Like the black mutation, blotched tabby is recessive: for a cat to have a blotched tabby coat, it must have two copies of the blotched version of the gene, one inherited from its mother and one from its father. One striped, one blotched, and the cat will have a striped coat. Despite this apparent handicap, in Britain and in many parts of the United States, blotched tabbies outnumber striped tabbies about two to one, meaning that more than 80 percent of cats carry the blotched version of the gene. In many parts of Asia, blotched tabbies are rare or even absent. The main exceptions are a few former British colonies such as Hong Kong, which were presumably simultaneously colonized by British cats, either ships" cats or the pets of the settlers.
For a new version of a gene, especially a recessive gene, to spread through a population, it must provide some advantage. Since (striped) cats had been in Britain since Roman times and probably earlier, blotched tabbies must have been rare to begin with. They probably reached 10 percent of the population by about 1500 CE, and then increased year after year until they reached their current near-ubiquity. In Britain, blotched tabby is sometimes referred to as "cla.s.sic" tabby, as if the striped version were the mutation, not the other way around.
The reason for the ascendancy of the blotched pattern is still unknown. British cat owners do not prefer the blotched to the striped coat, at least not to the extent that this could account for their proportions among British pets; in fact, when asked, they express a small preference for striped tabby, perhaps simply because it is (now) relatively unusual. Blotched tabby does not seem to provide any better or worse camouflage than striped, at least in the countryside. There has been a suggestion that the pollution caused by the Industrial Revolution, coating British cities in soot, favored darker cats-both blotched tabby and black-because they were less conspicuous, but this has never been confirmed.13 Still, we know that almost all genes have multiple effects, even though most are named for the most obvious change they bring about. Therefore, the blotched version of the gene possibly produces some other advantage, nothing to do with the coat, that somehow suited cats to life in Britain.
We see the rise of the blotched tabby gene in Britain reflected in the proportion of blotched tabbies in former British colonies all around the world. In the Northeastern United States-New York, Philadelphia, and Boston-settled in by Europeans in the 1650s, only about 45 percent of cats carry the blotched tabby gene, but this is considerably more than in originally Spanish-settled areas, such as Texas, at around 30 percent-where cats look much like those in Spain today. As shown in the nearby figure, the Atlantic Provinces of Canada, settled some 100 years later, have more blotched tabbies. European colonies settled in the nineteenth century are more variable: Hong Kong in particular has fewer than it should, probably because there was already a striped-tabby population of Chinese origin there, thus diluting the effect of British immigration. Australia on the other hand has more than it should, possibly the result of later waves of British immigrants in the twentieth century bringing their cats with them. The proportion in Britain was over 80 percent in the 1970s, and may have continued to rise since then.
How the percentage of the blotched tabby allele varied between locations colonized from Britain between 1650 and 1900, compared to England in 1950 We can explain this trend by making two a.s.sumptions. The first is that the proportion of blotched tabbies in Britain has been rising steadily since about 1500, for some reason unique to that country-otherwise the same change should have taken place in, for example, New York, Nova Scotia, Brisbane, and Hong Kong, resulting in blotched tabbies reaching 80 percent of the population today in those places as well. The second is that once a population of cats becomes established in a particular place, the proportion of blotched to striped doesn"t change. The latter a.s.sumption holds for other places and variations in coat color, too, so it may be universal (see box below, "Reconstructing the Origins of the Cats of Humboldt County, California"): however, given that it seems not to have occurred anywhere else, the rise of the blotched tabby in Britain becomes even more curious.
Reconstructing the Origins of the Cats of Humboldt County, California Domestic cats arrived on the West Coast of the USA by a variety of routes-by sea from the south and the north, and overland from the east. From the sixteenth to eighteenth centuries, Humboldt County, on northern California"s Redwood Coast, received a succession of visitors and settlers, including Russian, British, and Spanish vessels exploring the Pacific Coast, and farmers from both Missouri to the east and Oregon to the north. Feral cats, probably escapees from trading ships, were first recorded in Humboldt County in the 1820s, before the arrival of the first farmers, so today"s cats could be the descendants of either-or both.
In the 1970s, biologist Bennett Blumenberg recorded the coat colors and patterns of 250 local cats, and from these determined the proportions of the different versions of each gene. For example, 56 percent of the cats were black or black and white, from which he was able to estimate that the black ("non-agouti") version of the gene was present in 75 percent of the population-the difference being made up of cats that were carrying one black version and one tabby, and were therefore outwardly tabby. He also recorded the numbers of orange and tortoisesh.e.l.l cats, blotched vs. striped tabbies, pale coats, long and short hair, all-white cats, and cats with white feet and bibs: each one of these variations is controlled by a different and well-understood gene. He then compared these with cats from other parts of North America.14 The most similar were the cats of San Francisco, Calgary, and Boston, indicating that the ancestors of today"s Humboldt County cats had mainly arrived overland with farmers and prospectors, or in the fur-traders" vessels sailing out of Boston. However, he also found traces of cats of Spanish origin, left behind after the demise of New Spain and its occupation of much of what is now California. Some otherwise unaccounted for similarities were detectable with the cats of Vladivostok, homeport of the Russian-American Trading Company. Their ships also sailed from ports that are now in China, and could feasibly have carried cats of Chinese origin, but Blumenberg found no trace of Chinese cat genes in the Californian cats.
Polydactyl footprints Another rare mutation known as polydactyly gives cats an extra toe on each foot. Early in the establishment of Boston, one newly arrived cat must have produced a kitten with extra toes, and that kitten became the ancestor of many more, such that by 1848, extra-toed cats were common there; today, they form about 15 percent of the population. Cats with extra toes are also common in Yarmouth, Nova Scotia, a seaport founded by immigrants from Boston, whereas in nearby Digby, settled by New York Loyalists at the end of the Civil War, polydactyly is as rare as it is everywhere else.15 Relatively few of the domestic cats that colonized South America from Spain and Portugal were blotched tabbies, so scientists have had to turn to other variations in appearance to trace their history. Here also, it seems that once a population of cats becomes established, its genetics doesn"t change much, even over several centuries. It seems plausible that the cat population is set up when the initial (human) colonists bring their cats with them, and subsequent immigrants only adopt cats from the local population. For example, in the nineteenth century, Catalans from Barcelona established several towns along the river Amazon, and the cats of at least two of those towns, Leticia-Tabatinga and Manaus, remain similar to the cats of Barcelona more than a century later.16 As in Hispanic-settled parts of the United States, and in Spain itself, orange and tortoisesh.e.l.l cats are more common in South America than in most other places. The exceptions, where these colors are even more common, are Egypt-possibly one origin of this mutation (see the box on page 41, "Why Ginger Cats Are Usually Boys"); the islands off the north and west coasts of Scotland; and Iceland. Researchers have attributed these exceptions to a hypothetical preference for orange cats among the Vikings, who colonized those places around the ninth century CE, but it is unclear whether the Vikings first obtained their orange cats from the eastern Mediterranean, or whether orange appeared spontaneously and independently somewhere in Norway and was then transported around the Norwegian Sea in Viking ships.
