Researchers are investigating how solar eclipses influence animal behavior. This Wednesday (12th), a total solar eclipse will cover parts of Europe, including mainland Spain, where such an event has not been seen since 1905. This will also be the first total solar eclipse to cross the European continent in over two decades. The phenomenon causes temporary changes in the terrestrial environment because during totality, the Moon completely obscures the sunlight, resulting in a drop in temperature and a rapid darkening of the sky. For animals, this abrupt transition can be perceived as an unexpected change between day and night.
Summary of Previous Observations
Records from past eclipses indicate that certain species alter their routine. For example, during the total solar eclipse that occurred in the United States in 2017, researchers monitored various animals to document possible behavioral changes. Among notable cases, bees suddenly stopped their activities during totality. This behavior attracted attention because these insects depend on environmental signals, especially light, to manage tasks such as feeding, movement, and returning to hives.
In zoos, peculiar reactions have been noted. At Riverbanks Zoo, located in South Carolina, gorillas and elephants returned to their nighttime enclosures as soon as the sky darkened. This change seems to have anticipated the resting period, as if night had arrived earlier than usual. Galapagos tortoises also exhibited atypical behaviors; they gathered and showed mating behavior shortly before totality. However, these records do not imply that all species react in the same way.
The most plausible hypothesis lies in the environmental signals modified by the eclipse. The sudden decrease in luminosity can trigger mechanisms typically associated with twilight. Consequently, depending on the species, this can lead to rest, displacement, vocalization, interruption of feeding, or just a momentary change in attention.
Birds are a group of great interest to scientists. A study conducted on the total solar eclipse of 2024, which took place in North America, compiled over ten thousand observations from amateur scientists and tens of thousands of acoustic recordings. More than half of the analyzed species showed some modification in their behavior. A particularly relevant finding occurred after the end of totality, when many birds resumed singing, simulating the start of a new day. This phenomenon is classified as a type of 'false aurora,' given that the sudden darkness can be followed by behavioral signs similar to those seen at dawn.
This effect may be especially relevant in Iceland during the August 12th eclipse. According to a local portal focused on the event, it will occur near the end of the period known as midnight sun, when summer days are exceptionally long. Thus, the abrupt change between light and darkness can generate perceptible responses in birds inhabiting different regions of the country. In the town of Seltjarnarnes, near the capital Reykjavik, there are colonies of Arctic swallows. This species is very active in the summer and depends on light for various activities; one possibility is that some birds temporarily reduce flying and feeding as the eclipse intensifies.
On the cliffs of Látrabjarg, in the Westfjords, large colonies of puffins and other seabirds will also be in the area of totality. The high concentration of animals may facilitate the perception of collective changes, such as reduced activity or temporary return to nesting sites. Other species, however, will likely show less visible reactions. On Ytri Tunga beach, on the Snæfellsnes peninsula, common seals and grey seals usually rest or swim near the coast. Based on previous observations, there is no expectation of drastic changes in the behavior of these mammals.
A similar situation occurs in Faxaflói Bay, where whale watching tours take place. Humpback whales frequent the waters in August, but there is still little proof that these large mammals exhibit significant reactions during solar eclipses. Therefore, monitoring the fauna during the event should not be seen as waiting for a spectacular reaction, as the changes can be subtle, quick, and vary greatly among individuals of the same species. Additionally, factors such as climate, noise, human presence, and environmental conditions can also influence the observed behavior.
Citizen science will play a crucial role in this type of research. Records made by ordinary people, such as photos, videos, observations, and sound recordings, help researchers collect a larger volume of data during the brief minutes of totality.
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In Spain, an initiative called ECOECLIPSE aims to use the eclipse to study how the sudden reduction of light affects soundscapes and the behavior of birds and bats. This proposal functions as a natural experiment to investigate animal responses to an abrupt change in luminosity, whose results can aid research on the impacts of artificial night lighting and light pollution on these species.
To do this, researchers will install autonomous recorders in isolated locations, chosen to avoid areas with large crowds of people. The equipment will record the sounds of birds and bats for two days before the eclipse, on the day of the phenomenon, and on the two days following. The goal is to identify possible variations in the frequency, intensity, or timing of calls emitted by the animals. The focus, therefore, is not on observing the eclipse itself, but on capturing the acoustic transformations caused by the sudden passage from day to a condition similar to night.
According to Airam Rodríguez and Irene Mendoza, members of the project, the devices will not necessarily be placed in the ideal points to track the eclipse. In an interview with El País, the researchers clarified that they prefer quieter locations where human interference is minimal in the recordings. The campaign will continue during the solar eclipses of August 2, 2027, which will also be total, and January 26, 2028, which will be annular, allowing the team to compare different events and increase the database on fauna reactions to changes in luminosity.
Eclipses provide a rare opportunity to observe how animals react to an unusual environmental alteration. For them, the focus is not on understanding an astronomical event, but on responding to a sudden change in one of the most vital signals of their routine: daylight.
