Overcompensation and phase effects in a cyclic common vole population: between first and second-order cycles

Area of Science:

• Ecology
• Population Dynamics
• Mathematical Biology

Background:

• Population cycles in voles are often attributed to one-year delayed density dependence.
• Some research suggests common vole populations may exhibit first-order cycles due to strong overcompensation.

Purpose of the Study:

• To investigate the mechanisms driving a 3-year population cycle in a common vole (Microtus arvalis) population in western France.
• To compare overcompensating nonlinear models with traditional second-order models for explaining population dynamics.

Main Methods:

• Fitting several overcompensating nonlinear population dynamics models (Hassell, Maynard-Smith, Slatkin) to common vole population data.
• Analyzing the role of direct density dependence (DD) and delayed density dependence in population crashes.
• Investigating phase-driven modulation of direct density dependence.

Main Results:

• Overcompensating direct density dependence adequately describes winter population crashes.
• One-year delayed density dependence was not responsible for the observed crashes, indicating they are not classical second-order cycles.
• A phase-driven modulation of direct density dependence explains the 3-year cycle length by maintaining a low phase after peaks.

Conclusions:

• The common vole population exhibits first-order cycles with a low phase, rather than fully second-order cycles.
• Traditional log-linear second-order autoregressive models may misinterpret the timing of density dependence.
• Nonlinear models provide a better description of cyclic population dynamics, suggesting potential roles for parasites or food in population crashes.