Today, cats come in many colors and coat types, and many of these variations are undoubtedly the result of human preferences-even leaving aside pedigree cats, whose breeding is strictly under human control. The basic colors of cats-black, tabby (striped or blotched), ginger-are well established in populations all around the world, albeit in slightly different proportions. These colors persist in cats that have gone feral, so they do not seem to produce any major advantage-or disadvantage-to their wearers. However, many other variations in appearance seem to persist mainly because people like them. Cats with white feet and variable amounts of white on the body (the gene that controls this is rather imprecise in its effects) are less well-camouflaged than their plainer counterparts, putting the cat at a disadvantage when hunting. However, many people prefer their cats to carry white patches, especially the black-and-white "tuxedo" cat. Some people also favor cats that carry a gene that dilutes their coat color, such that black cats become a fetching shade of gray (often referred to as "blue"), and other colors are a few shades lighter than usual.
Some people like long-haired cats. Although it seems self-evident that these cats, which like all cats cannot sweat through their coats, should be at a natural disadvantage in warm climates, a recent study of Latin American cats indicates that human preference is a much more potent factor than the weather, although a thick coat, such as that of the Maine c.o.o.n and the Norwegian Forest Cat, is undoubtedly beneficial for outdoor cats in cold climates.17 In temperate climates, the main disadvantage of long hair is not that the cat overheats, but that its coat easily becomes matted, which, if left unattended, leads to infection or infestation of the skin. Long-haired cats are rarely seen in feral colonies, testifying to their unsuitability for a life without attention from humans.
The striped tabby pattern evidently suits wildcats the best, possibly because it provides the most effective camouflage for hunting. Presumably, mutations that affect appearance have occurred from time to time, but the wildcats that happened to carry them fared worse than their "normal" counterparts, so the mutation quickly died out. For a domestic cat, camouflage is probably less critical, allowing other coat colors to spread through the population.
A similar variety of colors and coat types has, of course, also become a feature of many other types of domesticated animal-dogs, horses, and cattle, for example. In the case of the cat, external appearance reflects two distinct factors, both of which affect how many offspring a cat is likely to have, and therefore how common its coat color and type are likely to be in the next generation. The first is whether these factors impede the cat"s hunting ability; this may not be so important today, but it certainly was in the past. The second is how appealing the cat is to its owner. Because human tastes vary from person to person and culture to culture, this second factor has produced many variations.
What seems to be missing here is any trace of each cat"s own preferences. Although never studied directly, we have no evidence for "color prejudice" among cats. Tabby females do not seem to spurn black toms in favor of other tabbies: a white bib and socks seems to be neither an advantage nor a disadvantage when it comes to finding a mate, except perhaps indirectly, if the cat"s conspicuousness has resulted in it catching less prey and thus looking less healthy than its better-camouflaged rival. Whatever criteria cats use to choose a mate, coat color seems to be well down the list.
Even today, most domestic cats exert a remarkable amount of control over their own lives, significantly more than other domestic animals, such as dogs. If we leave the pedigree breeds to one side for a moment (and these are still in a minority), most cats go where they please and choose their own mates (unless they are neutered-a relatively recent phenomenon). For this reason alone, cats cannot be considered completely domesticated.18 Full domestication means that humankind has complete control over what an animal eats, where it goes, and most crucially, which individuals are allowed to breed and which are not.
We certainly provide domestic cats with most or all of their food, but in this respect, too, cats are an anomaly. Science cla.s.sifies them as obligate carnivores, animals that have to obtain a mostly meat-based diet if they are to thrive (see box on page 71, "Cats Are the True Carnivores"). For a female cat to breed successfully, she must have a high proportion of flesh in her diet, especially in late winter, when she is preparing to come into season, and subsequently while she is pregnant. The domestication of such an animal takes some explaining; until recently, meat and even fish formed only a minor part of most people"s diets, and were often only seasonally available. Most domesticated animals will thrive on foods that we ourselves cannot eat, unlocking sources of nourishment that would otherwise be unavailable to us: cows turn gra.s.s, which we can"t digest, into milk and meat, which we can. (Though cla.s.sified as carnivores, even dogs are actually omnivores; they may prefer meat, but cereal-based foods can, if necessary, give them all the nutrition they need.) Cats Are the True Carnivores Cats are carnivores not by choice, but by necessity. Many of their relatives in the animal kingdom, though referred to as Carnivora, are actually omnivores-including domestic dogs, foxes, and bears-and some, like pandas, have reverted to being vegetarian. The whole cat family, from the lion down to the tiny black-footed cat from southern Africa, have the same nutritional needs. At some point many millions of years ago, the ancestral cat became such a specialized meat-eater that it lost the ability to live on plants: it became a "hypercarnivore." Once lost, such capabilities rarely re-evolve. Domestic cats might have been more successful if they could have gotten by, as dogs can, living on sc.r.a.ps, but they are stuck firmly in the nutritional dead end their ancestors bequeathed to them.
Cats require far more protein in their diet than dogs or humans do, because they get most of their energy not from carbohydrates but from protein. Other animals, faced with a shortage of protein in the diet, can channel all the protein they do get into maintaining and repairing their bodies, but cats cannot. Cats also need particular types of protein, especially those that contain the amino acid taurine, a component that occurs naturally in humans, but not in cats.
