Scientists who for decades have studied the delicate prey-predator balance between moose and wolves on Lake Superior's Isle Royale believe global warming -- by giving an assist to blood-sucking bugs -- ultimately could deal a deathblow to the national park's wolf population. Since 2002, the number of moose on the island has declined from 1,100 to 385, following a dramatic increase in winter ticks. The insects infest the moose, suck their blood and weaken them, making them easy prey for wolves.
If warmer temperatures persist -- causing ticks to keep increasing -- the wolves could die out because there won't be enough moose, their main food source, said John Vucetich, a biologist at Michigan Technological University. He spends nearly half the year on Isle Royale studying the creatures.
The island's wolves -- down to 21 from 30 in 2006 -- have faced other challenges over the past quarter century, including parvovirus in the 1980s, which brought their numbers from dozens to 12 within a span of several years. But losing the species' main meal ticket could be fatal. "The changes are dramatic," Vucetich said. "Humans have made temperatures increasingly hot, which exacerbates the number of ticks." And there's nothing scientists can realistically do to curb the ticks.
Vucetich's findings are the latest evidence in Michigan of global warming, already implicated for the disruption of species in North America and the Great Lakes states. Among other changes, opossums and white-footed mice are moving north, migratory birds are arriving earlier, and sugar maple sap is flowing sooner. Lower water levels in the Great Lakes also are believed to be linked to reduced ice cover, leading to greater evaporation.
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http://www.freep.com/apps/pbcs.dll/article?AID=/20070827/NEWS06/708270367/1048/COL08
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