As in structure so in habits, the cat may be considered the most specialized of all Carnivora, although they exhibit many features connecting them with extinct types. All the members of the group feed almost exclusively on warm-blooded animals which they have themselves killed, but one Indian species, _Felis viverrina_, is said to prey on fish, and even fresh-water molluscs. Unlike dogs, they never associate in packs, and rarely hunt their prey on open ground, but from some place of concealment wait until the unsuspecting victim comes within reach, or with noiseless and stealthy tread, crouching close to the ground for concealment, approach near enough to make the fatal spring. In this manner they frequently attack and kill animals considerably exceeding their own size. They are mostly nocturnal, and the greater number, especially the smaller species, more or less arboreal. None are aquatic, and all take to the water with reluctance, though some may habitually haunt the banks of rivers or pools, because they more easily obtain their prey in such situations. The numerous species are widely diffused over the greater part of the habitable world, though most abundant in the warm latitudes of both hemispheres. None are, however, found in the Australian region, or in Madagascar. Although the Old World and New World cats (except perhaps the northern lynx) are all specifically distinct, no common structural character has been pointed out by which the former can be separated from the latter. On the contrary, most of the groups into which the family may be divided have representatives in both hemispheres.
Notwithstanding the considerable diversity in external appearance and size between different members of this extensive family, the structural differences are but slight. The principal differences are to be found in the form of the cranium, especially of the nasal and adjoining bones, the completeness of the bony orbit posteriorly, the development of the first upper premolar and of the inner lobe of the upper sectorial, the length of the tail, the form of the pupil, and the condition and coloration of the fur, especially the presence or absence of tufts or pencils of hair on the external ears.