Cats can digest and metabolize fats, some of which must come from animal sources so that the cat can use them to make prostaglandins, a type of hormone essential for successful reproduction. Most other mammals can make prostaglandins from plant oils, but cats cannot. Female cats must get enough animal fat during the winter to be ready for their normal reproductive cycle, mating in late winter and giving birth in the spring.
Cats" vitamin requirements are also more stringent than ours. They need vitamin A in their diet (if need be, we can make ours from plant sources), sunshine doesn"t stimulate their skin to make vitamin D as ours does, and they need lots of the B vitamins niacin and thiamine.19 None of this is a problem if the cat can get plenty of meat-although raw fish, which contains an enzyme that destroys thiamine, can cause a deficiency if eaten in excess. It is slightly possible to construct a vegetarian diet for cats, but only if every single one of the cat"s nutritional peculiarities are carefully compensated for. Their taste buds also differ substantially from our own, having evolved to focus better on an all-meat diet. They cannot taste sugars; instead, they are much more sensitive than we are to how "sweet" some kinds of flesh are, compared to others, which they find bitter.
Cats do have two notable nutritional advantages over humans. First, their kidneys are very efficient, as expected for an animal whose ancestors lived on the edge of deserts, and many cats drink little water, getting all the moisture they need from the meat they eat. Second, cats do not require vitamin C. Taken together, these make cats well suited to shipboard life: they don"t compete with sailors for precious drinking water, getting all they need from the mice they catch, and they are not afflicted by scurvy, a common disease among mariners to the middle of the eighteenth century, when it was found it could be prevented by eating citrus fruits.
For most of their coexistence with humankind, cats were valued primarily for their skill as hunters. Since mice contain all the nourishment a cat needs, a successful hunter automatically ate a balanced diet; starvation was always possible for the less adept or the unlucky, but diseases due to specific nutritional deficiencies were unlikely. However, even historically, few domestic cats would have lived by hunting alone, most being provided with at least some food by their owners, supplementing their diet by scavenging. So long as some of their diet came from fresh meat, usually in the form of prey they had killed themselves, scavenging would not have tipped them into nutritional imbalance; still, giving up hunting entirely would have been risky.
Cats do not scavenge at random; they have some ability to make informed choices. They subsequently avoid foods that make them feel seriously and instantly ill. When eating food that they have not killed for themselves, they also deliberately seek out a varied diet, thereby avoiding a buildup of anything that might make them sick long-term, but might slip beneath the radar of immediate malaise.
To demonstrate this behavior, I laid out individual pieces of dry cat food on a grid on the ground, some of one brand, some of another, and then allowed rescued strays to forage over them, one at a time. In this way, I could record in precisely what order each cat picked up and ate the pieces of the two foods. When there were equal numbers of each type of food, the cats roamed across the grid, eating both foods but more of whichever food they liked better. However, when one of the two foods made up 90 percent of the total, every cat, whatever its preference, stopped grazing indiscriminately within a couple of minutes and started actively seeking out the rarer food. Thus, these cats demonstrated a primitive "nutritional wisdom," as if they a.s.sumed that eating a variety of food was more likely to produce a balanced diet than simply eating the food that was easiest to find (even though both the foods offered were nutritionally complete).20 When I gave similar choices to pet cats that had always had a balanced diet, few responded this way, most continuing to eat whichever of the two foods they liked better from the outset, or was just easy to find. Thus, although all cats probably have the capacity to deliberately vary their diets, it seems that this ability must be "awakened" by some experience of having to scavenge for a living, as most of the stray cats in our original experiment must have done before they were rescued.21 Most other animals have more varied diets than cats". Rats, the best-studied example, are omnivores with extremely wide tastes that suit them perfectly for a scavenging lifestyle. They employ several strategies that enable them to pick the right foods from the wide but unpredictable choices available to them. New foods are only nibbled at until the rat is sure that they"re not poisonous. As soon as each food starts to be digested, the rat"s gut sends information to its brain about its energy, protein, and fat content, enabling the rat to switch to another food with a different nutritional content if necessary. Cats are much less sophisticated in this regard, having traveled a different evolutionary path based on mainly eating fresh prey, which is by definition nutritionally balanced.
Given their limited ability to subsist by scavenging alone, cats were locked into the hunting lifestyle until as recently as the 1980s. Until science revealed all of their nutritional peculiarities, it would have been a matter of luck whether a cat that wasn"t able to hunt obtained a nutritionally balanced diet, unless its owner was both willing and able to give it fresh meat and fish every day. Although commercial cat foods have been available for over a century, there was initially little understanding that cats had very different requirements to dogs, and much of this food must have been nutritionally unbalanced. Commercial cat food that is guaranteed to be nutritionally complete has been widely available for only thirty-five years or so-only 1 percent of the total time since domestication began.
Cats foraging on a grid In evolutionary terms, this is just a blink of an eye, and we have yet to see the full effects of this improvement in nutrition on cats" lifestyles. Just a few dozen generations ago, the cat that was a skillful and successful hunter was also the cat that stood the best chance of breeding successfully. Those cats that depended entirely on man for their food would usually obtain enough calories to keep them going day-to-day, but many would not have bred successfully, because many of the cat"s unusual nutrient requirements are essential for reproduction. Nowadays, any cat owner can go to the supermarket and buy food that keeps their cat in optimum condition for breeding. That is, of course, if the cat has not been neutered-another development that has yet to show its full effect on the cat"s nature.
Today"s cat is thereby a product of historical turmoil and misconception. What would today"s cats be like if they had not gone through centuries of persecution? It is possible that the effects may not have been particularly long-lasting. After all, since serious attempts were made to exterminate black cats in continental Europe because of their supposed a.s.sociation with witchcraft, they should still be uncommon there today-and they"re not. Although undoubtedly many individual cats did suffer horribly, little lasting damage seems to have been done to the species as a whole. This is probably because, for most of the time and in most places, particularly in the countryside, cat-keeping was both enjoyable and practically beneficial, even if occasionally interrupted by an outburst of religious persecution. Changes have taken place-cats today are significantly smaller and more varied in color than when they left Egypt-but these changes appear to have been mainly local rather than global.
