Physical Characteristics

Tigers typically have rusty-reddish to brown-rusty coats, a whitish medial and ventral area, a white "fringe" that surrounds the face, and stripes that vary from brown or gray to pure black. The form and density of stripes differs between subspecies (as well as the ground coloration of the fur; for instance, Siberian tigers are usually paler than other tiger subspecies), but most tigers have over 100 stripes.

The pattern of stripes is unique to each animal, these unique markings can be used by researchers to identify individuals (both in the wild and captivity), much in the same way thatfingerprints are used to identify humans. It seems likely that the function of stripes is camouflage, serving to help tigers conceal themselves amongst the dappled shadows and long grass of their environment as they stalk their prey. The stripe pattern is also found on the skin of the tiger. If a tiger were to be shaved, its distinctive camouflage pattern would be preserved.

Like other big cats, tigers have a white spot on the backs of their ears. These spots, called ocelli, serve a social function, by communicating the animal's mental state to conspecifics in the gloom of dense forest or in tall grass.

Tigers have the additional distinction of being the heaviest cats found in the wild. They also have powerfully built legs and shoulders, with the result that they, like lions, have the ability to pull down prey substantially heavier than themselves. However, the subspecies differ markedly in size, tending to increase proportionally with latitude, as predicted by Bergmann's Rule.

Large male Siberian Tigers (Panthera tigris altaica) can reach a total length of 3.5 m "over curves" (3.3 m. "between pegs") and a weight of 306 kilograms,.This is considerably larger than the sizes reached by island-dwelling tigers such as the Sumatran, the smallest living subspecies, with a body weight of only 75–140 kg. Depending upon subspecies tigers may be 1.4-2.8 m (4.6-9.2 ft) long from along the head and body, while the tail may add a further 0.6-1.1 m (2-3.6 ft). At the shoulder, tigers may variously stand 0.7-1.2 m (2.1-4 ft) tall.

Tigresses are smaller than the males in each subspecies, although the size difference between male and female tigers tends to be more pronounced in the larger subspecies of tiger, with males weighing up to 1.7 times more than the females.In addition, male tigers have wider forepaw pads than females. Biologists use this difference to determine gender based on tiger tracks.The skull of the tiger is very similar to that of the lion, though the frontal region is usually not as depressed or flattened, with a slightly longer postorbital region. The skull of a lion has broader nasal openings. However, due to the amount of skull variation in the two species, usually, only the structure of the lower jaw can be used as a reliable indicator of species.

Tigers have round pupils and yellow irises (except for the blue eyes of white tigers). Due to a retinal adaptation that reflects light back to the retina, the night vision of tigers is six times better than that of humans.