Nature
PUBLISHED
In the winter of 1975, farmers in the fields surrounding the Chinese city of Haicheng were confused when they suddenly came across hundreds of dead snakes lying in the fresh snow.
Not long after, they noticed that their farm animals were refusing to go into their barns, and the chickens started running around like, well, headless chickens. Dogs started barking uncontrollably, and cats refused to enter their houses.
Taking heed of these unusual behaviors, local officials took the extraordinary decision to evacuate the city. And not a moment too soon.
Just a few hours later and Haicheng was hit by a 7.3 magnitude earthquake that rumbled through the city and damaged up to 90 percent of all buildings. Yet because the locals had paid attention to the warnings from their animal companions, only a few human casualties were reported and thousands of lives were likely saved.
Animal warnings
This isn’t the first time that people have seen animals behaving weirdly in the build up to earthquakes.
In fact, the first reports of this occurring date back to 373 BCE when the Greek historian Thucydides recorded various animals including rats and weasels fleeing the city of Helice days before an earthquake hit.
Since then, there have been a whole menagerie of animals recorded as behaving in strange ways, actively moving to higher ground, or moving out into the open such as the unfortunate hibernating snakes in China. This has included tigers, goats, horses, and buffalo.
Just last year elephants at San Diego Zoo Safari Park went viral for immediately performing an “alert circle” around the herd’s two young calves when a magnitude 5.2 earthquake shook the state.
And it’s not just land animals that seem tuned into these shifts in the Earth beneath our feet. Point Defiance Zoo & Aquarium in Washington state posted footage online of their fish and sharks making a dash for it when a 4.2 magnitude earthquake rumbled through Tacoma.
In 2022, a rescued sea turtle was released off the coast of eastern Australia with a little satellite tag attached. The GPS recorded the turtle swimming 1,867 kilometers (1,160 miles) almost due east into the Pacific Ocean, until doing an abrupt U-turn and heading back towards Australia.
Two days later, an underwater volcano erupted in island nation of Tonga triggering a tsunami with 15-meter-high (50-foot) waves. It appears the turtle sensed the incoming event and skedaddled out of there.
What are the animals sensing?
Yet despite this phenomenon having been anecdotally recorded for millennia, we’re still not entirely sure as to what is going on.
One theory suggests that in the buildup to an earthquake, the rocks deep underground are under extreme stress. This, it is hypothesized, could lead to the release of electromagnetic changes that flow to the surface of the Earth’s crust just above the epicenter and ionize the air molecules.
These spread out from the point of origin, possibly alerting any animals tuned in to pick up these perturbations. The stressed fault could also be releasing low frequency rumblings.
Another raises the possibility that the developing earthquakes could induce the creation of particular chemicals, such as hydrogen peroxide in the water or ozone on land. In 2001, for example, satellites recorded a surge in carbon monoxide in the days before an earthquake hit Gujarat, India.
It is feasible that these chemicals are being sensed by different animals in different environments.
In all likelihood, there probably isn’t a once size fits all solution. Different animals are probably reacting to different cues, for example we know that elephants communicate through ultra-low frequency waves while turtles are sensitive to magnetic fields.
Whether or not animals could be used to predict these events is harder still. More data is needed on the tracking of animals, which is hard to do on the scale that would be needed to create any model that could be of any use.
