Age and behavior

Age and life-stage patterns of behavior should be considered during behavioral and physical examinations. Normal patterns of behavioral change are predictable as the brain matures, whereas atypical changes may signal the development of a behavioral problem.

Puppies and kittens

The pre-, peri-, and postnatal environments are critical for creating calm, nonreactive animals. Calmer dogs and cats are easier to handle and train and may be less likely to become aggressive and fearful. If patients experience early stress (such as neglect, abuse, isolation, nutritional compromise, or environmental instability) or their mothers experience gestational stress, it’s likely that there will be adverse effects on early behavior. Clients and veterinarians must communicate about early behavior and risk.

Animals are best able to learn to respond to social and physical environments during specific neurodevelopmental life stages. Responses to stimuli during those periods may be accurate predictors of future behavior and should alert clients and veterinarians to early problems. Veterinarians should conduct multiple behavioral assessments throughout the first 18 mo in addition to those made during vaccine visits to ensure that the patient is progressing normally. While developmental landmarks have typical ages at onset (Tables 2 and 3), dogs and cats never stop learning from their experiences. Appropriate interventions should occur early and as needed.

‘‘Socialization’’ is loosely based on the changes that occur during sensitive periods for development. Given appropriate access, dogs and cats will expose themselves to social situations; however, human lifestyles may deny pets those opportunities. Clients should be encouraged to allow their pets to interact with other people, experience new places and activities, and encounter other animals or species in a positive manner during those sensitive periods.

There are two risks associated with the concept of socialization. First, the assumption that social exposure should occur only during certain periods is incorrect. There is extensive individual variation in development. Allowing dogs and cats the opportunity to develop at their own rate is important. Second, either the presence or development of fear during sensitive periods is aggravated by forced social exposure. Overexposure can make fearful dogs worse, creating a behavioral emergency. Clients should be advised that any dog either beginning to withdraw from interactions or exhibiting outright fear should not have more exposure unless recommended by their veterinarian. If the behavior is extreme, a veterinary behavior specialist should be consulted. Continuing to expose fearful puppies in the guise of ‘‘socializing them’’ instead sensitizes them. 

If dogs and cats are deprived of appropriate exposure during critical sensitive periods, they have an increased risk of developing problematic behavior. Because sensitive periods begin so early, social exposure should start under the supervision of the breeder. Puppies and kittens born to healthy, properly vaccinated mothers and engaged in an active vaccination program have a low risk of contracting infectious diseases. 23,24 There is no medical reason to delay puppy and kitten classes or social exposure until the vaccination series is completed as long as exposure to sick animals is prohibited, basic hygiene is practiced, and diets are high quality. 24,25 The risks attendant with missing social exposure far exceed any disease risk.

Puppies should not be separated from their littermates and dam until at least 8 wk of age. Puppies separated at 30–40 days versus 56 days experienced a greater incidence of problems related to the early separation, such as excessive barking, fearfulness on walks, reactivity to noises, toy or food possessiveness, attention-seeking behavior, and destructive behavior as adults. 26

The risk of behavioral problems can be assessed during vaccination appointments or preventive care exams. The development of fear and other behavioral pathologies can be detected at an early age. A few key tests and observations can be helpful in detecting high-risk animals (Table 4). Any worrisome behaviors should be taken seriously and addressed immediately to avoid the risk of relinquishment
and/or euthanasia.

Adolescents and adults

From ~6 mo of age to social maturity (12–36 mo in dogs and up to 48 mo in cats), dogs and cats are maturing physically and developing their first independent behavior patterns. The juvenile period is a period of intensive social exploration and learning, which ideally contributes to resiliency. If dogs and cats become less resilient, more withdrawn, or more reactive or aggressive, redress should be immediate. Veterinarians should advise clients during puppy and kitten visits that there is no evidence that pets ‘‘grow out’’ of behavioral problems as they socially mature. Any change warrants a professional assessment.

Mistaken or misinformed beliefs may become apparent early. Clients may not understand that some undesirable behaviors are normal (e.g., young puppies cannot last 8–10 hr without urinating). Clients may not understand the difference between a behavior that is undesirable but possibly normal and responsive to training (e.g., grabbing someone during play) and abnormal behavior that requires professional care (e.g., becoming aggressive if not permitted to play after grabbing). Clients may not know that treatment by a veterinarian is an option for problematic behaviors and that treatment may be needed for puppies or kittens. It is the job of the veterinary team to determine if a client is concerned or should be concerned about a pet’s behavior and to know when medical intervention, behavioral modification, or referral is appropriate. For such early intervention to occur, the clients must be encouraged to have a regular dialog with their veterinarian.