Thus, following the origin of their partnership in ancient Egypt, cats and humans continued to live alongside one another, for a further 2,000 years, without the cat ever becoming fully domesticated. Then, due to the nutritional discoveries of the 1970s, all cats, and not just the pets of the well-off, were relieved of the necessity to hunt for a living. However, their predatory past, so essential to their survival until recently, cannot be obliterated overnight. One of the most significant challenges facing today"s cat enthusiasts is how to allow their cats to express their hunting instincts without causing wildlife the damage which evokes so much criticism from the anti-cat lobby.
CHAPTER 4.
Every Cat Has to Learn to Be Domestic Cats are not born attached to people; they"re born ready to learn how to attach themselves to people. Any kitten denied experience with people will revert toward its ancestral wild state and become feral. Something in their evolution has given domestic cats the inclination-and it"s no more than that-to trust people during a brief period when they"re tiny kittens. This minute advantage enabled a few wildcats to leave their origins behind and find their place in environments created by the planet"s dominant species. Only one other animal has done this more successfully than the domestic cat, and that, of course, is the domestic dog.1 Like puppies, kittens arrive into the world helpless, and then have just a few weeks in which to learn about the animals around them-an even shorter time for cats than for dogs-before they must make their own way in the world. By comparison with our own infants, which are dependent on us for years, this is a very brief period. Even in their wild ancestors, the wolf and the wildcat, this window must have been open just a crack, waiting for evolution to allow the young animals of these two species to learn to trust us, and thereby become domesticated.
Kittens and puppies alike become more closely integrated into human society than any other animal can, but the way the two species achieve this differ. Early scientific studies of dogs from the 1950s established the notion of a primary socialization period, a few weeks in the puppy"s life when it is especially sensitive to learning how to interact with people. A puppy handled every day from seven to fourteen weeks of age will be friendly toward people and virtually indistinguishable from a puppy whose handling started four weeks earlier. For the next quarter century, scientists generally a.s.sumed that kittens must be the same, and that it was not essential to handle kittens until they were seven weeks old. In the 1980s, when researchers finally performed corresponding tests on cats, those recommendations had to change.
These experiments confirmed that the concept of a socialization period could indeed be applied to cats, but that this period was comparatively curtailed in kittens. The researchers handled some kittens from three weeks old, some from seven weeks old, and the rest not until the testing started at fourteen weeks. The kittens started learning about people much earlier than puppies do. As expected, the kittens handled from their third week were happy to sit on a lap when they reached fourteen weeks old, but those whose contact with people had been delayed to seven weeks jumped off within half a minute-though not as quickly as those that had never been handled during their first fourteen weeks, which typically stayed put for less than fifteen seconds.
Handling a feral kitten Could this be explained by the seven-week-handled kittens being more active than the three-week-in other words, no less happy to be on a person"s lap, just more eager to explore their surroundings? It quickly became obvious that this could not be the cause. When each kitten was subsequently given the opportunity to cross a room toward one of their handlers, only the three-week kittens did so reliably-and were quick to do it, too, giving every impression that they were attracted to the person, who was by then very familiar to them. The seven-week and unhandled kittens did not seem unduly frightened of the person, and would occasionally get close to her. Some even apparently asked to be picked up, but these two groups were more or less indistinguishable in their behavior.
The handling that those seven-week kittens received up to the point of testing had not produced the powerful attraction to people that was obvious from the behavior of the three-week kittens. For the scientists taking part, the tests simply formalized what was already obvious from the kittens" behavior. As the leader of the research team noted, "In observing and interacting with these cats during testing and in their home rooms, it was obvious to everyone working in the lab that the late-handled [i.e., seven-week] cats behaved more like the unhandled cats."2 The scientists concluded that cats need to start learning about people much earlier than dogs must. Dog breeders ought to handle puppies before they are eight weeks old, but if puppies are not handled until that age, then with the right remedial treatment they can still become perfectly happy pets. A kitten that encounters its first human in its ninth week is likely to be anxious when near people for the rest of its life. The paths that lead to an affectionate pet on one hand and a wild scavenger on the other diverge early in the cat"s life; indeed, if it were any earlier, few cats would be able to forge relationships with us.
Even though the most crucial changes start in the third week, the first two weeks of the kitten"s life are far from uneventful. For the first fourteen days of a kitten"s life, the most important feature in its world is its mother. Kittens are born blind, deaf, and incapable of moving more than a few inches unaided. They cannot regulate their own body temperatures. Especially if the litter is larger than average, and the kittens are correspondingly small, they carry little in the way of energy reserves, and even the loss of a fraction of an ounce in weight can lead to weakness and, if outside intervention is not forthcoming, death. Their survival, then, depends on their mother"s capabilities. Tomcats play no part in rearing offspring, and many mothers that give birth outside the home raise their kittens without help. The mother"s choice of nest site is crucial, especially when the luxury of giving birth indoors is not available. Kittens must be well protected from the weather and from potential predators. After the first twenty-four hours, which all mother cats spend suckling and grooming their kittens, she may have to leave them to find food; and if that involves hunting, as it would in the wild, that may take some time.
Once kittens are a few days old, the mother may move them to a different nest site if her instincts make her feel uncomfortable about the original den. Kittens have a special "scruffing" reflex that enables her to do this quickly and quietly, without drawing attention to their vulnerability: she grasps them in her mouth by the loose skin on the back of their necks, and they instantly go limp and apparently oblivious to their surroundings, until she drops them in the new nest, where they appear confused but otherwise unaffected (see nearby box, "Clipnosis").
"Clipnosis"
Unlike much infantile behavior, in some cats the "scruff" reflex mother cats use when carrying their kittens persists into adulthood. For those individuals, scruffing can be used as a gentle and humane method of quieting a fearful cat. The cat is simply grasped firmly by the skin on the back of its neck and, if the reflex is triggered, may go into what appears to be a trance, enabling it to be picked up and carried; its weight must be supported by the other hand. Veterinary nurses sometimes use a hands-free version, applying a line of several clothespins to the area of skin between the top of the head and the shoulders. By doing so, the nurses can complete an examination of the cat without causing it too much stress.3 Many mother cats try to move their litters at least once before they wean them, but science has yet to find out why. In the wild, a mother cat will inevitably carry a few fleas, and because she has to spend so much time in the nest, flea eggs acc.u.mulate there; when they become adult fleas three or four weeks later, a single hop will take them onto a kitten. Removing the kittens from such an obvious source of infestation seems a good strategy and may be one explanation for nest-moving, but so far no evidence has been found that this reduces the number of fleas that kittens carry. Nest-moving may simply be a response to a disturbance that made the mother anxious, or may sometimes be strategic, bringing the kittens closer to the source of food onto which their mother intends to wean them. The kittens may suffer if the mother cat moves them too early or chooses the wrong new nest site. Kittens are vulnerable to becoming chilled, especially in damp weather that also favors the transmission of respiratory viruses; many feral kittens, particularly those born in the autumn, succ.u.mb to cat flu.
