It could be argued that Selawik National Wildlife Refuge contains some of the most historically significant acreage in North America, as the refuge lands once formed part of the American portion of the vast Bering Land Bridge that, some scientists speculate, was the route followed by the ancestors of many of today's large mammals, as well as early humans, when traveling between Asia and the Americas some 12,000 years ago. Today, the refuge is home to a variety of wildlife. Hundreds of thousands of caribou from the Western Arctic Caribou Herd, the largest in Alaska, travel through the refuge in spring and fall. Portions of the herd sometimes winter in the area. Moose, brown bear, wolverine and other furbearers are present year-round. Selawik's approximately 24,000 lakes and wetlands also serve as breeding or stop-over resting places for hundreds of thousands of migratory birds, some arriving from as far away as Australia. And, in addition to the sheefish that gave the refuge its name, whitefish, arctic grayling and northern pike are present in Selawik's waters.