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 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.
Sight
Dogs were thought to be dichromats and thus, by human standards, color blind.1, 2 New research is now being explored that suggests that dogs may actually see some colour, but not to the extent that humans do. Because the lenses of dogs' eyes are flatter than humans', they cannot see as much detail; on the other hand, their eyes are more sensitive to light and motion than humans' eyes. Some breeds, particularly the best sighthounds, have a field of vision up to 270° (compared to 100° to 120° for humans), although broad-headed breeds with their eyes set forward have a much narrower field of vision, as low as 180°.1, 2
Hearing
Dogs detect sounds as low as the 16 to 20 Hz frequency range (compared to 20 to 70 Hz for humans) and as high as 70,000 to 100,000 Hz (compared to 20,000 Hz for humans)2, and in addition have a degree of ear mobility that helps them to rapidly pinpoint the exact location of a sound. They can identify a sound's location much faster than a human can, and they can hear sounds up to four times the distance that humans can.
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). Some breeds have been selectively bred for excellence in detecting scents, even compared to their canine brethren. Other than the oversimplified obvious, i.e. chemical compounds that affect chemical sensors in the nose, what a dog actually detects when he is scenting is not really understood; although once a matter of debate, it now seems to be well established that dogs can distinguish two different types of scents when trailing, an air scent from some person or thing that has recently passed by, as well as a ground scent that remains detectable for a much longer period. The characteristics and behavior of these two types of scent trail would seem, after some thought, to be quite different, the air scent being intermittent but perhaps less obscured by competing scents, whereas the ground scent would be relatively permanent with respect to careful and repetitive search by the dog, but would seem to be much more contaminated with other scents. In any event, it is established by those who train tracking dogs that it is impossible to teach the dog how to track any better than it does naturally; the object instead is to motivate it properly, and teach it to maintain focus on a single track and ignore any others that might otherwise seem of greater interest to an untrained dog. An intensive search for a scent, for instance searching a ship for contraband, can actually be very fatiguing for a dog, and the dog must be motivated to continue this hard work for a long period of time.
Direction and spatial sense
It has been observed that a lost dog can often find its way home, sometimes traveling over long distances.
Weather detection
Dogs also have the ability to sense inclement weather (mainly thunderstorms) many miles away. This is due to their keen ability to detect fluctuations in barometric pressure and can explain a dog's anxiety before and during a storm. The evolutionary ability of sensing weather can be traced back to when wolves used it to move the pack into proper shelter before a dangerous storm. |
