Solar eclipse may trigger behavior changes in the Earth's animals, birds and bees

Less than a week from now, when the sun partially disappears behind Long Island's moon — and entirely in places like upstate New York — many of the Earth's creatures will react to the eclipse.

Not all of them in the same way, according to scientists.

The scientific literature about past eclipses includes an account of a drastic decrease in honeybee foraging, suggesting that external cues may overwhelm their internal circadian rhythms. Other studies tell of tortoises incited to passion in a South Carolina zoo and of a juvenile chimpanzee who “stood upright and gestured in the direction of the sun and moon” at a primate research center in Georgia in 1984.

“We know that light is a cue that affects everything that happens on Earth, that all biological systems are in some way affected by light, lack of light, the rhythm of light,” said Cecilia Nilsson, a researcher at Lund University in Sweden. “It’s cool to have this natural experiment when light disappears, if only for a time.”

Nilsson, a behavioral ecologist, was lead author of a 2018 study, conducted while she was at Cornell Laboratory of Ornithology, that used weather surveillance radar stations to measure aerial activity by flying creatures in the “path of totality” in the United States in a 2017 eclipse.

Nilsson and her colleagues expected to find more activity by migrating birds that fly by night. What they instead found was “a lot of birds settling down, landing, stopping their normal activities. … One hypothesis might be, rather than thinking it’s going to be sunset, they might be interpreting the gathering darkness and slow decrease in light level as an approaching storm.”

Domestic animals, especially dogs, may react more to the behavior of humans around them than to their perceptions of the eclipse, said Kate Anderson, assistant professor of clinical sciences at Cornell's Duffield Institute for Animal Behavior.

“Sometimes the behavior of humans can be more distressing for pets than the actual eclipse,” she said. “Dogs are more evolved to human behavior.”

For anxious animals, especially dogs, any change in daily life at all, let alone “people deciding to bring animals to an eclipse viewing party or bring them outside,” can be stressful, she said.

A 2020 paper also using data from that eclipse, memorably titled “Total Eclipse at the Zoo,” found that about three quarters of 17 animal species observed at Riverbanks Zoo and Garden in Columbia, South Carolina, showed some signs of unusual behavior during the eclipse, though it was hard to tell why.

“Animals are more perceptive of things than we are, in certain respects,” said Adam Hartstone-Rose, a professor in the Department of Biological Sciences at North Carolina State University and the paper’s lead author. “We think of an eclipse as really about light and the sun going away, but the other thing that happens is that the drop in light corresponds to a drop in temperature.”

Hartstone-Rose noted the effect on Galapagos tortoises: “As the totality grew, they began moving more rapidly, and right at the peak, a pair of them started mating, which was remarkable to witness.”

The tortoises' behavior was not necessarily the most memorable of that day, Hartstone-Rose said. The zoo’s siamangs, a kind of primate, “made a loud call we never heard them make before or since,” he said.

“It is unclear whether this response should be interpreted as an anxious response, or simply an anomalous behavior induced by changes in light and/or atmospheric pressure,” Hartstone-Rose and his colleagues wrote.

Near totality, flamingoes “congregated tightly in the middle of their enclosure on a central island, with juveniles huddled in the center of the flock,” indicating anxiety, the researchers wrote. Some animals, like gorillas, appeared to behave as they would at night. Some, like kookaburras, exhibited no change in behavior.

"Scientific literature about animal behavior during eclipses remains a fairly niche topic," wrote Robert Ritson, Associate Research Scientist with the Wyoming Cooperative Fish and Wildlife Research Unit at the University of Wyoming, who was lead author of a 2019 study comparing social media observations of animals during the 2017 eclipse to published research.

That study suggested possible avenues for further "citizen science" research on the topic, broadening a body of literature that now includes many observational or experimental studies conducted decades ago, Ritson wrote.

Some recent work, like Nilsson's, uses modern technologies to produce "compelling results" that are easier for other scientists to parse, Ritson wrote. He is leading a team that will use GPS data to see if changes in animal movement patterns occur during the eclipse. "The influence of these events on daily behaviors of animals remains a curiosity," he wrote.

Bill Fonda, a spokesman for the New York State Department of Environmental Conservation, wrote in an email that animals reactions to the eclipse will vary. Nocturnal animals will become active during the eclipse if they are in a place where they sense the change in light, he wrote. 

"Birds that are singing will stop calling in the zone of totality and may be seen moving towards areas where they normally roost overnight as light fades. Insects normally active during the day may return to their hives or overnight roosting locations as the eclipse begins. Species normally active at night may become active, such as coyotes, crickets and cicadas, may begin calling as it becomes dark," Fonda wrote.

Some impacts may be less pronounced in New York during this eclipse because most song birds have not yet returned or begun their breeding season, and many insect species are still dormant, especially Upstate. 

At the Long Island Game Farm in Manorville, director Greg Drossel said he wasn’t sure what to expect. Some animals are exquisitely sensitive to weather changes, he said.

“When there’s a front coming through, a low coming through, deer don’t know whether it’s going to be a foot of snow or rain, so when they feel the low pressure, they’re going to feed,” Drossel said.

Chickens and turkeys may roost; certain fish accustomed to hunting in low light may prowl. He said during the eclipse he'll try to observe the farm’s cockatoos, parakeets and primates. “You can read their reaction a little better than, say, a llama.”

For Stony Brook University ecologist Carl Safina, the eclipse presents no window into the animal soul. “As cool and as unusual as a solar eclipse is, for other animals it is very much a passing thing,” he said.

“On a conscious level, they might be a little confused,” he said, “but on a more deeply biological level, their biological clocks are still ticking — their melatonin levels and all the other chemical triggers that give senses of the day-night cycle will not have time to readjust. It’s almost like being in a room and someone turns out the light.”