During the last total solar eclipse, the bees stopped buzzing. It was in August of last year, when the Moon hid the Sun casting a shadow over a large part of the United States. As the eclipse progressed, the insects adapted the rhythm of their activity until, during the less than three minutes of the whole phase, their buzzing ceased to be heard.
Researchers from the United States, helped by hundreds of volunteers placed a series of microphones in fields of flowers along about 3,000 kilometers of the trajectory that was to follow the total solar eclipse of August 21, 2017. This type of eclipses are of the least common, when the Moon hides (from the terrestrial point of view) the entire circumference of the Sun for a few minutes. On this occasion, the total shadow width was about one hundred kilometers. In its route, the eclipse was projected on several states of the USA, which allowed to study the behavior of different species of bees and bumblebees in different climatic environments.
"We anticipated that, given the many references in the literature, the activity of the bees would decrease as the light dimmed during the eclipse and would reach a minimum during the whole," says a biologist from the University of Missouri (EE). UU) and principal author of the study, Candace Galen. "But what we did not expect is that the change would be so abrupt, that the bees would continue flying to the totality and only then would they stop doing it, completely."
Indeed, of the hundreds of buzzes recorded, only one remained during the two minutes and 40 seconds that the total occultation of the Sun lasted. In the previous and subsequent minutes, the partial phases of the 92 minutes of the eclipse, the Hymenoptera kept buzzing. However, the buzzing was different from the rest of the day. When analyzing the sounds, the authors of the study found that as the eclipse progressed towards the totality, the humming decreased in intensity. Among the authors of the work, published in the journal Annals of the Entomological Society of America, there are several entomologists who see similarities between this pattern of behavior and that shown by bees at dawn and dusk: both at the beginning of the day and at sunset, the insects reduce their speed to adapt it to the lower visibility, something they repeated during the partial phases of the eclipse.
The drop in temperature of up to 15 ° during the eclipse did not affect the behavior of the bees
They also observed a tendency to move away from the buzz as the eclipse progressed until the bees were silent. The researchers assume that the bees returned to their hives, but they do not have all of them. These insects do not usually move more than three kilometers from the hive and can fly at a speed of 25 kilometers per hour, so it could give them time to return before they were made at night by the eclipse.
"There is some evidence of the eclipse in 1932 that the bees returned en masse just before the peak of the total eclipse," says the biologist also from the University of Missouri and co-author of the research, Zak Miller. On that occasion, a study of the time collects the testimonies of several beekeepers who saw the return of their bees. To confirm this, we will have to wait until April 2024, when this region of the planet returns to live a total solar eclipse.
The research helped confirm that this pattern of behavior is repeated among the different species of anthophiles. When crossing several ecosystems, the eclipse gave shade to diverse native species and all responded the same. More importantly, he confirmed that the determining factor for this alteration is light and not temperature. Due to its trajectory, the total eclipse could be seen both in the northeast of the US, on the Pacific coast, where in August the temperatures are not very high, as in the states of the Midwest, with a torrid continental climate.
Thus, although the thermal drop during the whole phase was between 10º and 15º, the temperature was very different between the different locations: for example, in Santiam Pass, in Oregon, it dropped to 14.2º while in, Shepard, Missouri , the western end of the studied area, the thermometer did not drop below 31.7º in full solar eclipse. For researchers, this makes it clear that it is the sunlight that guides the life of the bees.