Banyak perubahan perilaku binatang beberapa saat sebelum datangnya gempa. Anjing yang ribut menggonggong, kucing yang gugup melompat keluar rumah, burung yang ramai berkicau, tikus berlari keluar dari lubangnya, lebah berkerumun di luar sarangnya dan banyak lainnya adalah beberapa contoh yang sudah teramati (review Kirschvink, 2000). Kirschvink (2000) lebih lanjut mengatakan jika evolusi perilaku diperhatikan, sangat mungkin adanya hubungan antara getaran awal seismik kecil yang diterima oleh hewan kemudian dipersepsikan dengan tingkah laku penyelamatan diri hewan tersebut.
Meskipun gejala tersebut mungkin terlalu singkat untuk membuat suatu ‘prediksi’, namun untuk suatu ‘peringatan dini’, terutama untuk upaya penyelamatan diri, mungkin hal tersebut dapat digunakan.Laporan Grant & Halliday (2010) yang dipublikasi pada Journal of Zoology menyebutkan bahwa salah satu jenis kodok (Bufo bufo) diduga dapat mendeteksi adanya aktifitas seismik dan mengubah perilaku pemijahan ke modus perpindahan. Hingga 96% kodok jantan menggagalkan aktifitas pemijahan mereka lima hari sebelum terjadinya gempa bumi di L’Aquilla Italia pada tahun 2009. Bahkan, tidak ada kodok yang berpasangan pada tiga hari sebelum gempa terjadi. Lebih menariknya lagi, ternyata tidak ditemukan adanya pemijahan sejak gempa hingga lewat masa bahaya (gempa magnitude >4).
Researchers from The Open University reported that 96 per cent of male toads (Bufo bufo) in a population abandoned their breeding site five days before the earthquake that struck L’Aquila in Italy in 2009. The breeding site was located 74 km from the earthquake’s epicentre.
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. The number of toads breeding at the study site was known to increase during a full moon. However, following the earthquake the number of toads present during a full moon was 34, in comparison to between 67 and 175 individuals in previous years.
“Our study is one of the first to document animal behaviour before, during and after an earthquake. 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,” says lead author Dr Rachel Grant.
ref:
http://www.zsl.org/science/news/toads-earthquake-exodus,696,NS.html
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