Caribou Food
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The 160-thousand caribou in the porcupine herd migrate through Alaska and Canada. They munch on lichen in the winter. But as summer nears, they head for the arctic coastal plain hoping to arrive in time for green-up. Amy Mayer explains.

Amy: "The caribou aim to reach their coastal birthing ground by mid-June. Dave Klein, a retired biologist from the University of Alaska Fairbanks, says the females need to get there before the young are born.'

Dave Klein: "The calves aren't gonna be up to traveling across the flooded rivers and stuff after break-up so they need to get there before breakup."

Amy: "And, Klein says, the moms want to time it so they arrive just as the best food is springing up."

Dave Klein: "Shortly after the calves are born is the time of greatest physiological stress or demand on the female, they have to produce milk for a rapidly growing calf and they need high quality food. So they're going to be right there at the time that green-up is occurring and the food is the highest quality."

Amy: "UAF Plant biologist Skip Walker says the caribou eats what's available, but that green-up broadens its fare."

Skip Walker: "It feeds on cotton-grass early in the season when there's nothing else available, it's the only plant that has any flowers and they feed on the nutrient rich flowers of that plant and then later in the season they change over to other species that have greened-up at that point the willows and many of the forbes, the flowering plants, the typical bright (edit) flowers that we see on the tundra. Caribou like a lot of those."

Amy: "In the SUB-arctic, some caribou actually migrate UP in summer, searching for tundra-like conditions at the higher altitudes."

Correspondent Amy Mayer lives in the sub-arctic city of Fairbanks. Tomorrow she tells us how humans enjoy the midnight sun.