Text written in Basque and translated automatically by Elia without any subsequent editing. SEE ORIGINAL

Tremor of the eclipse

The astrophysicist Javier Armentia Fructuoso talks about the solar eclipse of 12 August with contagious emotions. “Beware: the probability that a person will see an eclipse in the place where he lives is less than 25%.” This makes it clear that this is a truly exceptional event. It is not surprising, then, that it has a significant impact on us. However, we are not the only species to notice the eclipse. Tremor is also observed in birds, bats and other living beings.

“The eclipse is much more than just an astronomical phenomenon. It is, of course, attractive to scientists in our field, although it does not have its historical importance as a natural laboratory. From a scientific point of view, it is not as productive as before; that is true. But turning the day into the night and then lighting up again is exciting in itself. And that emotion has something special; it's like it's out of our minds. In fact, it’s not so long before we can accurately predict eclipses.” It's Armentia's words. He does not hide his fascination with eclipses, although he knows perfectly the scientific explanation.

Or maybe even that. In fact, it is surprising that it happens by chance. There is no reasonable explanation for why the Moon is 400 times smaller than the Sun, and at the same time, 400 times closer to Earth. And so that the movements of both are aligned, once in a while. If the explanation is not known, the fact that the Sun disappears for a while would seem miraculous or terrifying. Therefore, when they were unable to understand the phenomenon scientifically, they explained it through myths.

Every culture and every era has its myth. For example, in Chinese mythology, it is said that a dragon ate the Sun. To repel the dragon and recover the Sun, they beat the drums and threw arrows into the sky. The Aztecs also believed that the sun disappeared by ingestion, but it was not eaten by a dragon, but by a jaguar. In the Scandinavian myth, two wolves try to hunt the Sun and the Moon; when they are caught, an eclipse occurs that announces the end of the world. For the Hindus it was a demon that ate the Sun, for the Egyptians it was a snake

Armentia also recounts them in the talks and informative actions that he has been giving here and there since the beginning of the year. “I am very focused on this, because I would like everyone to be aware that they will have the opportunity to experience an extremely special phenomenon,” he confesses. Remember that before there was someone who lived the arrival of an eclipse in his own way: “For example, the scientists of romanticism and later, and the rich people around them. They organized expeditions that crossed Europe to live and document the eclipse. They were also inspiring to make art and created wonderful paintings and writings. It is also clear that the attraction it generates is above scientific interest.”

In the Basque Country, the expectation generated by the solar eclipses of 1860 and 1905 has also been reflected in the media of the time. Nowadays, social networks are a good forum to look at the opinion or impression that a phenomenon has generated. For the example, Armentia cites a study on the footprint left by the 2017 eclipse on the social network Twitter. This study was conducted by psychologist Sean Goldy of the University of California. He analyzed the reactions that appeared in the tweets of almost three million users and confirmed that they were significantly affected by the eclipse: messages of surprise, gratitude and affection increased and people used the pseudonym “we” more often than “I”. Of course, that pleasant atmosphere lasted only 24 hours.

even during the eclipse of 2024, researchers observed a similar trend. Social media echoed a collective joy that was filled with photos that showed people in a group, united and happy. “All this shows that living an eclipse is transformative,” concludes Armentia.

In his lectures he gives advice on how to prepare the experience, what they will see, where they will see it best, how to observe it. “Just in case, we will repeat it, right? The eyes should be well protected with appropriate filters to avoid damage. Alternatively, indirect observation can be performed by looking at the shade with a perforated paper, or with a screen. It can also be seen in the shade of the leaves of the trees. There are also quite simple programs to convert light waves into sound waves and follow the eclipse by ear.”

Changes are not only noticeable in the light, but also in the wind. These changes are called eclipse winds. In Europe, they were investigated, for example, during the eclipse of 1999. Studies from that time show that for hundreds of kilometers, as the sunlight disappeared and the temperature decreased, the wind changed, even in places covered with clouds. For example, in Reading (England) it was cloudy and when the temperature dropped, a kind of cyclone was formed. After the eclipse, the wind returned to its original state. There were also changes in atmospheric pressure that lasted longer.

Astronomical, personal and social phenomenon

It's about living the eclipse. “We have to admit that total solar eclipses make us feel small and remind us that we need others. The phenomenon is astronomical, but the experience is not only personal but social.” Proof of this is how different the solar eclipses of 1961 and 1999 lived in Belgrade. Armentia explains the difference: “In 1961, with the help of information properly provided by the Yugoslav authorities, curiosity prevailed. On the other hand, in 1999, in that post-communist Serbia, terror broke out in the streets.”

In many places, certain superstitions associated with eclipses remain true, such as the fact that they pose a danger to pregnant women, or the fact that women in general do not have to leave their homes, no matter what happens. And, of course, they are also an incentive for all kinds of civilationist ideas. Faced with this, Armentia believes that journalism and dissemination can do a valuable job.

