Appearance
Eyes: 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.

Claws: Like domestic cats, tiger claws are retractable. Tiger scratches on trees serve as territorial markers.

Stripes: No one knows exactly why tigers are striped, but scientists think that the stripes act as camouflage, and help tigers hide from their prey. The Sumatran tiger has the most stripes of all the tiger subspecies, and the Siberian tiger has the fewest stripes. Tiger stripes are like human fingerprints; no two tigers have the same pattern of stripes.

Head: The tiger's head often carries the Chinese mark of wang or king on the forehead.

Color: Most tigers have an orange coat with dark brown or black stripes accented with white. Tigers that live in cold climates (Siberian tigers) have thicker fur than tigers that live in warm climates.

Tail: A tiger's tail is 3 to 4 feet long, about half as long as its body. Tigers use their tails for balance when they run through fast turns. They also use their tails to communicate with other tigers.

Paw prints: A tiger's paw prints are called pug marks.

Biology
Age: The life span of tigers in the wild is thought to be about 10 to 15 years. Tigers in zoos live to be between 16 and 20 years old.

Vision: Tigers can see in the dark six times better than humans can.

Fur: Tiger hair length varies geographically. In the southern subspecies the hairs are short (approximately 7 to 20 mm on the back and 15 to 35 mm on the stomach). The Siberian tiger has longer hair especially in the winter (approximately 40 to 60 mm on the back and 70 to 105 mm on the stomach). The density of fur is dependent on seasonal and geographical factors. The Sumatran tiger has approximately 1,700 to 2,000 hairs per square centimeters while the winter coat of the Siberian tiger has as many as 3,000 to 3,300 hairs per square centimeter.

Claws: A tiger's forefeet have five toes and the hind feet have four toes. All toes have claws. The claws are 80 to 100 mm in length.

Teeth: Adult tigers have 30 large teeth! The length of the canine teeth can be between 2.5 to 3 inches (74.5 to 90 mm.).

Chromosomes: Chromosomes are arranged in pairs and there are 19 pairs in a tiger, or 38 chromosomes altogether.

Size
Weight: Siberian tigers are the heaviest subspecies at 500 or more pounds (225 kg), with males heavier than females. The lightest subspecies is the Sumatran; males weigh about 250 pounds (110 kg) and females around 200 pounds (90 kg).

Measurements: Depending on the subspecies, the head-body length of a tiger is about 4 1/2 to 9 feet (1.4-2.8 m). The length of the tail is 3 to 4 feet (90-120 cm). The foot pads vary in size with age, resulting in inaccurate estimates when used in censusing wild populations.

Record Holder: The heaviest tiger recorded in the Guinness Book of World Records is a 1,025-pound male Siberian tiger.