Tara Montgomery

Zelda aged 14 weeks.

As a cat grows up, its behaviour develops with regularity and consistency. Most kittens open their eyes during their second week, for example, and start to eat their first solid food at around one month of age. Cats are also adaptable and modifiable in their behaviour, responding sensitively to changes in their environments. Moreover, they are highly variable in their habits. Some domestic cats spend much of their time hunting, while others seldom leave the comfort of their owner's armchair. Explaining how and why such consistencies and differences arise during development is the main theme of this seminar. The major changes that occur after birth are described and explained. The mechanisms depend on factors that are inherited and on the individual's own experience, a part of which it actively seeks.

The time from conception to birth is usually 63 days in the domestic cat. This is 3-7 days longer than in its supposed wild ancestor, Felis silvestris libyca, according to Haltenorth & Diller (A Field Guide to the Mammals of Africa including Madagascar, 1980). The mean birth weight is 100-110 grammes, which is of the order of 3 percent of adult body weight. The kitten is born with its eyes closed and with a poorly developed auditory system. Tactile sensitivity, however, is present in the embryo by day 24 of prenatal life and the vestibular righting reflex has developed by about day 54 of gestation.

The cat is like many other vertebrates in that the tactile system develops first, next the vestibular system, then the auditory system and finally the visual system. The sensory world of the kitten in the first two weeks of life is dominated by thermal, tactile and olfactory stimuli. Only from three weeks of age onwards does vision play a major role in guiding behaviour.

central role in the orientation of suckling, is present at birth, and more or less fully mature by three weeks of age. Hearing is also present early in life and is well developed by one month of age. Definite responses to sounds are seen by day five, orientation to natural sounds by about two weeks, and adult-like orienting responses are found in all kittens by the fourth week after birth.

Kittens' eyes remain closed until, on average, 7-10 days after birth, although the age at which they open ranges between two and 16 days. When eye-opening starts, two to three days usually elapse before both eyes are completely open. Visually guided behaviour develops rapidly in the following weeks. By the end of the third week, a kitten is able to use visual cues to locate and approach its mother. Visual orienting and following develop between 15 and 25 days, while response to a visual cliff, visually guided paw-placing, and obstacle avoidance all develop somewhat later, between 25 and 35 days.

The kitten's visual acuity has improved markedly by one month after birth, although the fluids of the eye do not become completely clear until about five weeks and some improvement in acuity continues until as late as 3-4 months. Overall, visual acuity improves 16-fold between two and 10 weeks after birth. Kittens under two months of age can be trained to perform complex visual pattern discriminations.

Kittens can regulate their body temperature to some extent by three weeks of age. However, even one-day-old kittens can detect and attempt to move along a thermal gradient, avoiding cold regions and approaching warmth. By seven weeks of age a fully adult pattern of temperature regulation is attained. Adult-like sleep patterns have also developed by 7-8 weeks after birth. Females become sexually mature at between seven and 12 months of age. Brain weight at birth is about 20 percent of adult weight, and reaches the adult level by about three months of age.

During the first two weeks after birth, kittens are relatively immobile and use a slow, paddling gait. Rudimentary walking appears during the third week, but not until four weeks of age can kittens move any distance from the nest. By the fifth week they show brief episodes of running, and by 6-7 weeks they have started to use all of the gaits found in adult locomotion. Complex motor abilities, such as walking along and turning around on a narrow plank, may not develop fully until 10-11 weeks after birth. The body-righting reaction is present at birth and fully mature by one month. The ability to right the body mid-air while falling (the air-righting reaction) starts to appear during the fourth week and develops smoothly over the next two weeks.

Limb-placing reactions develop progressively over the first two months, with internally controlled responses present at birth and visually controlled responses developing later, in parallel with the development of the visual system. Some tactile contact-placing is present at birth, while visually guided paw-placing starts to develop at around three weeks and is mature by 5-6 weeks. Teeth start to erupt shortly before two weeks of age, and continue until the fifth week. The change from milk teeth to adult teeth starts at about three and a half months after birth.

During the first three weeks after birth, the kittens depend entirely upon their mother's milk for their nutrition, and episodes of nursing are initiated entirely by the mother, who returns frequently to the nest to nurse her kittens. Under free-living conditions, mothers start to bring live prey to their kittens from four weeks after birth onwards and kittens may start to kill mice as early as the fifth week.

Four weeks is also the age at which kittens normally start to eat some solid food and marks the onset of the weaning period. As weaning progresses, the kittens become increasingly responsible for initiating bouts of nursing. By 5-6 weeks of age, voluntary elimination has developed, and kittens are no longer dependent on their mother to lick their perineum in order to stimulate urination. Many kittens when placed for the first time on loose earth or the commercially available material used in litter trays will dig a shallow hole, squat, urinate and then cover up the hole. Weaning is largely completed by seven weeks after birth, although intermittent suckling--without, necessarily, any milk transfer--may continue for several months, particularly if the mother has only one kitten.

Social play becomes prevalent by four weeks after birth. In the fifth and sixth weeks kittens start to hide while moving towards another kitten and to search for an object that has disappeared; in the seventh week such behaviour is integrated into playful social interaction. Social play, involving much chasing, continues at a high level until 12-14 weeks, when it begins to decline slowly. Social play-fighting can sometimes escalate into serious incidents, especially during the third month. Play with objects develops slightly later, as kittens start to develop the eye-paw coordination that enables them to deal with small, moving objects, and its incidence rises markedly at around 7-8 weeks after birth, while locomotor play also develops rapidly at around this age.

Many other major changes in behaviour have been recorded between one and two months of age. For example, at 4-5 weeks of age kittens first start to alternate spontaneously between entering one arm and then the other of a T-shaped maze. At about the same age, but not before, heart-rate can be conditioned to respond to a neutral event associated with an aversive one. One month is also said to be about the earliest age at which learned performance based on purely visual cues is possible. However, conditioned responses to sounds are seen by 10 days of age, and kittens show specific forms of learning--such as forming nipple preferences--shortly after birth. Kittens under one month of age differ from older kittens in passive avoidance (shuttle box) learning, though not in active avoidance (step-up) learning. According to Adamec, Stark-Adamec & Livingstone ('The expression of an early developmentally emergent defensive bias in the adult domestic cat (Felis catus) in non-predatory situations,' in Applied Animal Ethology, vol. 10, pp. 89-108, 1983), a predisposition to respond defensively towards large and difficult prey such as rats--a defensive 'personality'--develops during the second month. By 6-8 weeks of age, kittens have begun to show adult-like responses to threatening social stimuli, both visual and olfactory.