Peter Mather / Caribou (Rangifer tarandus) porcupine herd in winter near Dempster Highway, Yukon, Canada

Peter Mather / Caribou (Rangifer tarandus) porcupine herd crossing Blow River, Yukon, Canada

Peter Mather / Caribou (Rangifer tarandus) porcupine herd crossing river valley, Yukon, Canada

Peter Mather / Caribou (Rangifer tarandus) newborn calf nuzzling mother, of the porcupine herd, Arctic National Wildlife Refuge, Alaska

Peter Mather / Caribou (Rangifer tarandus) mother and newborn calf, of the porcupine herd, Arctic National Wildlife Refuge, Alaska

Peter Mather / Yukon River outside of Dawson City, Yukon, Canada

Peter Mather / River flowing through valley in autumn, Tombstone Mountains, Tombstone Territorial Park, Yukon, Canada

Peter Mather / Lowell Glacier and Alsek Lake, Kluane National Park, Yukon, Canada

Peter Mather / Winding river in boreal forest, Yukon-Charley Rivers National Preserve, Alaska

Peter Mather / Kathleen Lake beneath Kings Throne mountain, Kluane National Park, Yukon, Canada

Peter Mather / Northern lights reflecting in pond, Ogilvie Mountains, northern Yukon, Canada

Peter Mather / Canoe in Chilkat River, southeast Alaska