However, it is also possible that scientists, at some point, spread erroneous beliefs. Apparently, this has happened with a study that confirmed that conifers can predict the eclipse. This study was published in 2025 under the title “Bioelectric synchronization of Picea abies trees during a solar eclipse”. According to him, the trees were able to predict a partial solar eclipse based on electrical signals. Later, however, it was rejected by other scientists, who showed that the changes the researchers detected in the electrical signals could be explained by common reasons.

“We don’t need to be so incredulous to realize that a solar eclipse is a shocking phenomenon,” Armentia said. It aims to highlight the effects that anyone can see and feel, while expanding the scientific culture and alerting them to act responsibly. “I am particularly concerned about the fires. On August 12th the area will be dry and a cigarette can cause a huge catastrophe.” Waste management and car travel will be another two aspects to be rigorous. “I would ask everyone for respect and prudence. Always, but especially on that day,” he said. In fact, in other eclipses it has been observed that, once the eclipse is over, car accidents multiply, because everyone goes out to the road at the same time to leave the place where he has decided to observe the eclipse. The eclipse of August 12 is at dusk, so the risk is even greater.

“We are animals, social animals. Therefore, the eclipse affects both individuals and society. We have a great opportunity to live this phenomenon together,” concluded Armentia.

Agitation of animals

Those who experience an eclipse know it, and those who experience it for the first time will see it: people are not the only ones who notice it, it also affects other animals that suddenly turn the day into night and turn it back into light. Focusing on animals to document their behavior, citizen science projects have been organized for the August eclipse.

This curiosity for animals is not new. Maider Pérez de Villarreal Zufiaurre is a veterinarian, expert in ethology, who has studied the documents that collect the reactions of animals during eclipses. Find significant examples: “One of the first stories is that of the Italian Ristoro d’Arezzo. he described what had happened during the total eclipse of June 3, 1239: all animals and birds were terrified; and wild beasts were easily apprehensible.” on August 21, 1560, during an eclipse in Portugal, astronomer Christoph Clavius wrote: “As a whole, the stars appeared in the sky and an amazing spectacle occurred, as the birds fell from the sky to the ground because of such terrible darkness.”

Perez de Villarreal confirms that changes in both wild and domesticated animals have still been documented today. The crickets start singing, the birds return to the nest or become more active, the whales start jumping and the dairy cows enter the stable. Eclipse observer Tora Greve traveled on an expedition to Zambia in 2001 and, with the disappearance of the Sun, discovered that frogs began to sing and that birds of prey stopped flying. He was standing around a well and saw that the giraffes began to run in the entirety of the eclipse. When the sun appeared again, they calmed down and began to eat the leaves of the trees again.

Behind these strange behaviors, as Pérez de Villarreal explains, there are two dimensions: chronobiological and related to environmental uncertainty. “From a behavioral biology perspective, these events can be understood as natural experiments that allow us to study how animals respond to rapid changes in the main environmental signals. In the case of mammals, although empirical research is still limited, the available studies allow the identification of relatively consistent response patterns that combine chronobiological and behavioral mechanisms.”

The ethologist recalls one of the most complete studies carried out during a solar eclipse. it was carried out in 2017 at the Riverbanks Zoo in Columbia during a total solar eclipse. 17 studied the behavior of vertebrate species, including mammals such as primates, elephants, bears and ungulates. "The results showed that approximately 75% of the species studied underwent changes in behavior during the eclipse's integrity phase, which shows that eclipse is a significant environmental stimulus," he said.

In general, one of the most common responses observed in mammals is the activation of behaviors associated with sunset. As Pérez de Villarreal explains: “This phenomenon can be explained in the field of chronobiology, that is, in the study of biological rhythms regulated by environmental cycles. The sudden decrease in luminosity during an eclipse may suggest to the circadian system that night is coming. As a result, nocturnal behaviors such as slowing down activity, tendency to group or preparation for rest are activated. This pattern has been documented in domesticated mammals (cattle and sheep) as well as in wild species. And also in captivity, for example, in bears.”

Both wild and domesticated

However, it warns that this response is not uniform in all mammals. “In species of greater social and cognitive complexity (such as primates and elephants), behaviors that are not explained by mere obscuration have also been observed. In these cases, individuals show signs of nervousness, increased social activity, or changes in group organization. For example, in gorillas and baboons, social interaction and mobility have been observed to increase. Elephants also tend to group and change their patterns of movement. These behaviors suggest that, in addition to the chronobiological component, there is a dimension of evaluation of the environment, that is, the reaction to extraordinary and unexpected events,” he concludes.

In domesticated animals (dogs and cats) the evidence is more heterogeneous and often anecdotal in nature. Some dogs show nervousness or tend to approach caregivers, but many others do not notice any significant changes. In these cases, the human presence and daily routines have a great impact, which tarnishes the direct impact of the eclipse, according to Pérez de Villarreal.

