Physical characteristics
Main article: Dog anatomy
See also: Dog health
Modern dog breeds show more variation in size, appearance, and behavior than any other domestic animal. Within the range of extremes, dogs generally share attributes with their wild ancestors, the wolves. Dogs are predators and scavengers, possessing sharp teeth and strong jaws for attacking, holding, and tearing their food. Although selective breeding has changed the appearance of many breeds, all dogs retain basic traits from their distant ancestors. Like many other predatory mammals, the dog has powerful muscles, fused wristbones, a cardiovascular system that supports both sprinting and endurance, and teeth for catching and tearing.
Sight
A Greyhound, one of many breeds of sighthound
Like most mammals, dogs are dichromats and have color vision equivalent to red-green color blindness in humans.[34][35][36] Different breeds of dogs have different eye shapes and dimensions, and they also have different retina configurations.[37] Dogs with long noses have a "visual streak" which runs across the width of the retina and gives them a very wide field of excellent vision, while those with short noses have an "area centralis" — a central patch with up to three times the density of nerve endings as the visual streak — giving them detailed sight much more like a human's.
Some breeds, particularly the sighthounds, have a field of vision up to 270° (compared to 180° for humans), although broad-headed breeds with short noses have a much narrower field of vision, as low as 180°
See also: Dog health
Modern dog breeds show more variation in size, appearance, and behavior than any other domestic animal. Within the range of extremes, dogs generally share attributes with their wild ancestors, the wolves. Dogs are predators and scavengers, possessing sharp teeth and strong jaws for attacking, holding, and tearing their food. Although selective breeding has changed the appearance of many breeds, all dogs retain basic traits from their distant ancestors. Like many other predatory mammals, the dog has powerful muscles, fused wristbones, a cardiovascular system that supports both sprinting and endurance, and teeth for catching and tearing.
Sight
A Greyhound, one of many breeds of sighthound
Like most mammals, dogs are dichromats and have color vision equivalent to red-green color blindness in humans.[34][35][36] Different breeds of dogs have different eye shapes and dimensions, and they also have different retina configurations.[37] Dogs with long noses have a "visual streak" which runs across the width of the retina and gives them a very wide field of excellent vision, while those with short noses have an "area centralis" — a central patch with up to three times the density of nerve endings as the visual streak — giving them detailed sight much more like a human's.
Some breeds, particularly the sighthounds, have a field of vision up to 270° (compared to 180° for humans), although broad-headed breeds with short noses have a much narrower field of vision, as low as 180°
Hearing
According to hypertextbook.com, the frequency range of dog hearing is approximately 40 Hz to 60,000 Hz.[38] Dogs detect sounds as low as the 16 to 20 Hz frequency range (compared to 20 to 70 Hz for humans) and above 45 kHz[39] (compared to 13 to 20 kHz for humans),[38][35] and in addition have a degree of ear mobility that helps them to rapidly pinpoint the exact location of a sound.[40] Eighteen or more muscles can tilt, rotate and raise or lower a dog's ear. Additionally, a dog can identify a sound's location much faster than a human can, as well as hear sounds up to four times the distance that humans are able to.[40] Those with more natural ear shapes, like those of wild canids like the fox, generally hear better than those with the floppier ears of many domesticated species.
Smell
Scent hounds, especially the Bloodhound, are bred for their keen sense of smell.[41]
Dogs have nearly 220 million smell-sensitive cells over an area about the size of a pocket handkerchief (compared to 5 million over an area the size of a postage stamp for humans).[42][43] According to nhm.org, dogs can sense odors at concentrations nearly 100 million times lower than humans can.[44] According to Dummies.com, the percentage of the dog's brain that is devoted to analyzing smells is actually 40 times larger than that of a human.[42] Some dog breeds have been selectively bred for excellence in detecting scents, even compared to their canine brethren.
According to hypertextbook.com, the frequency range of dog hearing is approximately 40 Hz to 60,000 Hz.[38] Dogs detect sounds as low as the 16 to 20 Hz frequency range (compared to 20 to 70 Hz for humans) and above 45 kHz[39] (compared to 13 to 20 kHz for humans),[38][35] and in addition have a degree of ear mobility that helps them to rapidly pinpoint the exact location of a sound.[40] Eighteen or more muscles can tilt, rotate and raise or lower a dog's ear. Additionally, a dog can identify a sound's location much faster than a human can, as well as hear sounds up to four times the distance that humans are able to.[40] Those with more natural ear shapes, like those of wild canids like the fox, generally hear better than those with the floppier ears of many domesticated species.
Smell
Scent hounds, especially the Bloodhound, are bred for their keen sense of smell.[41]
Dogs have nearly 220 million smell-sensitive cells over an area about the size of a pocket handkerchief (compared to 5 million over an area the size of a postage stamp for humans).[42][43] According to nhm.org, dogs can sense odors at concentrations nearly 100 million times lower than humans can.[44] According to Dummies.com, the percentage of the dog's brain that is devoted to analyzing smells is actually 40 times larger than that of a human.[42] Some dog breeds have been selectively bred for excellence in detecting scents, even compared to their canine brethren.
