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Heres a program from our archives.For the past three decades, scientists have been studying the moose and wolf populations of Isle Royale, an isolated ecosystem off the northern coast of Lake Superior. They've found that the complex relationship between predator and prey has been slowly revealed over time. I'm Jim Metzner and this is the Pulse of the Planet.ambience, Moose We're listening to the sounds of a moose feeding. Telling us more about moose and the wolves that feed on them is Dr. Rolf Peterson, a professor at Michigan Technological University. Peterson: Our most important finding is that moose and wolves undergo a cycle of population increase and decline that takes over 30 years to unfold. And everything changes sort of in sequence. Initially, if moose are increasing, they have lots of calves that show very good survival, wolves have trouble killing them, but eventually moose build up to the point where their own welfare is sacrificed. They have less to eat per moose, old moose accumulate in the population. Old moose are very important to wolves because they're the easiest ones to kill. Wolves have more and more food, and as they have more and more food, their numbers increase. And so the moose population comes tumbling down over a period of many years. And finally it reaches such a low level that the wolves have basically run out of food themselves and then the wolves decline, and then moose start all over again. The whole thing takes about 30 years. And we didn't even glimpse the character of this so-called cycle until we were near year 25 or so.This archival program is part of our thirtieth anniversary celebration. If you want hear more, check out our podcast.