Italian toads can apparently sense earthquakes like the earthquake that struck L’Aquila on April 6th, 2009. We know this because Dr. Rachel Grant of the UK’s Open University was studying a toad population at San Ruffino Lake, around 74km from the quake’s epicenter at the time. What she found was interesting. Five days before the quake, the number of common males in the breeding colony dropped by 96 percent. If that wasn’t enough, most breeding pairs and males fled three days before the event. Something was alerting the toads to the impending quake.
So the evidence was circumstantial, but strong. Grant’s findings suggested that toads may be able to sense quakes by their pre-seismic cues, like the release of gases and charged particles, telling them that they need to find higher ground. This led to a further investigation, this time with the help of NASA, and charged particles do in fact appear to be the culprit.
We know that rocks under extreme tectonic stress release charged particles, which also travel through nearby rock and even into the atmosphere. This ionizes the air with tons of positive ions, which we know can affect animals. Humans can experience headaches and nausea for instance, or an increase in serotonin. It is likely that they affect toads in a similar way. They also believe that the ions might have reacted with the toads’ water, creating a possibly toxic hydrogen peroxide environment, making them seek a new area.
It will require further study, but they seem to be on the right track with ions.