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Airdate: Mar 13, 2018
Scientist: Rolf Peterson

A Case for Predators

A Case for Predators
Without wolves, there would be nothing to control the population of moose on Isle Royale.

A Case for Predators

Ambience: Wolves howling

In the 1950's a population of wolves established itself on Isle Royal in Lake Superior. They began preying upon the moose that also inhabited the island and thus began a text book case of interdependence. It's led to one of the longest running ecological studies in history. I'm Jim Metzner, and this is the Pulse of the Planet.

Peterson: Isle Royale is such a valuable scientific site to examine predator prey interaction. It would be a shame to leave it without the predator, and most national parks, in fact, do not have large carnivores. And we've learned from Isle Royale and, more recently, from Yellowstone, how significant wolves are.

Rolf Peterson is a Professor of Wildlife Ecology at Michigan Tech University. He says that without wolves, there would be nothing to control the population of moose on Isle Royale. They would overpopulate and eventually die out.

Peterson: Without wolves, Isle Royale moose would be in desperate condition most of the time, because there wouldn't be the limits on their own density. Moose don't regulate themselves. Most herbivores don't, and carnivores around the world have been so important in limiting herbivores that herbivores are always trying to reproduce as fast as they can.

So what controls the wolf population?

Peterson: Food, ultimately, and it's not just the number of moose, which is their main prey animal, it's the number of old moose that are present.

Other factors influence the dynamic of wolves and moose - including climate.

Peterson: There've been some major climate fluctuations beginning in 1998, very hot weather in the summertime, which greatly affects moose. It takes many, many years for wolves to feel those fluctuations because they eat, for the most part, very old moose. So, if moose calves are not numerous in a certain year, it won't affect wolves that much for 10 years because moose have to be that old before wolves are able to kill them in great numbers.

We'll hear more on moose and wolves in future programs. Pulse of the Planet is made possible by the National Science Foundation. I'm Jim Metzner.