One of the fundamental rhythms of the boreal forest is the dependable 10-year-long population cycle of the snowshoe hare. Diminutive though they may be, snowshoe hares are the dominant plant-eating animals of the boreal forest. They triumph through their enormous capacity to reproduce; each summer, a female hare can produce as many as four litters of 8 to 18 young! Over the course of the 10-year cycle, hare populations in the forest remain low for about three years, then begin to grow quickly until they peak and then suddenly crash.

Predators are a chief reason the snowshoe hare population periodically crashes. Snowshoe hares are a favorite, and sometimes the sole, prey of predators from lynx, red fox, hawks and owls to red and arctic ground squirrels (the squirrels prey on newborn hares). Populations of these animals -- especially lynx -- tag along just behind the rising curve of the hare population; eventually there are enough predators to outstrip the hares' reproductive abilities, and in short order these animals nearly clear the woods of hares. As this primary food source grows scarce, predator populations begin to plummet, and the cycle begins anew.

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Photo: Alan and Sandy Carey, courtesy Northwest Ecosystem Alliance