Between 2003 and 2007, Population Of Alaska's Largest Caribou Herd Dropped 20% - ADN

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Alaska's largest caribou herd shrank by more than 20 percent between 2003 and 2007, according to a new count from the state Department of Fish and Game. The Western Arctic Caribou Herd -- which ranges from the North Slope to Eastern Norton Sound and from the Chukchi Sea to the Koyukuk River -- declined by 113,000 animals after years of steady growth.

The herd is still twice the size of any other caribou herd in Alaska. It's a crucial source of subsistence hunting for dozens of villages, a major moneymaker for businesses that cater to sport hunters and a key link in the area's food chain, said Jim Dau, the state's lead biologist on the herd since 1988. So why did it shrink? That's not quite clear, but warm spells in the middle of recent winters may have played a role, Dau said.

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It could be that the recent decline is a natural occurrence as disease, predators and a shortage of food combined to thin the high numbers. But, Dau said, "I'm not absolutely sure that that's what happened here." That's because the herd suffered at least one particularly tough winter since the last census. In 2005, just before Christmas, temperatures grew unseasonably warm for four days -- including two days of rain, Dau said. After the rain came freezing temperatures, which covered the ground in an iron-hard crust of snow, he said. The caribou struggled to find food and died in droves.

In 2007 came another warm spell during the winter. This time, however, instead of another large die-off, the herd thrived as extended warm temperatures and high winds swept away the snow. Climatologists predict these mid-winter thaws -- which present a fine line between good times and disaster for caribou -- will only become more common, Dau said.

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http://www.adn.com/wildlife/story/409757.html