LONDON ��" Scientists may have a new ally in the struggle to predict deadly earthquakes ��" bufo bufo, the common toad. British researchers said Wednesday that they observed a mass exodus of toads from a breeding site in Italy five days before a major tremor struck, suggesting the amphibians may be able to sense environmental changes, imperceptible to humans, that foretell a coming quake. Researchers from the Open University were studying toads in central Italy when they noticed a sharp decline in the number of animals at the site. Days later, a 6.3-magnitude earthquake hit, killing hundreds of people and badly damaging the town of L'Aquila. Researcher Rachel Grant said the findings suggested "that toads are able to detect pre-seismic cues such as the release of gases and charged particles, and use these as a form of earthquake early warning system." Initially puzzled by the toads' disappearance in the middle of the breeding season, the scientists tracked the population in the days that followed. They found that 96 per cent of males ��" who vastly outnumber females at breeding spots ��" abandoned the site, 46 miles (74 kilometers) from the quake's epicenter, five days before it struck on April 6, 2009. The number of toads at the site fell to zero three days before the quake, according to the study, published in the Zoological Society of London's Journal of Zoology. "A day after the earthquake, they all started coming back," said Grant, the report's lead author. "The numbers were still lower than normal and remained low until after the last aftershock." She said one possibility is that the animals sensed a change in the amount of radon gas emitted by the Earth because of the buildup of pressure prior to a quake. Scientists also have surmised that animals may be able to detect minor tremors imperceptible to humans, or that they sense electrical signals emitted by rocks under stress before an earthquake. Grant said the sense might be the result of millions of years of evolution, a trigger that tells the toads to move to safer ground. "An earthquake could wipe out a population in that area," she said. "A landslide or flood could wipe out virtually 100 percent of the males, and quite a lot of the females." Since ancient times, anecdotes and folklore have linked unusual animal behavior to cataclysmic events like earthquakes, but hard evidence has been scarce.