As my own experience shows, not all cats are innately skilled at parenthood. My cat Libby, having a nervous disposition, was not the best mother. As the time for her to have her litter approached, we tried to keep her in the same room where she had herself been born, presuming she would find the surroundings rea.s.suring. But she was restless, patrolling the house and looking into every open cupboard and drawer, as if undecided as to the safest location. At least she showed no inclination to give birth outdoors. Eventually, she decided to produce her kittens within a few feet of where she herself had come into the world.
We should not have relaxed: a few days later, we discovered the kittens scattered all around the house. For a few hours after the birth, Libby lay with her three kittens and allowed them to suckle, but after that she appeared to lose interest, spending too much time away from them. Her mother Lucy was intrigued by the kittens, but at this stage played no part in looking after them. When we checked the kittens" weights, they seemed to be growing, so we were not unduly worried until Libby began to try to pick them up in her mouth and carry them away from the den we had built for her. Her inexperience as a first-time mother showed immediately, as she grasped the kittens rather roughly by the head, only occasionally and apparently accidentally gripping them correctly by their scruffs. Once she had gotten the hang of carrying them, she began to look for places to hide them.
Without our intervention, Libby"s kittens would surely have perished. She would find a secluded place to hide the first kitten, and then return to the other two, pick up another, and take that one somewhere else, ignoring the cries of the first. After taking the third to yet another location, Libby would wander off as if unsure what to do next. Each time this happened, we searched out all the kittens and put them back in the original den. Once or twice, we tried constructing a new den-in the same room, but with completely new bedding so that it smelled nothing like the first, hoping this might fool Libby into believing she had successfully moved the whole litter herself. Still, the removals persisted. Finally, grandmother Lucy, her maternal instincts aroused, began to retrieve the kittens herself. Libby, perhaps sensing that she should follow her mother"s lead, gradually gave up trying to move the litter. She continued to feed them, and they grew stronger, but from then on it was Lucy who groomed them and kept them together until they were ready to be weaned.
Lucy seemed to know the kittens by their appearance and by their smell, but first-time mothers can behave as if they do not immediately "know" what a kitten is. Rather, they respond to a single powerful stimulus that ensures that they take care of their newborns. This is the kitten"s high-pitched distress call, uttered if it is cold, hungry, or out of contact with its littermates. When the mother cat hears this sound coming from outside the nest, indicating that a kitten has strayed away, she should instantly begin a search and, when she finds the kitten, retrieve it by its scruff. If the kittens are all in the nest and calling together, her instinct is to lie down and encircle them with her paws, drawing them onto her abdomen and allowing them to suckle. Gradually, over the course of their first couple of weeks of life, she seems to recognize the kittens as independent animals, though whether she ever comes to know them as individuals is unclear.
Libby"s kittens preferred to curl up with Lucy Kittens are so vulnerable in the first few weeks of their lives that their survival depends almost entirely on their mother"s skill. Libby seemed to lack several components of maternal instinct, but even if just one is defective, the kittens" chances become slim. Yet if cats are as little removed from the wild as many researchers consider they are, they should-and most do-retain the ability to get everything right the first time. Research on free-ranging cats has produced little evidence to support the idea that first-time mothers are less successful than second-time mothers, although Libby"s inability to locate her kittens" scruffs is reportedly quite common in inexperienced mother cats (known as queens).4 Of course, domestication has provided an obvious safety net: the intervention of human owners.
For about the first two weeks of their lives, kittens define their world through smell and touch. At birth, their eyes and ears are still sealed, providing them with little useful information. Kittens recognize their mother immediately, initially just by her warmth and feel, and rapidly also learn her characteristic smell. They probably have little idea of what she is "supposed" to smell like; orphaned kittens fed on an artificial "mother" that smells nothing like a cat quickly learn its scent instead-a kind of "imprinting." In one cla.s.sic series of experiments, researchers constructed a surrogate mother from artificial fur fabric, through which latex teats protruded, only some of which provided milk. Each teat was scented differently, for example with cologne or oil of wintergreen. The kittens quickly learned which scent indicated a milk-delivering teat.5 Each kitten gradually develops a nipple preference, based also on the nipple"s odor rather than its position, since each kitten knows precisely where it wants to suckle whichever way its mother is lying. They find their preferred nipple by following the odor trail made up of their own saliva, and probably secretions from scent glands under their chins, left behind on their mother"s fur as they approach the nipple.6 Kittens are unusually flexible when bonding with their mothers, a quality that works in their favor when their mothers are part of a social group. Often these groups are composed of close relatives, say a female and her adult daughters, which have grown up together and know one another well enough to overcome their natural mistrust of other cats. Such cats will spontaneously share nests and pool their kittens.
Local authorities once asked me how to handle such a cat colony living underneath some temporary buildings. Having pointed them toward humane alternatives to putting out poison, I located an animal charity to trap the cats and relocate them.7 It was springtime, and three of the females were heavily pregnant; they gave birth within a few days of one another. Even though they were given three separate boxes, the mothers soon put all the kittens together, and each fed them indiscriminately. Ten kittens feeding from three queens, all within a few inches of one another, produced the loudest chorus of purring I have ever heard.
As this implies, mother cats can be equally indiscriminate when identifying their own kittens from those of other cats-or at least, those of their relatives, which may smell similar. For cats, the general rule appears to be that if a kitten is in your nest, it must be yours. Some cat rescue organizations exploit this quality to raise orphaned kittens: some mother cats will readily accept an extra kitten that is gently slipped in with their own, even if their ages don"t match up. Some will even suckle entire litters introduced to them as their own kittens are removed after weaning. This doesn"t seem to do the mother any harm, provided, of course, she gets enough to eat.
