Pollination on the Dark Side: Acoustic Monitoring Reveals Impacts of a Total Solar Eclipse on Flight Behavior and Activity Schedule of Foraging Bees

The total solar eclipse of 21 August 2017 traversed 5000 km from coast to coast of North America. In its 90-min span, sunlight dropped by three orders of magnitude and temperature by 10-15 degrees C. To investigate impacts of these changes on bee (Hymenoptera: Apoidea) pollinators, we monitored their flights acoustically in natural habitats of Pacific Coast, Rocky Mountain, and Midwest regions. Temperature changes during the eclipse had little impact on bee activity. Most of the explained variation (R-2) in buzzing rate was attributable to changes in light intensity. Bees ceased flying during complete darkness at totality, but flight activity was unaffected by dim light in partial phases before and after totality. Flights of bees during partial phases of the eclipse lasted longer than flights made under full sun, showing that behavioral plasticity matched bee flight properties to changes in light intensity during the eclipse. Efforts of citizen scientists, including hundreds of school children, contributed to the scope and educational impact of this study.