Cats – Part 4
The meow, the purr, and the tail.
Continuing this essay series on the global history of the housecat, this essay will explore their unique meow, purr, and tail.
As Jonathan Losos writes in his book The Cat’s Meow: How Cats Evolved from the Savana to Your Sofa:
Meowww! That’s a sound familiar to anyone who’s ever lived with a cat, and to most people who haven’t. The meow is the quintessential cat trait, the defining characteristic of catdom to many. But just what are cats trying to say when they meow, and to whom? And if they’re talking to us, does that mean the meow is a housecat trait that evolved during domestication? … [I]n similar studies with dogs barking in different situations, people have a much greater ability to identify the context. Why can’t people figure out what a cat’s trying to say? … [T]he researchers went to people’s homes and recorded cats meowing in four different contexts. Then they played the calls back to listeners to see if they could correctly identify the context of each call. An important difference from [Nicholas] Nicastro’s study, however, was that people who lived with each cat were included among the listeners. Participants were reasonably proficient when listening to the cat with whom they shared a home, correctly identifying the context sixty percent of the time. By contrast, when hearing an unfamiliar cat, they picked the correct context a paltry twenty-five percent of the time, no better than guessing randomly. These results suggest that each cat has her own specific meows that she uses in different situations, and that people who live with these cats learn to recognize what each meow means. However, these calls are cat-specific; there is no universal cat language, with one type of meow proclaiming “I’m hungry” and another indicating “I’m scared.” How these differences arise is unknown. Some scientists speculate that cats try out a variety of calls and learn which ones get the best response from their human companions in particular circumstances. Plausible, but I’m unaware of any data to back that up. Whatever the reason, the result is a private vocabulary shared between each cat and her human housemates. Keep in mind that these points pertain only to the sound we call a meow. Cats make many other sounds, and the meaning of some of them—hisses and growls, for example—are quite clear to anyone … [T]he meow sound is hypervariable. Sometimes, instead of starting with an m sound, cats substitute a w or u. And sometimes they add extra syllables, like “meow-ow” or “me-o-ow.” The range of permutations is almost endless. The “mew,” in particular, deserves discussion. A high-pitched meow in which the last, mouth-closing w syllable is omitted, mews are the adorable sound made by kittens when calling to their mothers. Some have suggested that the regular meow that our feline friends so commonly direct toward us is an extension of their juvenile behavior—they mewed to their moms, now they’re making a similar, more adult sound to us.
As Losos explains, a cat’s meow developed in unique connection with human beings:
If meows are used primarily to communicate with us, what does that say about the origin of meowing? Is it a feature that evolved when cats started associating with humans a few thousand years ago? Apparently not. Observations on zoo animals indicate that most small feline species also meow. And like their domestic brethren, these species only very rarely meow at each other, even less commonly than housecats. Another similarity is that kittens of these species mew to their mothers, just like domestic cat kittens. Unlike domestic cats, however, these wild species rarely meow toward people. A particularly important feline to consider, of course, is the African wildcat. By studying the meowing behavior of this species, we can understand which aspects of the housecat’s behavior were inherited from its ancestor and which evolved as the housecat adapted to living around humans. And that’s exactly what Nicholas Nicastro set out to discover in the second part of his doctoral research. In fifty hours of observations, he recorded nearly eight hundred meows, noting the circumstances in which each was uttered. Meows occurred when the wildcats were about to be fed, were engaged in aggressive encounters or were pacing back and forth. Only very rarely did one cat meow when engaging in friendly behavior with a person or another cat. Nicastro only studied adult cats, but other scientific reports indicate that African wildcat kittens mew to their mothers, just like other small felines. Nicastro wasn’t just interested in whether African wildcats meow or not. He wanted to know how those meows compared to those of housecats. To find out, he digitally analyzed the audiospectral qualities of the calls, comparing calls given in similar situations. Computer analysis clearly indicated the calls of the two species differ in all contexts: housecat meows are higher pitched and shorter in duration. The wildcat calls came across as more urgent, demanding. “Mee-O-O-O-O-O-W!” as Nicastro put it, compared to the domestic cats more pleasing “MEE-ow.” Nicastro then recruited college students to listen to recordings and say whether they found the calls of domestic or wildcats to be more pleasant. Each student listened to forty-eight calls, twenty-four from each species, and provided a pleasantness score for each on a scale of one to seven. Not surprisingly, they could tell the difference between the Africans and the local cats and overwhelmingly favored the sound of the home team. Is it a coincidence that to our ears, domestic cats meow in a more melodic way than African wildcats? Nicastro thinks not. He suggests that short, higher-pitched sounds are inherently more pleasing to our auditory system, perhaps because young humans have high-pitched voices, and domestic cats have evolved accordingly to curry our favor … [T]hese data indicate that domestic cats did not invent the meow. Nonetheless, they have adapted the utterance to live with us, altering the meow’s sound and using it in different contexts. They are not simply considering us to be fellow cats, communicating with us as they do to their feline brethren, because cats of all species rarely meow when talking to each other. The big difference is that domestic cats have evolved to meow to people as part of friendly interactions and correspondingly have altered the meow so that we find it more appealing.
