Do cats fart? An investigation into the mysteries of feline flatulence

A couple of weeks ago, my three-year-old tabby Archie climbed into his litter box, scuffled around a bit and let out a squeaky fart. The sound startled me—so much so that at first, I didn’t believe Archie had done it. My boyfriend was in the other room—the sound couldn’t have come from him. I was just feet away from Archie. To say I was puzzled is an understatement. I’ve lived with cats for nearly my entire life, and I had never heard or smelled one pass gas.

The incident sent me on a scientific quest: Why had I never heard my cat fart? Dogs are such prolific farters—so why aren’t cats?

I searched for academic papers on cat flatulence—with little luck. I reached out to animal behavior experts, pet gastroenterologists and university veterinary schools. One source politely declined to speak with me. Others didn’t respond at all.

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Finally, I found a few cat health experts who were open to talking—and I started to piece together an answer.

“Cats are farting all the time,” says Nick Cave, a specialist veterinarian at Totally Vets in Feilding, New Zealand, who has written about animal farts, including in the 2013 textbook Canine and Feline Gastroenterology. “They are passing gas.” Many other animals, including most mammals, snakes and some fish fart, too—although the jury is reportedly still out on spiders.

In general, “a fart is gas that passes the anus,” Cave explains. In cats, the fart typically has two primary sources: swallowed air and gas produced by bacterial fermentation.

Let’s start with swallowed air. Animals, including us, gulp in air when we eat or drink. Some of that air might escape from the stomach as burps—or what scientists call “eructation.” Swallowed gas that isn’t burped out passes through the gastrointestinal tract and exits as flatulence.

Several factors may influence how much air a cat or dog takes in, including how quickly that animal eats, how much it chews and what its breed is.

Cats may seem to fart less than dogs in part because they inhale less air, Cave speculates, noting that research on this question is sparse. Cats are smaller than many dogs, and they have distinct eating behaviors: “Different cats eat in different ways, but generally speaking, cats do not eat with the same kind of fervor that dogs do,” Cave says. Dogs could eat a day’s worth of food in one sitting, he adds, while cats tend to be grazers, noshing throughout the day.

Breed likely matters, too. The “brachycephalic” breeds—think squashed-in faces—tend to swallow “significantly” more air, Cave says. That means more gas. (Owners of French bulldogs, Cave notes, will know what he means.)

Flat-faced cats such as Persians and Himalayans may have similar issues. “If you have a short-snouted cat, that itself can predispose them to flatulence, just because they’re swallowing a lot of air all the time,” says Eric Dougherty, medical director of the Cat Practice in New York City.

Gas may also come from bacterial fermentation, which gives farts their foul odor.

In “monogastric” species—animals with a single-chambered stomach—such as cats, dogs and humans, most bacterial fermentation occurs in the colon, Cave says. There, certain microbes break down fiber that isn’t digested and other carbohydrates, producing carbon dioxide and hydrogen gasses, while other bacteria break down protein and amino acids, producing sulfur-containing gasses.

Those sulfurous gasses carry the most “offensive” odors, Cave notes. And that’s backed by science: In a foundational 2001 study, a group of brave researchers in England collected and sniffed dog farts. The team found that the concentration of hydrogen sulfide in those farts correlated with worse odor rankings.

An animal’s diet, environment and even health issues can all play a role in influencing the type of bacteria present in their gut—and thus, the smell of their farts. Switching a pet’s diet abruptly could cause gut problems that lead to more flatulence, Cave says.

Medication can play a role, too. One expert, Jennifer Van de Kieft, a cat behavior consultant at Cat Advocate, also in New York City, says she recently noticed her cat Oscar passing gas after eating food laced with MiraLAX that was intended for her other, constipation-prone cat. “As [Oscar] was walking by me, there was a smell. I didn't hear him fart, but it smelled like cat poop. It was a really strong—like, whoa.”

“Occasional flatulence” isn’t an emergency, Dougherty says. But he and the other experts I reached out to emphasize that if your cat is farting a lot, it’s worth consulting a veterinarian.

“If you’re coming home and your cat is ripping farts every day, you probably want to have it looked into,” Dougherty adds.

That could be a sign of deeper health issues, Van de Kieft agrees. Excessive flatulence in both cats and dogs is linked to all sorts of conditions, including parasites, inflammation, and more.

Thankfully, I haven’t noticed excessive farting in Archie. But I still have questions. Is my cat farting more or less than a small dog, say, a Chihuahua? What do cat farts usually smell like? And at what point is some farting too much farting? Research on these vital questions is limited—if it exists at all. “I don’t think anyone’s ever measured the exact quantity of cat farts in a scientific study,” Dougherty says.