CHAOS AND STABILITY IN RODENT POPULATION-DYNAMICS - EVIDENCE FROM NONLINEAR TIME-SERIES ANALYSIS

I explore the possibility that the dynamics of some vole populations may be chaotic. Using an approach based on response surface methodology for quantifying chaos in short data sets, I have analyzed 11 temperate and 23 northern time series documenting microtine population fluctuations. I found that temperate populations were characterized by negative Lyapunov exponents, implying stability. In northern populations, by contrast, 15 of 23 estimated Lyapunov exponents were positive. This result suggests that nonlinear endogenous dynamics of northern voles amplify exogenous noise, thus contributing to erratic jumps in their population density.