The Siberian tiger once inhabited much of the Korean Peninsula, Manchuria, and other parts of northeastern China, the eastern part of Siberia, and the Russian Far East, perhaps as far west as Mongolia and the area of Lake Baikal, where the Caspian tiger also reportedly occurred. During the late Pleistocene and Holocene, it was likely connected to the South China tiger population through corridors in the Yellow River basin, before humans interrupted gene flow. Today, its range stretches south to north for almost 1,000 km (620 mi) the length of Primorsky Krai and into southern Khabarovsk Krai east and south of the Amur River. It also occurs within the Greater Xing'an Range, which crosses into Russia from China at several places in the southwest of Primorsky Krai. This region represents a merger zone of the East Asian temperate broadleaf and mixed forest and the taiga, resulting in a mosaic of forest types that vary in elevation and topography. Key habitats of the Siberian tiger are Korean pine forests with a complex composition and structure. The faunal complex of the region is represented by a mixture of Asian and boreal life forms. The ungulate complex is represented by seven species, with Manchurian wapiti, Siberian roe deer, and wild boar being the most common throughout the Sikhote-Alin mountains, but rare in higher altitude spruce-fir forests. Sika deer are restricted to the southern half of the Sikhote-Alin mountains. Siberian musk deer and Amur moose are associated with the conifer forests and are near the southern limits of their distribution in the central Sikhote-Alin mountains. In 2005, the number of Amur tigers in China was estimated at 18–22, and 331–393 in the Russian Far East, comprising a breeding adult population of about 250, fewer than 100 likely to be sub-adults, and more than 20 likely to be less than 3 years of age. More than 90% of the population lived in the Sikhote Alin mountain region.