London, Dec 9: Two biology researchers from UK's Open University have done a study to say that toads can be used to predict earthquakes because certain species are able to sense chemical changes in groundwater immediately before any major seismic activity.
The researchers, led by Friedemann Freund from Nasa and Rachel Grant from the UK's Open University, hope their findings will inspire biologists and geologists to work together in improving earthquake prediction.
Rachel Grant, a biologist, was monitoring the toad colony as part of her PhD project in the days before the Italian earthquake disaster.
"It was very dramatic. It went from 96 toads to almost zero over three days. After that, I was contacted by Nasa," she told the BBC, reports Daily Telegraph.
Experts began investigating the theory after a colony of toads was observed abandoning a pond in L'Aquila, Italy, in 2009, days before the devastating earthquake.
They believe that stressed rocks in the Earth's crust release charged particles before an earthquake, which react with groundwater.
Animals living in or near groundwater, such as toads, are highly sensitive to such changes and may therefore notice signs of an impending quake.
Although not the first example of abnormal animal activity observed prior to earthquakes, the case of the L'Aquila toads was different in that they were being studied in detail at the time.
Scientists at the US space agency had been studying the chemical changes that occur when rocks are put under extreme stress and questioned whether they were linked to the toads' departure.
Lab tests have since suggested that changes in the Earth's crust could have directly affected the chemistry of the pond that the toads were living and breeding in at the time.
Dr Freund, a Nasa geophysicist, said that the charged particles, released from stressed rocks, react with the air when they reach the Earth's surface, converting air molecules into charged particles known as ions.
"Positive airborne ions are known in the medical community to cause headaches and nausea in humans and to increase the level of serotonin, a stress hormone, in the blood of animals," said Dr Freund.
They can also react with water, turning it into hydrogen peroxide, the scientist added.
This chemical chain of events could affect the organic material dissolved in the pond water, turning harmless organic material into substances that are toxic to aquatic animals.
Dr Grant added: "When you think of all of the many things that are happening to these rocks, it would be weird if the animals weren't affected in some way.
"Once we understand how all of these signals are connected, if we see four of five signals all pointing in [the same] direction, we can say, 'OK, something is about to happen'."
The team's findings are published in the International Journal of Environmental Research and Public Health.