Houghton - April 3,
2009
by Jennifer Donovan,
director of public
relations
The wolves on Isle
Royale are suffering
from genetically
deformed bones.
Scientists from Michigan
Tech blame the extreme
inbreeding of the small,
isolated wolf population
at the island national
park in northern Lake
Superior.
Researchers have
collected the first
scientific evidence that
inbreeding has caused
genetic deterioration of
the bones of the wolves
of Isle Royale. Rolf
Peterson and John
Vucetich of Michigan
Tech and their
colleagues, Jannikke
Raikkonen of the Swedish
Museum of Natural
History and Michael P.
Nelson at Michigan State
University, report on
the congenital bone
deformities in the
latest issue of the
journal Biological
Conservation.
The scientists found
that 58 percent of the
wolves on Isle Royale
exhibit a congenital
malformation in the
lumbosacral region, or
lower back, and 33
percent display a
specific deformity--lumbosacral
transitional
vertebrae--which can
cause full or partial
paralysis of the rear
legs and tail, as well
as back pain. It is a
condition also seen in
domestic dogs. Other
malformations were found
in the wolves as well.
For the last 12 years,
every one of the dead
wolves the researchers
have found has displayed
bone deformities. In
contrast, these
deformities occur in
only 1 percent of
studied wolf populations
that are not inbred.
"Until recently, we
didn't know if the
inbreeding was causing
problems for the
wolves," says Vucetich.
"There is now good
reason to think that
Isle Royale wolves have
been suffering from
genetic deterioration
due to inbreeding," the
researchers say in their
journal article.
Peterson and Vucetich
head a study of wolves
and moose on Isle Royale
that has been ongoing
for more than 50 years.
The four packs there
comprise 24 wolves, all
descended from one
female and one or two
males who crossed an ice
bridge from Canada
during an unusually cold
winter in the 1940s.
Since then, they have
been isolated on the
islands that make up
Isle Royale National
Park.
Winter Study 2009
Each winter since 1959,
researchers have been
tracking and observing
the wolves and the moose
that are virtually their
only prey. During this
year's winter study,
Vucetich and Peterson
found two dead wolves
with misshapen
vertebrae, one killed by
other wolves and the
other, which also had
severe arthritis, frozen
under the ice of a lake.
This was a particularly
cold, hard year on the
wolves and moose of Isle
Royale. The researchers
counted 24 wolves, close
to the long-term average
population size, but two
of the four wolf packs
did not have any pups
that survived, Vucetich
reported. East Pack's
numbers declined to a
sole surviving female
who has taken a new mate
from one of the other
packs.
The researchers
estimated the moose
population at 530 this
winter, a decrease from
last year and not even
half the average
long-term population
size.
Not only are fewer moose
surviving, making food
harder for the wolves to
find, but the wolves are
having to hunt older,
more arthritic moose,
Vucetich and Peterson
found. Three years ago,
the average age of a
moose killed by a wolf
on Isle Royale during
the winter was 12 years
old. Two years ago, it
was 13, and now it is
14.
Atypically, the wolves
didn't kill any moose
calves this winter,
although calf numbers
were low, "so the wolves
probably didn't save any
for the winter," said
Vucetich. In fact, a
pair of moose calf twins
both survived, a rare
occurrence.
Genetic Rescue?
"What we learned raises
the question of whether
the wolves of Isle
Royale should be
genetically rescued,"
Vucetich said.
Up to now, wildlife
management agencies in
the US and Scandinavia
have cited the Isle
Royale wolves as proof
that small wolf
populations can avoid
genetic deterioration
and remain viable.
"Our study removes one
more example that some
use to downplay the
consequences of genetic
deterioration," the
Swedish scientist
Raikkonen says.
Whether to intervene is
a question that should
be revisited, the
researchers suggest.
They are inviting the
public to weigh in on
the matter, through a
blog on their Isle
Royale Wolf-Moose Study
website,
www.isleroyalewolf.org
The decision is
complicated, Vucetich
observes. "It involves
balancing values
associated with
wilderness, scientific
knowledge, healthy
ecosystems and animal
welfare," he points out.
"If only one value
mattered, the decision
would be easier, but
here the values are
competing."
Adds Peterson, "This is
not a decision just for
scientists to make any
more." |