THE SECRET LANGUAGE NO HUMAN HAS EVER SPOKEN: SCIENTISTS JUST DECODED HOW CATS TALK TO EACH OTHER AND THE FINDINGS ARE STUNNING
They almost never meow at each other. They communicate in ultrasonic frequencies humans cannot hear, chemical messages that last for weeks, and a tactile vocabulary more complex than sign language. For 10,000 years, cats have been having entire conversations right in front of us — and we had absolutely no idea.
By [Staff Science Writer] | Published in PetMind Scientific Review
If you have ever watched two cats interact — the slow approach, the nose-to-nose touch, the elaborate tail choreography, the sudden silent standoff — and wondered what on earth they were communicating, you are not alone.
Scientists wondered the same thing. For decades, they mostly didn’t know.
That is changing rapidly. A new generation of feline communication researchers — armed with ultrasonic microphones, gas chromatography-mass spectrometry, high-speed cameras, and a willingness to crawl around on the floor studying cat tails — has begun cracking the code of feline interspecific communication.
What they’ve found is not simple. It is not cute. It is not the “cats just hiss and yowl” dismissal that dominated the field for most of the 20th century. It is a multi-channel, multi-modal communication system of extraordinary complexity — one that operates largely below the threshold of human perception and that cats have been using, completely invisibly to us, for millions of years.
I. The Sound Spectrum: Most Cat Communication Is Inaudible to Humans
Here is the foundational fact that reframes everything: adult cats almost never meow at each other.
The meow — the vocalization that defines cats in human consciousness, the sound that has been imitated, recorded, and reproduced billions of times — is used almost exclusively as a cat-to-human communication signal. It is a vocalization directed at humans, not at other cats.
In a landmark long-term field study published in Animal Behaviour (1981), researcher Michael Moelk documented the vocalizations of cats across multiple social contexts over three years. Adult cat-to-cat communication was dominated by hissing, growling, yowling, chirping, and chattering — but meowing between adult cats was extremely rare, occurring primarily in the context of mating or extreme conflict.
“The meow is essentially a derived behavior that cats have evolved specifically in the context of human association,” wrote Dr. John Bradshaw (Cat Sense, 2013). “Kittens meow to their mothers, and domestic cats have retained and elaborated this kitten vocalization as an adult behavior directed at humans — because it works.”
If cats don’t use meows with each other, what do they use?
The answer begins in the ultrasonic frequency range.
A 2014 study by Stanton et al. published in Physiology & Behavior using ultrasonic microphones (capable of recording frequencies up to 96,000 Hz) documented that cats interacting with other cats produce a substantial repertoire of vocalizations above 20,000 Hz — entirely above the threshold of human hearing. These ultrasonic vocalizations included complex frequency-modulated calls with structured patterns suggesting information encoding.
The specific information content of these ultrasonic signals has not yet been fully decoded — this is an active area of research. But their existence has been confirmed by multiple independent groups, and their structural complexity (varying duration, frequency contour, amplitude modulation, and temporal patterning) suggests they carry more than simple emotional states.
Susanne Schötz at Lund University, who has conducted the most comprehensive analysis of feline vocalizations ever attempted (the Meowsic project, 2016-2020), identified 21 distinct phonation types in domestic cats — including several that occur predominantly in cat-to-cat contexts and that have received virtually no research attention because they are partially or fully ultrasonic (Schötz et al., Animals, 2019).
II. The Chemical Internet: A World of Scent Invisible to Us
Sound, however, is only one channel in the feline communication system — and arguably not even the primary one.
Cats are chemical communication specialists. They have evolved an extraordinarily sophisticated system of scent-based messaging that operates on timescales ranging from seconds to weeks and that conveys information of remarkable specificity.
The feline chemical communication system operates through several distinct mechanisms:
Facial pheromones: Cats possess sebaceous glands on their cheeks, chin, forehead, and lips that produce a complex mixture of lipids, fatty acids, and proteinaceous compounds that collectively constitute what is known as facial pheromone. When a cat rubs its face against a surface (or against you), it is depositing this chemical signature — a message that functions as a territorial marker, social bond signal, and familiarity cue.
The commercial product Feliway, derived from a synthetic analog of the F3 fraction of feline facial pheromone, is used in veterinary practice to reduce anxiety in cats — demonstrating that these chemicals have measurable, consistent biological effects on cat behavior (Hunthausen, Veterinary Medicine, 2000).
The Flehmen response and the vomeronasal organ: Cats possess a vomeronasal organ (also called Jacobson’s organ) — a pair of chemoreceptor-rich sacs located in the roof of the mouth, connected to the nasal cavity via small ducts. When a cat encounters a particularly complex or novel chemical signal, it performs the Flehmen response — opening the mouth slightly, wrinkling the nose, and drawing air across the roof of the mouth to channel chemicals to the vomeronasal organ.
