From patterns to processes: Phase and density dependencies in the Canadianlynx cycle

Across the boreal forest of North America, lynx populations undergo 10-year cycles. Analysis of 21 time series from 1821 to the present demonstrates t hat these fluctuations are generated by nonlinear processes with regulatory delays. Trophic interactions between lynx and hares cause delayed density- dependent regulation of lynx population growth. The nonlinearity, in contra st, appears to arise from phase dependencies in hunting success by lynx thr ough the cycle. Using a combined approach of empirical, statistical, and ma thematical modeling, we highlight how shifts in trophic interactions betwee n the lynx and the hare generate the nonlinear process primarily by shiftin g functional response curves during the increase and the decrease phases.