“Therefore, the available evidence suggests that the response of mammals to total solar eclipses lies at the intersection of two dimensions: on the one hand, the automatic response of circadian rhythms regulated by light and, on the other, the ability to process and assess the environment in the face of unexpected events. Domesticated mammals generally show more predictable responses associated with the first dimension, while wild mammals, especially those with complex social structures, show greater behavioural diversity, indicative of a more active environmental assessment," he summarises.

He also mentioned boundaries. First, the strange and transient nature of eclipses makes it difficult to repeat investigations and obtain large samples. In addition, many studies are carried out in controlled environments, such as zoos, which raises doubts about the generalization of the results to wild populations. It therefore believes that, in the future, systematic observation and automated monitoring technologies will contribute significantly to a better understanding of the response of animals.

Flying, singing, nesting

Edorta Unamuno Mirandona agrees with Perez de Villarreal that there are few systematic studies on how eclipses affect animals. Unamuno is an ecosystem biologist who studies birds mainly at the Urdaibai Bird Center. Until now he has not had to live a total eclipse of the Sun and is looking forward to the arrival of August 12 and see how the birds around him respond. In fact, in some documented cases, it is explained that it is spectacular. On this occasion, being so close to sunset, Unamuno foresees that in some species the impact will be less pronounced, “but you will notice it, because clarity is of vital importance in birds,” he says. It also warns of the great diversity of birds, so the response will be very different from one species to another.

He explains that birds have multiple photoreceptors in their eyes and are very sensitive to light. During migrations, for example, according to photoperiod, certain hormones are secreted and many begin to eat to accumulate fat for migration. Night birds, on the other hand, are activated with sunset: owls, mochuelo, etc. And at the same time, other species are prepared for sleep. “The birds belonging to these groups will, of course, undergo a certain change in behavior when the light disappears,” Unamuno predicts.

And he continues: “At that time, on August 12th? By then, large swallows will begin to be harvested in the area during migration. The swallows migrate during the day and when the sunset arrives they look for a place to rest, usually marshes and carrizales of the marshes. They meet in large groups and we have seen, for example, that at 5:00 p.m. a great storm enters and the black clouds cover the Sun and the swallows descend before time to the places where they sleep. So I guess something like that will happen in the case of the eclipse as well.”

In addition to the eyes, the response of the birds at the time of the eclipse will be perceived by the ear. “Some will sing at dusk, that’s for sure. We, here, have the last singers and the first jokes. That day, as the eclipse takes place, they will perform songs of dusk and retreat, thinking that it is night. And soon, the day will come again. And they'll sing again. It'll be weird." Unamuno plans to record all these details through its cameras at the Urdaibai Bird Center.

Suddenly the question arises: What will the bats do? The zoologist Joxerra Aihartza Azurtza answers the question. To begin with, he makes it clear that, just as there is a lot of diversity among birds, so does the bats. However, bats have been much less observed during eclipses than birds. There is less documentation.

However, it anticipates that some species will not even detect it: “Those who live inside the caves and do not come out until they are completely awake will not be aware that the Sun has disappeared for a while. Because they live according to the chronobiological clock, not according to clarity. But not all bats are like that, much less. There are those who live hanging from trees, such as tropical species, as well as some who live quite high in North America. And some here live under the bark of trees, and in attics and such places. All of them will detect the change in luminosity. These are the most opportunistic, which are activated at sunset. The eclipse will encourage them to come out. But it won't change their behavior much. In fact, first some specimens come out and stay around the burrow making social songs. They walk in and out, and so they will walk during the eclipse, otherwise the sunset is near.”

He admits that he will follow the eclipse but does not intend to investigate with bats. In fact, he doesn't think it would have been significant. “Each eclipse occurs at a different latitude, with different climates, at different times, so the impact is different. And it also varies a lot depending on the species. It’s very difficult to do meaningful research on this issue.”

Citizen science

Citizen science projects help to fill the gaps in research, and some have also emerged around the eclipse. They have also been made in previous eclipses and some have been very productive. For example, NASA launched a project called Eclipse Soundscapes with the annular solar eclipse of 2023 seen from North America, which continued with the complete equipment of 2024. The project will be closed in 2026, while all the data collected by the volunteers is visible and audible (the recordings cover a total of 45,000 hours).

For audio recordings of birds, Birdnet has been used and the first results of the analyses have also been revealed. For example, it has been observed that birds belonging to the families Paridae and Icteridae tend to silence and begin to do so 22 minutes before the eclipse completes. After 45 minutes of total darkness, they return to sing as usual. The Corvidae and Strigidae, on the other hand, sing more when the Sun disappears.

On August 12, many citizens of the Basque Country will be able to confirm this type of behavior. And they will probably never forget the tremor that the eclipse has created in their bodies.