Behavior Problems in Adopted Cats & Dogs

Christine D. Calder, DVM, DACVB, Calder Veterinary Behavior Services, Portland, Maine

ArticleLast Updated April 202113 min readPeer Reviewed
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Millions of companion animals enter shelter and rescue organizations every year as strays and cruelty cases and due to hoarding and emergency situations (eg, pet owner hospitalization, domestic violence, loss of income, loss of housing).1 In some communities, surrendered or relinquished pets account for >50% of shelter intakes, with behavior problems cited as the primary reason for relinquishment in 40% of dogs and 28% of cats.2,3

The most common behavior problems that lead to relinquishment include house soiling, aggression toward humans or other animals, destructive behavior, fearful behavior (dogs), unruly behavior (eg, jumping, mouthing, being too active; dogs), escaping, coprophagia (dogs), and pica (dogs).

Clinicians can play a pivotal role in reducing the number of surrendered animals, as ≈67% of dogs and 53% of cats in shelters were taken to a clinic at least once in the year prior to relinquishment.2 Understanding at-risk behaviors and behavior assessments can help clinicians diagnose and treat problem behaviors, as well as provide owner education to enhance and preserve the human–animal bond.

Behavior Assessments

Many shelters perform formal behavior assessments of dogs to identify temperament, personality, risk for future aggression, and behavioral support needs. A formal behavior assessment test for cats is not currently available.

Behavior assessments in shelters have limitations, and studies have not identified them as a good predictor of behavior in the home.4-7 To obtain a comprehensive understanding of behavior in different situations and environments, information should be gathered from various sources (including previous owners, an intake questionnaire, medical examination, staff, volunteers), as well as through observations of play, walks, and behavior in foster homes.

Treatment in the Shelter

It can be difficult to treat behavior problems in the shelter environment, as the shelter can be stressful and very different from the previous home environment. The presence of unfamiliar humans, animals, sights, and smells often results in stress and can even suppress certain behaviors. A foster program can help increase the likelihood of success when implementing behavior modification programs.8-11

Enrichment Programs

Resources can vary, but all shelters should have an enrichment program. Use of food-dispensing toys, time out of the kennel, and exposure to classical music, audiobooks, and novel scents can help reduce stress and improve welfare.

Social interactions with humans and other dogs or cats are also important. Because many shelter animals have had little or no previous interaction with humans, positive reinforcement training can positively impact association of pleasant experiences with humans and provide opportunities to teach desired behaviors. Play groups and community rooms allow observation of interactions with other cats and dogs and the possibility to reinforce desired social interactions during play.


Psychopharmacologic medications can help improve welfare both during intake and time spent in the shelter. In dogs, trazodone (5 mg/kg PO) administered during intake and within 48 hours after arrival can help reduce transitional stress, decreasing illness and length of stay.12 Other long-acting (eg, selective serotonin reuptake inhibitors [eg, fluoxetine], tricyclic antidepressants [eg, clomipramine]) or short-acting (eg, clonidine, gabapentin) medications may be helpful if a behavior modification plan is needed.

Although no studies have been performed regarding trazodone use in shelter cats, one study found that trazodone reduced stress associated with veterinary visits in pet cats13; anecdotally, trazodone has also been used with success in shelter cats. Another study found that oral gabapentin administration in community cats confined for trap–neuter–release was effective in reducing the fear response.14

Behavior after Adoption

It can take several weeks to months for cats and dogs to adjust to a new living environment and routine. Problem behaviors are common during this time; thus, new pet wellness visits are ideal for owner education and early intervention.

House Soiling

In dogs, house-training regression is normal in the shelter, as kennel space and outdoor time are limited. Because shelter employee and/or volunteer schedules may differ from the dog’s normal elimination schedule, many dogs often eliminate in their kennel. It is important to encourage owners to follow the basics of house-training for all newly adopted pets. House-training can have an increased likelihood of success with the use of training basics including constant, direct supervision; keeping to a schedule with breaks for elimination at least every hour and after naps and meals (more frequently during play times); avoiding punishment; using positive reinforcement (eg, giving high-value treats) when elimination occurs in a desired area; and cleaning accident sites well with an enzyme-based cleaner.

Cats that are house soiling should first be checked for a medical cause. It should then be determined whether the cat is urine spraying (ie, vertical marking) or has found a new place for elimination. It is helpful to know the location of the elimination areas; the number, size, and location of available litter boxes; the type of litter; and the relationship between the cat and other animals and humans in the home. Conflict and anxiety often cause cats to urine mark; identifying particular triggers, implementing behavior modification, and administering medications can be beneficial in reducing marking behavior. In toileting cats, it is important to address litter box factors so that desired elimination spots are inviting and undesired elimination areas are uninviting.


