During a cold winter in the late 1940s, wolves made a 20-mile journey
across an ice bridge that had formed between the North Shore of Lake
Superior and Isle Royale.
Ever since, their descendants have lived and died on the wooded
island in sync with the moose that became their prey, in a natural drama
that would become the longest and most famous predator study ever
conducted.
But soon it could end.
Only nine wolves are left on Isle Royale, the lowest number ever recorded. Only one is known to be female.
Now the National Park Service faces a precedent-setting decision:
Whether to preempt nature and bring in new wolves to replenish the pack
in the nation's wildest national park, or to stick with a longstanding
hands-off philosophy that guides its mission in all national parks --
even if that means extinction for the wolves of Isle Royale.
That ethically complex decision will ripple across the entire
National Park system, according to Phyllis Green, superintendent of Isle
Royale. Many of the country's most treasured natural places are
becoming islands, ringed in by development, private landowners and
agriculture. All are affected by global warming, invasive species and
pollution, she said.
"The hand of man is everywhere in this world," she said. "If an
island is being turned into an ark, which animals get invited onto the
boat?"
Yet even debate itself is an acknowledgement that the island and its
wolves are now largely symbols of an untouched wilderness that no longer
exists. The wolves have declined in part because, thanks to global
warming, ice bridges are now exceedingly rare. Roads and development
along Lake Superior's North Shore act as a barrier to all wildlife that
might wander across the few that form. And a disease that almost wiped
out the wolves in the 1980s was somehow brought to the island by humans
or their dogs.
"The idea of pristine nature being out there is no more," said Doug
Smith, a biologist who runs the wolf program at Yellowstone National
Park. "You have to have more intervention if you want to keep this
looking like it used to. It's a sad fact, to be honest."
Prey and predator
No one knows how moose got onto Isle Royale. Presumably, researchers
say, they either swam or were brought there by humans sometime in the
early part of the 20th century. Without the predators they faced on the
mainland, their numbers soared to 3,000 or more within a few decades,
decimating the vegetation on the 206-square-mile island before they
crashed from starvation in the 1930s and again in the 1940s.
The cycle was so bad that managers of the island, which became a
national park in the 1930s, contemplated bringing in wolves to control
the moose -- while protecting them from a wolf extermination campaign
then underway across the country. In 1952, four captive-raised wolves
were brought to Isle Royale, even though wild wolves already had arrived
on their own.
Three of the captive wolves were killed or removed after they became a nuisance, and the fourth disappeared.
But the wild wolves flourished. Their success was documented starting
in 1958 by Durward Allen, a Purdue University ecologist, who recognized
the opportunity to study a perfect choreography of predator and prey in
a bubble. There are no deer on the island, and smaller prey is limited.
Moose make up 90 percent of the wolves' diet.
The two species kept each other in check for decades. Wolf numbers
averaged 25, rising at one point to nearly 50. Rolf Peterson, a
professor at Michigan Technological University in Houghton, Mich., took
over the research in the 1970s.
Ten years later, the wolves were struck by parvovirus, a disease
carried by dogs, and their number plummeted to 12, triggering concerns
that the now-famous predators might go extinct. At that point, the Park
Service first agreed to allow researchers to capture, test and
radio-collar some of their subjects to better understand what was going
on.
But in 1998, another wolf crossed the ice, an extraordinary event
that researchers only discovered later through genetic analysis. He
became the alpha wolf with remarkable affect. "His new genes were far
superior," Peterson said. "He perked things up dramatically."
In the past decade, moose have declined by half on the island, likely
as a result of warmer summers and winters, researchers say. That,
combined with more disease and perhaps unidentified problems related to
inbreeding, again pushed wolf numbers down to 21 by 2007, then 16 in
2011. And now nine.
A debate and a bet
Peterson said the only wolf he knows for sure to be female has almost certainly mated. "We saw the tracks in the snow," he said.
If she produces a litter at the end of the summer, and if one or more
of the pups is female, then the wolves' fate could change, he said.
David Mech, a wolf researcher for the U.S. Geological Service, said
he thinks it's premature to worry about their demise and what do about
it. "I'm betting on the w
lves."
Nevertheless, the question has touched off a debate among
naturalists. Other researchers, including Peterson, say that nine wolves
might not prevail even if new females are born this year.
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