Isle Royale National Park's inbred gray wolf population remains
dangerously low for a third consecutive year, while the moose on which
they feed have doubled during the same period — trends that could lead
to long-term problems for the Lake Superior archipelago's ecosystems,
scientists said Wednesday.
Only nine wolves roamed the park this winter — one more than the eight
recorded last year, which was the lowest total since wildlife biologists
began observing the relationship between Isle Royale wolves and moose
in the late 1950s. The study is the world's longest of a predator-prey
relationship in a closed ecosystem. "The wolves are struggling," said Rolf Peterson, a research professor
with Michigan Technological University and co-director of the study.
"There's definitely a chance they might not last much longer."
Meanwhile, the moose population rose to about 1,050, according to a
report by Peterson and co-director John Vucetich obtained by The
Associated Press ahead of its scheduled release. That is a sharp jump
from the 515 counted in 2011.
The wolf's decline on the island chain comes as its numbers in the
nearby states of Minnesota, Michigan and Wisconsin are also falling —
but for entirely different reasons. The mainland population had risen so
dramatically in recent decades that it exceeded 4,000 in the three
states by 2012, leading the U.S. Fish and Wildlife Service to remove
Great Lakes wolves from the endangered species list.
Since then, the three states have allowed managed hunts and their
combined total has fallen to roughly 2,900. But officials say the
populations are healthy and thriving, in contrast to Isle Royale's
beleaguered remnant.
Wolves and moose are relatively recent arrivals to the 45-mile-long
park, which consists of one large island and hundreds of smaller ones.
Moose made their way there in the early 1900s, possibly by swimming 15
miles from Canada. Wolves are believed to have wandered there in the
late 1940s over a winter ice bridge.
The moose have given the wolves a reliable food supply, while the wolves
have culled weaker members of the moose herd and prevented it from
getting too large. Wolf numbers have averaged about 23 over the years.
But with the recent slump, their ability to limit moose growth is
virtually nonexistent and will remain so for at least several more
years, Vucetich said.
Demonstrating the wolf's declining influence, moose numbers rose from
975 last year to 1,050 despite a severe winter that limited the
herbivore's access to the balsam fir that is its primary cold-weather
food source.
The deep freeze interrupted what had been a warming trend in the region.
If that longer-term pattern returns and the next few winters are mild,
the moose population may skyrocket, Vucetich said. At some point, they
may reach the point where they're severely over-browsing island
vegetation, which has happened before.
In the 1990s, following another wolf decline, moose numbers reached
about 2,400, leading to mass starvation during the harsh winter of 1996,
when about two-thirds of the moose died. "We know enough right now to know that moose are heading in that
direction and it may not be long before they start causing damage to
vegetation," Vucetich said.
He and Peterson are lobbying the National Park Service to bring more
wolves to the island to refresh the gene pool. They say there is growing
evidence that the wolves have lasted because newcomers periodically
crossed ice bridges and mated with island wolves. Analyzing decades of
field notes, they recently concluded that a pack of seven or eight
wolves migrated to Isle Royale in 1967. A lone male immigrant in 1997
had such an effect that by 2008, most of the island's wolves were his
descendants.
But ice bridges are forming less frequently, lowering the odds that more
wolves will arrive on their own, the scientists said. Although ice
provided a pathway for 25 days this winter, no wolves are believed to
have traveled to the island and one used the occasion to escape, only to
be shot dead on the mainland.
Park Superintendent Phyllis Green announced this month that officials
had decided not to intervene as long as a breeding wolf population
remains. Meanwhile, the agency will conduct a new environmental impact
study on moose and their effects on the forest, as well as their
relationship with wolves. "Bringing wolves to the island remains an option," Green said. "However,
the final decision will be based on the best available sound science,
accurate fidelity to the law and long-term public interest."
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