Cats are the world’s most popular pets, outnumbering dogs by as many as three to one. This popularity is undoubtedly helped by the fact that cats are simultaneously affectionate and self-reliant: They need virtually no training; they groom themselves; they can be left alone without pining for their owners, but most nonetheless greet us affectionately when we get home.
In a word, they are convenient.
Even so, cats remain aloof and inscrutable. Dogs tend to be open, honest and biddable. Cats, on the other hand, demand we accept them on their terms but never quite reveal what those terms might be.
I’ve studied cats for years and shared my home with quite a few, but I don’t feel that this has taught me very much about what they are really like. But science has begun to provide some answers, especially about their relationship to humans. Why are cats so choosy about their objects of affection? And what does it mean when they hold their tail straight up? Read on.
Cats and humans go back a long way. DNA evidence identifies the pet cat’s ancestor as the Arabian wildcat Felis silvestris lybica and places its origins between 10,000 and 15,000 years ago in the Middle East.
It is likely that the first people to tame wildcats were the Natufians, who inhabited the Levant from about 13,000 to 10,000 years ago and are widely regarded as the inventors of agriculture. As such, they were also the first people to be bedeviled by a new pest: the grain-loving house mouse. Wildcats probably moved in to exploit this new resource. Realizing how useful this was — cats, after all, had no interest in eating grain — people probably encouraged them to hang around.
These were not pet cats as we know them. They would have been more like today’s urban foxes, able to adapt to a human environment while retaining their essential wildness.
Of course, the cat’s other qualities probably did not go unnoticed. Their appealing features, soft fur and ability to learn to become affectionate toward us led to their adoption as pets. Yet cats still have three paws firmly planted in the wild.
In contrast to almost every other domestic animal, cats retain remarkable control over their own lives. Most go where they please and when they please and, crucially, choose their own mates. Unlike dogs, only a small minority of cats has ever been intentionally bred by people. No one has bred cats to guard houses, herd livestock or assist hunters.
Cats can be very affectionate, but they are choosy. This stems from their evolutionary past: Wildcats are largely solitary and regard most other cats as rivals. Domestic cats’ default position on other cats remains one of suspicion, even fear.
However, the demands of domestication — the need to live with other cats, and then the forming of bonds with people — extended cats’ social repertoire.
Social behavior probably started to evolve as soon as cats began to congregate around granaries. Any cat that maintained its antagonism toward other cats would have put itself at a disadvantage when exploiting this resource.
Even today, wherever there is a regular source of food, a colony of feral cats will spring up, assuming local people allow it. Colonies can build up until several hundred cats are living close to one another.
In these colonies, society tends to be based on cooperation between genetically related females. Mothers often drive away their male offspring after a few months to avoid inbreeding, leaving them to lead solitary lives.
Where colonies consist of more than one family, these groups compete with one another. Cats seem to be incapable of sustaining a large number of friendly relationships or of forming alliances between family groups in the way that primates do; negotiation skills this sophisticated lie beyond their capabilities.
The switch to social living required a quantum leap in communication as cats became domesticated. For an animal as well-armored as a cat, a tiff might escalate into a dangerous fight unless a system of signaling evolved that allows cats to assess others’ moods and intentions. And this is precisely what happened.
For domestic cats, my research has shown that the key signal is the straight-up tail. In colonies, when two cats are working out whether to approach each other, one usually raises its tail; if the other is happy to approach, it raises its tail, too. The tail-up signal almost certainly evolved during domestication, arising from a posture wildcat kittens use when greeting their mothers. Adult wildcats do not raise their tails to each other.
Once an exchange of tail-ups has been established, one of two things occurs. Either the cats rub heads, flanks and sometimes still-raised tails before separating, or they engage in mutual grooming, which has profound social significance in many animals. Both rubbing and grooming are probably a way of cementing an amicable relationship.
The most important social skill a cat must learn in order to become a pet is, of course, how to interact with people. Even at the earliest stage of domestication, cats needed humans to protect and feed them when mice were in short supply. The cats that thrived were those that were able to reward people with their company. Yet cats are not born attached to people. They are born with an inclination to trust people only during a brief period when they are tiny.
Studies of dogs in the 1950s established the notion of a “primary socialization period,” when puppies are especially sensitive to learning how to interact with people. For dogs, this is between 7 and 14 weeks of age. The concept also applies to cats, but it starts earlier. A kitten that is handled regularly between 4 and 8 weeks generally develops a powerful attraction to people. One that does not meet a human until 10 weeks or later is likely to fear people for the rest of its life.
Do cats exposed early enough to humans have an emotional attachment to their people, as dogs do? We know that they have the capacity to feel affection for other cats, and so it is probable that their attachment to their people is an emotional one.
Most owners would say that their cat displays contentment by purring. Purring clearly does occur when a cat is contented, but a purring cat also may just be hungry, or mildly anxious. Some continue to purr even when their body language indicates they are angry. Occasionally, cats have also been heard purring when they were in distress or even during the moments before death.
Purring, then, does not necessarily reveal a cat’s emotional state. Instead, it seems to be what behavioral ecologists refer to as a manipulative signal, conveying a general request: “Please settle down next to me.”
However, other signals, may be more genuine displays of affection. Relationships between adult cats seem to be sustained mainly through mutual licking and rubbing. Many cats lick their owners regularly, but scientists have not yet investigated whether this represents affection. We know that cats that do not like each other never groom each other.
Cat owners also engage in a tactile ritual with their pets when they stroke them. Most owners stroke their cats simply because it gives them pleasure and because the cat also seems to enjoy it. But stroking may also have symbolic meaning for the cat. Most prefer to be stroked on their heads, the area toward which cats direct their grooming.
Many cats do not simply accept stroking passively; they invite people to stroke them by jumping on their laps or rolling over. They also indicate where they wish to be stroked by offering that part of their body or shifting position. By accepting stroking, cats are engaging in a social ritual that is reinforcing the bond with their owner.
While touch is very important, the upright tail is probably the clearest way cats show their affection for us. A cat approaching its owner with a raised tail will often rub on its owner’s legs. The form that the rub takes seems to vary from cat to cat: Some rub just with the side of their head, others rub down their flank, some make contact with their tail. Many walk past without making any contact or perform their rubs on an object nearby.
Because many cats rub most intensely when they are about to be fed, they have been accused of showing nothing more than cupboard love. However, few cats confine their rubbing to mealtimes, and when two cats rub, they exchange no additional reward. So an exchange of rubs is a declaration of affection.
Another way cats attract our attention, of course, is by meowing. The meow is part of the cat’s natural repertoire, but they rarely use it to communicate with each other. Feral cats are generally rather silent. While all cats are apparently born knowing how to meow, each has to learn how to use this most effectively.
Once cats have learned that their owners respond to meows, many develop a range of sounds that, by trial and error, they find are effective in specific circumstances. In this way, many cats and their owners gradually develop an individual “language” that they both understand but that is not shared by other cats or owners.
So cats demonstrate great flexibility in how they communicate with us, which rather contradicts their reputation for aloofness. We could consider some of this behavior manipulative, but only to the extent that two friends negotiate the details of their relationship. The underlying emotion on both sides is undoubtedly affection.
Bradshaw is the director of the Anthrozoology Institute at the University of Bristol School of Clinical Veterinary Science in Britain. He has studied cat behavior for more than 30 years. This article, published in New Scientist, is based on Bradshaw’s new book, “Cat Sense” (Allen Lane/Basic Books).