Lynx and snowshoe hares.
Lynx and snowshoe hares have been studied in Canada. The lynx is a cat which feeds on snowshoe hares. Snowshoe hares are primary consumers which turn white in the winter for camouflage in order to avoid the lynx. If the frequency of hares goes down then the lynx finds it difficult to find food and the numbers of the lynx go down. This means that the frequency graph of the lynx follows that of the hare:
