Musings From the River's Bend

Musings from the bend of the Missouri River

Friday, June 20, 2008

Dogness, How They Are

We just got a new dog, my first in many MANY years!

So I thought I'd do a little research, you know, sort of a brush up on dogs.

Dogs. They've been our best friends forever. Well, it sure seems that way as they've been around 14,000 years since they started hanging around our campsites. In that enduring span of time they have become our companions, protectors, and hunting partners.

We spend so much time with our pet dogs, and they with us as their pack leader, it's impossible not to pause on occasion and wonder how our beloved buddies perceive the world. How do they sense us and their surroundings?

Just like us, dogs have the standard five senses - sight, smell, hearing, touch, and taste. However, your dog's senses, and thus their perceptions, are tuned quite differently from their human masters.

SMELL

Every dog and it's owner knows that dogs are built to smell and smell very well. In fact, your pet dog's nose is capable of incredible feats of sniffing and discerning scents. Just as eye-sight has evolved to be a human's most dominant sensory system, a dog's nose has become their primary go-to sense.

A physiological comparison make it clear how powerful their sense of smell really is.

Humans and dogs both share a scent-decoding center located in the brain called an olfactory bulb. A human's olfactory bulb weighs about 1.5 grams, on average. Though it varies by breed, a dogs olfactory bulb may be as large as 6 grams, or 4 times larger.

Now, considering that a dog's brain is perhaps 1/10th as large as a humans, the proportion of the dogs brain dedicated to smells is approximately 40 times that of a human. One can readily see the emphasis that is placed on smell.

SIGHT

Vision is a human being's most vital sense. But your dog sees its surroundings quite differently than it's owner does.

Each component of their eyes is constructed such that the ability to see fine detail is sacrificed in favor of the ability to track movement, and see in the low-light conditions that occur at dusk and dawn.

Dogs also cannot discern depth as well as humans can. Their pupils are much larger, taking up nearly the entire eye, and cannot shrink as small as ours can. This feature lets in more light but sacrifices depth of view, or the near-to-far distance over which objects are in clear focus.

A noticeable trait is the shine that a dogs eyes gives off at night when caught in the shine of a light. This eerie effect is caused by a reflecting mechanism located behind the retina, and serves as a second chance to capture light during the darkness of night. It's estimated that dogs need only one quarter of the light humans do to see clearly. Of note, cats need only a seventh the amount.

HEARING

Along with their noses, dogs generally have a much better sense of hearing than people do. The largest difference is the upper range of frequencies our dogs are capable of hearing.

A person can hear sounds with frequencies of up to 20,000 Hz. Dogs, on the other hand, can detect sounds ranging anywhere from 47,000 to 65,000 Hz, depending on the breed of dog.

By way of comparison, take a piano's keyboard and imagine adding 28 keys to the right side. The far right key would vibrate at around 20,000 Hz. If a dog were to play the piano, not only would it be quite a spectacle, that dog could have 48 extra keys on its piano, with the last twenty remaining silent to us puzzled humans in the audience.

TASTE

One look at typical pet food aisle in the supermarket might lead one to believe that dogs have a very refined sense of taste. Menu items range from bacon to bagels.

In truth, the sense of taste is enabled not by menu choice, but by the taste buds found on our tongues. Humans typically have around 9000 individual taste buds. Dogs have substantially fewer with about 1700, while cats have even less at roughly 500.

Of course, just one viewing of your dog as it inhales its dinner doesn't leave much accounting for taste. There's little doubt that this behavior is based on its distant ancestor's need to literally wolf down their prey item before being potentially disrupted by competition for its meal.

TOUCH

Different areas of a dog have different degrees of sensitivity to touch. It makes sense that the nose and muzzle are rich in sensory nerves. The pads of their paws also convey a lot of information pertaining to touch, such as levelness and firmness of the ground on which they are traversing. Indicative of this sensitivity, dogs often would rather you didn't fuss with their paws overly much.

Of course their whiskers are also a primary touch-sensitive spot. Like a cat, a dog's whiskers are stiff and embedded deeply in the dog's skin. The whisker acts as a lever and can amplify the most subtle of touches. In fact, 40% of the brain area devoted to touch is dedicated to the face and upper jaw, indicating its importance.

Unfortunately, a common and controversial practice of show dog groomers is to remove these whiskers to achieve a more streamlined effect. Every dog surely disapproves of this, even more than the worst hair cut and frilly outfit imaginable.

In sum, it should be no surprise that dogs and their human owners perceive the world around them in their own unique ways.

Humans primarily rely on their vision, while canines are mostly dependent on their sense of smell. Still, humans and dogs share all five senses to one degree or another. We just don't lick and sniff ourselves quite as much.