A powerful hunter with sharp teeth, strong jaws, and an agile body, the tiger is the largest member of the cat family. It is also the largest land-living mammal whose diet consists entirely of meat. The tiger's closest relative is the lion. Without the fur, it is difficult to distinguish a tiger from a lion. Like a human fingerprint, no two tigers have the same pattern of stripes on their coats.
Tigers range in size from the diminutive Sumatrans to the large Amur tigers. Sumatran females weigh between 165 and 242 pounds (75 to 110 kilograms) and males weigh between 220 and 310 pounds (100 to 141 kilograms). The largest mainland tiger females weigh between 220 and 352 pounds (100 to 160 kilograms) and males weigh between 396 and 570 (180 to 259 kilograms). Total length ranges from seven to 12 feet (2.1 to 3.7 meters).
The tiger's current distribution is a patchwork across Asia, from India to the Russian Far East. Tigers require large areas with forest cover, water and suitable large ungulate prey such as deer and swine. With these three essentials, tigers can live from the tropical rainforests of Sumatra and Indochina to the temperate oak forest of the Amur River Valley in the Russian Far East
Tigers can communicate with one another by rubbing heads, roaring and grunting. Scent marks and visual signposts, such as scratch marks, allow tigers to track other tigers in the area, and even identify individuals. A female tiger knows the other females whose territories abut hers; in many cases, a neighbor may be her daughter. Females know their overlapping males (and vice versa) and probably know when a new male takes over. All tigers can identify passing strangers. So, solitary tigers actually have a rich social life; they just prefer to socialize from a distance.
Tigers are built to kill large prey. Their hind limbs are longer than their fore limbs, enabling the tiger to jump long distances. Tigers have heavily muscled forelimbs and shoulders, and paws equipped with long, retractable claws, which enable them to grab prey and drag it to the ground to deliver a killing bite with powerful jaws and long canines.
While other cats are able to swim, tigers are willing swimmers who often go in the water to escape flies or cool off, and can easily cross rivers and lakes 5 miles (8 kilometers) wide.
In the wild, tigers prey primarily on wild boar and other swine, and medium to large deer such as chital, guar, red deer and sambar. When near human development, tigers also kill domestic animals such as cows and goats.
Tigers depend less on smell and more on keen eyesight and acute hearing to ambush and capture prey, primarily between dusk and dawn. Unlike lions that hunt in prides in open country, the solitary tiger prefers to hunt in the cover of dense foliage. Tigers can travel from 6 to 20 miles (9.6 to 32 kilometers) in a night in search of prey.
A typical predatory sequence begins with a slow, silent stalk. A lightening fast rush to close the gap follows when the tiger is within striking distance from its prey, about 30 to 35 feet (9 to 11 meters). The tiger charges and grabs its prey in its forepaws, brings it to the ground, and finally kills the animal with a bite to the neck or throat. Large prey is bitten in the throat and usually dies from suffocation. Smaller animals are killed with a swift bite to the back of the neck. The carcass is then dragged to a secluded area where it is consumed. A tiger eats 30 to 40 pounds (13.6 to 18 kilograms) of meat in an average night, and must kill about once per week. Catching a meal is not easy; a tiger is successful only once in ten to 20 hunts.
At the Smithsonian's National Zoo, tigers eat ground beef. Twice a week, they receive knucklebones or beef femurs and once a week they receive rabbits, which exercise the cats' teeth and jaws.
Female tigers are sexually mature at about 3 or 4 years of age and males at about 4 to 5 years. Mating may occur any time during the year, but most frequently takes place from November to April. Females enter estrus every three to nine weeks and are receptive for three to six days. A male and female meet only during this brief time to mate; however, he may stay in the area. The female tiger is an induced ovulator, meaning that her ovaries do not release eggs until mating occurs. After a gestation period of about 3.5 months, the female tiger gives birth in a secluded den to two or three, blind and helpless cubs. Litters may range from one to six cubs. The female rears the cubs alone.
Cubs weigh just over 2 pounds (0.9 kilograms) at birth and can nurse up until they are 6 months old. Depending on the food supply the cubs can start eating meat as early as a month. After a week or two, the cub's eyes open and its first teeth begin to grow. During the next 18 months, they gradually become independent and follow their mother on hunts. At about two years of age, the young tigers strike out alone to find their own territory. Females may establish a territory adjacent to that of their mother, or even take over part of their mother's territory. Adult females generally produce a litter every two years.
The wild life span is ten to 15 years and can reach 20 years in human care. In the wild, most tigers do not live as long as 12 years. Only half of all cubs survive to independence from their mother; only 40 percent of these survivors live to establish a territory and begin to produce young. The risk of mortality continues to be high even for territorial adults, especially for males, which must defend their territories from other males.
Of the nine tiger subspecies that once existed, only six remain (Bali, Javan and Caspian tigers have become extinct in the last 40 years) and the South China tiger is thought to be nearly extinct in the wild. The primary reason for the decimation of wild tiger populations is human overpopulation, poaching and the destruction and fragmentation of habitat. The demand for tiger bones and other body parts used in traditional Asian medicines is also contributing to the tiger's decline. Many governments and scientists are currently working on ways to educate the public on other sources for these "medicinal" compounds.
All five remaining tiger subspecies are endangered or critically endangered. Only an estimated 1,500 to 3,200 tigers exist in the wild (300 to 400 Sumatran tigers), and less than 200 in North American zoos. The future existence of tigers in the wild is in jeopardy.
The Smithsonian Institution and the World Bank Group announced a new program under the Global Tiger Initiative to help stabilize and restore wild tiger populations and save this endangered species from extinction in their natural habitats. Under the new agreement signed in 2009, the World Bank and the Zoo established a Conservation and Development Network that trains hundreds of rangers, foresters, and other habitat managers in the latest cutting-edge practices in biodiversity management, with a specific focus on preserving and increasing wild tiger populations.
The Conservation and Development Network links the leading knowledge institutions in China, India, Indonesia, Russia, Thailand and other tiger range countries with globally significant centers of excellence in conservation science and professional training.
The training aims to create more effective measures against illegal trade and trafficking of tiger parts, and intensify surveillance, detection and conviction of poachers. In addition to promoting stricter implementation of conservation laws and laws against illegal trade and traffic, the network allows countries to more efficiently share information about poaching activity, leading to more robust efforts to combat the problem.
Scientists have classified tigers into nine subspecies: Bali, Java, Caspian, Sumatran, Amur (or Siberian), Bengal, South China, Malayan and Indochinese. The first three subspecies are extinct. However, recent analysis suggests that there is little reason for dividing living tigers into these subspecies; all are nearly identical both genetically and physically. Some scientists suggest making a simpler distinction between island tigers and mainland tigers.