There have been loads of reports of animals acting strangely shortly before an earthquake occurs. This has caused researchers to wonder whether animals can provide forewarnings to future quakes. Some seismologists say that the movement of underground rocks before an earthquake sends an electrical signal that only animals can sense. Other theories have also been proposed. The US Geological Survey has noted that animals are more likely to perceive of the signals emitted from earthquakes sooner than humans, meaning they can pick up on them before the shaking is felt.
This is interesting for a number of reasons, but could reports of early detection of earthquakes by animals lead to new ways of preparing for earthquakes that could save lives? What is known is that prior to large-scale earthquakes such as the Tōhoku earthquake in Japan and the Wenchuan earthquake in China, a wide variety of animals including zebras, tigers, elephants and dogs were reported to have been acting erratically prior to both earthquakes. Coincidence? Maybe. After all, don’t animals act bizarrely for other reasons regardless of whether an earthquake is about to hit or not? But incidents of animals behaving strangely prior to an earthquake are far from a recent phenomenon, it goes back to ancient history.
According to the USGS, in Greece in 373 BC, ‘Rats, weasels, snakes, and centipedes reportedly left their homes and headed for safety several days before a destructive earthquake. Anecdotal evidence abounds of animals, fish, birds, reptiles, and insects exhibiting strange behaviour anywhere from weeks to seconds before an earthquake.’ So not only do we have anecdotal evidence from the present alluding to earthquake forewarnings from animals, but even ancient civilizations have reported similar sightings. But the portrayal of such happenings seems less like science and more like a growing collection of forteana, in other words, unexplainable anomalies that usually have no factual basis beyond first or even secondhand reports.
Should science simply ignore these reports or hypotheses regarding possible connections between animal behaviour and earthquakes, or could there be something to’em? While some scientists have been fervent about developing techniques to detect earthquakes ahead of time, we are still clueless as to when they occur. Maybe animals hold a missing piece to the puzzle, as we often forget that even what we call ‘science’ is still a product of our senses and if we were to experience the world through the eyes and ears of some of our close and distant relatives in the animal kingdom, our perception would transform dramatically. If animals are giving warnings for when earthquakes occur, perhaps it would be wise to listen in.
In 1975, the city of Haicheng in China was evacuated days before a 7.3 mag earthquake, if they had not been evacuated 150,000 people could have been killed or injured. According to Chinese officials, the reason the evacuation took place is because of the ‘strange antics’ of animals prior to the quake, but there was a series of foreshocks reported before the earthquake which likely led to the evacuation. But it’s important to keep in mind that environments change in sometimes subtle, but significant ways prior to and after an earthquake occurs. Since many animals are far more sensitive to their immediate environments then say humans that spend most of their time indoors. In other words, animals have the capability of knowing things people simply can’t experience, which is one of the reasons why they are studied in the first place. Animals as small as zooplankton or as big as polar bears tell us something about the environments we live in that simply cannot be known without them. Despite the foreshocks, in Haicheng there were nearly 100 sightings of snakes coming out of hibernation during below freezing temperatures within one month prior to the earthquake, anecdotal or not, it is difficult to ignore.
According to a study published last summer in the International Journal of Environmental Research and Public Health, common toads were observed to behave unusually prior to the 6.3 mag earthquake in L’Aquila, Italy. A few days before the earthquake the toads left a small lake about 75 km from the epicentre, not returning until after the subsequent aftershocks from the quake. Authors of the study examined potential changes in groundwater chemistry prior to the seismic event and what effects they have on animals. Why would toads leave their beloved breeding site suddenly without warning five days before a fairly large earthquake? Researchers note that ‘there was a major extension of the earthquake-related phenomena to the north of the epicentre, including earthquake lights and electrical anomalies’.
Of course the conventional explanation is that the toads stopped breeding because of more usual changes to the environment, but if this were the case it wasn’t immediately obvious as lack of rainfall, for example. In fact it was rainier than usual at the time so the toads should have been breeding more. But there is an interesting explanation that while strange in itself is still physical in nature, although one that demands further study. The disturbance that led to the evacuation of the toads from their happy breeding ground may have been due to the build-up of electrically charged particles at ground level caused by physical processes prior to the earthquake. These charge carriers inject positive airborne ions into the Earth’s atmosphere that affect the ionosphere — the magnetic field that goes around the whole planet — shielding it from the solar wind whose interactions with the field create spectacular displays of light better known as the ‘aurora borealis‘ or ‘northern lights’.
These disturbances consist of changes in the transmission characteristics of radiowaves along direct great circle paths between two stations. The changes arise between sunset and sunrise, e.g., during the dark hours, when the ionosphere above the region of interest, in this case central Italy, moves out of and back into the influence of the ionizing solar radiation, respectively. Processes that occur at the Earth surface before major earthquakes have an influence on the concentration profile of free electrons in the ionospheric plasma [48,49]. Electrons contribute primarily to the mirror-like reflection of radiowaves, which allows them to be transmitted over long distances. Therefore a change in the vertical distribution of electrons in the ionosphere causes a distinct shift in the so-called terminator times, e.g., in the transmission characteristics around sunset and sunrise [50,51]. (Ground Water Chemistry Changes before Major Earthquakes and Possible Effects on Animals)
According to the study, this ionospheric disturbance coincided with the time the toads left the lake. Lights have also been reported or ‘cold flames’ that are visible prior to the earthquake. This video of ‘earthquake lights’ was supposedly taken 30 minutes prior to the 2008 Wenchuan earthquake in China.
The combined evidence provided by the toad observation at the lake near L’Aquila and the ionospheric disturbance data as derived from radiosounding suggests that the toads were able to perceive in their environment some pre-seismic cues, which warned them of the impending earthquake. The toads may have responded to pre-seismic signals as a simple avoidance reaction to an adverse stimulus or as an evolved adaptation . A possible reason for the toads’ apparent movement to higher ground  might be found in an evolutionarily imprinted response to the danger of landslides and flooding. However, both of these explanations lack credibility, in particular the flooding argument because common toads are semi-aquatic during the breeding season and would be unlikely to leave flooded lowlying land around the lake. (Ground Water Chemistry Changes before Major Earthquakes and Possible Effects on Animals)
Above is an illustration of the charge carrier concept from the study. Charge carriers activated by tectonic stresses build-up along the Earth’s surface affecting the ionosphere.
While the relationship between earthquakes and animal behaviour seems credible to some degree, there seems a great deal more to explain when it comes to understanding how this could be integrated into any programme of earthquake risk management in the future, if at all. But simply because the cause of strange animal behaviour prior to earthquakes is not well understood or is viewed as too anomalous to be of importance, doesn’t mean it couldn’t lead to useful ways for preparing for or forecasting earthquakes. Indeed, like many of the lesser known realms that science explores, maybe it could lead to something incredible. Maybe.
References and Further Reading
Can Animals Sense Earthquakes? National Geographic
Ground Water Chemistry Changes before Major Earthquakes and Possible Effects on Animals. International Journal of Environmental Research and Public Health
The earthquake lights (EQL) of the 6 April 2009 Aquila earthquake, in Central Italy. Natural Hazards and Earth System Sciences
Grant, R., Halliday, T., Balderer, W., Leuenberger, F., Newcomer, M., Cyr, G., & Freund, F. (2011). Ground Water Chemistry Changes before Major Earthquakes and Possible Effects on Animals International Journal of Environmental Research and Public Health, 8 (6), 1836-1856 DOI: 10.3390/ijerph8061936