BySarah Kuta
Published September 28, 2023
• 6 min read
Why are cats such picky eaters when dogs seem willing to wolf down just about anything they encounter? It’s a question many pet parents likely ask themselves while coaxing their feline friend to swallow a pill or prying another slobbery piece of mulch from their puppy’s mouth.
There’s still a lot scientists don’t know about animal taste preferences. But, thanks to a small but growing body of research, researchers are starting to unravel some of the mysteries around our four-legged friends’ flavor fancies. Here’s what we know so far.
What can cats taste?
Accidentally drop a cupcake on the ground and your dog will probably scarf it down in one bite. Your cat, on the other hand, may turn up her nose. One possible reason for their differing behaviors? Cats can’t taste sweetness.
Since they couldn’t just ask cats directly, researchers figured this out by analyzing their DNA. House cats, tigers, and cheetahs have a “broken” version of the gene Tas1r2, which works with another gene, Tas1r3, to enable sweetness detection. Though Tas1r3 appears to function perfectly fine in cats, Tas1r2 is an “unexpressed pseudogene” that’s missing 247 letters. Without them, Tas1r2 does not produce a crucial protein needed to form a receptor for sweetness on cats’ taste buds.
But if cats can’t detect sweetness, what can they taste? Given cats’ meat-centric diet, scientists long suspected they could taste umami, the rich, savory, meaty flavor Japanese speakers describe as the “essence of deliciousness.” And, recently, they found evidence to confirm this hunch. After sequencing the feline genome, they discovered cats express both genes necessary to form umami receptors on their taste buds, Tas1r1 and Tas1r3.
To take the study a step further, they gave 25 felines the choice between a bowl of plain water and one that’d been spiked with molecules that provide umami flavor. As expected, the cats strongly preferred the umami water, and more specifically, water containing umami compounds present in tuna. That may help explain why felines love the saltwater fish so much. “We think umami is the main driver of intake for cats,” says Scott McGrane, a flavor scientist at the Waltham Petcare Science Institute, which is owned by Mars Petcare UK, which makes pet food and treats. “Tuna hits the umami sweet spot for cats.”
Dogs, by contrast, can taste sweetness and umami. And both cats and dogs have bitter taste receptor genes, though cats have 12 (seven of which are functional) and dogs have 15. What remains unclear, however, is how the number of bitter receptor genes affects the animals’ actual perception of bitterness, says McGrane.
You are (genetically) what you eat
The sense of taste helps animals evaluate potential food sources. Sweetness, for example, indicates a food is rich in carbohydrates, which are a good source of energy. Umami signals protein, while saltiness denotes sodium, an essential nutrient. Sourness is a bit more complicated, but scientists believe it may communicate acidity, which could be helpful for ingesting vitamin C or for determining if rotting fruit are actually safe to eat (since the “good” bacteria that makes them taste sour would kill off any “bad” bacteria during fermentation). The evolutionary purposes of bitterness are also up for debate, though the long-held belief is that it may signify toxicity.
The ability to detect these tastes shows up in animals’ DNA: Specific genes are responsible for producing different types of taste receptors on animals’ taste buds. Sometimes, these taste receptor genes randomly mutate. If the animal survives just fine with the mutation, they’ll pass that trait along to their offspring until, eventually, it becomes the norm. Scientists think this is likely why carnivorous cats can’t taste sweetness, why bamboo-eating pandas can’t taste umami, and why some marine mammals that swallow their food whole, like dolphins and whales, have no functioning taste receptor genes at all. At some point in history, some of these species’ taste receptor genes stopped working properly and, because of their dietary needs, they simply stayed that way. “There’s a correlation between what you eat and what is reflected in your genome,” says Peihua Jiang, a researcher at the Monell Chemical Senses Center in Philadelphia.
The taste differences between cats and dogs also make sense in the context of their diets. Cats are “obligate” carnivores, which means they can get all the nutrients they need from animal flesh. Dogs, on the other hand, are opportunistic feeders who take advantage of whatever food sources are available—whether meats, plants, or grains. “One reason why dogs may not be as fussy is because they are quite happy and able to eat a range of different foods,” says McGrane.
‘Their own sensory world’
Pets perceive the world differently than we do. Understanding these differences could provide valuable insights not only for pet owners, but also for veterinarians, pharmaceutical companies, and pet-food manufacturers.
For example, if your cat has no appetite because of an illness, you might try amping up the umami in his food, like Japanese food scientist Yasuka Toda did while interning at a veterinary hospital in college. “To get cats with no appetite to eat food on their own, I sprinkled a small amount of dried bonito flakes—which is a very common umami ingredient in Japan and contains a lot of the nucleotide inosine monophosphate—on their food, and it worked very well,” she says.
Leaning into the research could also lead to the development of supremely yummy foods and more palatable medicines for cats and dogs, though scientists say more work needs to be done to fully understand our pets. “Every species is living in their own sensory world,” says Jiang. “But our research is actually just the tip of the iceberg. There are lots of other things we clearly do not understand.”
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