Wood Bison

Wood bison are the larger of the two subspecies of modern American bison. Adult males are approximately 6 feet tall at the shoulder, 10 feet long, and weigh more than 2,000 pounds. The females are smaller, generally weighing around 1,200 pounds. The wood bison has curving horns that point upward and hair on the chin that resembles a beard. Their head and shoulders are large compared to their hindquarters, with a pronounced hump ahead of the front legs. The wood bison's hump rises almost straight up from the neck, and then slopes downward to the hips. The bone structure of this giant, forward hump has evolved in the wood bison to support a massive muscle structure that helps them sweep their head through deep northern snows to access grasses and sedges in winter. They have a dense coat of soft, durable hair that is not hollow like moose caribou and sheep, but is more like human hair. The hair color ranges from dark brown to black along the legs and lower body, to light brown along the hump. Wood bison begin to lose their winter coat as temperatures warm in the early spring. By mid-summer the coat is completely shed and has been replaced with new hair.

Plains bison (*B. bison bison*) are the other subspecies of American bison in Alaska, but only wood bison occurred naturally in Alaska. A small population of plains bison was established in 1928 near Delta Junction, thousands of miles from their natural range. Although plains bison are similar in appearance to wood bison, wood bison are on average about 15% heavier than plains bison. A wood bison's hump is taller and has its highest point forward of the front legs. The wood bison has woolly hair along its ribs, where plains bison have very short hair. The hair of the wood bison's beard, throat latch, ventral neck mane, chaps, and penis tuft are much less developed than that of plains bison. Wood bison vocalizations are different vocalizations from those of plains bison, and the wood bison's social interactions during the rut tend to be less violent than plains bison. All of these differences are evidence of the wood bison's adaptation to its northern environment: pockets of grassy meadow habitat within the sea of boreal forest, where temperatures can be quite cold and snow can be deep for extended periods. Female wood bison are sexually mature around 2 years old and can have their first calf when they are 3. They generally have a single calf, twice in every three years. Wood bison are pregnant for nine months and can give birth from April to August, with most calves born in May. Newborn calves are reddish in color, similar to moose calves. In order to evade predators, calves can stand within 30 minutes of birth and can run and kick within hours. After a week, calves will begin grazing but will continue to nurse for several months. After 10 weeks, their coats begin to darken to a deep brown by about 15 weeks of age. Wood bison are primarily grazers, mainly eating grasses, sedges, and forbs. They can also use a variety of other plants; for example, silverberry and willow leaves make up part of their summer diet. Wood bison graze in meadows, around lakes and rivers, and in recent burns. Wood bison once ranged across northwestern Canada and were also found in a large portion of Interior and Southcentral Alaska. Alaska's population was extirpated by the early 1900s, although several small herds persisted in Canada.

In 2015, 130 wood bison were released to the wild along the Innoko River near the community of Shageluk in Southwest Alaska. About 16 wild-born calves were recruited into the population in the summer of 2015. As of October 2015, the core range of these wood bison, known as the Lower Yukon/Innoko Rivers Herd, was within 30 miles of Shageluk, except for two lone bison that have explored habitats along the Yukon River from Russian Mission to Galena.