How Do Dogs Taste Food?

Dogs will eat things that make us gag and then turn their nose up at an expensive food we thought smelled lovely. Both behaviours make more sense once you know how a dog’s sense of taste actually works — and how little of the job it is doing.

The numbers

Humans have roughly 9,000 taste buds. Dogs have around 1,700. Cats, for comparison, have fewer than 500.

So a dog’s sense of taste is considerably less refined than ours. What it lacks in taste it more than makes up for in smell, with 200 to 300 million scent receptors against our six million.

The practical consequence is that a dog’s experience of food is dominated by aroma. Taste confirms; smell decides.

What dogs can taste

Dogs have receptors for the same basic categories we do:

Sweet. Dogs can taste sweetness, which is unusual among carnivores — cats cannot, having lost the functional gene. It is thought to reflect the omnivorous side of the dog’s ancestry, since fruit and vegetable matter featured in the wild canid diet. It also explains the enthusiasm for anything containing fruit.

Salty. Dogs detect salt but appear far less responsive to it than we are. Meat naturally contains sodium, so a meat-eating animal has less need for a strong salt-seeking drive. This is one reason adding salt to make food more appealing does not really work on dogs.

Sour. Detected, and generally avoided, as in most species. Sourness signals fermentation and spoilage.

Bitter. Detected and strongly disliked. Bitterness is the classic warning signal for toxins, and a dog’s aversion to it is why bitter anti-chew sprays work at all — though plenty of dogs simply decide to put up with it.

Umami. The savoury, meaty taste of glutamates and nucleotides. Dogs are highly sensitive to it, which is exactly what you would expect from an animal whose diet centres on meat.

The taste dogs have that we do not

Here is the genuinely interesting bit. Dogs have taste buds at the tip of the tongue that respond specifically to water.

These receptors become more sensitive after the dog has eaten salty or sugary food — in other words, exactly when the body needs to rehydrate. It appears to be a mechanism that makes water actively more appealing when dehydration is a risk.

Cats and other carnivores have them too. Humans do not.

Where the taste buds are

Mostly at the tip and edges of the tongue, with some at the back and a few on the palate and in the throat. The centre of the tongue, which does most of the mechanical work of drinking and swallowing, has relatively few.

Dogs also have the vomeronasal organ, sometimes called Jacobson’s organ, in the roof of the mouth. It detects heavy, non-volatile molecules, especially pheromones, and it sits at the boundary between taste and smell. When a dog licks something and then works its tongue against the roof of its mouth, it is sampling with this organ.

Why dogs eat revolting things

Several reasons, none of them about taste being bad.

Smell drives the decision. Rotting meat produces exactly the volatile compounds a scavenger evolved to home in on. To a dog it does not smell bad; it smells like an opportunity.

Scavenging is ancestral. Dogs evolved alongside humans partly by eating our refuse. Discrimination was not an advantage.

Fewer bitter receptors means fewer things taste actively unpleasant.

Texture and novelty matter. Some things get eaten because they are interesting, not because they taste of anything.

Using this practically

For a fussy dog:

• Warm the food to just below body temperature to release aroma
• Add a small amount of something strongly smelling — a spoonful of the wet version of the same food works well
• Feed in a quiet place, away from other animals
• Take uneaten food away after fifteen minutes rather than leaving it to go stale

For medication:

• Bitter tastes are the problem, so wrapping a tablet is about preventing contact with the tongue rather than masking flavour
• Do not crush bitter tablets into food. You will make the whole bowl unacceptable and the dog will remember.

For training:

Use smell to grade your rewards. Dried liver, cheese and hot dog are high value not because they taste better in some abstract sense but because they smell dramatically stronger. Save them for genuinely hard exercises.

A different world

Your dog does not really taste dinner the way you taste dinner. It smells it, in extraordinary detail, and then confirms with a comparatively blunt set of taste receptors on the way down.

Which rather puts the ten seconds it takes to empty the bowl into perspective. The interesting part already happened, before the first mouthful.