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Toads ‘predict earthquakes’

0443 cropped.JPGToads may be able to predict earthquakes, according to a serendipitous set of observations made in Italy.

After every earthquake stories emerge of animals behaving strangely before the ground shook. But hard evidence of animals responding to some kind of mysterious pre-earthquake cue has been lacking.

Now, Rachel Grant of the Open University in Milton Keynes, UK, reports that common toads (Bufo bufo) showed a dramatic change in behaviour five days before an earthquake shook L’Aquila, Italy in April 2009. Grant and her colleague found the toads abandoning spawning days before the shaking started, they report in the Journal of Zoology.

“Our study is one of the first to document animal behaviour before, during and after an earthquake,” says Grant. “It was a serendipitous thing that happened.”

She has been studying frog reproduction during the lunar cycle for four years, and was at a site 74 km from the epicentre of the quake with her assistant between the new moons of March and April. This meant they were watching the ‘seismic toads’ before, during, and after the magnitude 6.3 event.

Male toads usually stay at the breeding sites until spawning is complete, but 96% them abandoned the pool five days before the quake and numbers remained low until 10 days afterwards. The number of amplexed pairs—where males grasp females tightly with their arms—declined to zero just three days before the earthquake and stayed low until the last aftershock.

“One day there were no toads,” says Grant. “I was actually very annoyed. I thought my research was all going down the drain. And the earthquake happened, and then they all started coming back the day after.”

The team suspect the strange toad behaviour was triggered by pre-seismic perturbations in the ionosphere, which were detected by very low frequency radio sounding.


But according to Grant, many of these reports are just anecdotal and they are often taken after the earthquake has happened.

Toads may be the best candidate for earthquake predicting animals, but repeat evidence is unlikely to be forthcoming soon. “Testing this hypothesis would … be very difficult, given the rarity and unpredictability of [earthquakes],” says the paper.

Image: © 2001 John P. Clare


  1. Report this comment

    Friedemann Freund said:

    Obviously the toads do not “predict” earthquakes. All they do is respond to some stimulus in their environment, which is normally absent but rises to some irritation level before a major earthquake like the one that damaged L’Aquila in Italy in April 2009. The scientifically correct question to ask is: What causes the toads to behave in such an unusual manner?

    There are two processes to consider, both driven by the activation of a specific type of highly mobile, highly reactive electronic charge carriers when rocks are subjected to increasing levels of stress: (i) the formation of hydrogen peroxide at the ground-to-water interface and (ii) massive ionization of air at the ground-to-air interface.

    These two processes have been described in two recent scientific papers: (i) Balk, M. et al. Oxidation of water to hydrogen peroxide at the rock–water interface due to stress-activated electric currents in rocks. Earth Planet. Sci. Lett. 283, 87-92 (2009) and (ii) Freund, F. T. et al. Air ionization at rock surface and pre-earthquake signals. J. Atmos. Sol. Terr. Phys. 71, 1824–1834 (2009).

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    karl said:

    This is an interesting study even if it is just a well documented anecdote. I am not sure that it can be considered correlative because there was only one toad colony and one earthquake observed. Perhaps the authors could find two or more locations that are matched in all regards except their probability of having earthquakes. This would be useful in testing if there really is correlation between earthquake activity and toad behavior. By gathering more than one data point the authors would be able to make a stronger case for correlation. Even better would be to show causation by stochastically inducing earthquakes and observing the behavior of toads before and after induction. There is some evidence that large hydroelectric dams induce earthquakes. Additionally, enhanced geothermal power pilot plants are known to induce ~3 magnitude earthquakes. The authors could team up with altarock or some other enhanced geothermal company. They could then monitor toad activity in the area before altarock begins inducing earthquakes. By comparing the toad behavior before drilling and during earthquakes (and carefully controlling for weather, or other likely confounding variables) the authors could build a case for causation.

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    Muhammad Abu Bakar said:

    A moderate earthquake was felt in Khyber Pakhtunkhwa, Northern Areas, FATA and Punjab.

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