With their keen sense of smell, they can find food even when its buried under layers of snow. The caribou's challenge is not only to survive the winter, but to have the energy and strength they will need for the spring migration. Ironically, when the snow finally begins to melt, conditions can be worst of all. Snow that melts on warm spring days can re-freeze when temperatures drop, making it impossible to dig for food. The caribou's winter diet is predominantly lichens.
Lichens grow very, very slowly.
Because the growing season is so short, it can take several decades for a lichen to grow a few inches. This helps explain why caribou need so much room to roam. After all, the food they eat today will not grow back for many years. In the arctic, life is strong and fragile at the same time. Caribou are one of the few animals that can eat this abundant plant because of the acid it contains.