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Tigers (Panthera tigris) are mammals of the Felidae family and one of four "big cats" in the panthera genus. They are predatory carnivores and the largest and most powerful of all living cat species. The Indian subcontinent is home to more than 80% of the wild tigers in the world. Tigers breed well in captivity, and the captive population in the United States may rival the wild population of the world.

Most tigers live in forests and grasslands, for which their camouflage is ideally suited, and where it is easy to hunt prey that is faster or more agile. Among the big cats, only the tiger and jaguar are strong swimmers; tigers are often found bathing in ponds, lakes, and rivers. Tigers hunt alone and eat primarily medium-sized herbivores such as deer, wild pigs, and buffalo. However, they will also take larger or smaller prey on occasion. Humans are the tiger's only serious predator and often kill tigers illegally for their fur. Their bones and nearly all body parts are used in Chinese medicine for a range of purported uses including pain killers and aphrodisiacs. Poaching for fur and destruction of habitat have greatly reduced tiger populations in the wild, and it has been placed on the endangered species list.

Physical traits
Although different subspecies of tiger have different characteristics, in general male tigers weigh between 180 and 325 kg (400 lb and 715 lb) and females between 100 and 180 kg (220 lb and 400 lb). The males are between 2.6 and 3.3 metres (8 ft 6 in and 10 ft 9 in) in length, and the females are between 2.3 and 2.75 metres (7 ft 6 in and 9 ft) in length. Of the living subspecies, Sumatran tigers are the smallest, and Amur or Siberian Tigers are generally the largest. However, recent studies show a decline in average bodyweights for tigers, especially in the Amur (sometimes referred to as siberian) subspecies. This may be caused by excessive poaching, a weakened prey base and habitat decline. Individual tigers living in the wild weighing significantly more than 270 kgs (around 600 lbs) have not been seen in quite a while. The legendary 700 lb+ tigers of the past are no longer to be found outside of zoos or circuses.

The stripes of most tigers vary from brown or hay to pure black, although White tigers have far fewer apparent stripes. The form and density of stripes differs between subspecies, but most tigers have in excess of 100 stripes. The now extinct Javan tiger may have had far more than this. The pattern of stripes is unique to each animal, and thus could potentially be used to identify individuals, much in the same way as fingerprints are used to identify people. This is not, however, a preferred method of identification, due to the difficulty of recording the stripe pattern of a wild tiger. It seems likely that the function of stripes is camouflage, serving to hide these animals from their prey (few large animals have colour vision as capable as that of humans, so the colour is not as great of a problem as one might suppose). The stripe pattern is found on a tiger's skin and if you shaved one, you would find that its distinctive camouflage pattern would be preserved.

Several obscure references to various other tiger colors have also been found, including most notably the reference to the "blue" or slate-colored tiger.

Tigers have the longest and biggest canine teeth of all the wild cats. A tiger's canines are larger and longer than those of a similar-sized lion. The reason for this is likely due to the habit of preying on large herbivores in its habitat whose bones are thick and large; the tiger's canines have to be strong enough to break the bones of their prey. Moreover, as tigers hunt alone to bring down their prey, they have to work harder than lions, which hunt in groups.

Method of killing

Tigers often ambush their prey as do other cats (including the domestic cat). Tigers overpower their prey from any angle, using their body size and strength to knock prey off balance. Once prone, the tiger bites the back of the neck, often breaking the prey's spinal column, piercing their windpipe, or severing the jugular vein or carotid artery. For large prey, a bite to the throat is preferred. After biting, the tiger then uses its muscled forelimbs to hold onto the prey, bringing it to the ground. The tiger remains latched onto the neck until its prey dies. Powerful swimmers, tigers are known to kill prey while swimming. Some tigers have even ambushed boats for the fishermen on board or their catch of fish. They almost never hunt people, except for protection.

In the wild world, tigers can leap as high as 5 m, and as far as 9 m -10 m, making them one of the highest-jumping mammals, perhaps second only to the puma.[citation needed] They have been reported to carry domestic livestock weighing 50 kg while easily jumping over fences 2 m high. Their forelimbs, heavily muscled, are used to hold tightly onto the prey's and avoid being dislodged, especially by large preys such as gaurs. A single tremendous blow of the paw can kill a full-grown wolf or heavily injure a 150 kg Sambar deer.

Biology and ecology
Adult tigers are mostly solitary. They do not maintain strict territories, but their home ranges are often maintained unless threatened by other tigers. They follow specific trails within their ranges. A tigress may have a home range of 20 sq km while the ranges of males are much larger, covering 60-100 sq km. Male home ranges may overlap those of many females, but males are intolerant of other males within their territory. Because of their aggressive nature, territorial disputes can leave both tigers injured. To identify his territory the male marks trees by spraying urine and anal gland secretions on trees as well as by marking trails with scat. Males show a behavior called flehmen, a grimacing face, when identifying the condition of a female's reproductive condition by sniffing their urine markings.

A female is only receptive for a few days and mating is frequent during that time period. A pair will copulate frequently and noisily, like other cats. The gestation period is 103 days and 3-4 cubs of about 1 kg each are born. The females rear them alone. Wandering male tigers may kill cubs to make the female receptive. At 8 weeks, the cubs are ready to follow their mother out of the den. The cubs become independent around 18 months of age, but it is not until they around 2-2 1/2 years old that they leave their mother. The cubs reach sexual maturity by 3-4 years of age. The female tigers generally own territory near their mother, while males tend to wander in search of mates before taking over the territory of another male tiger. Over the course of her life, a female tiger will give birth to an equal number of male and female cubs.

In the wild, tigers mostly feed on deer, wild boar, and wild cattle, including gaur and water buffaloes, young rhinos and elephants, and sometimes, leopards and bears. Sambar and wild boar are their favored preys in India. Young elephants are another of their favourite food items. However, as young calves and juveniles always travel in herds with their mothers and relatives, the possibility for a lone tiger to catch a young elephant is quite low, as the tiger usually have to deal with the calves' protectors, which outnumber it. Tigers prefer large preys such as sambar and gaur because they provide more meat and last for many days, avoiding the need for another hunt. In all of their range, tigers are the top predators and they do not fear from any other carnivores other than the dhole or Indian wild dog, which makes up for strength in numbers. They generally do not prey on large mammals such as elephants, and rhinos, although they will prey on weak young whenever they have an opportunity. However, a hungry tiger will attack anything it regards as potential food. Of all the land carnivores, tiger is the only species that has been known to charge and take down even full-grown male elephants, one-on-one. For centuries in Asia, especially in Indochina, where elephants used to be utilized in military as weapons, minor ethnic tribes, who are specialized in capturing and training elephants, have the traditions of testing captured male elephants by pressing one against a tiger. If an elephant survives the fight, it is considered ideal for battles. Today, however, due to the depletion of both species, these extraordinary confrontations become exceedingly rare and are hardly ever witnessed by humans in the wild.

Tigers have been studied in the wild using a variety of techniques. The populations of tigers were estimated in the past using plaster casts of their pugmarks. In recent times, camera trapping has been used instead. Newer techniques based on DNA from their scat are also being evaluated. Radio collaring has also been a popular approach to tracking them for study in the wild.