Anxiety, Bedtime and Mating: How Animals May React to the Eclipse

While millions of people are preparing to watch the total solar eclipse that will make its way across North America on Monday, the animals in that affected area — in homes, on farms, in zoos and in the wild — missed the news that the moon will block the sun, briefly turning day into night.

How they react to that swift and unexpected change of light and temperature, which in some places will last as long as four-and-a-half minutes, is anyone’s guess.

Cows may mosey into their barns for bedtime. Flamingoes may huddle together in fear. The giant, slow-motion Galápagos tortoise may even get frisky and mate.

Circadian rhythms might take a noticeable hit, with nocturnal animals mistakenly waking up and starting their day only to realize that, whoa, nighttime is already over. And then there will be some animals, perhaps particularly lazy domestic cats or warthogs focused on foraging, who might not give the dark sky a second thought.

“Everybody wants to see how they are going to react,” said Robert Shumaker, the chief executive and president of the Indianapolis Zoo, which will experience nearly four minutes of darkness. It’s one of several prominent zoos situated along the path of totality, a gentle arc stretching from Texas to Maine, where researchers, animal keepers, volunteers and the public will be studying the animals’ response to the eclipse.

Dr. Shumaker, an expert in animal behavior and cognition, said that “most of the animals, of course, they’re going to notice that there’s something unusual happening.”

Most animals will likely be confused by the darkness and will start their nighttime routines, said Dr. M. Leanne Lilly, a veterinary behaviorist at Ohio State’s College of Veterinary Medicine.

But the way humans react to the eclipse — looking at the sky, expressing excitement or gathering in a group — could affect domesticated animals, like dogs or cats, because pets can act strangely when their humans are acting strangely, Dr. Lilly said.

“That can make any of our domestic animals feel like things are not as safe and predictable as they are supposed to be,” Dr. Lilly said, adding that any unusual human behavior can disturb pets because they are “domesticated to attend to us.”

“We might be the problem,” she said, with a laugh.

How animals will react to solar eclipses can only give hints of animal behavior because the relatively few studies of the topic are often conflicting. One study in 1560 cited that “birds fell to the ground.” Other studies said birds went to roost, or fell silent, or continued to sing and coo — or flew straight into houses. Dogs either barked or whimpered, or did not bark or whimper.

A study of the 1932 eclipse, which was thought to be the first comprehensive research conducted on the subject and included observations from the public, explained that it received “a good deal of conflicting testimony” from people who had observed mammals. It concluded that several animals showed the strongest responses: squirrels ran into the woods and cattle and sheep headed for their barns.

Zoo animals, the study said, showed little or no response, and Dr. Shumaker does not expect the animals at the Indianapolis Zoo to show much of an unusual response, because “they take a lot of things in stride.”

“We’re thinking that this will be a very casual and easy experience for the animals,” he said, adding that some might experience “a little bit of confusion” about what’s going on. “I certainly don’t anticipate that it will be alarming to them.”

Dr. Shumaker is as curious as anyone to see what the animals will do, and in 2017, Adam Hartstone-Rose, now a professor of biological sciences at North Carolina State University, tried to get some answers. Before that total solar eclipse crossed the United States, he launched a formal study of animals at the Riverbanks Zoo & Garden in Columbia., S.C., and it resulted in what was likely the broadest study of animals during an eclipse since the 1932 effort.

Just as he is doing next week at the Fort Worth Zoo, Dr. Hartstone-Rose assembled a group of researchers, animal keepers and volunteers to observe animals before, during and after totality.

About three-fourths of the 17 species his team studied, including mammals, birds and reptiles, displayed a behavior response to the eclipse, with many of those animals thinking that the change in light meant it was time to prepare for bed. A smaller group of animals, including the giraffes, baboons, gorillas, flamingoes, lorikeets (a type of parrot) and one Komodo dragon showed behavior that was out of the ordinary and could be interpreted as anxiety.

According to the study, the baboons ran around their enclosure as totality approached, and one paced and walked in circles for about 25 minutes. One male gorilla charged the glass. The flamingoes huddled together, encircling their young, vocalizing loudly and looking toward the sky, which is “the kind of thing they might do if they think there’s an aerial predator around,” Dr. Hartstone-Rose said.

