mammals, 130 species of fish, and an estimated 32,000 species of insects. Insects play a critical role as pollinators, decomposers, and as a part of the food web. Many nesting birds, rodents, and small carnivorous mammals rely on them for food in the summer months. The cold winters (and short summers) make the taiga a challenging biome for reptiles and amphibians, which depend on environmental conditions to regulate their body temperatures; there are only a few species in the boreal forest, including red-sided garter snake, common European adder, blue-spotted salamander, northern two-lined salamander, Siberian salamander, wood frog, northern leopard frog, boreal chorus frog, American toad, and Canadian toad. Most hibernate underground in winter. Fish of the taiga must be able to withstand cold water conditions and be able to adapt to life under ice-covered water. Species in the taiga include Alaska blackfish, northern pike, walleye, longnose sucker, white sucker, various species of cisco, lake whitefish, round whitefish, pygmy whitefish, Arctic lamprey, various grayling species, brook trout (including sea-run brook trout in the Hudson Bay area), chum salmon, Siberian taimen, lenok and lake chub. The taiga is mainly home to a number of large herbivorous mammals, such as Alces alces (moose), and a few subspecies of Rangifer tarandus (reindeer in Eurasia); caribou in North America). Some areas of the more southern closed boreal forest have populations of other Cervidae species, such as the maral, elk, Sitka black-tailed deer, and roe deer. While normally a polar species, some southern herds of muskoxen reside in the taiga of Russia's Far East and North America. The Amur-Kamchatka region of far eastern Russia also supports the snow sheep, the Russian relative of the American bighorn sheep, wild boar, and long-tailed goral. The largest animal in the taiga is the wood bison of northern Canada/Alaska; additionally, some numbers of the American plains bison have been introduced into the Russian far-east, as part of the taiga regeneration project called Pleistocene Park, in addition to Przewalski's horse. Small mammals of the taiga biome include rodent species such as the beaver, squirrel, chipmunk, marmot, lemming, North American porcupine and vole; as well as a small number of lagomorph species, such as the pika, snowshoe hare and mountain hare. These species have adapted to survive the harsh winters in their native ranges. Some larger mammals, such as bears, eat heartily during the summer in order to gain weight, and then