The rich aspen parkland vegetation is an extremely productive habitat for a widely diverse and abundant wildlife. There are 44 species of mammals ranging from North America’s largest, the wood bison, to its smallest, the pygmy shrew. The white-tailed deer, coyote, snowshoe hare, mink, weasel and ground squirrel have stable populations here. The once-threatened beaver, nearly wiped out by trappers, is now thriving. In September, the bull elk can be heard bugling challenges throughout the park. In the 1700’s, plains bison roaming throughout the continent were estimated to number in the millions. By 1870, the bison was almost eliminated and other large herbivores were rare. The wood bison, whose population had fallen to almost 300 by 1891, once traversed the forested regions of northwestern Canada in great numbers. Today, to maintain a population of no more than 350 animals in the park, between 30 to 60 surplus bison are translocated each year to establish other free roaming populations in Canada. Similarly, elk, moose, and plains bison are shipped all over the continent for the re-introduction and upgrading of other herds. There are 230 species of birds in the park where the numerous kettles provide for a high density of dabbling ducks, particularly mallards, shovellers and pinwheels; red-necked grebes also nest along the shores. Beaver Hills is the most northern breeding range for mourning doves and a few black-crowned night herons, and the easternmost limit for the mountain-dwelling Barrow’s goldeneye. The great grey owl and both the three-toed and black-backed woodpecker winter here. Warblers are everywhere in the spruce and aspen forests. Living close to the ponds are the tiger salamander, wood frogs, the boreal chorus frog, the northwestern toad and the western garter snake.