On the afternoon of August 21, 2017, at about 2:41 PM local time, the sun vanished completely behind the moon over Columbia, South Carolina. This period of near-total darkness lasted approximately two minutes and thirty-six seconds. Within that timeframe, at a mid-sized zoo just outside the city, a group of researchers stood in designated spots with clipboards and stopwatches, eager to observe how a collection of seventeen different species of mammals, birds, and reptiles would react when midday transformed into a brief night.
The observations recorded in the primary-source documentation of the study reveal one of the most genuinely peculiar episodes ever captured in modern comparative zoology.
## The animals’ actual reactions
According to [the peer-reviewed research published in March 2020 in the journal Animals by Adam Hartstone-Rose, Edwin Dickinson, Lisa M. Paciulli, Kaitlyn Leonard, and colleagues from North Carolina State University, along with Ashley Deutsch from the University of Florida, Leon Tran from the University of Hawaii, and Grace Jones from the University of South Carolina, titled “Total Eclipse of the Zoo: Animal Behavior during a Total Solar Eclipse”](https://pmc.ncbi.nlm.nih.gov/articles/PMC7222787/), the researchers established baseline behavioral observations for each of their seventeen species in the days prior to the event. They were aware of the typical actions of each animal during an August afternoon in South Carolina. They subsequently compared these baselines with the animals’ behaviors during totality.
Thirteen out of the seventeen species, roughly seventy-five percent of the sample, exhibited measurable changes in their behavior. Not slightly. Drastically.
The Galápagos tortoises in the reptile exhibit, which had been basking in the sun as Galápagos tortoises typically do, started mating. Actively. In the afternoon. This behavior is not what Galápagos tortoises usually engage in at that time on a summer day. The siamang gibbons in the primate house began producing extended vocalizations characteristic of their species that occur at unusual times, using tones that the researchers had not previously observed from those particular individuals during their baseline assessments. Meanwhile, the gorillas, located on the other side of the primate enclosure, congregated and initiated the settling behaviors they typically exhibit at bedtime. The Hamadryas baboons ran and paced in coordinated groups, huddling around their young. The flamingos assembled in the center of their enclosure and vocalized. The rainbow and coconut lorikeets became quite loud. And the giraffes, which are large, slow, typically placid animals that usually spend their days strolling calmly and eating leaves, momentarily ran.
Giraffes do not typically run. Dr. Adam Hartstone-Rose, the lead author of the study, later told reporters that giraffes are, in his exact words, somewhat delicate, and that they run only when fleeing from a predator. There was no predator present. There was only, for a brief period, an unexpected darkness in the sky.
## What the scientists aimed to observe
Prior to the eclipse, the research team devised a classification framework for the responses they anticipated. Any behavior exhibited by a given animal during the eclipse would be categorized into one of four groups. The first was normal, indicating the animal behaved similarly to how it had all afternoon. The second was evening or nighttime behavior, meaning the animal acted as it would typically at dusk or as it transitioned to sleep. The third was novel behavior, indicating the animal engaged in new actions not typically observed at any regular time of day. The fourth was apparent anxiety, signifying that the animal exhibited movements, vocalizations, or clustering deemed as fear responses according to standard ethological literature.
The team had privately expected, as noted in their pre-registration of the study, to observe substantial instances of category three. A total solar eclipse is, in the strict evolutionary context, an event that no living animal has previously encountered as a recurring stressor. Total eclipses over a specific point on Earth occur, on average, every three hundred and seventy-five years. No captive animal in any zoo has ever experienced one before. Neither have their evolutionary ancestors, within any reasonable timescale for their genomes to adapt.
Thus, the logical prediction was that the animals would perceive the eclipse as what it truly was: an unprecedented environmental occurrence, and respond with novel behaviors typically reserved for encounters with things they had never seen.
## What truly surprised the researchers
However, that is not what the animals displayed.
The most significant response category among the thirteen species that exhibited behavioral changes, according to the study’s final analysis, was not novelty.