Both mother cat and kittens are unusually trusting during the first few weeks after birth. For the mother, this is due to a wave of the hormone oxytocin, which drives her to make her kittens her top priority. For her kittens, the factor may not be a hormone such as oxytocin, but instead their early inability to produce stress hormones such as adrenalin. A kitten that suckles for a few seconds too long and is accidentally dragged out of the nest as its mother leaves should be terrified; after all, this is potentially the most traumatic experience it has had in its short life. We can see the latent danger in this situation: the last thing such a kitten should do is make an a.s.sociation between the mother"s smell and the shock of falling to the ground outside the nest. If it does, when the mother returns it might shy away from her, rather than immediately attaching to her to feed as it should. However, thankfully, kittens" inability to produce stress hormones means that such incidents leave no lasting impression.
Once a kitten reaches two weeks of age, its eyes and ears open and it begins to take its first faltering steps around the nest (see the figure on page 85). Its stress mechanisms then begin to function, enabling it to learn both what"s bad and what"s good about the world. From this point, what the kittens learn depends on whether their mother is present. If she"s there, the kittens take their lead from her, but do not become stressed, so may not remember much about anything untoward that happens to them. Only if she is absent, and they must make their own decisions on how to react, do their stress levels rise abruptly, cementing their memory of the trauma and whether they dealt with it effectively or not.
The development of the senses and other critical events in the life of a kitten This "social buffering" is probably adaptive for cats in the wild. A mother that is absent for long periods is probably having difficulty finding enough food for her litter or to replenish her milk, so the kittens must start to learn about the world soon if they are to stand any chance of survival. Kittens whose mother is usually with them in the nest can delay learning about any perils that may await them, because they can rely on their mother to protect them.
The personalities of cats are powerfully affected by what they learn when they"re tiny kittens. Most kittens born in houses will be looked after both by their mothers and by their mothers" owners, but those unfortunate enough to undergo prolonged stress in their first few weeks of life may grow up to have enduring emotional and cognitive problems. For example, kittens that are abandoned by their mothers and are then hand-raised can become excessively attention-seeking toward their first owners, though some subsequently seem to grow out of this. Based on what we know about other mammals in similar situations, we can a.s.sume that after the mother"s departure, the kittens" brains endure high levels of stress hormones. These consistently high levels cause permanent changes in their developing brains and stress hormone systems, such that they may overreact to unsettling events later in life.
Such cats may not make particularly satisfying pets, but this is by no means to say that they are mentally defective. Rather, their apparently abnormal behavior is an evolved adaptation. A mother that has struggled to raise her kittens was likely affected by some difficulty that has made food hard to find. A kitten whose mother has struggled to raise it therefore expects to emerge into an uncertain world, in which it may have to live on its wits and thereby outcompete its littermates and any other kittens born in the vicinity. The kittens of a relaxed, well-fed mother are likely to be able to depend on a more stable world, one in which they will have the time to hone their social skills and reproduce several times over a period of years. Such kittens, of course, are likely to make better pets than kittens that have been stressed in early life.
As a kitten begins its third week, it embarks on the most crucial six weeks of its life, as far as its development is concerned (see box on page 87, "Stages of Development"). From this point onward, its eyes, ears, and legs begin to function reliably, and, guided by its hormones, it begins to make decisions about whom and what it should interact with, and whom and what it should keep away from. At the same time, its brain is growing rapidly, every day adding thousands of new nerve cells and millions of new connections among them, establishing the framework for storing all the new knowledge it acc.u.mulates. Its mother is still a crucial influence during this period, but from now on a kitten gradually becomes able to distinguish its littermates from one another, and to learn about the other animals around it, including people. Kittens born in the wild also begin to learn how to hunt, for within a few short weeks they will need to feed themselves.
Stages of Development The way a cat reacts to the world around it develops for at least the first year of its life, but most of the crucial changes take place in the first three or four months. Biologists divide this into four periods, each of which has a different significance for the growing kitten.
During the prenatal period, especially the second month of the queen"s pregnancy, the kitten is largely-but not entirely-isolated from the outside world. The composition of the amniotic fluid and the blood in the placenta both reflect the mother"s environment. For example, if the mother eats a strongly flavored food during this period, the kittens may prefer to be weaned onto a food with the same flavor, showing that they gain the ability to learn well before they emerge into the world. Female kittens that are adjacent to male kittens in the womb absorb some of their testosterone and are briefly more aggressive in their social play than kittens in all-female litters. Such inclinations are likely to be short-lived, but more far-reaching changes are also possible. Based on what we know of other mammals, if the mother is highly stressed during her pregnancy, her stress hormones may cross the placenta and impair the development of her kittens" brains and endocrine systems.
During most of the neonatal period, from birth to about two and a half weeks of age, the kitten is deaf and blind, relying on its senses of smell and touch to bond to its mother.
The socialization period begins as the eyes and ears open and begin to function in the third week of life, enabling the kitten to start learning about the world around it, including the people that are caring for it and its mother. At the same time, it learns to walk and then to run. When they are not sleeping, kittens spend much of this period engaged in play, initially with one another and then increasingly with objects.
The beginning of the juvenile period, at eight weeks of age, coincides with the customary time to rehome a kitten (except pedigree kittens, traditionally homed at thirteen weeks). By this point, the sensitive period for socialization is virtually over. The juvenile period ends at s.e.xual maturity, sometime between seven months and one year of age; many pet cats will of course be neutered before the end of the first year.
Most of the kittens" interactions with one another are playful, and for the first half of the socialization period, most of their play is directed at other kittens. However, we do not know if early on each kitten recognizes that what it is playing with is another kitten; most of the actions performed are similar to those used later toward objects. Bouts of play are short and disorganized, and it may be that the movements of the other kitten trigger each attempt at play. By the time they are six weeks old, though, kittens will play on their own with the objects around them, poking, pouncing, chasing, batting them with their paws, and tossing them in the air. These are all actions adult cats use when they capture prey, so biologists have looked for an elusive link between the amount of play that kittens perform and their hunting ability when they grow up. While play with objects hones the kittens" general coordination, it"s probably not the most important factor in determining whether a cat grows up to be capable of catching enough prey to keep itself fed.
