Carnivores

Carnivores, which are generally believed to have appeared along with other mammals during the Tertiary period approximately seventy million years ago, may be broadly divided into two groups, the plantigrades and the digitigrades.

Those in the former group, such as raccoons, bears, and weasels, walk on their heels, while those in the latter, such as dogs, cats, and hyenas, walk on their toes.

 Comparatively, digitigrades are usually faster and capable of running longer distances. Dogs have five toes on the front and four on the rear limbs, sometimes with dewclaws, but unlike cats, they cannot retract their nails.

As to traits and senses, those of the dog have been passed down from its wild ancestor, in which most of these abilities were necessary for survival.

The nose, for example, with its big nostrils, has a complex wrinkled lining that allows for a vast number of extremely sensitive olfactory cells to be exposed to the air within a relatively small area.

Of all land animals, dogs are said to have the sharpest sense of smell, approximately twelve million times more acute than that of humans.