Making Sense of Your Dog: Smell and Sight (Part 1)
Courtesy: Péter Göblyös / Pixabay
You and your pup have the same five senses (not counting the ESP your pooch demonstrates when he intuits it’s time for a walk). But the strength of those senses varies widely between you, which means you and your pet experience the world very differently.
Courtesy: Sonia Ugarte from Pixabay
Your Dog’s Sense of Smell
Your dog has 50 times as many olfactory receptors as you do. The part of his brain dedicated to analyzing smells is 40 times greater than yours. Plus, dogs display a trait called neophilia, which means they love to sniff out new and interesting odors. They can detect substances at a concentration of one part per trillion – a single drop of liquid in 20 Olympic-size swimming pools. Even Michael Phelps couldn’t do that!
Learn how dogs can be trained to sniff out cancer in our last blog post!
Dogs’ noses are also structurally superior to ours for smell detection. When humans exhale, we push air out through the same orifice it came in. When a pooch exhales, the spent air exits through the slits in the sides of his nose, swirling in a way that ushers in new smells simultaneously. Thus, he can sniff more or less continuously. Also, a dog can wiggle his nostrils independently and determine the direction of the stinky things grabbing his attention. This explains why your pup weaves back and forth across the sidewalk when you’re out for a stroll. There’s an interesting smell here! And one there! And another over there! What an interesting world!
Your Dog’s Sense of Sight
Analysis of the make-up of a dog’s eye has given us a good idea of what they can see and what they can’t.
Courtesy: Sabrinasfotos / Pixabay
Do your pups discern color? Yes, to a degree. Their ability to differentiate along the color spectrum approximates that of a color-blind human – some colors are visible to them, whereas others fade into shades of gray. A dog’s retina (like yours and mine) contains photoreceptor cells for identifying color (cones) and cells for picking up motion and seeing in dim light (rods). But the canine retina contains only about one-tenth as many cone cells as the human eye. They can distinguish blue-violet and yellow and differentiate between shades of gray, but they don’t pick up the other color spectrum nuances you can see. Seeing-eye dogs, for instance, can’t distinguish between green and red stoplights, so they look at the brightness and position of the light and check other cues (noise, traffic flow) to know when to guide their humans across the street.
Whereas excellent human vision is calibrated as 20/20, most dog breeds score no more than about 20/75 (which means they need to be 20 feet from an object a human can spot at 75 feet). Some breeds see better, however. Those seeing-eye Lab canines can score closer to 20/20.
Courtesy: Popovicmjeljica / Pixabay
So how does a sighthound so effectively spot and pursue prey? Prey species (those squirrels in your backyard, for instance) tend to have their eyes positioned on the sides of their heads. This gives them a wide field of vision to spot the approaching animals that want to make a meal of them. Predator species, like dogs, wolves and humans, have relatively narrow-set eyes, positioned toward the front of their faces.
But whereas human eyes point straight ahead, dogs’ eyes are usually set at about a 20-degree angle. This positioning increases their peripheral vision, which can extend to as much as 270 degrees. Moreover, the predominance of rod cells in dogs’ eyes, along with stereoscopic vision (three-dimensional perception), enables them to see moving objects (again, think scampering squirrels) better than they see stationary ones.
Sighthounds also tend to be tall, lean and leggy, with coil-spring backbones. They can see moving prey over large vertical dimension and then use their race-car bodies to hit high speeds quickly. They are the fastest pooches in the dog park – when they get a case of the zoomies, they burn rubber!
Sense-ational Partnerships
Humans employ their dog partners’ senses in a variety of ways. We use our pooches’ sniffing talents to identify substances ranging from disease indicators to narcotics to explosives. Sighthounds, such as Greyhounds, Borzois and Salukis, have been employed by their humans as hunting companions since at least the time of the ancient Egyptians.
But what about your pet’s other senses – hearing, touch and taste? How do those figure into our relationships with our canine companions? We’ll explore these questions in the second part of this blog.