Today, a total solar eclipse was visible in much of North America. It was an amazing sight, with darkness falling in the middle of the afternoon. But does the solar eclipse have any direct effects on the brains of animals here on Earth?
Animal activity closely follows the day-night cycle. Most animals, including us humans, have a clear preference for being active during the day or during the night—our brains have been tuned by evolution to take advantage of predictable cycles of light and dark. Therefore, when darkness falls much earlier than usual, there could be effects on the living things below.
Indeed, there are many stories of animals behaving unusually during an eclipse. The Verge has a summary of observed changes in animal behaviour, from chirping crickets to grumpy hippos to violent chickens.
Humans change across the day-night cycle too. As we’ve discussed, morning people and night owls have patterns of cognitive performance that vary according to the time of day. Our hormone levels and body temperature also go up and down in predictable daily rhythms. When the human circadian rhythm is disrupted (e.g. by travel, job requirements, or drugs), effects can include health problems, trouble sleeping, and big changes to mood.
So is the darkness of an eclipse enough to disrupt humans? No, not really. There are no known physical effects, according to NASA.
They do mention that psychological effects are real, however. A sense of awe can accompany the direct observation of the movement of celestial bodies that we all depend on, yet rarely think about. You never know, a little awe may be good for the brain.