The term ‘‘social maturity’’ is used to describe the neurodevelopmental stage characterized by an increase in neuronal modification. It is a common time for behavioral problems to either develop or progress and for clients to notice behavioral changes.

Dysregulation of some previously acquired behaviors may occur, requiring clients to monitor and report changes in learning ability, recoverability, or the development of fears and aggressions. Those behavioral changes are not associated with hormones or sexual maturity (6 mo in cats and 6–9 mo in dogs). While many dogs and cats emerge from social maturity calmer and more attentive, those with behavioral pathologies invariably worsen. Most dogs and cats relinquished to shelters, euthanized for behavioral problems, or abandoned are 1–3 yr old and in the midst of social maturity. 1,12,27 Changes in pet behavior are potentially life-threatening, yet many of the problems emerging during that time can be addressed with simple intervention. Because there is a gap between the last puppy or kitten vaccine visit, which is generally at 16 wk of age, and the first adult preventive care visit, which is at either 1 yr of age or 1 yr after the last vaccine (16 mo of age), this Task Force recommends that veterinarians educate clients about pet behavior at a 6 mo visit and that a behavioral health check be implemented at 1 yr of age. Additionally, clients should be reminded to consult their veterinarian at the first signs of any problematic behavior. A list of those behaviors (Table 5) should be provided to and reviewed with all clients.

Senior dogs and cats

Canine and feline behavioral changes can be physiological or cognitive and both may be amenable to treatment and intervention. 13 Monitoring both age-associated cognitive and physiological changes should be conducted at least annually in dogs (starting at 5–8 yr for larger breeds and 8–10 yr for smaller breeds) and cats (starting at 10–12 yr). Those evaluations can be combined with annual preventive care examinations (Table 4). Clients are usually excellent at monitoring older pets if told what to look for. 

Providing clients with older pets an assessment tool to be completed q 2–3 mo provides guidance regarding the potential rate of behavioral change, shows empathy, and encourages the client to intervene on behalf of their pet.

Clinical signs of behavioral anomalies in senior pets may include house soiling, changes in elimination patterns, decreases/changes in interactions with other pets or humans, onset of aggression in a normally nonaggressive dog, disorientation, poor problem solving (e.g., getting stuck behind doors), changes in sleep patterns, changes in vocalization, and recent onset of novel phobias. There are medications, diets, supplements, and behavioral or environmental interventions that can help aging dogs and cats and improve their quality of life and that of their owners. All interventions work best if they can be implemented as soon as possible after onset of the problem.

Many early changes in reactivity and problem-solving behavior are associated with loss of either visual or auditory acuity and physical flexibility. Low-level lighting, clear verbal signals augmented by either visual or tactile cues, and range-of-motion exercises all may help and should be part of any intervention for aging, distressed dogs and cats.


Behavioral Development in Dogs14


Behavioral patterns and relevant stimuli

Potential problems if exposure during relevant period is absent

0–13 days
  • Exposure to handling, especially tactile and thermal stimuli
  • Hyperreactivity
  • Altered sensitivity to touch (consider role for tactile stimuli and attendant neurodevelopment in dogs with docked/bobbed tails and docked ears)
13–20 days
  • Exposure to handling by humans and other dogs
  • Exposure to novel auditory and visual stimuli
  • Concerns with visual and auditory acuity (based on laboratory animals)
3–8 wk
  • Puppies begin to eat semisolid food by ~3 wk and solid food by ~5 wk
  • As the period progresses and puppies become more co-ordinated, they engage in pouncing, rolling, rough and tumble play, mouthing, grabbing, and growling at other puppies or older dogs that play with them
  • Species identification may occur as early as 2.5–3 wk of age. Puppies raised only with cats from 2.5–13 weeks of age do not recognize dogs (consider the concern of raising dogs of one breed with only dogs of that breed, which is a common occurrence in very small breeds)
  • Heightened reactivity to dogs
  • Heightened reactivity to other species, including humans
  • Lack of inhibition in both arousal levels and behavioral responses to arousal
  • Learn to be calm/settle/relax. Such learning has profound responses for how dogs later handle situations that are potentially anxiety provoking
From 5–7 wk to 12 wk
  • Beginning at ~5 wk, puppies begin to recognize “other” and interact with/seek out other species, including humans. This interaction is more complex than the approaching that they will begin to do at 3 wk of age
  • Maximum distress, as indicated only by vocalization, occurs at the 5th wk of development.
  • At 5 wk, dogs begin to truly hone intraspecific skills
  • Interaction with humans intensifies beginning around >6 wk
  • Housetraining is most successfully learned at ~8.5 wk when there is sufficient cortical development to (1) make an association with preferred substrate; and (2) understand that inhibition of micturition may be desirable. Note that puppies with small bladders and high metabolisms may still need to go out hourly even if they are housetrained.
  • Dogs begin to bark by 4–5 wk and growl shortly thereafter. The amount of vocalization and age of onset is affected by breed.
  • By 7 wk, weaning is normally completed
  • Fear of humans and other species
  • Fear of the approaches of humans
  • Lack of learned inhibition for elimination of feces/urine
  • First true pathological fear responses reliably reported for laboratory animals in genetically susceptible lines
From 10–12 wk to 16–20 wk
  • Intense period of learning how to explore/learn about novel environments. Puppies learn about risk and how to make a mistake successfully.
  • Play becomes rougher/appears to be about successfully making and learning from mistakes
  • Neophobia
  • Lack of plasticity in responses
  • Inappropriate play and lack of play
14–20 wk
  • Dogs not allowed to explore new environments by 14 wk will not voluntarily do so. If forced, they freeze and become extremely distressed
  • Normal marking behaviors may begin to appear as dogs approach sexual maturity
  • Neophobia
  • Profound panic
  • Plasticity of response is characteristic of normal behaviors. Lack of plasticity in response is characteristic of abnormal behaviors