For feral kittens, their mother enables them to learn how to fend for themselves. As soon as they are old enough, she brings recently killed prey back to the nest; as they become better coordinated, she brings back prey that is still alive. This gives the kittens the opportunity both to handle prey and to find out what it tastes like. The mother doesn"t seem actively to teach them how to deal with prey; rather, she simply places it in front of them and allows their predatory instincts to take over. If they show no interest, she may draw attention to the prey by starting to feed on it herself, stopping when the kittens begin to join in. Of course, this process rarely happens with owned cats, unless the mother happens to be an accomplished and habitual hunter herself, in which case small, gory "presents" may find their way into the nest.
Whether a cat is destined to be a hunter or (more likely) not, among the most important events in a kitten"s life is when its mother decides to start weaning it. This typically occurs in the fourth or fifth week of the kitten"s life, but may be earlier if the litter is large-six or more kittens-or if the mother is unwell or stressed. Whatever the circ.u.mstances, the mother cat drives this process; kittens rarely if ever decide to wean themselves. At the decisive moment, the mother starts to spend time away from the kittens or simply blocks access to her milk by lying or crouching with her abdomen pressed firmly to the ground. Not surprisingly, the kittens begin to get hungry, and for a few days their weight gain, steady since birth, slows down or even stops. Hunger drives them to become much more inquisitive about other possible sources of food.
In the home, with human owners supplying the grub, the new source of food should be special kitten food. In the wild, mother cats bring prey back to the nest and dissect it, making it easier for small mouths to chew. The kittens continue to pester her for milk, but for the next couple of weeks or so she will ration them, to force them to develop their ability to eat-and digest-meat. As their eating habits change, so do their insides. Meat takes longer to digest than milk, so kittens" intestines become lined with villi, small finger-shaped projections that increase the amount of nutrients that can be absorbed. Lactase, the enzyme that breaks down milk sugar, is permanently replaced by sucrase to break down the sugars in muscle, such that many adult cats find milk indigestible. The mother cat is simply being cruel to be kind: when the kittens become fully weaned at about eight weeks of age, she may spontaneously allow them to suckle occasionally, possibly as a way of reinforcing family ties-although in a domestic situation, they may no longer be with her.
Scientists have sometimes portrayed the weaning process as a conflict between mother and offspring. One theory holds that an animal such as a cat that can have several litters in a lifetime should behave in a way that balances out the survival of each of her litters. For example, the demands of an extra-large litter might become excessive, jeopardizing her own health and therefore her chance of having any more litters. In some mammals, including mice and prairie dogs, mothers with large litters may kill one or two of the weakest members, presumably to ensure the survival of the rest. However, this tactic has never been recorded with cats, although a sickly kitten may simply be ignored by its mother, presumably because it does not produce the right signals to induce her to care for it.
Each kitten must do its best to survive, regardless of whether it is its mother"s favorite; if it does not survive to maturity, it will never leave any offspring of its own. Given that female cats tend toward promiscuity, no kitten can be sure that it is closely related even to its littermates, let alone to any of the members of its mother"s next litter.8 It therefore has to put its own interests first, even more so than if it could be sure that it shared both parents with its littermates. It therefore has no incentive to give up suckling, even to the point of weakening its mother.
A mother cat cannot afford to be too hardhearted toward her offspring; after all, she cannot be at all certain that she will have the chance to breed again. She therefore carefully a.s.sesses their needs, keeping them hungry enough to want to try meat while not significantly compromising their health. For example, if her milk temporarily dries up before she"s finished weaning them, she will start nursing them again before weaning is over, as soon as her milk comes in again; this ensures that that they don"t miss out on any essential nutrients. Likewise, the kittens themselves cannot be too aggressive in demanding milk from their mother, for (in the wild) they need to keep her on their side for several weeks longer, as she teaches them essential hunting skills. Furthermore, if her milk supply starts to fail early, kittens increase the amount of time they spend playing, presumably to prepare themselves for learning how to hunt. While most young animals-mice, for example-play less when they"re hungry, presumably to conserve energy, for kittens play is preparation for hunting behavior. Responding to their mother"s predicament, such kittens are thereby preparing themselves for a premature independence.
Play prepares kittens not just for hunting, but also for getting along with other cats. If domestic cats were as solitary as their ancestors, they would have little need for social graces. For animals whose individual contact is restricted to brief courtship and mating, and then the raising of each litter by its mother, social play is unsophisticated and brief. For domestic kittens, play with littermates becomes increasingly sophisticated as they get older, and no longer revolves around the elements of hunting behavior.
By about six to eight weeks of age, kittens begin to use specific signals aimed at persuading their littermates to play with them, such as rolling onto their backs (see "Belly-Up" in the drawing on page 92), placing their mouth over another kitten"s neck ("Stand-Up"), or rearing onto their hind legs ("Vertical Stance"). By ten weeks-a.s.suming the litter is still together, since many kittens are homed at eight weeks old-each kitten will have come to learn the "correct" response to each of these-Belly-Up for Stand-Up (and vice versa), and Belly-Up for Vertical Stance. As the kittens get older, play tends to get rougher, and occasionally one of the kittens gets hurt. To avoid any confusion between play and a real fight, kittens will use a "Play Face" to indicate their friendly intentions, particularly when in the vulnerable Belly-Up position. They may also use special movements of their tails to signal playfulness, but so far no scientist has been able to decode these. Older kittens also have a special signal showing when they want to stop playing: they arch their back, curl their tail upward, and then leap off the ground.
If a litter is left together after the normal age for homing, social play occupies more and more of the kittens" time, peaking somewhere between nine and fourteen weeks of age. All this sophistication confirms that domestic kittens are designed to become social adults, a process that begins when they are just a few weeks old and, unless interrupted, continues for several months.
Surprisingly, we know little about the optimum time for cats to learn how to interact with other cats. Experiments pinpointing the sensitive period for socialization to people have yet to be repeated to uncover the same for cat interaction, but we can a.s.sume that there is more than one sensitive period, each tailored to the social environment in which the kitten finds itself. The first period spans the kitten"s first two weeks, when kittens form their attachment to their mother, based on olfaction.
