section epub:type=”chapter” id=”c0012″ role=”doc-chapter”> Gary Landsberg and Jacqueline Mary Ley The development of kittens from birth to adulthood is complex. The kitten changes from a creature of limited behaviors that is reliant upon its caregiver for warmth, food, and waste elimination to an independent animal that expresses a wide range of behaviors and that can form social relationships with members of its own species and others. Understanding what is happening at each stage of development allows identification of potential problems and allows owners to be given the best advice to raise a mentally healthy cat. Cat; Kitten; Development; Sensitive Periods; Development of Hunting; Play; Suckling; Reflexes; Vision; Hearing; Olfaction The development of a kitten from a dependent neonate with a limited ability to perceive and respond to stimuli to an independent creature with a fully developed physiology that is able to care for itself, hunt, and interact with other cats is a rapid yet complex process that is affected by many factors. These include the genetics of the sire and dam, the environment of the uterus, and the kitten’s environment after birth. There is a complex ballet of neurologic, physiologic, musculoskeletal, and psychologic development that must occur in the correct sequence if the kitten is to develop normally. One of the most important stages in a kitten’s development is the socialization period, wherein kittens are most receptive to learning about the social and physical environment that they should avoid, ignore, or can derive benefit from. Problems can occur at any stage of development and can have far-reaching effects for the kitten, especially in the role of a companion cat. Cats whose behavior does not meet owner expectations are at risk of being surrendered to a shelter,1 where they may be euthanized. Understanding normal kitten development allows owners to provide the right environment for healthy development. It is also important that veterinarians understand the behaviors that kittens normally display at various stages of development and educate owners accordingly. Cats are unique among domesticated animals because most of their breeding is not controlled by humans. Many kittens are the result of opportunistic matings wherein male social skills and female preferences dictate who sires the kittens. The breeding season for the modern domestic cat is based on multiple estrous cycles throughout the year, especially spring through summer, with a second peak in kitten numbers in late autumn. The domestic cat can produce two or three litters annually, depending on how long the kittens remain with the queen after weaning. Natural selection pressures are working, as opposed to human preferences for coat and eye color, size, and temperament. Although this works to keep the feline population relatively free of genetic diseases, it can have important effects on the suitability of kittens as companion animals. Development of behavior is the result of the complex interrelationship among inherited factors (i.e., genetics), learning from previous experiences (good, bad, and neutral), as well as environmental influences. The environment in the uterus during pregnancy can have extensive effects on the behavior and development of the individual kitten. Poor quality of nutrition for the queen during pregnancy has been shown to produce a wide variety of behavioral and physical abnormalities in kittens. Kittens from queens fed a low-protein diet during late gestation and through lactation have been found to be more emotional and move and vocalize more frequently than kittens from queens fed an adequately formulated diet.2 These kittens also lost their balance more often and had poor social attachment and fewer social interactions with the queen. It is not clear if the restricted protein leads to the emotionality or if changes in the queen’s behavior caused by the protein deficiency lead to the change in the kittens’ behavior. In another study, when queens were restricted to half of their nutritional requirements, the kittens demonstrated growth deficits in some brain regions (e.g., cerebrum, cerebellum, and brain stem).3 These areas initiate and coordinate movement and actions. Delays were apparent in many areas of development, including suckling, eye opening, crawling, posture, walking, running, playing, and climbing. Tactile sensitivity is present in the embryo by day 24 of prenatal life, and the body righting reflex is present at birth.4 Kittens are generally born after a 63-day gestation. Good maternal behavior is essential for healthy kitten development. As kittens are born blind, with limited ability to move and regulate body temperature, they are totally dependent on their mothers. Kittens may be communally reared by other female cats, especially in environments where food is abundant.5 The queens are usually related, either sisters or mother and daughter. Kittens that were separated from their mother and hand raised from 2 weeks of age were more fearful and aggressive