Tigers are the most variable in size of all big cats, much more so than lions. The Bengal and Siberian subspecies are the tallest at the shoulder and thus considered the largest living felids, ranking with the extinct Caspian tiger among the biggest that ever existed. An average adult male tiger from Northern India or Siberia outweighs an average adult male lion by around 45.5 kg (100 lb). Males vary in total length from 250 to 390 cm (98 to 154 in) and weigh between 90 to 306 kg (198 to 675 lb) with skull length ranging from 316 to 383 mm (12.4 to 15.1 in). Females vary in total length from 200 to 275 cm (79 to 108 in), weigh 65 to 167 kg (143 to 368 lb) with skull length ranging from 268 to 318 mm (10.6 to 12.5 in). In either sex, the tail represents about 0.6 to 1.1 m (24 to 43 in) of total length.
Bengal tigers in particular live in many types of forests, including wet, evergreen, and the semievergreen of Assam and eastern Bengal; the swampy mangrove forest of the Ganges Delta; the deciduous forest of Nepal, and the thorn forests of the Western Ghats. In various parts of their range they inhabit or have inhabited additionally partially open grassland and savanna as well as taiga forests and rocky habitats.
Adult tigers lead largely solitary lives. They establish and maintain home ranges. Resident adults of either sex generally confine their movements to a territory, within which they satisfy their needs and those of their growing cubs. Individuals sharing the same area are aware of each other's movements and activities. The size of the home range mainly depends on prey abundance, and, in the case of males, on access to females. A tigress may have a territory of 20 km2 (7.7 sq mi), while the territories of males are much larger, covering 60 to 100 km2 (23 to 39 sq mi). The range of a male tends to overlap those of several females, providing him with a large field of prospective mating partners.
Unlike many felids, tigers are strong swimmers and often deliberately bathe in ponds, lakes and rivers as a means of keeping cool in the heat of the day. Among the big cats, only the jaguar shares a similar fondness for water. They may cross rivers up to 7 km (4.3 mi) across and can swim up to 29 km (18 mi) in a day. They are able to carry prey through or capture it in the water.
Young female tigers establish their first territories close to their mother's. The overlap between the female and her mother's territory reduces with time. Males, however, migrate further than their female counterparts and set out at a younger age to mark out their own area. A young male acquires territory either by seeking out an area devoid of other male tigers, or by living as a transient in another male's territory until he is older and strong enough to challenge the resident male. Young males seeking to establish themselves thereby comprise the highest mortality rate (30–35% per year) among adult tigers.
To identify his territory, the male marks trees by spraying urine and anal gland secretions, as well as marking trails with scat and marking trees or the ground with their claws. Females also use these "scrapes", as well as urine and scat markings. Scent markings of this type allow an individual to pick up information on another's identity, sex and reproductive status. Females in oestrus will signal their availability by scent marking more frequently and increasing their vocalizations.
In the wild, tigers mostly feed on larger and medium sized animals, with most studies indicating a preference for native ungulates averaging 90 kg (200 lb) at a minimum. Sambar, chital, barasingha, wild boar, gaur, nilgai and both water buffalo and domestic buffalo, in descending order of preference, are the tiger's favored prey in India. Sometimes, they also prey on other predators, including other large species such as leopards, pythons, sloth bears and crocodiles. In Siberia the main prey species are manchurian wapiti and wild boar (the two species comprising nearly 80% of the prey selected) followed by sika deer, moose, roe deer, and musk deer.