Isle Royale is located in the northwest portion of Lake Superior. It is ~50 miles long and ~8 miles wide.
Isle Royale is home to a population of wolves and moose. These wolves are the sole predator of the moose, and moose represent ~90% of the wolves’ diet.
The wolves, the moose, and their interactions have been studied continuously and intensively since 1958. This is the longest study of any predator-prey system in the world. more...
The moose of Isle Royale
The wolves of Isle Royale
Studying the wolves and moose on Isle Royale
Wolves first came to Isle Royale in about the year 1950. They arrived by walking on an ice bridge from Canada. In a typical year, Isle Royale has ~24 wolves living in three packs.
The challenge in a wolf’s life is to get enough food to survive another season. The food they eat - moose - is dangerous to kill and not always plentiful.
The setting - Isle Royale
Moose first came to Isle Royale in about the year 1900. They probably swam to Isle Royale. In a typical year, Isle Royale has ~1000 moose. Except for the close bond between cow and calf, moose live solitary lives.
During the summer moose eat enormous amounts of food (~40 lbs per day). They feed on the leaves of dozens of herbs, ferns, shrubs and trees. During the summer a moose will increase its body weight by ~25%. All of this weight is lost each winter.
Every summer we spend time on Isle Royale. We observe moose forage, assess the impact of moose ticks, perform necropsies on moose carcasses, measure vegetation upon which moose depend, collect wolf scat (for DNA) and moose scat (for diet analysis). We share much of these experiences with volunteers whose work is invaluable to the project.
What have we learned?
Moose bones
Although splendidly adapted to the lives they experience, the life of a wolf is difficult in ways that may be beyond most of our imaginations. While a wolf is able to live for 12 years, most die before their 4th birthday. The most common causes of death are starvation and being killed by other wolves. When wolves kill wolves they are - ultimately - fighting over food. more...
As with wolves, moose are splendidly adapted to the lives they experience. However, being a moose is far from easy. Although the maximum life span of a moose is ~17 years, most moose die before reaching 9 years of age. The difficulties of being a moose are numerous... avoid being killed by wolves, endure loads of blood-sucking and life-draining ticks, feed in the summer heat that moose find sweltering... more...
Every winter from mid-January to early-March, we count the number of wolves and moose on Isle Royale. We also estimate rates at which wolves kill moose and perform necropsies on wolf-killed moose. Most of these observations are made from a small aircraft that lands on a frozen harbor on the shores of Isle Royale. During the winter field study we share our field notes on line. Look for this to appear in mid January 2008.
Scat
Decades of effort have produced the world’s largest collection of moose bones. We have bones of more than 4500 different moose. These bones represent as much mystery as they do knowledge.
From these bones, we learn the age of death and the some aspects of its health at the time of death. Moose bones are records of, for example, whether it has jaw necrosis, arthritis, osteoporosis.
Through knowledge of a moose’s health at the time of its death we learn a great deal about moose population dynamics and the influence of predation on moose dynamics. more...
Wolf scat is also an increasingly important source of information about Isle Royale wolves. We find wolf scats on trails and at kill sites. When we find a scat we place a tiny bit in a storage tube. Later, in the lab, we extract DNA and a DNA “fingerprint” from each sample. Because we collect and analyze hundreds of scat, we just about guarantee getting a DNA fingerprint from every wolf in the population...
more details coming in late Sept 2007
Some other important members of the Isle Royale community
When wolves kill a moose, the result is a carcass that is ten times the size of any wolf. Ravens depend importantly on moose carcasses, and wolves lose significant portions of their carcasses to ravens. But the connections between wolves and ravens are much deeper. more...
Wolves, moose, Isle Royale... they represent an intricate, dynamic, interconnected set of relationships. Observing that which is beautiful inspires wonderment and respect... more
Moose scat (a.k.a. poop) is becoming an increasingly important source of information about moose. During the winter time, moose eat needles and twigs of balsam fir and cedar, and twigs of deciduous trees and shrubs, such as aspen and hazel. From this coarse diet, moose deposit scat that looks up-close a bit like saw dust packed into little pellets. These saw-dust-like particles - all that’s left of twigs and needles - are identifiable as belonging to one species or another under a microscope... more
Isle Royale foxes are also inextricably tied to the dynamics of wolves and moose. During the summer, foxes have a varied diet - insects, squirrels, hares, fruits, and hand-outs from backpackers. However, during the winter, moose carcasses are an important source of food for foxes
more to come soon ...
image by G. Desort
image by G. Desort
Albipictus dermicentor is the scientific name for a species of tick also know as the moose tick or winter tick. This tick has a particular life style - it is active in the winter and bothers only members of the deer family - like moose.
These ticks - each the size of your fingernail - likely have a profound effect on the entire Isle Royale community. Ticks weaken moose, and this effect translates into effects on wolves and how the forest grows... more
Red squirrels depend importantly on the seeds of spruce cones. Because spruce is one of the few species that moose do not eat, spruce has gradually become more abundant over the years. The century long increase in spruce abundance has likely resulted in an increase in squirrel abundance.
While the summer diet of moose is diverse and relatively rich, the winter diet is not. During winter, balsam fir comprises 30-60% of a moose’s diet. Balsam fir is not very nutritious, but is it relatively abundant - so moose eat it. Because balsam fir is such an important part of a moose’s winter diet, the moose and forest are connected importantly through balsam fir ... more
Isle Royale’s wolves and moose have been valuable for informing us about the limits of our ability to predict and understand natural systems, the nature of predation, and many particulars about why and how wolves and moose are the way they are. To learn details about some of our discoveries over the years continue reading below...
return to... wolf-moose home
The deer mouse
more to come soon...
Copyright © John A. Vucetich — All rights reserved
Why do we do it?
