BY JEFFREY KLUGER
SPACE
OF ALL OF THE ANIMALS WORTH observing during a total solar eclipse, perhaps none are more intriguing than humans. They stop what they’re doing; they stare skyward; they lower their voices to a hush. Some may even shed tears. Other species of animals display other kinds of behavioral changes, as the weather and lighting and nature itself seem to turn on their axes. And the total eclipse on April 8, which crosses the U.S. from the southwestern edge of Texas to the northern tip of New England, is no exception.
Some of the greatest changes during a total eclipse occur far above us, in the ionosphere, the band of atmosphere that ranges from an altitude of 37 to 190 miles. Defined by the abundance of electrically charged particles, or ions, the ionosphere is denser during the day, turbocharged by incoming radiation from the sun. That means during an eclipse, the overall concentration of ions in the ionosphere falls. This reduction can lead to a cooling of the upper atmosphere, which in turn can cause local depletions known as “ionospheric holes.” Those cavities may disrupt radio signals and lead to anomalies in GPS navigation systems. But according to researchers, in most cases the disruption is transitory and too mild to notice.
Other natural changes are more universally detectable, not least the dimming of sunlight—the closer to the arch of totality, the deeper the darkness experienced. Temperatures can drop by anywhere from 5°F to 15°F as sunlight retreats. Falling temperatures may also cause what’s known as an “eclipse wind,” or a slowing of the winds. That’s the result of low-level air becoming cooler than higher-level air, which makes it harder for that more-elevated atmosphere to mix with the air closer to the ground, eliminating the temperature and density differences that lead to breezes and gusts. As totality ends, the winds pick back up. Another effect falling temperatures may have is the appearance of a fleeting thunderstorm, as cooler air closer to the ground pushes warmer, more humid air upward, where moisture then condenses and rains out.
All of this affects nonhuman animals in multiple ways. Insects, ba