Dogs instinctually keep their “den” clean; therefore, dogs sometimes engage in coprophagia when confined and forced to eliminate in their living space. This behavior can continue as the dog transitions to a new home.15 Management through supervision and immediate clean-up is key to reducing this behavior.

Separation & Confinement Anxiety

Separation anxiety is typical in newly adopted shelter dogs and may have been the initial cause for relinquishment. Clinical signs for separation anxiety include destructive behavior, excess vocalization, and improper elimination. Many dogs pant, pace, whine, and sometimes break through barriers and escape the room, house, or yard. Owner recordings of the dog in the home can help in providing a diagnosis and monitor the treatment plan. A trial run with the dog out of confinement while being recorded can help differentiate between separation anxiety and confinement anxiety.

Treatment for both separation and confinement anxiety should include trying to help the dog avoid separation, including sending the dog to daycare (if they get along with other dogs), having a friend or family member watch the dog when the owners are away from the home, or accompanying the owner to work if allowed. Medications are often the first line of treatment. Serotonin-enhancing daily medications (eg, fluoxetine [1-2 mg/kg every 24 hours] or clomipramine [1-3 mg/kg every 12 hours]) can be helpful but can take up to 6 to 8 weeks to reach full efficacy.16-18 Other situational medications (eg, trazodone [3-8 mg/kg every 8-12 hours]), clonidine [0.007-0.049 mg/kg every 12 hours], alprazolam [0.02-0.1 mg/kg every 4 hours], lorazepam [0.02-0.5 mg/kg every 8 to 12 hours]) can be helpful in the first 3 to 4 weeks after diagnosis.16-18

Establishing a safe haven using classical music, food-dispensing and puzzle toys, warm soft bedding, low lighting, and reduced visual stimulation (eg, closed blinds and curtains) can help create a calming effect. In some cases, pheromones can also be helpful. Long-term treatment should encourage independence and exploration through puzzle toys and games (eg, search and scent activities [eg, nose work, “find it”]). Conditioned relaxation on a mat can reinforce calm behavior and relaxation.

Fearful Behavior

The fear response can have varying levels. Some dogs and cats may retreat and have minimal interactions with humans, whereas others may freeze, growl, lunge, snap, or bite. Owners often assume abuse has taken place, but this behavior is likely a result of lack of experiences and exposure during the socialization phase (dogs, 4-14 weeks of age; cats, 2-7 weeks of age). Genetics can also play an important role.19

Nonaggressive, fearful dogs and cats should be provided a safe haven area and given space and time to adjust to their new environment. Once these dogs and cats learn a routine and feel safe, they should start to interact more frequently with humans and other animals. In some cases, daily medications (eg, fluoxetine [dogs, 1-2 mg/kg every 24 hours; cats, 0.5-1.5 mg/kg every 24 hours], clomipramine [dogs, 1-3 mg/kg every 12 hours; cats, 0.25-1.3 mg/kg every 24 hours], buspirone [dogs, 0.5-2 mg/kg every 12 hours; cats, 0.5-1 mg/kg every 12 hours]) may be beneficial in lowering overall anxiety and fear. Short-term medications (eg, benzodiazepines, trazodone, clonidine) can also help during transitions.

Medication may be needed in fearful dogs and cats that are aggressive.20 It is also imperative that fearful stimuli be identified, as avoiding these can help reduce the aggressive response. Understanding body language can help in assessment of the emotional state. Behavior modification (ie, desensitization and counterconditioning [DSCC]) can later be used to attempt to change the response to these stimuli.


Aggression in dogs and cats can be offensive (eg, direct staring, barking, growling, hissing, swatting, snapping, biting) or defensive (eg, piloerection, stiff body posture, looking away, leaning away). Regardless of the display, these behaviors should be recognized, and the stimuli should be identified and removed or avoided.

Aggression can have a variety of motivators (eg, conflict, fear, territorial, play, pain, maternal, redirection [especially in cats]). Regardless of the cause, treatment should include management to reduce the need for an aggressive response and avoidance of the triggers. Providing a safe haven area and avoiding aggressive triggers can be helpful. Positive reinforcement training should be used, and positive punishment (eg, saying, “No,” yelling, hitting, placing in “time out”) for the behavior should stop. Tools such as a basket muzzle, gates, and exercise pens can increase safety. In cats, separation behind closed doors or crate training may be necessary.

