How Cicadas, Squirrels, and Bees React to Solar Eclipses

Hyungwon Kang / Reuters

Cross your fingers for clear skies, space fans: A partial solar eclipse will grace the skies on Thursday afternoon over most of North America. According to NASA's predictions, the moon will pass between the Earth and the sun and cast a shadow that will obscure up to 81 percent of the yellow star.

If you're planning on gazing at the sun, you've hopefully prepared by gearing up with filtered telescopes, binoculars, viewfinders, or—if you're handy—pinhole projectors. That's the human reaction to an eclipse: get out the telescope and start looking.

The rest of the animal kingdom seems less interested in studying the sun. It's not that animals don't notice these kinds of eclipses—they certainly do, and some may be far more sensitive than humans to them. But their responses to the darkening sun tend to be less about curiosity and wonder, and more about survival.

Among insects, desert cicada have been found to be particularly sensitive to partial eclipses. In the summer of 1991, researchers at the University of Illinois and Florida's Barry University traveled to Arizona to observe cicada behavior. A partial solar eclipse happened to occur while they were there, and they observed whether cicada behavior changed, discovering the following:

On the day of the eclipse, Diceroprocta semicincta (Davis) and Cacama valvata (Uhler) began calling in Tucson before 8:00 AM and were calling normally as the eclipse began, at 10:15 AM. Soon after the coverage of the sun had reached approximately 50%, the cicadas ceased calling. The interruption in calling continued for about 40 min during the eclipse; about 20 min on each side of the maximal eclipse.

In other words, they all went silent when a few degrees lowered under the eclipse's shadow. That's because the cicada's call is energy intensive, and the researchers think that below a certain temperature it becomes impossible for the bugs to maintain the body heat they need to sing.

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In India, a similar study targeted bees. Researcher M. L. Roonwal of the Zoological Survey of India studied rock bees during an eclipse in June 1955, finding that the number of them leaving and returning to their hive every minute increased dramatically during a partial solar eclipse. As the sun dipped behind the moon more than 150 bees buzzed about, when normally, only 25 or so would move away from the hive. "It would appear that during the partial solar eclipse on the 20th June, the rock bees became distinctly restless and more active," Roonwal concluded.

Since the 1970s, many studies have focused on non-insect behavior as well: In 1973, researchers found captive squirrels became just as restless as the bees, as the length of their "non-stop running sessions were much greater than normal during and for two hours after the eclipse." In 1983, a group of ox-like Blue bulls spent different amounts of time feeding and resting during a partial solar eclipse.

Are humans less sensitive to the minuscule changes in the environment caused by space phenomena? Probably not. But it's fascinating to observe the animal kingdom's behavioral reactions, especially when triggered by slight changes in light and temperature. When the eclipse begins in your area, it might be a good idea to keep an eye or ear out for the wildlife nearby—they're likely to show signs they know what's going on.