While vertebrates all have tongues, the number of taste buds differs by species. And just as the strength of our sense of smell depends on the number of olfactory receptors, a species' taste sensitivity depends on how many taste buds it has.
Differences in Taste Buds
Birds generally have very few taste buds. For example, chickens have only about 30. Humans, on the other hand, have about 10,000. Man's best friend has around 1,700, while cats average just under 500.
But herbivores like cows and pigs have even humans beat. Cows have around 25,000 while pigs have 14,000.
"Herbivores have so many taste buds because they need to be able to tell if a specific plant contains dangerous toxins," according to Dr. Susan Hemsley, a veterinary science professor at the University of Sydney.
But the real winner when it comes to taste sensitivity is the catfish. These whiskered bottom-dwellers typically have more than 100,000 taste buds that line their body and are concentrated around their mouths.
An advanced sense of taste is critical for catfish because they hunt in murky waters where visibility is low.
Biology of Taste
But taste isn't just a numbers game. Even if cats had thousands more taste buds than we do, they still wouldn't be able to taste the presence of sugar because they don't need that ability for survival.
In evolutionary terms, animals have used taste to determine if food is safe to eat. A bad taste generally indicates a substance is potentially harmful while a good taste indicates digestible food.
Most mammals' tongues have taste receptors, proteins that bind to incoming substances and signal the brain, which interprets the sensation as taste.
Humans have five kinds of taste buds — sweet, salty, sour, bitter and umami (savory) — and scientists suspect we might also be able to taste fat.
But not all animals have this wide of a taste spectrum. Take the ability to taste sweet, for example.
The sweet taste receptor is composed of coupled proteins generated by two genes known as Taslr2 and Taslr3. However, cats lack the 247 base pairs of amino acids that make up the DNA of Taslr2, so cats are unable to taste sweets.
But cats aren't the only creatures that lack this ability.
Researchers at the Monell Chemical Senses Center found that in addition to cats and their wild relatives like lions and tigers, other carnivores also have genetic mutations that make them unable to taste sweets, including dolphins and sea lions.
For omnivorous creatures like dogs, these genes are still present because sweetness is a sign of carbohydrates, an important food source for animals that consume plants.
Because cats are carnivores, sweetness receptors aren't necessary for survival. However, cats can detect bitter flavors, which helps them avoid rancid meat.
Cats can also taste something humans can't: adenosine triphosphate, a molecule that supplies energy to every living cell. (It's present in meat, which is why cats can taste it.)
Cats and dogs also have special taste buds that are tuned for water. This sense is located at the tip of the tongue, the part that comes into contact with water during drinking.
While this area of the tongue always responds to water, it becomes more sensitive when the animal eats something salty and the need for water increases.
This is useful for animals that consume a lot of meat, which has a high salt content.
But even people taste foods in different ways. Learn more about this in the video below.