Foraging and homing behavior of honey bees (Apis mellifera) during a total solar eclipse
Exceptional natural phenomena, such as those that occur during a total solar eclipse, provide unique opportunities to study animal behavior outside the naturally evolved context, which can be informative in more general terms. Circumstantial descriptions of abnormal animal behavior during solar eclipses abound, although scientific studies conducted during an eclipse are relatively rare due to inherent logistical difficulties. Here, honey bee foraging and homing behavior were studied during the total solar eclipse of August 21, 2017. In the first experiment, we studied foraging behavior of honey bees during the progression of the solar eclipse and found that the foraging activity drastically decreased but did not completely cease during the totality of the eclipse, in contrast to previous reports of complete cessation. The data indicate that the level of ambient light can largely overrule the internal circadian rhythm of foraging honey bees. Furthermore, colonies with a higher need for foraging decreased their foraging activity less than satiated colonies, consistent with the hypothesis that individual foraging decisions may be influenced by colony state, which affects cost-benefit analyses. In a second experiment, the temporal dynamics of homing of released workers and drones was compared in periods before, during, and after the solar eclipse. During the totality of the eclipse, very few bees arrived back at their hive, while homing before the total eclipse was accelerated, particularly in drones. The results suggest that, while the homing abilities of honey bees are not compromised until the sun is completely eclipsed, they may still interpret the diminishing light as an indicator of deteriorating flight conditions. Our unique study provides some insight into the control of honey bee foraging behavior when external cues and internal circadian rhythms are at odds, lent support to the notion that food deprivation can lead to riskier foraging, and indicated that homing in honey bees is possible even with very small amounts of sunlight.
KeywordsSolar eclipse Circadian rhythm Navigation Animal behavior Honey bee Risky foraging Homing behavior
We would like to thank Clemson University for facilitating the research. The exact timing of the eclipse was calculated by NASA and helped in the advance experimental design.
The project idea was conceived by OR and PW. SB, JT, and OR designed the experiment. Colonies were prepared and provided by JT. All authors participated in the data collection. Data analysis and interpretation was performed by PW, SB, JT, and OR. PW and SB wrote the initial draft of the manuscript, which was significantly revised by OR, before going through a final set of revisions and approvals from all authors.
Financial support was provided by the University of North Carolina at Greensboro, the US Army Research Office (W911NF1520045), Clemson University, and the USDA National Institute of Food and Agriculture, Hatch project 1005512.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflicts of interest.
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