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The Wolves of
Go back to Ben Kilpela's Isle Royale Home Page For the official web site of the Moose-Wolf
Study, go to: http://www.isleroyalewolf.org/ Also, for the complete annual Moose-Wolf reports from 1996-2004, go to: http://www.dartmouth.edu/~chance/teaching_aids/books_articles/WolfReport.html This
Year's Moose-Wolf Study Report: 2004 Moose Count: just 750 in 2004, down from
900 in 2003. Wolf Count: 29 in 2004, up from 18 in 2003.
The Story: Wolves are up and moose are down this
spring at The moose population has slid to 750 on
this What's bad for moose has been good for the
wolves, and moose throughout North America have been hit hard by warmer
temperatures that began in 1998 with El Nino and never let up, according to
Professor Rolf Peterson of Michigan Technological University, who has lead
the study of Isle Royale's wolves and moose for 34
years. "What we think is happening is that
wolves are cashing in on moose vulnerability that's been induced by a warmer
climate," Peterson said. The
moose population has been stressed by higher temperatures, particularly the
drought of 1998 and then warm fall of 2001. "Moose can't feed in the
summertime if it's too hot," Peterson said. "They have a big fur
coat on, and they can't sweat. They just sit in the shade or in the
water." When moose don't eat enough in summer, they
can become weak, sickly and easy prey for wolves during the winter. And heat precipitates another
blight for the big herbivores: ticks.
"Warm weather in spring and fall leads to ticks the following
winter, and ticks can kill moose," Peterson said. A single moose can be
host to tens of thousands at a time, several per square inch, and each tick
can suck up about a cubic centimeter of blood. Rather than browse, the moose
scratch themselves against trees or bite their hair out trying to remove the
parasites. Weight and blood loss often prove such a handicap that the moose
don't survive. As the moose population struggles against
the heat and ticks, the wolves have thrived, largely because it's been easier
for them to bring down their biggest prey.
"The wolves are killing about twice as many moose as they did last
year," Peterson says, which allows them to maintain their peak
population. Initially, researchers didn't know what
warmer temperatures would mean for As to what has been causing the warmer
temperatures, Peterson cites climate models presented in the journal Science
that suggest that greenhouse gases may be the culprit. While researchers do
not have proof that increasing levels of carbon dioxide and other gases are
warming the Earth's atmosphere, the best computer models of climate can only
account for such higher temperatures if greenhouse gases are included. Peterson's study is funded by the National
Park Service, the National Science Foundation and Earthwatch. Contact information: Rolf Peterson,
906-487-2179, ropeters@mtu.edu; Marcia Goodrich, Michigan Tech media
relations manager, 906-487-2343, mtunews@mtu.edu Last
Year's Report: 2003 Moose Count: 900 this year, down from 1100
in 2002. Wolf Count: 19 this year, up from 17 in
2002. The Story: Ticks Reduce A tick infestation accounts for the changes
in the annual wolf-moose survey at Peterson, a professor of wildlife ecology
at Michigan Tech, said the 2003 survey counted 19 wolves on the island, as
opposed to 17 last year. The island's moose population decreased from about
1,100 last year to 900 in 2003. "Winter ticks will slow the moose down
for a couple of years,” Peterson said. "The tick infestation resulted from
an early, warm spring in 2001 and an unusually mild autumn that year. This
was an event that affected moose herds from The “Our objective is to understand how the
moose and wolves interact when humans are not affecting the outcome,” he
said. Peterson said there is a lag
time before the moose feel the effects of the tick infestation. The ticks
attach themselves to the moose in the fall and are on the moose all winter. “The biggest effects are in late winter as
female ticks withdraw blood to support their own reproduction in the spring,
when they drop off the moose,” Peterson said.
Weather continues to play a role in another way. The lack of snow benefits the moose,
because they can freely roam the island. A larger snowfall causes the moose
to hunker down in conifer swamps, making them easier prey for the wolves.
Typically the wolves attack old moose and young calves. "Many moose died in 1996,” he said,
“so the average moose is only five or six years old. There a lot of young
adults, which are hard moose to bring down.” The The wolf-moose study is supported by 2002
Summary on the Annual Moose-Wolf Study HOUGHTON MI -- The lack of winter weather
explains many of the changes in the annual wolf-moose survey at "The significant factor was a lack of
winter," Peterson said, referring to the very light snowfall this year.
