Considering that daylight plays an important role in a bee's busy schedule, would a total solar eclipse thwart their plans? Would the bees think it's time to turn in for the night when the Moon passes in front of the Sun and blocks out its light? These are the questions researchers from the University of Missouri set out to answer when they tracked bee activity during the last total solar eclipse on August 21, 2017.
Their findings, published today in the Annals of the Entomological Society of America, yielded some surprises. Lead author Candace Galen said they expected to see bee activity gradually diminish as the sky darkened. "But we had not expected that the change would be so abrupt, that bees would continue flying up until totality [of the eclipse] and only then stop, completely," Galen said in a statement. "It was like 'lights out' at summer camp! That surprised us."
Of the 16 locations they tracked, only one bee was heard flying during the eclipse. This is one of the first studies to analyze how bees respond to a solar eclipse, and few studies like this have looked at similar behavior in other insects or animals. A 1991 study found that desert cicadas in Arizona stopped chirping for about 40 minutes during a partial solar eclipse. Another study from 1973 found that captive squirrels became restless and ran around far more during an eclipse, while other research showed that Blue bulls at a zoo in India altered their feeding and resting periods during a partial solar eclipse.
Before the latest bee study kicked off, researchers used tiny microphones and temperature sensors to track bee pollination by listening to them buzz about. That same method was applied to the solar eclipse experiment, and 16 monitoring stations were set up along the eclipse's path of totality in Oregon, Idaho, and Missouri. More than 400 scientists, citizens, and elementary school teachers and students assisted with the experiment.
The microphones were hung on flowers that bees had pollinated in semi-remote locations away from foot and vehicle traffic. After the eclipse, the recordings were sent off to Galen's lab, where researchers matched up flight activity with the different eclipse periods. In doing so, it was discovered that bees (mostly bumble and honey bees) kept flying during the partial-eclipse phases before and after the total eclipse. Practically no buzzing was recorded during the period of totality, save for one flight picked up by microphones.
Researchers also noticed that bees' flights were longer during those partial-eclipse phases, but they were likely slower flights as a result of the reduced light. They may have been returning to their hives, believing that it was time to rest, researchers suggested.
"The eclipse gave us an opportunity to ask whether the novel environmental context—mid-day, open skies—would alter the bees' behavioral response to dim light and darkness," Galen said. "As we found, complete darkness elicits the same behavior in bees, regardless of timing or context. And that's new information about bee cognition."
The next total solar eclipse in North America will take place on April 8, 2024, at which time Galen's team plans to do a second experiment. The researchers hope to improve their audio-analysis software to determine whether a bee is leaving or returning to its colony. That way, they'll be able to tell whether bees head home during a total eclipse.