Losos then explains the unique nature of a cat’s purring sounds:
The meow isn’t the only sound cats make that has been shaped by their association with us. Consider their other marquee sound. Cats purr in many situations. Not only when they’re happy, but when they’re waiting for food, stressed, and sometimes even when they’re in pain. Just as with their vocalizations, the sound a cat makes when she purrs differs from one situation to the next. In particular, cats are known to have loud, insistent purrs when they’re about to be fed—think about the cat at your feet, perhaps rubbing against your legs, as you open a can of wet food. A team of scientists decided to see what the cats might be trying to tell us when they change their purr. To do so, they recorded the purrs of ten cats in two situations. The first was when the cat was stroked by her companion at a calm time, producing the contented purr we all cherish. The second was in the morning, feeding time for the cat; but instead of getting up to take care of culinary duties, the cat’s human companion was instructed to remain in bed. Up onto the mattress the cat would jump, positioning herself to maximize purr decibels received. And this “solicitation” purr was not the agreeable thrumming of a content cat but an insistent chainsaw br-rr-oom demanding attention. At the end of the scientific paper reporting these results, the scientists suggested that the acoustic structure of the solicitation purr shared similarities with the cry of a human baby. Humans are known to be particularly sensitive and responsive to this sound; the scientists suggested that cats had evolved to tap into our preexisting sensitivity to create a purr that would get our attention. When I read this, I thought it was nonsense. It’s one thing to do a fancy-pants statistical analysis to detect similarities on a computer, but just because the properties of a purr and a crying baby share some digital similarities doesn’t mean they really sound like each other. Then I listened to the audio files the authors made available online with their paper. And what do you know? When I played the recordings, I could hear the similarity to a crying baby! People have long suggested that cats have us wrapped around their little toes, masterfully manipulating us to get what they want. The data on meowing and purring show this idea to have an evolutionary basis.
As Thomas McNamee writes in his book The Inner Life of Cats: The Science and Secrets of Our Mysterious Feline Companions:
The fundamental frequency of the purr in all domestic cats is about twenty-five hertz (cycles per second, abbreviated as Hz). With only narrow variation, that tone is the same in cats of both sexes, all sizes, and any age, from kittenhood to senior citizenship. Twenty-five hertz is lower than the lowest key on an eighty-eight-key piano. It’s barely above the average low limit of human hearing—twenty Hz—and for that reason quite a few people can’t hear the basic tone at all. What anybody with ordinary hearing hears are the overtones produced by the fundamental frequency. It is the “chordal” nature of the overtones that make the cat’s purr such a rich and complicated sensation. Usually, both the sound and the palpable vibrations hardly vary between in-breath and out-breath, and the pause between in-and out-is barely perceptible. Because the fundamental frequency is so low, it is audible only within a couple of feet. This is truly intimate communication. In purring, the vocal folds don’t stretch; they just open and close really fast. And as for the humming you feel under your hand, “The surface vibrations are caused by the same pressure difference across the larynx as is the sound. Pressure changes propagate as sound waves from the trachea to the surface of the lung at speeds approaching three hundred m/s (meters per second).” … [P]urring is intended for human understanding alone.
The communicative role of a cat’s tail has an interesting link to their relatively greater sociality among felines. As Losos writes:
Domestic cats use [a] flagpole signal when they interact with each other: the upright tail means “I come in peace” or maybe “Glad to see you!” An approaching cat raises his tail as a signal that he wants to engage in other friendly behaviors like head and body rubbing, nose touching, and sniffing; the other cat returns the vertical salute to indicate he is receptive to such an interaction. Clearly, a tail held high is a friendly cat message. The fact that cats use their tails to signal amiable intentions to us as well is a great tribute, indicating we’ve attained honorary cat status.
