Dogs cannot see as well as humans and are considered color blind. A dog sees objects first by their movement, second by their brightness, and third by their shape.
A dog's heart beats between 70 and 120 times a minute, compared with a human heart which beats 70 to 80 times a minute.
A female carries her young about 60 days before the puppies are born.
Irish Wolfhounds rank as the largest dog, and Chihuahuas as the smallest dog. The St. Bernard is the heaviest dog and other breeds range in size between these extremes.
Tough or not, most dogs can lick the entire family.