Kittens performing Belly-Up with a Play-Face (left) and Stand-Up (right) During the first four weeks or so of life, each kitten learns how to interact with its siblings; it may have little need to recognize its littermates as individuals, but that probably follows soon after. Kittens are likely born with a template as to what another kitten looks like, but this is easily overwritten if there are no other kittens available. Thus, a kitten raised in a litter of puppies accepts the puppies as its littermates, and does not appear to "know" that it itself is a kitten. However, if a puppy is introduced into a litter of kittens, even though they are perfectly friendly toward the puppy, the kittens still prefer one another"s company. Cats" brains must be constructed in such a way that they form stronger attachments to cats than to other four-legged animals.
From the fifth week onward, kittens certainly learn a great deal from their littermates, in particular the most effective way to play. If a kitten from a litter of one is introduced to a kitten that has grown up with other kittens, it will play much more roughly than normal. Hand-raised kittens are even more inept: some turn out to be so aggressive that other kittens actively avoid them. Others become excessively bonded to their human owners and seem barely to realize that they are cats at all.9 We do not yet know why some go one way and some the other, but possibly some important interactions between socialization to cats and socialization to people help to produce a cat that doesn"t overreact to new situations-a balanced individual, if you like. Hand-reared kittens may develop extreme personalities because they miss out on these interactions, due to their lack of contact with other cats.
Kitten inviting play using Vertical Stance Littermates that are homed together usually form a stronger bond with one another than two unrelated cats. In August and September of 1998, a student and I studied this by recording the behavior of pairs of cats in boarding catteries (people who have a pair of cats that get along together at home will usually ask for them to be housed together when they board them). We compared fourteen pairs of littermates that had lived together since birth with eleven pairs of unrelated individuals that had not met each other until at least one of the pair was more than one year old. Despite the hot weather, all the littermate pairs slept in contact with each other, but we observed only five of the unrelated pairs ever lying in contact with each other, and even those only occasionally. Many of the littermate pairs groomed each other; the unrelated pairs never did. Almost all the littermates were happy to feed side by side; we had to feed most of the unrelated pairs from separate bowls or in turns.10 This study does not clarify whether just being littermates makes cats friendly to one another, but this seems the most likely explanation. It"s unlikely that it was simply the age difference between the unrelated pairs that made them unfriendly, since if a kitten is kept with its mother rather than being homed, the mother and kitten generally remain friends for life. However, scientists have yet to investigate whether littermates can recognize one another as relations, say if they are separated and reintroduced months later (as dogs can), or whether cats use a simple rule of paw, and try to remain friends with any cat that they"ve lived with continuously since the second month of their life-that is, during the socialization period.
Unlike most kittens born in homes, feral kittens can continue to interact with their littermates, and any other nearby litters, until they are at least six months old. Most kittens born outdoors are born in the spring. By autumn, their mother severs all ties with her male offspring and may actively drive them away-a sensible precaution against risk of inbreeding. Up to that point, the kittens will have had many opportunities to learn more about what it means to be a cat, opportunities generally denied to pet cats of the same age. Female kittens, on the other hand, often do not leave their natal group until they are several years old, so they have even more scope for learning feline social graces.
We often see a corresponding difference between the s.e.xes in kittens" choice of company. As they grow, feral male kittens spend most of their time with brothers from the same litter. They rarely interact with kittens from other litters, even those they are related to; in any one year, most litters born within a feral colony will be first or second cousins. Male cats, a.s.suming they avoid being neutered, are destined to lead solitary lives, and when they reach maturity, must compete with one another for female attention. Female feral kittens initially spend most time with their littermate sisters, but at a few months old will probably also regularly interact with both their aunts and their aunts" or other female relatives" kittens.
The third and fourth months of a kitten"s life are full of play, regardless of whether they are male or female. We do not know whether denying kittens the opportunity to play with other kittens during this period has significant consequences. Perhaps because cats are often conceived of as solitary creatures for which a social life is a luxury, not a necessity, we have not scientifically investigated this topic. However, it seems possible that continued interaction with their peer group during adolescence could make a major contribution to cats" development as social animals.
The most important social skill a cat must learn to become a pet is, of course, not how to interact with cats (though that is useful), but how to interact with people. In this respect, cats rank second only to dogs. Like dogs, cats can learn how to behave toward their own kind and toward people not only virtually simultaneously, but also without confusing the two. Nearly all other domestic animals are not as adaptable. For example, a lamb that has to be hand-raised will attach itself very powerfully to the person that feeds it, as if that person was its mother. Unless introduced to other, mother-reared lambs as quickly as possible, its behavior may be abnormal for the rest of its life. Moreover, whether sheep are tame or not, their social behavior is always primarily directed at other sheep.
Cats, like dogs, are capable of multiple socialization, the ability to become attached to animals of several different species-and not just people and other cats. Kittens raised in a household with a cat-friendly dog will continue to be friendly toward that dog, and potentially other similar dogs, for their entire lives. We do not know precisely how cats (or dogs) achieve this, but we can speculate that cats keep the "rules" for interacting with each separate species in discrete parts of their brains, as the human brain stores different languages in physically distinct areas of the frontal lobes.
Kittens with a dog Between the ages of four and eight weeks, kittens form their view of people, or at least the people they meet. Kittens that meet only women during that period, as can happen in some breeding catteries, may turn out fearful of men or children once they are homed. A kitten that is handled by only one person may become very strongly attached to that person, purring whenever it is picked up and in sistently pestering that person for attention-an intensity that suggests that the person has, in the kitten"s mind, taken the place of its mother.11 Introducing a kitten to a wide variety of people before the age of eight weeks seems to produce an approachable cat. Doing so seems to block the development of a strong attachment to one person, and instead builds a general picture of the human race in the cat"s mind. Whether (say) three categories-men, women, children-develop simultaneously, or whether kittens learn to place all humans in a single category is unknown, but the end result is self-evident: a cat that is not fearful of humans.
Kittens need a lot of daily exposure to people to become optimally socialized to them. In one study, fifteen minutes handling each day produced a kitten that would approach people, but not as enthusiastically as a kitten that had been handled for forty minutes per day. Likewise, the fifteen-minute kitten would not stay on a lap for as long as the forty-minute kitten.12 Fortunately for them, most kittens born in homes get this much attention without any special effort being taken, thanks to their irresistib