For almost 60 years, scientists have been examining the relationship between wolves and moose on Isle Royale National Park in the longest continuous predator-prey study in the world. Moose likely came to Isle Royale, an island about 580 square kilometers in size in Lake Superior, in the early 1900s by swimming from the mainland. Without any predators around, the population shot up and then crashed in 1934 from starvation. A wolf population was established on the island in the late 1940s, probably after crossing an “ice bridge” from the mainland. In 1958, scientists started monitoring the cyclical rise and fall of moose and wolf numbers, with one population influencing the other, but also responding to other factors, such as disease, tick outbreaks, severe winters, and immigrant wolves. The wolf population grew to as many as 50 individuals in 1980, and 24 wolves lived on the island as recently as 2009 (when the photo was taken). But numbers have been steadily declining as a result of inbreeding caused by lack of wolf immigration over the ice in recent winters. Climate change has resulted in a steady reduction in ice cover over the Great Lakes. Currently, the wolf population is down to two individuals and destined to disappear. Without wolves, the already-large moose population is on track to double in the next few years and decimate the native vegetation. The National Park Service will soon decide whether to introduce 20 to 30 new wolves to the island.
The wolf pup was photographed on Isle Royale from a small airplane, using a telephoto lens.
Rolf Peterson, PhD, School of Forest Resources and Environmental Science, Michigan Tech., Houghton, MI