tiger

The first tigers were members of the Felidae family of big cats that lived in northern Asia during the Late Pleistocene epoch. They migrated south and east and evolved into specific types of larger tigers according to their habitats. The ancient saber-tooth tigers were not ancestors of modern tigers. Three of the eight tiger subspecies, Bali, Caspian, and Javan, became extinct during the twentieth century.

Anatomy
Tigers range in weight according to their subspecies and gender. Sumatran male tigers are the lightest, weighing 110 kilograms (250 pounds). Females weigh approximately twenty kilograms less. Siberian male tigers weigh as much as 225 kilograms (500 pounds). The heaviest known tiger weighed 465 kilograms (1,025 pounds). From head to the base of the tail, tigers measure from1.4 to 2.8 meters (4.5 to 9 feet) long, and their tails are from 90 to 120 centimeters (3 to 4 feet). They use their tails to balance and to communicate. Tiger skulls have a big saggital crest which anchors a large jaw muscle. Tigers' vertebra and joints are flexible. Their hind legs are longer than their front legs, providing impulsion and assisting leaping when they are chasing game. They have five toes on their front paws and four toes on their hind paws. Each toe has a retractable claw which is 80 to 100 millimeters (3 to 4 inches) long and helps them restrain prey and climb trees.Mature tigers have thirty teeth. The canine teeth are 75 to 90 millimeters (2.5 to 3 inches) long. Tigers have triangular, erect ears set atop broad skulls, with their eyes positioned on the front of their face. Tigers' eyes have reflecting retinas which enable excellent night vision. Tigers' sense of smell is also acute; they can distinguish different animals by smell and exhibit the flemen response. Tigers have nineteen pairs of chromosomes, which determine genetic patterns. Their coats are colored shades of orange, with black or brown stripes of varying widths and lengths and white accents around the eyes, ruffs, and other body parts. Rarely, Bengal tigers with the two necessary alleles are born with a white foundation coat and blue eyes. They are not albinos or a separate subspecies. Tigers' stripes vary according to subspecies, with Sumatran tigers having the most and Siberian tigers having the fewest. Each tiger's stripes are unique and function as camouflage. Fur thickness varies with seasonal changes and geography. Siberian tigers have almost twice the number of hairs per square centimeter than Sumatran tigers.

Behavior
Tigers are solitary, preferring to hunt alone.Amale tiger's territory averages twenty-six to seventyeight square kilometers (ten to thirty square miles), depending on the availability of prey. Some Siberian tigers roam territories of 1,036 square kilometers (400 square miles). Tigers' territories often overlap, with several females sharing territorial space with one male. Tigers scratch on trees, leave fecal droppings, and spray urine to mark their territory. Male tigers occasionally fight. Tigers have several vocalizations to communicate aggression and receptiveness to other tigers. Females attain sexual maturity at age three and males at age four. After a four-month gestation, females have litters of two to five cubs which are born blind and are vulnerable to predators such as pythons. The cubs drink their mother's milk for two months, then feed at her kills until they are about two to three years old and capable of hunting alone. Tigers can catch and kill prey as large as 160 to 900 kilograms (440 to 2,000 pounds). They stalk and ambush ungulates, knocking prey to the ground and biting the neck or throat to sever the spinal cordor suffocate the animal.Tigers can consume twenty to twenty-five kilograms (sixty to seventy pounds) of meat daily. They drag carcasses into vegetated areas and gorge on a kill, then fast. Tigers also eat termites and snakes. Some tigers, especially in the Sunderbans river delta of India and Bangladesh, have attacked and killed humans.

Conservation
Adult tigers are hunted by poachers for their hides, bones, teeth, and body parts or for sale to exotic pet traders. Much of their jungle habitat has been destroyed during wars or for agricultural use. As a result, only about five thousand to seven thousand tigers are alive in the wild. Authorities estimate that an equivalent number are kept as exotic pets in North America and in zoos, sanctuaries, and circuses. Tiger censuses have been taken by counting pugmarks in known tiger habitats. In captivity, tiger hybrids include ligers, the hybrid of lion fathers and tiger mothers, and tigons, produced by tiger fathers and lioness mothers. Conservation breeding programs are aspiring to preserve and increase the tiger population.