toward people and other cats, were more sensitive to novel stimuli, learned poorly, and developed poor social and parenting skills.6,7 These effects may be attenuated, at least in part, if kittens are hand-reared in a home with other cats.6,8 When queens are fed a calorie-reduced diet, their kittens were more active, engaged in more object-directed play, and were more likely to hunt compared with kittens of queens fed a normal calorie diet.9,10 Stressors on the queen before and after the birth of her kittens can affect the behavior of her kittens. Kittens from queens fed a restricted-protein diet were found to vocalize more than kittens from queens fed a balanced diet.10 Though the tom is not involved in raising the kittens, he appears to have a strong effect on the kitten’s social development. Studies of cat personality have identified three personality types: sociable, confident, and easygoing; timid and nervous; and active and aggressive.11 Although maternal genetics and the influence of the mother and offspring on early development are important, paternal genetic factors appear to have the strongest influence on the development of personality. Kittens sired by toms considered to be “bold” have been found to be significantly friendlier to familiar people, less stressed by the approach of unfamiliar people, and more likely to spend time near a novel object.12 Of course, the socialization of kittens is a complex process that involves the interplay of genetics, environment, and learning. The interplay among these three factors affects the suitability of an individual cat to be a companion animal. It is likely that some feral cats are genetically shy, which hinders their ability to live close to humans. Their kittens are likely to be similarly affected and, if this is the case, their socialization to humans and their suitability as pets may be less certain. Like the patterns identified in dogs during puppy development, kittens have several sensitive periods of intense development from birth to 6 months of age. They tend to have shorter sensitive periods than do puppies, and the 8-week-old kitten is quite different from the 8-week-old puppy with regard to its physical, mental, and social development. The earlier stages of development, the neonatal and transition period, tend to occur very quickly. Important milestones occur in each of the sensitive periods that correspond to the physical development of the kittens. For example, the myelination of nerves must occur before the kitten can show the fine motor control to send social signals by using changes in body posture or to practice hunting behaviors such as pouncing. The neonatal period is a time primarily of nursing and sleeping in which the kitten is fully dependent on its mother. During the first 2 weeks, nursing and eliminative behaviors are initiated by the queen, who provides food and warmth, cleans the kittens, and stimulates defecation and urination by licking the anogenital area of the kittens (Fig. 12.1). The kitten is guided by tactile, thermal, and olfactory stimuli to find the queen and littermates. Kittens are unable to hear at birth and are deaf until the ear canals open by the fifth day. Kittens maintain their body temperature by huddling together and with the queen. The actions of newborn kittens are initially very clumsy, but as the nervous system and muscles mature and behaviors are repeated, their actions become smoother and more efficient. For example, by 4 days after birth, most kittens are proficient at locating and attaching to their preferred teat.13 While there is a preference for the more posterior teats, overall teat preference is not affected by the location and milk production of the teat, but actually by the kitten’s learned preferences.14 Olfaction is present and highly developed at birth, insofar as kittens use their sense of smell to locate the queen’s teats and find their preferred teats. This is important when kittens have upper respiratory tract infections because they will not actively suckle and may need artificial feeding. Even 2-day-old kittens will show pronounced avoidance of offensive odors.15,16 The neonatal kitten has a limited range of behaviors. It can orient its body toward touch and warmth, move by squirming along with swimming movements of the forelimbs, suckle, and vocalize. Kittens begin vocalizing soon after birth. These sounds attract the queen and increases the likelihood that she will allow nursing. She will also locate a lost kitten by its vocalizations and carry it back to the nest.13 Kittens have several reflexes present at birth. If touched on the face, a kitten will turn toward the side that was touched (auriculonasocephalic reflex). A kitten will also turn to the side being touched when it is touched on the flank. The rooting reflex, where the kitten burrows into its mother, littermates, or any warm material, may be present for up to 16 days. This behavior is used to locate teats. Newborn kittens have a strong suckling reflex, which is initially stimulated by objects in the mouth