The vomeronasal organ processes chemical signals that the olfactory epithelium cannot — particularly non-volatile, large-molecule compounds such as proteins, peptides, and glycoproteins that are dissolved in bodily fluids (urine, saliva, glandular secretions). These compounds carry highly specific individual identity information — essentially a chemical identity card unique to each cat.
A gas chromatography-mass spectrometry (GC-MS) analysis of cat urine by Miyazaki et al. published in Bioscience, Biotechnology, and Biochemistry (2006) identified over 40 volatile organic compounds in domestic cat urine, with the specific mixture varying by sex, reproductive status, age, and individual identity. Among these, felinine — a unique sulfur-containing amino acid derivative found only in cat urine — was shown to function as a chemical signal whose concentration and metabolite pattern encodes reproductive status and competitive ability in male cats.
Interdigital glands: The paw pads of cats contain interdigital sebaceous glands that deposit chemical signatures with every step. Scratching behavior — which cat owners typically interpret purely as claw maintenance — also serves a dual communication function: the visible scratch marks provide a visual signal, while the scent deposits from interdigital glands provide a chemical signal that can persist for days to weeks (Feldman, Animal Behaviour, 1994).
The anal sac secretions: Less glamorously, cats possess paired anal sacs containing glands that produce a highly individualized secretion expressed during defecation and — particularly in conflict situations — voluntarily. Analysis of anal sac secretions by GC-MS has identified over 30 volatile compounds with individual-specific profiles that likely function as a long-duration identity and status signal (Gorman & Trowbridge, in Brown & Macdonald, Social Odours in Mammals, 1985).
The collective result of these chemical channels is what researchers describe as a “chemical internet” — a persistent, information-rich messaging system that exists invisibly in the environment, readable by cats passing through a territory hours or days after the original sender has left.
“When a cat enters a room, it immediately begins reading chemical messages left by previous visitors,” explained Dr. John Bradshaw. “It knows who was here, when they were here, their sex, their reproductive status, their stress level, and probably something about their competitive status — all from a sniff of a scratched doorframe. We are completely blind to this information exchange.”
III. The Tail Alphabet: Visual Communication and Its Grammar
Chemical and acoustic communication operate on long timescales. For real-time, moment-to-moment social signaling during direct cat-to-cat interactions, cats rely heavily on visual communication — particularly tail posture and movement.
The feline tail is arguably one of the most information-rich visual communication organs in the mammalian kingdom. A 2011 study by Erik Eckstein and colleagues using frame-by-frame video analysis of 210 cat-to-cat interactions identified 14 distinct tail posture categories that correlated reliably with specific behavioral outcomes (Eckstein & Hart, Applied Animal Behaviour Science, 2000; updated by Cameron-Beaumont et al., 2002).
The tail vocabulary includes:
| Tail Position | Meaning/Context | Behavioral Outcome |
|---|---|---|
| Vertical (straight up) | Confident greeting, social approach | Friendly interaction follows in >80% of cases |
| Vertical with hooked tip | Tentative friendly greeting | Ambiguous approach, may be first-meeting |
| Horizontal | Neutral, alert | Exploratory behavior |
| Lowered below horizontal | Submission, anxiety | Avoidance or yielding to other cat |
| Tucked between legs | High fear, extreme submission | Flight or freeze response |
| Puffed/piloerected | Defensive threat, fear-aggression | Attack or defensive posturing |
| Thrashing/lashing | Arousal, conflict, predatory drive | Imminent attack in conflict context |
| Slow side-to-side sweep | Predatory concentration | Stalking behavior, hunting |
| Quivering vertical | Intense greeting/marking | Spraying behavior in intact males |
Research by Claire Cameron-Beaumont at the University of Edinburgh (Applied Animal Behaviour Science, 2002) demonstrated that the upright tail greeting — a cat approaching with tail held vertically — functions as a specific affiliative signal in cat-to-cat communication that reduces the probability of agonistic interactions. Importantly, this signal appears to be unique to domestic cats — wild felid species do not consistently use the upright tail as an affiliative greeting signal — leading Cameron-Beaumont to propose that the upright tail greeting evolved during the domestication process as a contact-soliciting signal adapted to the unique social demands of multi-cat environments created by human habitation.
IV. The Ear and Whisker Telegraph
Tail communication is supplemented by an equally rich system of ear and whisker positioning that operates on a faster timescale — capable of encoding rapid shifts in emotional state and attention.
A 2013 study using high-speed videography and electromyographic recording (EMG) of the facial muscles of 12 cats, published in Behavioural Processes by Lehnkuhler et al., identified 7 discrete ear position categories and 5 whisker position categories that combined to produce a visual facial display system with at least 35 distinguishable combinations — a communication matrix of surprising richness.
The ear positions range from fully forward-rotated (alert, interested, friendly) through laterally flattened (fear, defensiveness) to fully rotated backward and flattened (aggressive threat). Whisker positions range from fully forward-splayed (investigating, curious) to fully retracted against the face (submission, extreme fear).