Behavioral Development in Cats14


Behavioral patterns and hallmarks

2 days Purring begins
10–14 days Eyes open
2 wk Age at which separation from mother leads to fearful/aggressive behavior to cats/humans
2–4 wk Closeness of other kittens has a calming effect
End of 3rd wk Kittens able to recognize their mother by sight and smell
3 wk Queen begins to teach predatory behavior
3 wk Kittens eliminate voluntarily
3–7 wk Age at which singleton kittens emerge from nest box
3–4 wk Normal social play behavior starts
4 wk Age at which kittens exposed to another species (e.g., dogs) show no fear at 12 wk
4 wk Age through which kittens cannot retract their claws
5 wk Age at which kittens will use scratching material if provided
2–5 wk Early period for social play. Early exposure to humans essential
5–6 wk Kittens independent in their ability to eliminate and find suitable substrates. Appropriate materials should be provided
~6 wk Adult-like response to visual/olfactory stimuli, including the silhouettes of adult cats/adult cat urine
5–7 wk Middle period for social play. Continued exposure to and play with humans/other species essential
~6 wk Gape/Flehmen response appears (open mouth sniff to volatilize compounds through the vomeronasal organ)
7 wk Gape/Flehmen response fully developed
Birth to 45 days During this period, if kittens are handled regularly, their approach to unfamiliar objects is rapid and more time is spent with objects and environment at 4–7 mo
5.5–9.5 wk Age at which if kittens are handled by multiple people less fear is shown later/more interest in people later. More complex interaction recommended
7 wk Kittens begin to cover their urine/feces if they are going to do so
7–10 wk Late period for social play. Last age at which first exposures to humans can still readily ease the extent to which cats are comfortable with humans. More time/day with humans than required earlier to get the same result
By 60 days Object play increases
4–12 wk No sex differences in social play behavior
6–12 wk Pounce, belly-up, and stand-up displays are 90% effective in obtaining play response from another kitten
By 12 wk Social play patterns become more associated with predatory behavior/social fighting
Birth to 12–14 wk Handling kittens for only 15 min/day produces kittens more solicitous of people
14 wk Postsocial play period
14 wk Social fighting may start
12–16 wk Sex differences appear in social play behavior
12–14 wk Social play behavior begins to decline

Key Behaviors Used in Clinical Settings to Identify Fearful Dogs and Cats

Behavior patterns associated with normal development

Behavior patterns associated with problematic development

Approaches unfamiliar people Will not approach/actively avoids unfamiliar people
Approaches and/or plays with other friendly and/or solicitous animals Doesn’t interact or play with other solicitous animals, avoids them or responds aggressively to their solicitations for play
Not fearful of most noises and recovers quickly from exposure to loud noises Fearful of many noises and does not immediately recover from exposure to loud noises
Takes treats and explores exam room Doesn’t take treats, hides, freezes, or panics in the exam room
Uses litter box/eliminates outside when taken out and does not soil the house if otherwise given reasonable access House/litter box training is either not progressing or regressing

Cat and Dog Behaviors Appearing During Social Maturity that Should Prompt Veterinary Assessment

Fear of/withdrawal from people or other dogs/cats
Aggression to people/other dogs or cats
Stereotypical/repetitive/ritualistic behaviors (e.g., circling, overgrooming, licking, sucking)
Elimination changes and elimination in inappropriate areas
Development of fears/phobias associated with environments/stimuli (e.g., storm phobias, fear of car rides, leash walks, new places/toys)
Distress when left alone
Increased reactivity in any situation
Profound changes in activity level (either less or more) and reactivity when resting or asleep