Common toads (Bufo bufo) can detect impending seismic activity and alter their behaviour from breeding to evacuation mode, suggests a new study in the Zoological Society of London's (ZSL) Journal of Zoology.

Researchers from The Open University reported that 96 per cent of male toads in a population abandoned their breeding site five days before the earthquake that struck L'Aquila in Italy in 2009.

The number of paired toads at the breeding site also dropped to zero three days before the earthquake. No fresh spawn was found at the site from the date that the earthquake struck to the date of the last significant aftershock (magnitude >4.5).

Breeding sites are male-dominated and the toads would normally remain in situ from the point that breeding activity begins, to the completion of spawning.

This shift in the toads' behaviour coincided with disruptions in the ionosphere, the uppermost electromagnetic layer of the earth's atmosphere, which were detected using very low frequency (VLF) radio sounding.

The release of radon gas, or gravity waves prior to an earthquake have both been attributed to changes in atmospheric electric fields and currents. In this case the cause of the ionosphere disruptions was not determined.

Other environmental changes that affect toad behaviour, including lunar phases and changing weather conditions were accounted for.

"Common toad, Bufo bufo. (Credit: iStockphoto/Alasdair Thomson)"

Source: Zoological Society of London