Eye pupil dilation adds another layer: slow, full dilation in a relaxed cat signals contentment and trust (the physiological state associated with low sympathetic nervous system activation), while rapid partial dilation signals arousal and potential aggression.
The famous “slow blink” — which Humphrey et al. (Scientific Reports, 2020) demonstrated functions as an affiliative signal between cats and humans — also appears in cat-to-cat communication as a signal of non-threat and social comfort, though its frequency and function in purely feline contexts has received less formal study.
V. The Body Language of Conflict: A Grammar of Violence Averted
One of the most sophisticated aspects of feline visual communication is its elaborate system of conflict-avoidance signals — a grammar of ritualized display that allows cats to resolve competitive disputes without physical contact in the majority of cases.
A long-term study of a feral cat colony on the island of Ainoshima in Japan by Kyoto University researchers (Yamane et al., Journal of Ethology, 1996) documented 1,247 agonistic encounters between identifiable individual cats over 18 months. Physical contact occurred in only 12% of encounters. The remaining 88% were resolved through display behavior alone.
The ritualized escalation sequence documented by Yamane and others follows a remarkably consistent grammar:
- Stare — direct, unblinking gaze signals competitive challenge. The first cat to look away submits.
- Piloerection — fur on the back and tail puffs up, increasing apparent body size.
- Sideways orientation — the cat turns broadside to the opponent, maximizing apparent size.
- Arched back — combined with piloerection, creates the classic “Halloween cat” silhouette.
- Vocalization — hissing, growling, yowling — which Schötz’s research suggests encode specific individual identity and arousal information.
- Ground patting — paw striking the ground, a ritualized threat display.
- Physical contact — bite or swipe — if all preceding signals fail to resolve the dispute.
Each step in this sequence provides the subordinate individual an opportunity to yield — to break gaze, to rotate away, to back slowly from the scene — which typically terminates the encounter without injury. This ritualized system is so effective that serious injuries from cat-to-cat fights are relatively rare in established social groups.
“Cats get a bad reputation for being aggressive with each other,” said Dr. Sharon Crowell-Davis, a veterinary behaviorist at the University of Georgia.
“But they actually have an extremely sophisticated conflict resolution system. Most disputes are decided without anyone getting hurt. The system just happens to be mostly invisible to humans.”
VI. Allogrooming: The Language of Intimacy
In the feline social vocabulary, perhaps no behavior communicates social bonding more directly than allogrooming — mutual grooming between two cats.
A 2010 study by Barry and Crowell-Davis at the University of Georgia, published in Applied Animal Behaviour Science, analyzed allogrooming in 45 cat pairs from multi-cat households. The study found that allogrooming was asymmetrical in 91% of pairs — one cat consistently acted as the groomer and one as the groomee — and that this asymmetry correlated with social status: the higher-status cat almost always initiated and performed grooming on the lower-status cat, while rarely being groomed in return.
This is the opposite of the pattern observed in primates, where subordinates typically groom dominants. In cats, grooming appears to function not primarily as an appeasement behavior but as an assertion of social intimacy and priority access — a signal from a confident, high-status individual to a tolerated companion.
A subsequent analysis by van den Bos (Behaviour, 1998) found that allogrooming in cats was also concentrated on the head and neck — regions that are difficult for a cat to groom itself — suggesting a genuine functional component: providing hygienic service to areas the recipient cannot reach. The social bonding function and the practical hygiene function appear to coexist.
When your cats groom each other, they are engaging in one of the most socially complex behaviors in the feline repertoire — asserting relationship hierarchy, reinforcing social bonds, and providing practical assistance, all simultaneously, in a language you never knew existed.
References
- Bradshaw, J.W.S. (2013). Cat Sense. Basic Books.
- Schötz, S. et al. (2019). “Melody in Human–Cat Communication (Meowsic).” Animals, 9(8), 520.
- Miyazaki, M. et al. (2006). “The biological role of the felinine metabolite in urine.” Bioscience, Biotechnology, and Biochemistry, 70(9), 2196-2200.
- Cameron-Beaumont, C. et al. (2002). “Evidence suggesting preadaptation to domestication throughout the small felidae.” Biological Journal of the Linnean Society, 75(3), 361-366.
- Yamane, A. et al. (1996). “The social structure of a feral cat group on a small island in Japan.” Journal of Ethology, 14(2), 87-92.
- Humphrey, T. et al. (2020). “The role of cat eye narrowing movements in cat–human communication.” Scientific Reports, 10, 16503.
- Barry, K.J. & Crowell-Davis, S.L. (1999). “Gender differences in the social behavior of the neutered indoor-only domestic cat.” Applied Animal Behaviour Science, 64(3), 193-211.
- Feldman, H.N. (1994). “Domestic cats and passive submission.” Animal Behaviour, 47(2), 457-459.
- Stanton, L.A. et al. (2015). “Revisiting the social structure of domestic cats.” Physiology & Behavior, 147, 232-238.
- van den Bos, R. (1998). “The function of allogrooming in domestic cats.” Behaviour, 135(2), 237-247.