Why do cats trill?
Trilling. It’s one of those just-cat things that make you love cats even more. As if that were possible.
A trill is a precious little sound, somewhere between the coo of pigeon, a hum, and the sound my electric toothbrush makes. I’ve heard it described as a Spanish-language rolled “R,” or like a toy helicopter, but none of these descriptions really do the trill justice. You’ll have to let Delilah demonstrate here:
We know very little about the sounds cats make, including the trill
What is a cat trying to say when he trills? Go on and Google this question. Everyone seems to “know” what cats mean when they trill. But we don’t really know. Not yet. Science is just beginning to take the idea of cat communication seriously.
One group of scientists recognized how little we know about cat sounds and worked together to come up with an “ethogram” of cat sounds, which is like a catalogue of every noise we think cats make (the current count is 21; they probably make more).
Researchers acoustically analyzed the sound waves of each vocalization in an effort to distinguish them all, because they can be difficult to tell apart. When does a hiss end, and a spit start, for example? They also tried to figure out under what circumstances cats used each sound.
Amazingly, house cats produce a greater variety of sounds than any other carnivore on the planet. This comparison includes dogs, who are more social than cats and might thus be expected to want to communicate more precisely, and the domestic cat’s closest cat relative, the African wildcat.
The crazy thing is that cats, while predators themselves, are really small prey animals. Small prey animals tend to vocalize less than large predators, because animals that make a lot of noise tend to turn into somebody else’s supper more quickly. It was a really surprising finding.
Cats are fascinating little enigmas, aren’t they?
Trills versus chatters, chirps, chirrs, and chirrups
These scientists also assigned specific words to each sound so that future scientists could all agree that a trill is a trill, and not a chatter, or chirp, or chirr, or a chirrup. If you Google “cat trill” today, you’ll find that not everyone agrees what this sound is called, and many “experts” will wrongly claim that a chatter, for example, and a trill, are really the same thing. They’re not.
(If you want to learn more about what cat chatter is, read this post, “Why does my cat chatter her teeth?”)
This particular study called the trill a “greeting call.”
Cats who are feeling fine will trill
That research paper was just done in 2020. That’s how far behind we are in understanding cat communication with sound.
The study called the trill a greeting call, but didn’t provide any evidence to support that contention.
Another study tried to dig a little deeper. A bunch of scientists in Brazil studying 74 cats tried to figure out which sounds cats used in pleasant situations and which sounds cats used in unpleasant situations. They divided the group in half, giving the “pleasant” group a snack, and the “unpleasant” group a pretend ride in a car.
Only the snack group trilled. The cats who thought they were going for a ride in the car, did not trill. In other words, we now know that cats only use the trill when they are feeling good.
Interestingly, trilling is a sound that cats make with their mouths closed. The scientists noticed that the snack cats tended to only make closed-mouth noises, including purrs and squeaks in addition to trills.
Cats in the car-ride group tended to make open-mouthed noises, something the researchers called “forced-intensity sound,” including growling and chattering. It’s no surprise that these types of sounds, especially growling, are the kind that cats make when they are feeling less-than-terrific.
Cats who feel friendly or playful will trill
An ongoing study in Sweden is continuing to learn more about how cats communicate with their humans using sound. The scientists call their study, MEOWSIC – a made-up word that is a combination of “music” and “meow” because they are trying to learn more about how cats use patterns of rhythms and intonation in their voices.
This study found that there is more than one kind of trill. There were sounds they called chirrs or chirrups that were high-pitched trills with a rising melody. There were grunts or murmurs that were lower-pitched trills. There were murmurs or coos that had no “rolling R” sound at all.
And there were sound combinations. Cats in this study frequently combined purrs and trills, as well as trills and meows, which they named, appropriately enough, a trill-meow.
This study concluded that cats are not using the trill to transmit a specific message per se. But cats use their trill during specific types of interactions.
Cats trill during friendly greetings (have you ever been trilled at after you’ve come home from work?). They trill during play. And they use the trill to make a friendly request – perhaps for a treat or a cuddle.
Kittens respond to the trills of their mother
A study on momma cats and their kittens found another context in which cats trill.
These scientists learned that kittens respond to their own mother’s trills, more so than other sounds that she might make, even her meows. Kittens didn’t respond to just any trills, however. They learn the trills of their own mothers, and tend not to respond to the trills of any other cat mother.
Humans respond to cat trills, too
Here’s another interesting study about cat communication and humans. In 2003, research scientists played cat sounds to people. Some of the sounds were from participants’ own cats. Some of the sounds were from strange cats.
Based on the recorded sounds, people could accurately classify the context of cat sounds – but only of their own cats! They didn’t do so well with strange cats.
One thing we need to be clear on when talking about trills, or any other cat sounds, is that they are sounds, not language. Cats are not trying to have a conversation with us when they make a noise like a trill. The sounds are innate and often automatic. They reflect a cat’s inner emotions, and are often an attempt to get us (or another animal) to do something that they want, but they are not language.
But we seem to understand them anyway! Through our long association with cats, we have learned how our own cats sound in different contexts, and what the noises that they make might mean.
“Cats are domesticated animals that have learned what levers to push, what sounds to make to manage our emotions,” research scientist Nicholas Nicastro told the Cornell Chronicle in 2002. “And when we respond, we too are domesticated animals.” 
So, when your cat trills, there’s no need to go running to Google. You probably already know what she’s trying to tell you.
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Dawn LaFontaine is a lifelong animal lover who always seems to have a little pet hair in her keyboard. Her blog, Kitty Contemplations, helps cat guardians better understand and care for the special beings they share their lives and homes with. Her cat-products business, Cat in the Box, sells beautiful, well-made, and award-winning products that she designed to meet the biological needs of cats.
 Tavernier, Chloé, et al. “Feline Vocal Communication.” Journal of Veterinary Science, The Korean Society of Veterinary Science, Jan. 2020, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7000907/#B2.
 Fermo, Jaciana Luzia, et al. “Only When It Feels Good: Specific Cat Vocalizations Other than Meowing.” MDPI, Multidisciplinary Digital Publishing Institute, 29 Oct. 2019, https://www.mdpi.com/2076-2615/9/11/878/htm.
 SCHÖTZ, SUSANNE, et al. “Melody in Human–Cat Communication (MEOWSIC).” About, http://vr.humlab.lu.se/projects/meowsic/about.html.
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 Szenczi, Péter, et al. “Mother–Offspring Recognition in the Domestic Cat: Kittens Recognize Their Own Mother's Call.” Wiley Online Library, John Wiley & Sons, Ltd, 3 Mar. 2016, https://onlinelibrary.wiley.com/doi/10.1002/dev.21402.
 “Classification of domestic cat (Felis catus) vocalizations by naive and experienced human listeners.” American Psychological Association, American Psychological Association, https://psycnet.apa.org/record/2003-02590-007.
 Terrace, Herbert S. “Why Animal Communication Is Not Language | Psychology Today.” Why Animal Communication Is Not Language The Gap between Expressing Emotion and Sharing Knowledge., 3 Sept. 2019, https://www.psychologytoday.com/us/blog/the-origin-words/201909/why-animal-communication-is-not-language-0.
 Segelken, Roger. “It's the Cat's Meow: Not Language, Strictly Speaking, but Close Enough to Skillfully Manage Humans, Communication Study Shows.” Cornell Chronicle, 20 May 2002, https://news.cornell.edu/stories/2002/05/meow-isnt-language-enough-manage-humans.