There are stretches of Alaska tundra holding 12 million mosquitoes per acre. Twelve million. A 900-pound bear that cannot sweat has every reason to find a snow patch. That is the first of four reasons brown bears spend their summers above the tree line.Reason one is bugs. Alaska has 35 species of mosquitoes, more than any other state. Caribou and moose flee to snowfields and windy ridges to escape the swarms. Bears do the same. Cold air sitting on snow grounds the swarm. Without that escape, a s