CHAPTER 9 Kitten Development
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,36 where they are likely to be euthanized. Understanding normal kitten development allows owners to provide the right environment for healthy kitten development. It is also important that veterinarians understand the behaviors that kittens normally display at various stages of development and educate owners accordingly.
Influence of Parental Factors on Behavioral Development
Genetics
Cats are unique among domesticated animals because the majority of their breeding is not controlled by humans.11 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 modern domestic cat is capable of producing two or three litters annually, depending on the length of time that 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 to be companion animals. Development of behavior is the result of the complex interrelationship between inherited factors (i.e., genetics) and noninherited environmental influences.6
In Utero Effects
The environment in the uterus during pregnancy can have far-reaching 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.20 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).38 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 vestibular righting reflex develops by approximately day 54 of gestation.6 Kittens are generally born after a 63-day gestation.
Maternal Factors
Good maternal behavior is essential for healthy kitten development. In fact, because kittens are born blind, with limited ability to move and regulate body temperature, they are totally dependent on their mothers (Figure 9-1). Kittens may be communally reared by other female cats, especially in environments where food is abundant.18 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.34,37 These effects may be attenuated, at least in part, if kittens are hand reared in a home with other cats.15,34 When queens are fed a rationed diet, their kittens were more active, engaged in more object-directed play, and were more likely to hunt.1,7 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.7
Paternal Factors
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 easy-going; timid and nervous; and active and aggressive.29,32 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.32
Behavioral Development
Sensitive Periods
Neonatal (0 to 7 Days)
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. The kitten is guided by tactile, thermal, and olfactory stimuli to find the queen and littermates. Kittens are unable to hear at birth, but hearing is present 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.9 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.8,27
The neonatal kitten has a limited range of behaviors. It can orientate 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 increase the likelihood that she will allow nursing. She will also locate a lost kitten by its vocalizations and carry it back to the nest.9
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, wherein 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.24 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.28 The suckling reflex usually disappears after approximately 20 days.28
Transitional (7 to 14 Days)
Communal nesting results in kittens leaving the nest earlier: 20 days compared with 30 days for kittens raised in single-litter nests.19
Socialization (14 Days to 7 Weeks)
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. Full visual acuity may not be achieved until 3 to 4 months of age. Rudimentary walking begins at approximately 3 weeks and develops into brief episodes of running by 5 weeks; kittens use all gait patterns of adult locomotion by 6 to 7 weeks of age.6 Between the third and sixth weeks, kittens develop air righting, which is the ability to land on their feet.23
At 4 weeks weaning begins, and kittens begin to eat solid foods. By 7 to 8 weeks weaning is largely completed, although suckling may continue intermittently for several more weeks.6,30 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.13 Kittens generally share their mother’s food choices and choice of prey.13 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.39 Time of weaning is associated with a change from social play to object play.3 In fact, kittens weaned early showed higher rates of play.7,31 Locomotor play also begins at around this age.
Fearful reactions to threatening stimuli may begin to be displayed by 6 weeks of age.27 Individual differences in behavior begin to be displayed during the second month of life, owing to both genetic influences and contrasting early environments.2
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