A dog's sense of taste

Taste is a very old sense in evolutionary terms. Sensations of pleasure and revulsion provided by taste serve as a survival function. A reasonable rule of thumb, at least for natural substances is that bad tastes are a signal that the animal has encountered something that is potentially harmful, indigestible, or poisonous, while good tastes signal useful, digestible, edible  substances.

Because it is important for survival, it is not surprising to find that taste is one of the earliest senses to begin functioning in dogs.

Just like humans, the dog's sense of taste depends upon special receptors called "taste buds". An animal's sensitivity to taste depends not only on the number  of taste buds it has, but also the type of taste buds it has. In much the same way that sensitivity for smell depends upon the number of olfactory receptors an animal has. Humans win the sensitivity contest for taste with approximately 9000 taste buds in comparison to just 1700 for the average dog.

Traditionally, when talking about human tastes, scientists have identified four basic taste sensations. These correspond to the tastes that we call sweet, salty, sour and bitter. Early research did show that the taste receptors of dogs responded to the same kind of chemicals that trigger human taste sensations. There was one clear difference though, and that has to do with the taste of salt. Humans, and many other mammals for that matter have a very strong taste response to salt. We seek it out, and like it on our food. Salt is needed to balance our diet and there is not much of it to be found in vegetables and grains. Dogs however are primarily carnivores, and in the wild most of their diet consists of meat. Because of the high sodium content in meat, the wild ancestors of dogs already had a sufficient amount of salt in their diet and did not develop our highly tuned salt receptors and the strong craving we have for salt.

Dogs, are not exclusively carnivorous, generally they are classified as omnivores, meaning that they  not only eat meat but plant material as well. Nonetheless, in the wild, more than 80 percent of a dogs diet will be made up from meat. For this reason dogs also have specific taste receptors that are tuned for meats and fats. Dogs will tend to seek out, and clearly prefer the taste of things that contain meat or flavours extracted from meat.

The sweet taste buds in dogs respond to a chemical called furaneol. This chemical is found in many fruits. It appears that dog's do like this flavour, and it probably evolved because in a natural environment dogs frequently supplemented their diet of small animals with whatever fruits happen to be available at the time.

Unlike humans, dogs also have taste buds that are tuned for water. This taste sense is found at the tip of the dog's tongue, which is the part of the tongue that all dogs curl to lap water.