The lorikeets grew active and loud just before totality, and during totality flew together to one side of their exhibit. One Komodo dragon rushed to his den but the door was closed, and he “ran erratically” around until daylight returned.

He noted that it was “entirely possible” that the behaviors were triggered not by the eclipse, but by the large crowds and the noises at the zoo, which included fireworks exploding in the distance.

Yet the giraffes’ behavior that day in South Carolina was similar to the animals’ behavior elsewhere during eclipses, including at the Nashville Zoo in 2017, and also in the wild in Zambia during a 2001 eclipse.

“Most of us expected that the giraffes would just kind of be like, ‘Oh, it’s dark,’ so it’s bedtime,’” said Alyson Proveaux, curator of mammals at the Riverbanks Zoo and one of the observers of the giraffes in 2017. But their reaction was much more dramatic.

Normally, the Riverbanks Zoo giraffes chomp on lettuce, chew their cud, mill about or play with their enrichment toys. But when the sky went dark, according to the study, they stopped eating and huddled in the back of their enclosure, with one pacing and swaying. As the daylight slowly returned, several broke into a gallop for several minutes, which was extremely out of character. Giraffes also galloped during the eclipse at the Nashville Zoo and in Zambia.

“They are creatures of habit,” Ms. Proveaux said. “So we just rocked their world.”

In another part of the Riverbanks Zoo, the Galápagos turtles did something even stranger just before totality that the study described as a “novel response.” Instead of moving slowly around their area, as they usually do, they grouped together and two started mating. During totality, all four tortoises moved faster than usual.

Dr. Hartstone-Rose is curious to see if these responses will be repeated by animals at the Fort Worth Zoo, where he will likely be monitoring the bonobos, which are similar to chimpanzees. He said bonobos often exhibit sexual behavior to alleviate anxiety and that it will be fascinating to see their response to the unexpected darkness.

He also is asking the public to formally observe the animals around them during the eclipse and submit those findings to him so he can include them in his study. Those animals include pets, livestock, as well as wild animals, who also are known to alter their behavior during eclipses.

Scientists have used different types of technology to record wild animal responses to an eclipse. For the 2017 solar eclipse, scientists used radar data from weather stations across the country to study how flying animals responded when day turned into night.

As the sky darkened, the amount of biological activity in the atmosphere fell, they found, suggesting that insects were landing and birds were beginning to roost. In some places, there were also brief pulses of activity during totality, when some nocturnal creatures — which may have included bats, some insects and birds that migrate at night — came to life.

Still, the brief bout of darkness did not seem significant enough to completely convince animals that night had descended. “It’s kind of a muted response,” said Andrew Farnsworth, a visiting scientist at the Cornell Lab of Ornithology who was an author of the study.

Some animals, including many butterflies, are especially sensitive to temperature. During the 2017 eclipse, Robert Michael Pyle, an ecologist and butterfly expert in southwestern Washington, spent hours carefully logging the conditions in his yard and as the temperature dropped, the woodland skippers, a common butterfly species, disappeared. “Two degrees put the butterflies back to bed,” he said.

Although they have been the focus of less research, plants, which require the sun for sustenance, are also affected by eclipses. “As the sun goes away, photosynthesis goes down,” said Daniel Beverly, an ecophysiologist at Indiana University who documented that slowdown in big sagebrush during the 2017 eclipse. The findings highlight the importance of circadian rhythms beyond the animal kingdom, he said.

And careful observations of what organisms do during an eclipse can yield new insights that extend beyond the event itself. The eclipse “is a sort of natural experiment, manipulating light and temperature on a grand scale,” said Candace Galen, an evolutionary ecologist at the University of Missouri who found that bees went quiet during the period of totality in 2017.

In the end, Dr. Hartstone-Rose said, “who knows what’s going through the head of a giraffe.” But his aim is to collect as much data as he can, to try to find out.

He does have one definite answer to a question posed to him again and again: During an eclipse, should you put protective glasses on your dog?

“As a fashion statement, I’m all for it, so go for it,” he said. “But as a safety precaution, no, that’s not something they need to do. Animals do not look at the sun.”