Caribou in Kobuk Valley National Park, Alaska, USA

© Staffan Widstrand/Minden Picture

Peak travel season. Traffic jam on the caribou highway

Today we're in Kobuk Valley National Park in Alaska, USA, to witness one of the world’s great annual migrations. Every spring, a 250,000 caribou come together to form the Western Arctic Herd and pass north through the 1.8 million-acre park to their summer calving grounds in the Brooks Range and its foothills. Then in the fall, the herd makes the reverse trip, heading south back through the park to where they spend the winter in the Nulato Hills and the Seward Peninsula. One of the best spots to see the herd on the move is when they cross the Kobuk River at Onion Portage. This area is a major archeological site too. For thousands of years, the crossing has drawn native groups that relied on caribou meat, a tradition that continues to this day.