The tiger has adapted to a great variety of environments, from the Siberian taiga, where nights can be as cold as −40 °C (−40 °F), to the mangrove swamps of the Sundarbans, where the temperatures reach more than 40 °C (104 °F). Tigers haunt the ruins of buildings such as courts and temples and are at home in habitats ranging from dry grassland to rainforest. Grasslands, mixed grassland-forests, and deciduous rather than densely canopied forests support maximum population densities, as these habitats maintain the highest number of prey species. Having evolved in the temperate and subtropical forests of eastern Asia, the tiger is less tolerant of heat than other large cats, which may explain why it is an adept swimmer that appears to enjoy bathing. Under stress it may climb trees.

The tiger usually hunts by night and preys on a variety of animals, but it prefers fairly large prey such as deer ( sambar, chital, and swamp deer) and wild pigs. A special liking for porcupines, despite the danger of injury from their quills, is an exception. Healthy large mammals are generally avoided, although there have been recorded instances of the tiger's having attacked elephants and adult water buffalo. Cattle are occasionally taken from human habitations, and some tigers can thrive on domestic livestock. After making a kill and consuming what it can, it makes a deliberate attempt to hide the carcass from vultures and other scavengers so that another meal can be obtained. Tigers are not averse to commandeering a kill from other tigers or leopards, and they sometimes eat carrion. Skill in killing and obtaining prey is only partly instinctive, maternal training being essential for proficiency. For this reason, tigers raised in captivity would not fare well if released into the wild. As the top predator throughout its range, the tiger plays a major role in controlling not only its prey population but that of other predators such as the leopard, dhole (Asiatic wild dog), and clouded leopard. No trait of the tiger has fascinated humans more than man eating. A number of reasons account for this—disability caused by age or injury, paucity of prey, acquisition of the habit from the mother, or defense of cubs or kill. With the reduction in the number of tigers, the occurrence of man-eating tigers has become rare except in the Sundarbans, the northeast Indian state of Uttar Pradesh, and neighbouring Nepal in and around Royal Chitwan National Park.

As solitary animals, tigers (especially males) establish and maintain their own territories, the size and nature of which vary with the number and distribution of prey, the presence of other tigers in the area, the nature of the terrain, the availability of water, and individual characteristics. Spacing between individuals and maintenance of territories are achieved through vocalization, scrapings on the ground, claw marking of trees, fecal deposits, scent deposited by the rubbing of facial glands, and spraying of urine mixed with scent secreted from the anal glands. The solitary nature of the species also helps minimize territorial conflict. Nonetheless, confrontations do occur, sometimes resulting in injury and even death.

The readiness of a tigress to mate is announced through vocalization and scent production. There is no fixed breeding season, though the preponderance of mating appears to occur in winter, with striped cubs being born after a gestation period of more than three months. The normal litter size is two to four, though up to seven cubs have been recorded. They are born blind, and, even when their eyes open, opacity prevents clear vision for six to eight weeks. There is thus a long period of weaning, tutelage, and training during which cub mortality is high, especially if food is scarce. During this time the offspring must endure long periods of absence by the mother while she is away hunting. Weaker cubs get less food because of the aggressiveness of their stronger siblings as food is less frequently made available. The cubs remain with the mother until about the second year, when they are nearly adult and are able to kill prey for themselves. Male cubs grow more quickly than females and tend to leave their mother earlier. Though cub infanticide (mainly by males) is known, it is not very unusual to find a male with a tigress and cubs, even sharing a kill. Such associations, however, do not last long. The tigress does not breed again until her cubs are independent. The average life span of a tiger in the wild is about 11 years.

Next to the elephant and the lion, no wild animal is so frequently portrayed in Asian art and lore. The persistent practices of using tiger parts as talismans, tonics, or medicine, despite all scientific evidence contrary to their efficacy, are manifestations of beliefs that emanate from the aura of the tiger and the awe that it has inspired for millennia. Certain animist communities still worship the tiger. Every 12th year of the Chinese calendar is the year of the tiger, and children born in it are considered especially lucky and powerful. In Hindu mythology the tiger is the vahana (vāhana) (“vehicle”) of the goddess Durga. Tigers are represented on seals from the ancient Indus civilization. The greatest of the Gupta (Gupta dynasty) emperors of ancient India, Samudra (Samudra Gupta), minted special gold coins depicting him slaying tigers. Tippu Sultan even vented his frustration at his inability to defeat the British by ordering a special life-size toy, replete with sound, of a tiger mauling an English soldier.

Serious concern for the declining number of tigers was expressed during the latter half of the 20th century, and gradually all countries in the tiger's range took measures to protect the animal, but with varying degrees of success. The tiger is now legally protected throughout its range, but law enforcement is not universally effective. India, which accounts for half the world's tiger population, declared it the national animal and launched Project Tiger in 1973, a successful program under which selected tiger reserves received special conservation efforts and status. Nepal, Malaysia, and Indonesia have set up a string of national parks and sanctuaries where the animal is effectively protected; Thailand, Cambodia, and Vietnam are pursuing the same course. China, the only country with three subspecies of tigers, is also giving special attention to conservation. In Russia, where poaching seriously endangered the Siberian tiger, concentrated effort and effective patrolling have resulted in a revival of the subspecies.

In the 1970s tiger hunting for sport was banned in most countries where tigers lived, and the trade in tiger skins was outlawed. Nevertheless, tiger skins are still highly valued for display and for worship, as are claws, teeth, and clavicles for talismans. Skulls, bones, whiskers, sinews, meat, and blood have long been used by Asians, especially the Chinese, in medicines, potions, and even wine. These products are presumed to be useful in the treatment of rheumatism, rat bites, and various other diseases, for the restoration of energy, and as aphrodisiacs; whiskers are believed to cause intestinal ulcers in one's enemies. poaching and the underground trade in tiger parts continue despite seizures and destruction of the confiscated parts.

Although poaching has been responsible for keeping the number of tigers low during the past three decades, wild tigers would still be threatened even if all poaching ceased. In countries such as India, the needs of rapidly growing human populations over the last two centuries have reduced both the quantity and the quality of habitat. Forests and grasslands so favoured by the tiger are cleared for agriculture. Reduction in prey populations results in greater dependence on livestock and the consequent retribution from man. Fortunately, the status of the tiger has aroused widespread empathy, and its cause has received substantial international support. The World Wide Fund for Nature (WWF) has been a pioneer and the largest contributor, along with corporate donors and nongovernmental organizations. The Convention on International Trade in Endangered Species is entrusted with the task of controlling illegal trade in tiger derivatives.