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How animals react to a solar eclipse

  • On Monday, August 21, people living within a narrow 70-mile-wide band across the United States will see a total solar eclipse.
  • Studies on how a solar eclipse affects animals or plants are sparse, mainly because an eclipse event is rare and credible observations are difficult to make.
  • But we present five examples of what some researchers have observed and recorded in the past few decades.

For a few minutes on Monday, August 21, the moon will blot out the sun completely, causing a total solar eclipse. The skies along a narrow 70-mile-wide band across the United States will plunge into darkness and air temperatures will drop. Tens of millions of people are expected to witness this historic event.

While a total solar eclipse is exciting for most people, what about non-human animals? How does a darkened sky and a drop in temperature under the eclipse’s shadow affect them?

There aren’t a whole lot of studies that look into this, mainly because an eclipse event is rare and credible observations are difficult to make. But on August 21, several scientists will be setting up experiments and observing plants and animals to see how they react to today’s eclipse conditions.

“Will they think that it’s nighttime and react as though it’s time to shut down for the day? Or will they go about things as if nothing is changing? It should be an interesting experience,” Tim Reinbott, assistant director of the Agricultural Research Centers at the University of Missouri, who will be part of a team studying the response of plants and livestock to the total solar eclipse, said in a statement.

The California Academy of Sciences is also encouraging citizen scientists to use their iNaturalist app to observe eclipse-related animal behavior around them.

While we try to build our understanding of how other animals react to a solar eclipse, here are five examples of what some researchers have observed and recorded in the past few decades.

A captive chimpanzee. Photo by Rhett A. Butler.

1. Captive chimpanzees

When the sky began to darken and temperatures began to fall during the solar eclipse of May 30, 1984, researchers observed that a group of captive chimpanzees at the Yerkes Regional Primate Research Center in Atlanta, moved to the top of a climbing structure within their enclosure. As the eclipse progressed, the chimpanzees turned their bodies in the direction of the sun and moon and faced upwards — a behavior that the scientists had not observed before. “One animal gestured as if pointing in the direction of the sun and moon,” the authors wrote in a study published in the American Journal of Primatology. Once the eclipse had passed and sunlight had increased, the animals descended the structure and went back to their daily activities.

“The behaviors observed in the present study were undoubtedly not characteristic of the group under normal conditions nor during sunset on normal days,” the authors wrote. “Unfortunately, the low frequency of occurrence of a total solar eclipse in any given area makes subsequent studies with a group of subjects very difficult.”

2. Cicadas

During a partial solar eclipse on July 11, 1991, researchers found that as soon as half the sun was covered by the moon, cicadas in their study area in Arizona — Diceroprocta semicincta and Cacama valvata — stopped calling for about 40 minutes. The researchers thought that the drop in temperature under the darkened sky could have caused the cicadas’ silence.

“The decrease in radiative heat gain during the eclipse appears to be responsible for the inhibition of calling in the cicadas,” the authors wrote in a paper published in The Florida Entomologist. “Without the normal degree of radiant energy present in their environment, the cicadas may not have been able to maintain the elevated body temperature that is necessary for activity.”

3. Hippos

As part of a team of 250 people, astronomer Paul Murdin documented the effects of a total solar eclipse on Zimbabwe’s wildlife 2001. They had all gathered at the Mana Pools National Park on June 21, observing animals as the moon moved in front of the sun, casting a massive shadow over the park. As soon as the skies darkened, Murdin observed that the hippos that were sleeping on an island in the middle of the Zambezi river stood up and slipped into the river and started walking towards the riverbank.

“The diminishing light and warmth evidently reminded the hippos of sunset, when they normally disperse off the mid-stream sandbank and walk to the riverbanks along the bottom of the river (they are too heavy to swim). On land they graze through the night,” he wrote in Astronomy and Geophysics. Before the hippos could reach the shore, sunlight had returned and the hippos “paused and looked nervous,” he added.

Hippos have been observed to respond to solar eclipse. Photo by Rhett A. Butler.

4. Birds

The team in Zimbabwe also observed that most birds — doves, egrets, oxpeckers, ibis, trumpeter hornbill and geese — fell silent during the eclipse. Only owls called loudly as darkness set in. Waders and herons, though, seemed to remain impassive.

In Serbia, during the solar eclipse in 1999, scientists observed that pigeons were “agitated and aggressive”, hens stood completely still in one place, while swallows “acted normally.”

5. Fish

On February 26, 1998, scientists observed several fish species at Pinta Island, Galapagos, responding to a solar eclipse. As soon as light levels fell during the eclipse, most of the diurnal fishes stopped feeding and retreated into crevices between boulders and branching corals.

Several nocturnal fish species, on the other hand, began leaving their daytime shelter of caves and crevices in response to the darkness, the scientists reported in a study published in the Journal of Fish Biology.

Total Solar eclipse, 1999, in France. Photo by Luc Viatour / (From Wikimedia Commons/CC BY-SA 3.0)
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