As Losos describes, cats and lions are connected by their tails and their unique sociality:
Only one other feline species uses its tail in a similar way. Surprisingly, it’s not another small feline species, but, rather, the King of the Jungle. When greeting each other, members of a lion pride will raise their tails—though in a more curved semicircle than straight up … Domestic cats and lions seem like an unlikely pair of felines to share this unusual behavior. In fact, however, there is a ready explanation, one that highlights the most significant evolutionary leap domestic cats have made from their wildcat ancestors … A common characterization of pets is that dogs are loving, gregarious, social animals, whereas cats are aloof loners. This difference makes sense given that dogs are descended from a species that lives in packs, the wolf, whereas cats come from a line of species commonly thought to live on their own. However … the social lives of domestic cats—and to some extent their larger relatives—are much more complex than commonly realized. Lions, of course, have always been known as the exception to feline asociality, famous for living in prides composed of as many as twenty-one related females (though five is a more typical number). Pride members live in association with one to several males (rarely as many as seven) that are unrelated to the females. The strong social bonds that tie a pride together are evident in the endearing displays of affection by pride members, who rub up against, groom, and lie on top of each other. The social nature of lion prides is also evident in how they hunt cooperatively, working to bring down prey too large for any one lion to kill, sometimes even a giraffe or a midsize elephant. These are true coordinated operations, rather than just several lions independently prowling in the same area. The lions use complex strategies and coordination, such as several lionesses driving prey in the direction of hidden compatriots lying in ambush. Social interactions extend beyond hunting, permeating all aspects of pride life. Females that have cubs at the same time will jointly raise them, nursing each other’s cubs and leaving one lioness behind to mind the crèche when the rest go out on a hunt. Pride members also work together to defend their territories against other prides. By contrast, tigers and leopards spend most of their time living by themselves or, in the case of females, with their young. Unlike lions, neither tigers nor leopards stay together in groups, nor do they hunt, defend food or space, or raise their young cooperatively. For the most part, all other cat species follow the tiger-leopard model. The solitary lifestyle of feral cats parallels that of almost all feline species. But things are different when cats live around us. In many places, large numbers of outdoor cats live in the vicinity of humans, subsisting primarily on discarded food or handouts. These clowders were long considered nothing more than aggregations of a lot of cats with no particular social tendencies. However, once researchers started conducting detailed studies on cats on farms and in urban localities where they are fed, they realized that domestic cat colonies are much more than a bunch of cats that happen to live in the same place. Rather, colonies are often divided into subgroups, each composed of related females. Members of a subgroup are amicable with each other, while often behaving aggressively to other females in the vicinity. Kittens are reared communally, a queen nursing any hungry kitten from the subgroup. Females will even assist others in giving birth, essentially serving as a midwife. One queen, for example, was observed severing the umbilical cord and cleaning another female’s newborn kittens. The social structure of high-density domestic cat colonies thus shares many similarities with lion prides. In both, groups are composed of related females that stay with their family when they mature; males leave the group and move elsewhere to try to reproduce; and mothers jointly raise cubs born at the same time, even nursing each other’s offspring. The similar group living of domestic cats and lions explains why the two species, and no other felines, exhibit the tail-up display. It’s not surprising that cats living in close proximity have developed a way of visually signaling friendly intentions. The tail is the perfect body part for feline visual communication. Its independent recruitment for social signaling by both domestic cats and lions is an example of adaptive convergent evolution, similar features evolving independently in species that experience similar situations.
As Losos explains, sociality is associated with food abundance:
[H]ow can we explain this convergent behavioral evolution in cats and lions and the lack of comparable sociality in other felines? Abundance is the key … [F]ood availability determines cat numbers. Abundant food understandably leads to a concentration of cats, but that doesn’t explain why the cats live in social groups. What’s the advantage of forming these cliques, as opposed to continuing to live life as an unsocial loner, albeit one who bumps into neighbors quite frequently? Keep in mind there’s a cost to being hostile—you could get hurt—plus there’s no reason to defend food when there’s enough for all. Consequently, it’s easy to imagine that living in places with abundant food selects for less aggressiveness … [L]et’s start with lions. For decades, researchers have asked the same question about them: why do lions live in social groups … [W]hat’s the advantage to group living? In a word: defense. In open settings like the Serengeti Plain, there are no secrets. When a successful hunt occurs, other animals will see it, and the presence of circling vultures will transmit the news for miles. A single lion can be pushed off a kill by a group of hyenas. The greater the number of lions in a pride, however, the less often large packs of hyenas will be able to drive them away. Living in groups thus allows lions to retain their kills after they make them. And more generally, large prides get the best territories and can keep other prides from encroaching on them … The origin of permanent human habitations, combined with ample foods stored in central locations, led to a vast concentration of rodents and other potential prey. Cat populations boomed. High densities around rich food sources guaranteed that cats would come into proximity regularly. Like mountain lions sharing an elk, the African wildcats had to be able to coexist without slaughtering each other. Fighting risks injury and is unnecessary if there’s enough food for all. Consequently, as living peacefully at high density became the norm for these felines, they evolved to be better able to get along. It was probably for this simple reason that sociality evolved in domestic cat ancestors living around early agrarian communities.
Kneading is another element of cats’ evolved sociality with humans. As Losos writes:
[H]ousecats do a lot of things that seem like they might be the result of evolution around humans. Consider making biscuits. If you live with a cat, you may have experienced the delight or aggravation (or both) of Mr. Patches standing on your belly, rhythmically pushing down with one forepaw, then the other, a vacant look in his eyes. Seemingly in a trance, cats may continue for many minutes before settling down for a nap. Kneading is a behavior that kittens exhibit while nursing, presumably to promote the flow of milk from mama cat. Scientists and cat enthusiasts have long speculated why adult cats comfortable in the presence of people retain this behavior and direct it toward us. All agree that in some way it exhibits contentment, but the actual explanation for why such juvenilization[*] occurs is unclear. Wild feline species knead as kittens, just like housecats. But then they stop … [T]he data currently in hand suggest that adult kneading as a sign of contentment in the presence of humans may be a housecat adaptation to living with us. Why it evolved is unclear. Perhaps in some ways it builds stronger bonds or otherwise induces people to treat cats more nicely.
In the next and final essay in this series, we’ll explore modern cat history and modern cat needs.