend to establish and defend their territories. They may show aggression toward newly introduced cats, and occasionally other animals or people, that encroach upon their established domain. In some cases, cats may even attack resident cats that were previously accepted but were away from the home, such as for a hospital stay. This aggression commonly takes the form of swatting, chasing, and attacking the encroaching individual.
The most important thing to keep in mind when dealing with territorial aggression is not to rush an introduction or reintroduction. New or returning cats should be confined to their own room with separate litter box, water, and food. After a few days, replace the new or returning cat with the aggressive cat and close the door for about 30 minutes, then return the cat being introduced/reintroduced back to his own room and the aggressor back to the rest of the house. This step can be repeated daily for several days.
The next step is to place the cats on opposite ends of the same room in carriers or on leashes with harnesses, so that they can see and smell each other but cannot interact. Feed the cats so that they associate the positive experience of being fed with the presence of the other cat. If they won’t eat, move them farther apart. This step should be done repeatedly over several days, with a smaller distance between the cats each time. Lastly, once the cats have become acclimated to each other’s presence with restraint and feeding, release them in the same room, at a distance, and feed them. If any signs of aggression occur, resume restraint and feeding in the same room until the cats calm down.
This process can take weeks to months, depending upon the cats involved. In some cases, your veterinarian may have to prescribe medication to one or both cats to prevent adverse interactions, but it is important to note that medication must be used in conjunction with the gradual desensitization process outlined above.
It is crucial that you never put your hand or any other body part between cats that are fighting, as you can be seriously injured. Using barriers such as baby gates or panels made of cardboard, light wood, or plastic to separate aggressive cats can be very effective.
Queens that have recently given birth and are nursing kittens may demonstrate aggression toward individuals that approach them. Owners should provide a quiet, low-stress environment, keep visitors to a minimum, and avoid contact with the queen and kittens if they observe aggression. Maternal aggression will usually subside as the kittens get older and more independent.
Male, and more rarely female, cats may demonstrate aggression toward other male cats as they approach social maturity between two and four years of age. The first step in addressing this behavior is to neuter or spay all cats involved, as sexual hormones may play an important role in this type of aggression. Territorial aggression may also play a role, as described above. If neutering and spaying does not improve the situation, the cats should be separated and reintroduced using the technique outlined above.