Wolves on Isle Royale National Park in Michigan are threatened by the disappearance of an ice bridge, scientists say. The bridge used to form routinely in winter, allowing wolves on the island and the mainland to mingle. In recent years, however, temperatures have warmed and the bridge fails to materialize most of the time, The Detroit News reported Saturday. That means the Isle Royale wolves have become too inbred. There were 50 wolves on the island in 1980 but this year the population is down to eight. \"This last year was the first in more than four decades of monitoring that we haven\'t been able to detect any evidence of reproduction,\" said John Vucetich, a population biologist at Michigan Technological University. Scientists say the situation would be worse except for a wolf nicknamed the Old Gray Man. He got to the island in 1997, enlarging the gene pool. Ironically, while wolves are disappearing from Isle Royale they are flourishing in the Upper Peninsula. That has led to a political battle this year about whether to allow the state\'s first wolf hunt in many years. Wisconsin and Minnesota initiated wolf hunts in the past year.