Nonlinear population dynamics are ubiquitous in animals.

Area of Science:

• Ecology
• Population Dynamics
• Nonlinear Science

Background:

• Nonlinear dynamics, where output changes are not proportional to input changes, are common in nature, like biochemical kinetics.
• Animal population dynamics are complex due to interacting environmental and biological factors, suggesting nonlinear, state-dependent drivers.
• Previous identification of nonlinear dynamics was limited to model organisms and specific natural systems.

Purpose of the Study:

• To investigate the prevalence of nonlinear population dynamics across a diverse range of animal taxa.
• To determine if nonlinear dynamics are ubiquitous in nature, as suggested by ecological theory.
• To assess the predictability of animal population trends and identify factors influencing nonlinear dynamics.

Main Methods:

• Analysis of 747 population datasets from 228 species using nonlinear forecasting techniques.
• Statistical evaluation of population trend linearity and dimensionality across different animal groups.
• Correlation analysis between reproductive rates, dynamics dimensionality, and nonlinearity.

Main Results:

• Nonlinear population dynamics were found to be ubiquitous, present in 74% of insect, 58% of mammal, 49% of bony fish, and 35% of bird populations.
• Faster-reproducing species exhibited more nonlinear and high-dimensional population dynamics, aligning with ecological predictions.
• Predictability of population time series was limited, with only one-third predictable beyond two years.

Conclusions:

• Linear, equilibrium-based models may be inadequate for predicting population dynamics in many animal taxa.
• The inherent complex, nonlinear dynamics in animal populations could facilitate regime shifts and ecological transitions.
• While nonlinear dynamics are widespread, the limited long-term predictability highlights challenges in forecasting animal population trends.