The oldest definitively identified tiger fossils date to roughly two million years ago and were found in China, which is where many scientists believe the species first evolved and then disseminated itself across Asia.
The tiger is the largest member of the cat family, with the Amur tiger being regarded as their largest representative. Nine different subspecies are recognised, three of which became extinct in the latter part of the 20th Century; the Bali (P. t. balica), Javan (P. t. sondaica) and Caspian tigers (P. t. virgata). The remaining subspecies are the Amur (P. t. altaica), South China (P. t. amoyensis), Sumatran (P. t. sumatrae), Indochinese (P. t. corbetti), Malayan (P. t. jacksoni) and Bengal tigers (P. t. tigris). The different subspecies vary in their body size, coat colour and markings, with the Sumatran tiger being the smallest and darkest, whilst the Amur tiger is the largest and palest subspecies. Markings and coat colour can overlap between subspecies and are not often used to differentiate. Generally however, tigers have a reddish-orange to yellow-ochre coat with a white belly and black markings, the pattern of which is unique. Like the other big cats, tigers are well adapted for hunting large prey and have short, heavily-muscled forelimbs and long, sharp, retractable claws.
Tigers have a bad reputation of being man-eaters, and it must be said that tigers have taken a ferocious toll on humans. Some scholars estimated that tigers have killed approximately a million Asians over the last four hundred years. The majority in India, but heavy losses were suffered in East Asia, too.
Tigers are likely to forage optimally when taking the largest prey that can safely be killed, often ungulates their own size or larger. Nevertheless, Amur tigers have been reported eating everything from eagles to seals to brown bears. In the Sikhote-Alin area, where about 90% of Amur tigers can be found, the most preferred prey are red deer and wild boar. Probably due to climate changes, Sika deer are replacing red deer in the coastal area of the Sikhote-Alin. This may not be beneficial for the tiger population.
Tigers demonstrate a spacing system in which females defend territories that overlap little with neighbouring females, and males defend territories that include one to nine tigresses. Depending on prey abundance the home range size of tigresses vary between 440 km2 (Amur tiger, Sikhote-Alin) to 21 km2 (Bengal tiger, Chitwan National Park), which equalises the total prey biomass per female home range. Without the constraints of rearing cubs, home ranges can increase to ensure sufficient availability of prey, like male Amur tigers maintain home ranges on average in excess of 1000 km2.
In historical accounts the Amur tiger descriptions always refer to the enormous size of the animal. Larger than any other tiger species. This no longer seems to be the case. Scientists have speculated that this has been caused by hunting. When it was still allowed, sport hunters eagerly killed the biggest Amur tigers. This, together with the decreasing number of reproductive animals, reduced the possibility of 'large gene' transfer, with one result being that postwar specimens no longer seem to be much larger than Bengal tigers.