The Amur tiger is a subspecies of tiger which once ranged throughout Western Asia, Central Asia and eastern Russia, though it is now completely confined to the Amur-Ussuri region of Primorsky Krai and Khabarovsk Krai in far eastern Siberia, where it is now protected.
It is the biggest of the eight recent tiger subspecies and the largest living felid, attaining 320 kg in exceptional specimens.
Amur tigers reach sexual maturity at four years of age. They mate at any time of the year. A female signals her receptiveness by leaving urine deposits and scratch marks on trees. She will spend a week with the male, during which she is receptive for three days. Gestation lasts from three to 3½ months. Litter size is normally three or four cubs but there can be as many as six. The cubs are born blind in a sheltered den. Cubs are divided equally between genders at birth. However, by adulthood there are usually two to four females for every male. The female cubs remain with their mothers longer, and later they establish territories close to their original ranges. Males, on the other hand, travel unaccompanied and range farther earlier in their lives.
Source: en.wikipedia.org/wiki/Siberian_tiger - 07.05.2010