Prenatal Factors

The factors that affect a kitten’s behavioral development and subsequent behavior as an adult begin in utero. Kittens from undernourished mothers not only exhibit abnormal physical development but also abnormal behavioral development. When queens were fed one-half of their ad libitum intake during the second half of gestation and the first 6 weeks of nursing, serious behavioral changes were seen in the kittens when compared with queens who had adequate nourishment. Even after being fed a nutritionally appropriate diet for 10 weeks, kittens were more prone to accidents when playing and performed poorly on certain behavioral tests. In addition, male kittens showed increased aggressive social play and females showed less climbing behavior and more random running. Multiple factors have been shown to cause behavioral changes in kittens from undernourished mothers, including abnormal development of the cerebrum, cerebellum, and brainstem, fewer queen/kitten interactions, and increased irritability/aggression of the queen toward the kittens. If queens are nutritionally restricted to one-half of their ad libitum food intake during the entire gestation period, kittens show delayed posturing, crawling, suckling, eye opening, running, playing, climbing, and predatory and exploratory behavior. In addition, these kittens have difficulty learning new tasks and exhibit fear, aggression, antisocial behavior, and increased reactivity toward stimuli. Unfortunately, many kittens are adopted from litters of feral queens who had a poor plane of nutrition, leaving them predisposed to behavior problems. Kittens of queens subjected to severe nutritional restriction have suppressed play, whereas kittens from queens who had a less restricted but less than adequate diet show increased contact play. Although developmental changes may be obvious early in life, behavioral changes may not be brought to the veterinarian’s attention until adulthood when a behavior problem has become chronic or unbearable for the owner. Although it can be challenging to obtain an accurate history of a chronic behavior problem, it is critical that an extensive history be taken with all behavior appointments, regardless of the age of the animal, so that early life experiences can be taken into account. This allows the clinician to educate the owner on the factors that have caused the final, intolerable behavior and construct an accurate diagnosis list and treatment plan.

Another factor shown to increase reactivity in rats that most likely occurs in other mammals, including cats, is the degree of physiologic and psychological stress of the mother during gestation and nursing. In general, when gestating mammalian mothers are chronically stressed, anxious, or fearful, the offspring exhibit increased reactivity to stimuli, increased emotionality, and decreased learning. As the brain of the fetus develops, it is subjected to the hormones that are secreted by the mother. The brains of neonates and nursing animals whose mothers are under stress are organized differently than the brains of those whose mothers are not. Animals subjected to stress release endogenous glucocorticoids as part of the normal physiologic stress response. When the animal is a gestating mother, those glucocorticoids are passed on to the neonate. It is postulated that the increase in endogenous glucocorticoids chronically causes an impairment of the negative feedback mechanism of the hypothalamic-pituitary-adrenal (HPA) axis in the offspring. This in turn causes the offspring of stressed mothers to respond with increased reactivity when placed in situations in which they are under stress. Depending on when the physiologic or psychological stress occurs in gestation, the changes in the HPA axis of the offspring can be permanent. This “up-regulation” of the HPA axis is suspected to underlie many behavioral problems in animals that involve impulsivity and aggression. Typical feline behavioral disorders of this type include fear-related aggression, conflict-related aggression, predatory aggression, and redirected aggression to people or other animals.

Early Development

The early behavioral development of the kitten is guided by the extent to which other body systems and senses have developed. In addition, other factors, such as the variability of the kitten’s environment, handling, genetics, age of the queen, mothering style of the queen, weaning, sex of the kitten, and exposure to stimuli, all influence the kitten’s development. Kittens are altricial, which means that they are born relatively helpless with eyes and ears closed; however, tactile sensitivity is present. Until the kitten is 2 weeks old, tactile, thermal, and olfactory senses guide its behavior (Table 12-1). The kitten’s development is divided into stages: neonatal, transitional, socialization, juvenile, and adulthood. The neonatal stage lasts from 0 to 9 days of age. For the most part, the kitten is completely dependent on the mother at this stage and spends most of its time nursing and sleeping. The transitional stage is the stage between complete reliance on the mother and the beginning of independence for the kitten. It lasts from 10 to 14 days of age. The eyes open during this stage, and the kitten begins to orient to sounds. The socialization period lasts from the second to the seventh week of age. This period is filled with exploration, development of locomotor function, formation of social relationships, development of predatory behavior, and increased motor skills. The juvenile stage starts at the end of the socialization stage and extends to sexual maturity (7 to 12 months of age) when adulthood begins.

TABLE 12-1 Feline behavioral development (birth to 23 weeks)

By 5 days of age, kittens respond to sounds; by 10 days of age, they have the ability to exhibit conditioned responses to sounds (Box 12-1); and by 2 weeks of age, they orient to natural sounds. On average, kittens open their eyes 7 to 10 days after birth. One study found four factors that affect when a kitten will open its eyes. They include light exposure, sex of the kitten, age of the mother, and paternity. Of the factors studied, paternity was found to have the strongest influence on how early kittens opened their eyes. Additionally, dark-reared kittens opened their eyes earlier than light-reared kittens; female kittens opened their eyes earlier than male kittens; and kittens from young mothers opened their eyes earlier than kittens from older mothers.

By 3 weeks of age, many sensory systems are developing rapidly, with some having already developed to their adult state (see Table 12-1). The olfactory system reaches full development, but vision takes the lead in guiding the kitten’s behavior. During this time, kittens move from paddling to rudimentary walking and oral self-grooming emerges. Between 15 and 25 days, kittens gain the ability to visually orient toward and follow objects, including the queen. One influential change in kitten development at this time is a decrease in initiation of nursing bouts by the queen in preparation for weaning (see section on Weaning). At 4 weeks, the visual and auditory systems have developed further as evidenced by more adult-like hearing and vision, as well as better coordination and motor skills. Behavioral development reflects these physical changes as the kitten begins to show play and hunting skills. At this age, the kittens orient to sounds as an adult cat would and begin to stray farther from the nest. Also, during this period (between 25 and 35 days), kittens can learn tasks with visual cues alone and their heart rate can be classically conditioned to respond to a neutral event paired with an aversive event (see Box 12-1). Additionally, at 4 weeks weaning (see section on Weaning) is typically underway. By the fifth week of life, kittens have developed the motor skills to run. They are becoming more adept hunters, and some will kill the prey that the queen brings to the nest (see section on Predatory Behavior).

Between 6 and 7 weeks, kittens show more adult responses to stimuli (see Table 12-1). They are capable of all of the gaits exhibited by adults. This new-found mobility and coordination allows kittens to engage in the complex interactions that make up typical kitten play (see section on Play). Another adult response that emerges with adult-like frequency by 7 weeks of age is the gape, which may imply that the vomeronasal organ is developed more completely. The gape (also called a grimace) is a variation of the flehmen response seen in horses and cattle. It is typically demonstrated by cats who encounter another cat’s urine or a novel smell. It allows the cat to pull odors, such as pheromones, into the vomeronasal organ. Pheromones are present in urine and facial secretions, making the expression of the gape an important part of sexual and social behavior. At 6 weeks of age, kittens will orient toward a silhouette of a cat in a socially threatening position, and by 8 weeks of age, kittens display adult responses, including piloerection to a silhouette and to cat urine. By 10 to 11 weeks of age, kittens are starting to exhibit the complex motor abilities needed when climbing, walking, and turning along thin tree branches.