1 December 2011
By Victoria Gill – Science reporter, BBC Nature
Can pond-dwelling animals pick up pre-earthquake signals?
Animals may sense chemical changes in groundwater that occur when an earthquake is about to strike.
This, scientists say, could be the cause of bizarre earthquake-associated animal behaviour.
Researchers began to investigate these chemical effects after seeing a colony of toads abandon its pond in L’Aquila, Italy, in 2009 – days before a quake.
They suggest that animal behaviour could be incorporated into earthquake forecasting.
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” – Rachel GrantThe Open University
The team’s findings are published in the International Journal of Environmental Research and Public Health. In this paper, they describe a mechanism whereby stressed rocks in the Earth’s crust release charged particles that react with the groundwater.
Animals that live in or near groundwater are highly sensitive to any changes in its chemistry, so they might sense this days before the rocks finally “slip” and cause a quake.
The team, led by Friedemann Freund from Nasa and Rachel Grant from the UK’s Open University hope their hypothesis will inspire biologists and geologists to work together, to find out exactly how animals might help us recognise some of the elusive signs of an imminent earthquake.
The L’Aquila toads are not the first example of strange animal behaviour before a major seismic event. There have been reports throughout history of reptiles, amphibians and fish behaving in unusual ways just before an earthquake struck.
STRANGE OR NOT
- In July 2009, just hours after a large earthquake in San Diego, local residents discovered dozens of Humboldt squid washed up on beaches. These deep sea squid are usually found at depths of between 200 and 600m
- At 5.58am on 28 June 1992 the ground began to shake in the Mojave Desert, California, right in the middle of a scientific study on desert harvester ants. Measurements revealed the ants did not change their behaviour at all during the earthquake, the largest to strike the US in four decades.
In 1975, in Haicheng, China, for example, many people spotted snakes emerging from their burrows a month before the city was hit by a large earthquake.
This was particularly odd, because it occurred during the winter. The snakes were in the middle of their annual hibernation, and with temperatures well below freezing, venturing outside was suicide for the cold-blooded reptiles.
But each of these cases – of waking reptiles, fleeing amphibians or deep-sea fish rising to the surface – has been an individual anecdote. And major earthquakes are so rare that the events surrounding them are almost impossible to study in detail.
This is where the case of the L’Aquila toads was different.
Ms Grant, a biologist from the Open University, was monitoring the toad colony as part of her PhD project.
“It was very dramatic,” she recalled. “It went from 96 toads to almost zero over three days.”
Ms Grant published her observations in the Journal of Zoology.
“After that, I was contacted by Nasa,” she told BBC Nature.
Scientists at the US space agency had been studying the chemical changes that occur when rocks are under extreme stress. They wondered if these changes were linked to the mass exodus of the toads.
Their laboratory-based tests have now revealed, not only that these changes could be connected, but that the Earth’s crust could directly affect the chemistry of the pond that the toads were living and breeding in at the time.
All of the toads left the breeding colony days before the 2009 earthquake
Nasa geophysicist Friedemann Freund showed that, when rocks were under very high levels of stress – for example by the “gargantuan tectonic forces” just before an earthquake, they release charged particles.
These charged particles can flow out into the surrounding rocks, explained Dr Freund. And when they arrive at the Earth’s surface they react with the air – 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.
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.
It’s a complicated mechanism and the scientists stress that it needs to be tested thoroughly.
But, Dr Grant says this is the first convincing possible mechanism for a “pre-earthquake cue” that aquatic, semi-aquatic and burrowing animals might be able to sense and respond to.
“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,” she said.
Dr Freund said that the behaviour of animals could be one of a number of connected events that might forecast an earthquake.
“Once we understand how all of these signals are connected,” he told BBC Nature, “if we see four of five signals all pointing in [the same] direction, we can say, ‘ok, something is about to happen’.”
* * *
Toads can ‘predict earthquakes’ and seismic activity
Wednesday, 31 March 2010
By Matt Walker
Editor, Earth News
Common toads sense danger
Common toads appear to be able to sense an impending earthquake and will flee their colony days before the seismic activity strikes.
The evidence comes from a population of toads which left their breeding colony three days before an earthquake that struck L’Aquila in Italy in 2009.
How toads sensed the quake is unclear, but most breeding pairs and males fled.
They reacted despite the colony being 74km from the quake’s epicentre, say biologists in the Journal of Zoology.
It is hard to objectively and quantifiably study how animals respond to seismic activity, in part because earthquakes are rare and unpredictable.
Some studies have been done on how domestic animals respond, but measuring the response of wild animals is more difficult.
Even those that have been shown to react, such as fish, rodents and snakes tend to do so shortly before an earthquakes strikes, rather than days ahead of the event.
However, biologist Dr Rachel Grant of the Open University, in Milton Keynes, UK, was routinely studying the behaviour of various colonies of common toads on a daily basis in Italy around the time a massive earthquake struck.
Her studies included a 29-day period gathering data before, during and after the earthquake that hit Italy on 6 April 2009.
The quake, a 6.3-magnitude event, struck close to L’Aquila city, about 95km (60 miles) north-east of Rome.
Dr Grant was studying toads 74km away in San Ruffino Lake in central Italy, when she recorded the toads behaving oddly.
Five days before the earthquake, the number of male common toads in the breeding colony fell by 96%.
That is highly unusual for male toads: once they have bred, they normally remain active in large numbers at breeding sites until spawning has finished.
Yet spawning had barely begun at the San Ruffino Lake site before the earthquake struck.
Also, no weather event could be linked to the toads’ disappearance.
Three days before the earthquake, the number of breeding pairs also suddenly dropped to zero.
While spawn was found at the site up to six days before the earthquake, and again six days after it, no spawn was laid during the so-called earthquake period – the time from the first main shock to the last aftershock.
“Our study is one of the first to document animal behaviour before, during and after an earthquake,” says Dr Grant.
She believes the toads fled to higher ground, possibly where they would be at less risk from rock falls, landslides and flooding.
Exactly how the toads sense impending seismic activity is unclear.
The shift in the toads’ behaviour coincided with disruptions in the ionosphere, the uppermost electromagnetic layer of the earth’s atmosphere, which researchers detected around the time of the L’Aquila quake using a technique known as very low frequency (VLF) radio sounding.
Such changes to the atmosphere have in turn been linked by some scientists to the release of radon gas, or gravity waves, prior to an earthquake.
In the case of the L’Aquila quake, Dr Grant could not determine what caused the disruptions in the ionosphere.
However, her findings do suggest that the toads can detect something.
“Our findings suggest 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,” she says.
Ants ignore quakes
One other study has quantified an animal’s response to a major earthquake.
Researchers had the serendipitous opportunity to measure how the behaviour of the desert harvester ant (Messor pergandei) changed as the ground began to tremble in the Mojave Desert, California, on 28 June 1992.
The largest quake to hit the US in four decades struck during the middle of an ongoing study, which measured how many ants walked the trails to and from the colony, the distributions of worker ants and even how much carbon dioxide the ants produced.
However, in response to that 7.4 magnitude quake, the ants did not appear to alter their behaviour at all.