Introduction
Cats sometimes behave in ways that owners may find difficult to understand and/or manage. Problems can occur at any stage of development, and these can have far-reaching effects for a kitten, especially when it comes to the role of being a household pet and part of the family; it is therefore essential to understand the different feline developmental periods in order to help kittens grow into great cats and become good companions. Behavior is determined by several factors, including the cat’s genetic predisposition, the genotype of the sire and dam, what the cat has learnt from past experiences (good, bad and neutral), as well as the environment in which it finds itself at any given time. Epigenetics also has a role to play.
Knowing what to do to help kittens grow into well-mannered cats is important, and it starts with the breeder. Deciding which queen to breed with which tom, and when, is just one aspect that affects what the future might hold. Understanding how to handle the queen before, during and after pregnancy, how to help build resilience in the kittens, and how to raise them before they go to their new home are just some of the things that need to be considered, and the veterinarian should be willing and able to advise on all these aspects. Just as importantly, the owners of a new kitten need to be educated about how best to look after its physical and mental health, as both factors are important if cats are to make good companions. Having realistic expectations of what a kitten can and should do at any given time helps create a strong bond between the cat and its care giver.
The development of a kitten from a totally 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 members of its own species — as well as other species — happens rapidly. Yet the process is complex and delicate, and it is affected by many factors. Several different developmental periods have been identified; these are the prenatal, neonatal, transitional, socialization, juvenile, adult and senior periods, and each has an influence on a cat’s behavior (Table 1). As the kitten grows, all the various body systems, including the musculoskeletal and neurological systems, as well as the psychological (emotional) side of things, must develop in the correct sequence if the kitten is to develop neurotypically (i.e., normally). Much focus has been given to the socialization period, as this is when kittens are weaned, may be re-homed, and may be neutered, so there are many stresses on the animal during a very sensitive period of development. However, it is not the only period that needs to be considered. It should also be noted that the development periods are not rigidly fixed and will vary with each individual kitten — and in addition, different authorities will sometimes use different time frames for each period.
Table 1. The different life stages of a cat and the approximate ages.
Prenatal period
The prenatal period, i.e., conception until birth, at typically 63 days, is more significant than may be realized in terms of a kitten’s future characteristics. The different phases in embryonic development, that starts with fertilization of an ovum and leads on to implantation in the lining of the uterus (roughly two weeks after fertilization) involve a tremendous amount of change. Since cats are multiparous, this process is repeated by multiple zygote-morulas, possibly from matings with different males. Once pregnancy is established, the uterine environment also has extensive effects on the future behavior and development of the individual kitten. Research has shown that Kittens from queens fed a low-protein diet during late gestation and throughout lactation have been found to be more emotional and to move and vocalize more frequently than kittens from queens fed a balanced and complete diet 1. These kittens also lost their balance more often and had poor social attachment and fewer interactions with the queen. 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) 2. These areas initiate and co-ordinate movement and actions, and delays were apparent in many areas of development, including suckling, eye opening, crawling, posture, walking, running, playing, and climbing. However, much research on the impact of diet on epigenetics still needs to be done. The feline microbiome is also an area that is increasingly being investigated, and its effects on kitten development are, as yet, not fully understood.
Neonatal period
The neonatal period starts at birth and lasts until approximately two weeks of age, although some authors consider the period to only last about 7 days. However, as the queen initiates nursing and elimination (perineal stimulation being necessary for urination and defecation) during the first 2 weeks of life, it is likely that the neonatal period lasts up to this point. Good maternal behavior is essential for healthy kitten development (Figure 1); as kittens are born blind and practically deaf, with limited ability to move and regulate their body temperature, they are totally dependent on the mother for survival.
Eating and sleeping are the most significant activities for kittens at this stage, and they will spend (on average) about 4 hours a day suckling in the first week of life. As kittens are born with their eyes closed (although many visual reflexes, such as the blink reflex, may be present before birth 3) and with poor hearing, they are reliant on their sense of smell, touch and ability to detect warmth. As the neonatal kitten cannot regulate body temperature, the ability to detect a thermal gradient is important for survival, whilst teat location is done using their sense of smell. However, although kittens do not vocalize much, they will purr when suckling and cry in response to physical discomfort. As kittens are born neurologically immature, movement is limited at birth and their legs are not strong enough to support their bodyweight until about the second week of life. However, kittens are able to reposition themselves if they are rolled onto their back, as this righting ability develops before birth.