"Moose were in places where we don't normally see them in the winter--on
hillsides and out of the conifer swamps." The Peterson said the wolves suffered a
mortality rate of almost 50 percent this winter and that last year's seven
pups kept the population near steady. The "The Typically the wolves prey on old moose and
young calves. But with little snow cover, the moose could move more freely
and avoid the wolves. "Last year, two-thirds of the kills were moose
calves," Peterson said. "This year, it was about 20 percent. The
wolves had to work hard to find a moose to kill." Peterson also said
that all three packs had breeding activity, so he expects three litters of
pups to be born in late April. While the moose have fared relatively well
this winter, Peterson says they could begin to have problems this spring and
summer. "The trend of warmer temperatures, and a warm, dry spring, could
mean an increase in tick infestation of moose," he said. High winds in
December also caused a large blow-down of the balsam firs on the western half
of the island. The moose prefer these for food. "We lost 16 percent of
the fir trees on the western half this winter," he said. "In the
last 13 years, about three-quarters of these trees have disappeared. Younger
trees can't grow because the moose are eating them. While I expect the moose
to increase over the summer, there are some big uncertainties ahead." The wolf-moose study is supported by 2001
Annual Summary Report "This winter wolves have the
advantage.... This is about as good as it gets for a wolf.'' Dr. Rolf
Peterson, Michigan Tech scientist who directs the surveys for the National
Park Service. The number of wolves on The 31st annual winter survey of wolves on
the The decline in wolves can be attributed to
inter-pack warfare and a smaller crop of moose calves in 1999. There were
fewer calves that year probably because of the hot, dry summer of 1998,
Peterson said. It's yet another example of the complex predator/prey
relationship on the island that has become a wild laboratory for Peterson and
other scientists. The relationship is considered unique because wolves are
the only predators and moose the only major prey. Peterson has tracked both
populations to see what impact changes in one species have on the other, all
in a controlled environment with little human interference. The animals can't
leave the isolated island and there are no vehicles, poachers or hunters to
affect the population. During the easy winter of 2000, wolves on "The 2000 calf crop produced between
200 to 300 animals,'' said Peterson. "And heavy
snow makes traveling tough for calves, so this winter wolves have the
advantage.... This is about as good as it gets for a wolf.'' The snow in
northern On 2000
Annual Summary Report Last year, the world’s longest running
wildlife research project – the 42nd year of the wolf and moose monitoring
program – continued during January and February of 2000, as usual. This
annual "Winter Study" project provides the best opportunities for
aerial surveying of the wolf and moose populations, with leaves off the trees
and snow on the ground. In 2000, the ISLE ROYALE WOLVES were also
doing well. Last winter, the prediction was that the wolves should continue
to hold their own in the foreseeable future, according to the completed
survey of the island's wolf and moose populations. Park Superintendent
Douglas Barnard said the island's wolf packs added five pups to the total
population during 1999, but one adult wolf was killed in 2000, leaving the
park with 29 wolves last winter. Just two years before, 1998, the population
had plummeted to 14, and biologists and park officials were concerned about
the species' continued survival. But those concerns seem to have been allayed
by the wolves' remarkable ability to withstand nature's challenges. "In general the island's wolves appear
to be in good health, and the packs are experiencing normal reproductive
success," said Barnard last winter. "We see no reason why this
trend shouldn't continue over the next few years." MTU Wildlife
Biologist Dr. Rolf Peterson, who has conducted the annual wolf/moose survey
for the National Park Service for the better part of three decades, reported
last year that there had been a realignment of pack territories on the
island. "Whereas we used to have three packs dividing the island, now
there are essentially only two," said Peterson. "The Middle Pack,
which had three surviving pups from last year and now numbers 12 animals, has
virtually taken over the former West Pack territory. The West Pack's numbers
have steadily declined, and they are simply no longer able to defend their
territory. There may be a couple of them still alive, but we haven't been
able to determine that for certain." He said there are also two other
adult pairs roaming the island, as well as a single adult wolf. The East Pack
successfully raised two pups from last year and now has 10 members, which
continue to control the east end of the island. Biologists picked up the carcass of one
wolf that succumbed to interpack warfare and
witnessed the near demise of another. "An independent adult pair of
wolves had been roaming the border area between the East and Middle Pack
territories for some time," said Peterson. "One day we were flying
over that part of the island tracking the signal from a radio collar of a
male wolf that indicated the animal had died. When we located the site from
which the signal was coming, we saw the Middle Pack standing there. Later we
returned to the area and found the carcass of a wolf where the pack had been
earlier. It turned out to be the male of the pair that had been using the
border area. It had been killed by the Middle Pack. "Two days later we were flying along
the shoreline of the island. We saw a female standing on a rock out in "When we returned to the site nearly
three hours after the attack, we noticed a lone male from the Middle Pack
casually walking along the shoreline trail. He had not been with the pack
earlier and apparently was trying to catch up with them. When he came to the
site of the battle, he became very uneasy and then noticed the body of the
female. To our surprise, when he approached her, she raised her head and
looked at him. After a while she was able to pull her forelegs up under her,
but she was still unable to stand. The male wolf then went over to a nearby
rock where he lay down and watched the female, who was in heat. "We had planned on landing at a nearby
inland lake and then hiking to the shore to pick up the female's body. When
we saw she was alive, we left the area and went to check on other wolves.
When we returned two hours later to check on the situation, both animals were
gone. We saw them again five days later about a half-mile from the battle
scene. They were standing atop a little knob, and we were able to see clearly
that the male was licking some wounds on the female's neck. We never saw them
again, so we don't know for sure whether or not she made it." Peterson also said last year that the
Middle Pack was controlling about three-fourths of the park's area, and by
taking over the west end of the island they have increased the number of
moose available to them for food. The East Pack, however, while having a
smaller territory, still maintained control over that part of the island with
the greatest number of moose. "[1999] was almost a non-winter on Go back to Ben Kilpela's Isle Royale Home Page |