We’ve all seen honey bees fly in the rain. A light sprinkle or a short shower seems to have little effect on a foraging bee. On the other hand, a storm with heavy rainfall will keep the bees inside their hive. How do the honey bees decide when it’s safe to fly?
Based on a number of studies and a lot of anecdotal evidence, we know the honey bees are good at predicting the weather. In fact, honey bees seem to be more accurate than The Weather Channel when it comes to predicting rain. Not only can they predict it, but they can estimate its intensity. That is why a light drizzle may not influence their foraging patterns, but a heavy storm can keep them home.
Bad weather can trigger defensiveness
In a paper entitled “The Effects of Meteorological Factors on Defensive Behaviour of Honey Bees”1, researchers found that honey bees are more defensive during the approach of bad weather. The authors found that these spikes in defensiveness were largely the result of meteorological factors, including temperature, humidity, amount of solar radiation, wind speed, and barometric pressure.
Some beekeepers speculate that this increased defensiveness occurs because the bees “know” they must protect their food stores for the lean times ahead. Since honey bees are always “mindful” of the future, they increase the defense of their food stores.
Bees work harder before the storm
In a more recent study, “RFID Monitoring Indicates Honeybees Work Harder Before a Rainy Day”2, researchers tagged honey bees with RFID devices in order to track their foraging activity. They found that honey bees spent more time foraging on days immediately before a significant storm. Furthermore, they found that honey bees worked later into the evening on the day prior to a storm. Their theory is that the bees “predict” that food will be in short supply during the stormy weather, so they work extra hard before the storm hits.
These researchers point to prior studies, such as the one on defensive behavior, and speculate that honey bees predict the weather based on factors such as temperature, humidity, barometric pressure, and carbon dioxide levels. Many animals are able to predict inclement weather, just as we humans often do. We say things like, “Feels like rain” or “Smells like snow,” probably due to similar signals from our environment.
My own anecdotal evidence
Last year I inadvertently tested this theory with a lawn sprinkler. On a hot and sunny July afternoon I decided to water the lawn next to one of my hives. I set up a sprinkler which rained down on the hive and the surrounding grass. By all appearances, the bees were unperturbed by this turn of events, coming and going with pollen and nectar as usual. Even the accumulation of water on the landing board did not seem to upset them.
This type of observation lends credence to the idea that it is not the raindrops themselves that determine behavior, but the atmospheric conditions. When honey bees continue to forage during light showers and summer sprinkles, it is probably because the atmospheric indicators, the ones we can’t see, are telling the bees that it is safe to forage. “Get over it and keep working; there’s nothing to worry about!”
Behavior to watch for
In the future I intend to watch their behavior more carefully. Do bees foraging in the rain mean the weather will soon clear, or at least not get worse? Do unusually high levels of activity on a dry day mean a storm is near? Do drones behave any differently? And how about other species? Now that I’m thinking of this, I can’t wait till spring.
Honey Bee Suite
1Southwick, E.E. & Moritz, R.F.A. Int J Biometeorol (1987) 31: 259. doi:10.1007/BF02188929
2He, X.-J., Tian, L.-Q., Wu, X.-B. and Zeng, Z.-J. (2016), RFID monitoring indicates honeybees work harder before a rainy day. Insect Science, 23: 157–159. doi:10.1111/1744-7917.12298