Winter ecology of honey bees: identifying early-warning indicators of colony collapse
PhD student: Etienne Minaud
Post Doc: Elise Verrier
Supervisors: Fabrice Requier and François Rebaudo
Lab: UMR EGCE, France
Over the past 20 years, abnormal high mortality rates of honey bee colonies have been revealed in several regions of the world where it can reach up to 25–50% every winter leading to strong impacts on beekeeper economy and sustainability. However, the ecology of winter bees and mechanisms leading to colony mortality during winter are only slightly little studied. This knowledge gap is mainly due to the technical challenges studying honey bees in winter. Opening the hive threads colony thermoregulation, i.e. a critical trait of colony survival in winter. Thus, the hive is considered as a black box by beekeepers in winter.
The main objective of this PhD project is to study the winter ecology of honey bees and the mechanisms of colony collapse during this period, through the development and use of information and telecommunication technologies (ICT) as automatic monitoring of honey bee colony dynamics.
Winter bees emerge in autumn and differ from summer bees in their physiology, behavior and longevity (up to 200 days). However, their life history and behaviors remain poorly understood although they could drive winter survival of the colony. We study life history traits of winter bees over their entire lifespan using automated tracking tools. This monitoring will help understanding their functional roles in the colony.
During winter, honey bee colonies thermoregulate to survive cold temperatures. To do so, winter bees group together to form a cluster. Cluster size, spatial structure and movement are indicators of colony health and could be directly affected by climate. We developed connected frames to track the dynamic of the cluster with multiple temperature sensors. We equipped hives with such connected frames along a climatic gradient to assess how climate affects the colony dynamics during winter.
The combination of multiple stressors can lead to the winter mortality of honey bee colonies. Although most of the stressors occur in summer, their effects can carry over into winter. Thus, overwintering failure of the colony may be causal linked with delayed effects of disturbances within the colony mechanisms. We aim at disentangling these causal links by monitoring core colony traits over several years. We use several ICT devices to automatically measure the colony weight and temperature. These data are completed with visual inspections in order to measure the biotic pressures, quantity and quality of the reserves, and the demographic state of the colonies. Studying these causal links would help identifying early warning indicators of colony collapse.