Behavior modification with DSCC can include reintroduction of triggers. Redirection and reducing arousal (eg, via target training or conditioned relaxation on a mat) can be helpful. Consistent interactions through a cue–response–reward interaction can reduce both aggression among dogs and resource guarding; this can also benefit cats. Daily and situational medications can help lower overall arousal levels and reactivity.20,21

Leash Reactivity

Leash reactivity (ie, barking, pulling, lunging, and, in some cases, snapping and biting) is common in many dogs and can have several motivators. These dogs may be fearful or territorial. Many of these dogs are frustrated greeters (ie, the dog attempts to greet another dog but cannot reach them, which results in barking, whining, and pulling on the leash). The owner often contributes to this behavior by providing tension on the leash, correcting the dog, and forcing the dog to sit and stay. Human body language and emotional state (eg, increased respiratory rate, tension) can also contribute to or become a cue for the behavior. Treatment often involves use of appropriate equipment (eg, front clip harness or head collar, nonretractable 4-6–ft leash). Management should involve avoidance via emergency U-turn (ie, a 180-degree turn away from the trigger/stimulus), moving away from the trigger, hiding behind objects, and creating space between the dog and the trigger. Leash handling and walking skills should be taught along with rewarding the dog for focusing on the owner. Conditioned relaxation and DSCC are key to changing the dog’s long-term response to triggers (eg, other dogs, unfamiliar humans, vehicles). Situational medications may be needed, especially if behavior modification is not progressing.

Food Aggression

Food-related aggression is often considered normal in dogs, but there may be an underlying anxiety involving humans or other animals near food. Although studies show that consistent resource guarding in the shelter is likely to also occur in the home, food aggression exhibited in the shelter does not always necessitate euthanasia.22

Managing food-related aggression should include providing consistent, predictable interactions with humans and a routine feeding time and space. A gate or door can improve safety, and food should never be removed while the dog is eating. It is important not to force human presence (including petting or sitting near or directly in front of the dog) while the dog is eating. A second food bowl can be placed and high-value treats or items tossed in the bowl from a distance that is decreased over time to help gradually reduce the behavior.

Resource Guarding (Nonfood Related)

In dogs and cats that resource guard space, toys, objects, and/or humans, the underlying motivation (eg, anxiety) should be identified and treated. Management through removal of or restricted access to guarded items can be beneficial. In dogs, trading up for higher value items can be practiced (see Trading Up). Dogs and cats should not be moved from their resting area. The dog or cat should always be called and a reward offered for coming to the caller. Teaching alternative behaviors (eg, touch) can help in redirection and nonconfrontational removal (see Targeting/Touch).

Introducing New Cats & Dogs

Careful introduction of newly adopted animals in the home is important. This is especially true for cats, as cats are selective with other cats and can be territorial. Before bringing a new cat into the home, adequate resources (eg, beds, hiding areas, feeding spaces, elimination areas) and a safe haven area (eg, behind a closed door) to separate the cats for the first few weeks should be provided. Gradual introductions with play and food can help form positive associations. A gate placed in the doorway, with cats fed on opposite sides of the gate, can be helpful. Puzzle and food dispensing toys can help create a positive association with the presence of the other cats. The door should be closed when one cat finishes eating. Small, frequent meals should be given throughout the day. Over time, the barriers can be removed and the cats can intermingle.

Dogs new to the home should first be introduced in neutral territory. Taking both dogs for a walk together can be a fun bonding experience. In the home, barriers should be placed until the owner is comfortable with how the dogs interact. Body language should be monitored to ensure both dogs are relaxed. Limiting high-value items (eg, food, toys) can help reduce guarding behaviors.

Mixing Cats & Dogs

Introducing a dog in a home with cats (or a cat in a home with dogs) requires extra precautions. A transition spot (eg, a quiet area or, preferably, a room with a door) should be provided. Many dogs in the shelter environment are not cat-tested, and there is potential for aggression toward the resident cat, which should have a secure place where it can retreat and hide if needed. New dogs and cats should not be left unsupervised, as this can have life-threatening consequences. Introductions should be slow and gradual and should reinforce calm behaviors. Calm behaviors should be reinforced and frequent check-ins should be made away from the other animal. A muzzle (dogs) may be needed initially for safety.


Rescued dogs and cats can make great companion animals. Clinicians can improve retention in the home through early intervention and owner education. Recognizing potential behavior problems early can promote the human–animal bond and improve quality-of-life for the owner and animal.