Toads behavior predicts earthquakes.
Yannick -Ed
This article from BBC derives from a paper published on 31 march 2010
in the Journal of Zoology. The complete .pdf paper is here :
http://www3.interscience.wiley.com/cgi-bin/fulltext/123337858/PDFSTART
"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.
Sensing danger :
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. "