A dog’s five senses

We all know that dogs have a sophisticated sense of smell, much more developed than ours. But what about their other senses? How do they compare to ours? All explanations are synopses based on the wonderful research and detail in the book by John Bradshaw, Dog Sense, unless otherwise noted.

Sight

I think everyone has heard that saying that dogs only see in black and white, right? Not true. They have poor color vision (compared to ours) and good night vision (again compared to ours), but definitely a world of color. Humans have three types of cones (yellow, green, and violet). Many animals have four (reptiles and birds). It is interesting to note that as many  as half of women (distinctly women) have a fourth cone (yellow-green) that allow them to distinguish millions of reds, oranges, yellows that the rest of can’t.

From an evolutionary perspective, it is more important for the dog to see all the time than to see in perfect detail. Humans have very refined color vision, dogs have adequate vision in bright light but more refined vision in half light and at night. Have you shined a flashlight at your dog’s eyes at night or taken a flash picture and seen how they glow? The eye has a reflective layer of cells behind the retina that doubles the sensitivity of the eye in low light.

Dogs can’t focus very well. Anything closer than a foot away from their nose they are not going to see very well and their sense of smell is going to take over. Dogs only have two cones (blue-violet and yellow-green). They don’t have the yellow cone which means they can’t distinguish red from orange or orange from yellow. The heavy super-science is that there is also a gap between the sensitivity of the color range of the cones so turquoise appears gray to dogs.

So, an example. It’s a beautiful sunny afternoon and you are playing at the park with your dog and you throw the tennis ball. It rolls into a patch of sunny looking marigolds. Your dog does not have superior vision in bright sunlight and can’t distinguish a yellow tennis ball from the yellow marigolds it rolled into. If he didn’t have a sense of where the ball went initially, he won’t find it without sniffing it out. If he saw the path of the ball, he will probably trample the marigolds, sniffing along the way until he finds the ball.

Hearing

A dog’s sense of hearing is much more sensitive than ours. The low range frequency is similar to humans, but they can hear high pitch frequencies that we can’t (think dog whistle). Side note: cats can hear even higher pitch frequencies than dogs.

Being that their hearing is more sensitive, approximately four times more sensitive, as an owner we should be respectful and careful of this. Noisy kennels, the car radio, loud televisions, have sounds in the high frequency range that can damage the hearing of extremely sensitive ears, and at the very least must be uncomfortable.

As dogs age it is very common that they have hearing loss. Perhaps that is because of habits and things that we have contributed to as their owners over the years- something to think about!

Smell

Humans sense of smell is remarkably underdeveloped in the animal kingdom, and dogs are actually average. For example, bears have a more sophisticated sense of smell than dogs. The area that traps the odor molecules differs by breed, but the German Shepherd’s is typical at about the area of a CD cover. A human’s is 30 times smaller, about the size of a postage stamp. Up to 2 billion nerves link this area to the dog’s brain to process the odor information. That’s 100 times more than we have. And the olfactory part of the brain that processes the information? Over 800 receptor genes have been identified. We have receptor genes as well, but with less ability to discern detail. Humans also need a much higher concentration of odor before we can detect anything.

Dogs have been used for tracking for quite some time. Dogs are now used to detect cancer, epileptic seizures, pests, bedbugs, and recently in Europe dogs are being used to link criminals to crime scenes.

Taste

Just as humans have taste bud receptors commonly labeled as sweet, salty, sour and bitter, dogs have receptors too. Theirs are sweet, sour, and bitter (no salt) and one other one specific to meat. The taste buds are not distributed equally across the tongue. The bitter area is located at the back of the tongue. This is why many sprays and anti-chewing items are made from peppers or other bitter things.

At the tip of the tongue, dogs (as well as cats and other carnivores) have taste buds that are sensitive to water. Humans do not have this. The tip of the tongue is the part that curls to lap water.

Touch

Dogs have sensory nerves all over their bodies, just as humans do. Gentle stroking and petting has been shown to lower blood pressure and heart rate, calm nerves, and increase levels of dopamine and oxytocin. Their paws have a thick fatty layer that acts as a natural insulator to protect them in cold and heat. The paw pad skin layer can be thicker or thinner depending on the breed (think Great Pyrenees versus Greyhound) but it has sweat glands and can also be absorptive.

Dogs are sensitive creatures, much more so than we may realize. I admit I will certainly be more mindful of sound after researching this blog topic. We strive to care for pets in the best way we can, in so many different ways, this is important to be cognizant of too!

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