It's a scenario every dog owner is familiar with: you're out on a stroll when he starts sniffing at something in the grass. You look away for a split second, and when you look back he's scarfing down the moldy remnants of a meal long-discarded next to the trash can. Cue falling to your knees and yelling "what are you eating?!" while forcing their jaws open in an attempt to retrieve the soggy item. Naturally, a human would take one look at these "ground presents" and be nauseated by the thought of eating them. One would think that dogs, whose sense of smell is roughly 10,000 to 100,000 times better than humans, would be more discerning about what they put in their mouths based on smell alone. Just how good is a dog's sense of taste?
Can dogs taste?
Despite their proclivity for eating truly gross things, dogs have the same four taste classifications that humans do and are able to taste and differentiate between sweet, sour, salty, and bitter. Dogs have about 1,700 taste buds, compared to around 9,000 in humans, meaning their sense of taste is about 1/6th as sensitive as ours. A dog's tongue also possesses specialized taste buds that react solely to water. These are located at the tip of the tongue, where the tongue curls when a dog drinks water. These taste buds are also more sensitive after eating sweet or salty foods, and it is thought this may have an evolutionary basis as dog ancestors would have needed to drink more water after consuming foods that would have dehydrated them.
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How smell affects a dog's taste
A dog's sense of smell is truly remarkable. They possess up to 300 million olfactory receptors in their noses, compared to just 6 million in humans. Dogs also have an additional scent-detecting organ that humans do not, the vomeronasal organ (also called Jacobson's organ), which helps them pick up on chemical signals and hormones that are undetectable to us. The vomeronasal organ is also partly responsible for a dog's ability to taste. It is located on the roof of the mouth and helps connect their senses of smell and taste by translating captured scent molecules into taste by the dog's brain.
What tastes do dogs like?
Many dogs will enthusiastically devour whatever is in front of them, but some are more picky eaters. In general, the more aromatic a food is, the more likely a dog will be interested in it — which is largely due to their fantastic sense of smell. Wet dog food tends to retain a strong aroma due to its water content, while dry kibble does not smell as strongly due to having been dehydrated. Dogs are opportunistic eaters and will jump at the chance to eat most things with a strong smell, even if they're well-fed.
Though dogs can taste all the same taste classifications as humans, their taste receptors do not indicate an affinity for salty foods. This is likely based on their evolutionary history, as dog ancestors' diets consisted of about 80 percent meat, which contains the amount of salt their bodies need. With salty foods being less compelling to dogs, their biology helps to prevent them from excess salt intake and dehydration.
Sweet foods do appeal to a dog's taste preferences, which also likely has an evolutionary basis. Dogs are omnivores and can digest both meat and plant material, as their ancestors likely supplemented their meat-based diets by foraging for fruits and vegetables.
Dogs tend to avoid sour, bitter, and spicy tastes, as these send a chemical signal to their brains that they are bad to eat. Supposedly, dogs will avoid foods that contain toxins or bacteria indicating they are spoiled, though observations of the author's dog suggest otherwise.
In summary
Even though dogs possess a powerful sense of smell, their palate is not quite so discerning. Their strong sense of smell may make them interested in just about anything with a strong scent, but they can't taste complex flavors. Dogs are able to taste sweet, sour, salty, and bitter foods, but their comparatively low number of taste buds means that they don't experience flavors in the same way humans do.