Can Toads Predict Earthquakes?

(March 30) -- For thousands of years, people have been speculating that animals can foresee natural disasters. Birds, snakes, chickens, dogs and cows have all been reported to have this seemingly magical ability. Yet all of the evidence has been anecdotal -- a story here, a rumor there, but nothing reliable.

Now, a pair of scientists may have documented proof that this foresight could be real. In the current issue of the Journal of Zoology, behavioral biologists Rachel Grant and Tim Halliday of the Open University report that large numbers of toads fled a breeding area five days before a magnitude-6.8 earthquake struck L'Aquila, Italy, in April 2009.

The scientists have not answered the critical question -- exactly how the toads might have sensed the disaster -- but they do suggest a way of studying the phenomenon in the future.

For the four years prior to the quake, Grant had been regularly studying the breeding habits of toads at San Ruffino Lake, which is 46 miles from the epicenter. Normally, as the full moon approached, more and more toads would come down to a shallow pool at the lake's edge from the surrounding hills to breed. Grant would monitor their numbers, recording the weather and other environmental conditions.

Last year, she and an assistant were tracking the toads leading up to the full moon when they noticed a surprising change. "Their numbers were increasing," Grant told AOL News, "and then one day we came and there were hardly any toads. The next day there was one. And then none."

Typically the population ranged from 67 to 115. Five days before the earthquake, 96 percent of the male toads were gone. In the past, Grant had seen that a change in the weather could keep her subjects away for a day or so. "But usually the day after, they come back. I'd never seen it happen where there were none for several consecutive days," she said.

A few days after the last toads disappeared, the earthquake struck L'Aquila, and Halliday e-mailed Grant to see if she and her assistant were safe. "I wrote back, 'I'm OK, but the toads are all gone,' " Grant recalled.

Yet she admits that she didn't make the connection -- it was Halliday who pointed her to the theory that animals may have some ability to sense impending disasters and suggested that they explore it further. Grant checked the climate records to see if there were any weather-related changes that might have spooked the frogs, but temperature, humidity, wind speed and rainfall were all normal.

The study isn't proof that this apparent phenomenon -- which the U.S. Geological Survey lists among its common earthquake-related myths -- is real. Grant and Halliday only speculate about what sort of environmental signals the toads might have picked up prior to the earthquake that encouraged them to flee, citing the creatures' innate sensitivity to changes in naturally occurring magnetic fields as one possibility.

Andrew Michael, a seismologist with the U.S. Geological Survey, suggests that foreshocks, or smaller earthquakes that occurred in the run-up to the big event, probably triggered the exodus instead. Michael is generally doubtful that animal behavior can reliably predict these large events, but says that more reliable information is always welcome.

"If someone has good observations like this, then there's something to learn. Even if it doesn't give us something new about earthquakes," Michael said, "maybe it teaches us something new about toads."

Still, Grant hopes that she'll be able to explore the phenomenon again in the coming years. She says she hopes to enlist volunteers -- ideally, scientists who are already studying amphibians -- in earthquake-prone areas such as Indonesia to see if the behavior occurs again.

As for the fact that the phenomenon is often considered more urban legend than hard science, Grant isn't concerned. "Just because something is popularly noted by people doesn't mean it's not true," she said with a laugh. "The fact is that we have to study it properly, in a scientific way, to determine whether it's true or not."