[Animals] Why did dogs eat practically everything, but cats didn't?

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Why would dogs eat practically everything, but cats not?
There's a reason your dog would gobble up every cookie in the house while your cat turns her nose up, analyzes and weighs. The answer lies in the genes, scientists say.

A blue Persian cat gazes intently at a goldfish in a fish tank in a photo from the November 1938 issue of National Geographic. Researchers have discovered that cats are genetically predisposed to foods rich in tasty umami, such as tuna.

PHOTOGRAPHY BY WILLARD CULVER, NAT GEO IMAGE COLLECTION
Why are cats such picky eaters while dogs seem ready to gobble up anything that comes their way? It's a question many pet owners probably ask themselves as they convince their feline friend to swallow a pill or remove another piece of napkin from their pup's mouth.

Scientists still don't know a lot about animals' taste preferences. But, thanks to a small but growing number of studies, researchers are beginning to unlock some of the mysteries surrounding the culinary tastes of our four-legged friends. This is what we know so far.

(Related: Are Dogs Smarter Than Cats? Science Might Have an Answer)

What can cats taste?
If you accidentally drop a muffin on the floor, your dog will probably devour it in one bite. Your cat, on the other hand, may turn up its nose. A possible reason for their different behaviors? Cats do not perceive sweet taste.

Since they couldn't ask the cats directly, the researchers found out by analyzing their DNA. Domestic cats, tigers and cheetahs have a "broken" version of the Tas1r2 gene, which works with another gene, Tas1r3, to enable the detection of sweet taste. Although Tas1r3 appears to function perfectly in cats, Tas1r2 is an "unexpressed pseudogene" missing 247 letters. Without them, Tas1r2 does not produce a crucial protein needed to form a sweetness receptor in cats' taste buds.

But if cats can't detect sweetness, what can they taste? Given cats' meat-centric diet, scientists have long suspected that they could taste umami, the rich, savory, meaty taste that the Japanese describe as the "essence of delicious." And recently, they have found evidence that confirms this hunch. After sequencing the feline genome, they discovered that cats express the two genes necessary to form umami receptors in their taste buds, Tas1r1 and Tas1r3.

To take the study a step further, they gave 25 felines a choice between a bowl of normal water and another with umami flavor molecules. As expected, the cats preferred umami water and, more specifically, water containing umami compounds present in tuna. This could explain why cats like saltwater fish so much. "We think umami is the main driver of cat intake," says Scott McGrane, a scientist at the Waltham Petcare Scientific Institute, owned by Mars Petcare UK, which makes pet food and treats: "Tuna hits the spot for umami for cats."

Dogs, on the other hand, can taste sweet and umami. And both cats and dogs have bitter taste receptor genes, although cats have 12 (seven of which are functional) and dogs have 15. What remains unclear, however, is how the number of genes affects bitter taste receptors to the actual perception of bitter taste by animals, says McGrane.

(Related: What do cats think of us?)

A terrier and a schnauzer watch a long-haired cat eat. Dogs have receptor genes that allow them to taste both umami and sweet, making them less "picky" at dinner time.

PHOTOGRAPH BY BRIAN GORDON GREEN, NAT GEO IMAGE COLLECTION
We are (genetically) what we eat
The sense of taste helps animals evaluate possible food sources. Sweetness, for example, indicates that a food is rich in carbohydrates, which are a good source of energy. Umami indicates protein, while saltiness denotes sodium, an essential nutrient. Bitterness is a little more complicated, but scientists think it can communicate acidity, which could be useful for ingesting vitamin C or determining whether rotten fruit is actually safe to eat (since the "good" bacteria that give them sour taste would eliminate any "bad" bacteria during fermentation). The evolutionary purposes of the bitter taste are also the subject of debate, although the most widespread belief is that it may signify toxicity.

The ability to detect these flavors appears in the DNA of animals: there are specific genes that produce different types of taste receptors in the taste buds of animals. Sometimes these taste receptor genes mutate randomly. If the animal survives well with the mutation, it will pass that trait on to its offspring until, over time, it becomes the norm. Scientists believe this is probably why carnivorous cats cannot taste sweet, pandas that eat bamboo cannot taste umami, and some marine mammals that swallow food whole, such as dolphins and whales, They do not have taste receptor genes. At some point in history, the taste receptor genes of some of these species stopped working properly and, due to their dietary needs, they simply stayed that way. "There is 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 (United States).

The taste differences between dogs and cats also make sense in the context of their diets. Cats are "obligate" carnivores, meaning they can get all the nutrients they need from animal meat. Dogs, on the other hand, feed opportunistically and take advantage of any available food source, be it meat, plants or grains. "One of the reasons dogs may not be so picky is that they are very happy and can eat a wide variety of foods," says McGrane.

(Related: Cats recognize their names, but it's harder for them than dogs)

Your own sensory world
Pets perceive the world differently than we do. Understanding these differences could provide valuable information not only to pet owners, but also to veterinarians, pharmaceutical companies, and pet food manufacturers.

For example, if your cat has no appetite due to illness, you can try increasing the umami of his food, as Japanese scientist Yasuka Toda did while interning at a veterinary hospital. "To get the cats with no appetite to eat on their own, I sprinkled a small amount of dried bonito flakes (a very common umami ingredient in Japan that contains a lot of the nucleotide inosine monophosphate) on their food, and it worked very well" , Explain.

Relying on research could also lead to the development of highly palatable foods and more palatable medications for dogs and cats, although scientists say more work needs to be done to fully understand our pets. "Each species lives in its own sensory world," says Jiang. "But our research is just the tip of the iceberg. There are many other things we clearly don't understand."

https://www.nationalgeographic.es/video/tv/las-aguilas-son-las-mejores-aliadas-de-los-cazadores-nomadas-de-mongolia