Dynamic modelling of honey bee (Apis mellifera) colony growth and failure

Rates of honey bee colony failure have increased significantly across much of North America and Europe, which has directed attention to the need to better understand the process of bee colony growth and development, and the factors that can cause colony failure. Here we present a simple model of honey bee colony dynamics as a tool to explore what factors may have the strongest influence on colony growth and survival. Our model focuses on how internal demographic processes within a colony interact with food availability and brood rearing to alter growth trajectories. The model is implemented as a series of difference equations operating at discrete time steps to model changes in bee population day by day. We base our rate equations on the analytic models of Khoury et al. (2013), and go further by simulating colony growth across three years to capture seasonal and annual growth cycles. Our resulting model successfully captures realistic seasonal variations in colony populations. Sensitivity analysis of the model suggests that colony survival is strongly influenced by rates of forager bee mortality, food availability and factors that influence the age at which worker bees transition from working inside the hive raising brood to working outside the hive as foragers. We discuss these findings with reference to known agents that can cause colony failure. The presented model is very simple, and makes minimal assumptions, but could easily be extended to more accurately simulate the performance of field honey bee colonies and/or specific environmental or pathogen pressures.