or being touched on the face. The suckle reflex is strongest on waking. Kittens rapidly develop teat preferences and will preferentially feed from one or two teats.14 The suckling reflex can be stimulated initially by touching a large area of the kitten’s face or putting small objects in the mouth. However, as the kitten gains experience, the area that will produce this response is reduced to the lip area. At the same time, foreign bodies placed in the mouth will be rejected.17 The suckling reflex usually disappears after approximately 20 days.17 During the transitional period the kitten changes from expressing limited neonatal behaviors to beginning to show adult behaviors in eating, elimination, locomotion, and social interactions. From about 2 weeks of age, kittens begin to raise their bodies off the ground and move with a slow, paddling gait. The eyes open at around 7 to 10 days (range 2 to 16 days) and kittens will begin to visually orient and follow by the third week although full visual acuity may develop until 3–4 months.4 Although hearing is present by the fifth day of age, the kitten does not begin to orient to sounds until approximately 2 weeks of age. Olfaction is fully mature by 3 weeks. Dental development commences between 2 and 3 weeks of age. Communal nesting results in kittens leaving the nest earlier: 20 days compared with 30 days for kittens raised in single-litter nests.18 During the socialization period, kittens begin to explore their environment and learn its hazards and pleasures. Visual orienting and following develop in the third week, but obstacle avoidance is not developed until 4 to 5 weeks of age. Rudimentary walking begins at approximately 3 weeks and progresses to short bouts of running by 5 weeks. By 6 to 7 weeks of age, they can use all the gaits of adult locomotion.4 Between the third and sixth weeks, kittens develop air righting, which is the ability to land on their feet.19 By 4 weeks the kitten begins to move away from the nest and develops social relationships with people and other animals in its environment. Social play with siblings and the mother begins at approximately 4 weeks and includes wrestling, rolling, and biting. When there are no other kittens or cats present, these behaviors may be directed toward human hands and other moving body parts. Social play peaks at 7 to 9 weeks and continues at a relatively high level to approximately 12–14 weeks before it begins to decrease.4,20 At 4 weeks weaning begins, and kittens begin to eat solid foods (Fig. 12.2). By 7 to 8 weeks, weaning is largely completed, although suckling may continue intermittently for several more weeks.4,21 From about 4 weeks of age, the mother may begin to bring dead prey; over the next several weeks, the mother may bring home weakened and then live prey, which she releases at the nest, providing the kittens with an opportunity to hunt and kill.22 Kittens generally share their mother’s food choices and choice of prey.22 Kittens that are weaned early (4 weeks) are more likely to be mouse killers, whereas late weaning (9 weeks) is associated with a delayed development of predation and reduced propensity to kill mice.23 Time of weaning is associated with a change from social play to object play.24 In fact, kittens weaned early showed higher rates of play.10,25 Locomotor play also begins at around this age. By 5 to 6 weeks of age, the kitten has full voluntary control of elimination, and digging and covering feces and urine on loose soil may begin. The gape (flehmen) response begins to appear around 5 weeks of age and is fully developed by 7 weeks.19 Fearful reactions to threatening stimuli may begin to be displayed by 6 weeks of age.16 Individual differences in behavior appear during the second month of life, owing to both genetic influences and contrasting early environments.26 The juvenile period is associated with kittens becoming ready to disperse from the queen’s home range and become fully independent for their food needs. Play and exploration of inanimate objects and locomotory play begins to escalate at approximately 7 to 8 weeks of age and peaks at approximately 18 weeks of age.24 Social play, on the other hand, is most prevalent from about 4 weeks to 14 weeks of age. Social play begins to take on aspects of predation in the third month. Object play may be social or solitary and may consist of pawing, stalking, leaping, and biting of objects and securing them with the paws (Fig. 12.3). This type of play simulates a variety of aspects of the predatory sequence. The juvenile period is considered finished with the onset of puberty when sexual reproduction is possible.
Kitten Development
Abstract
Keywords
INTRODUCTION
INFLUENCE OF PARENTAL FACTORS ON BEHAVIORAL DEVELOPMENT
Genetics
In Utero Effects
Maternal Factors
Paternal Factors
BEHAVIORAL DEVELOPMENT
Development after Birth
Sensitive Periods
Neonatal (0 to 7 Days)
Transitional (7 to 14 Days)
Socialization (14 Days to 7 weeks)
Juvenile (7 Weeks to Sexual Maturity)
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