Finding a giant oarfish washed up on the beach is a rare occurrence, since the fish is a deepwater species that's rarely seen at all. So when a second oarfish was found just five days later, the rumor mill kicked into high gear.
An 18-foot-long (5.5 meters) oarfish carcass discovered on Oct. 13 was considered a once-in-a-lifetime event for beachgoers on Catalina Island off the coast of Southern California. But that event was followed five days later by a second oarfish, measuring 14 feet (4.3 m), found on a beach in San Diego County.
Now, some are claiming that oarfish washing ashore is a sign that an earthquake will soon follow. Shortly before the 2011 Tohoku earthquake and tsunami struck Japan, about 20 oarfish stranded themselves on beaches in the area, Mark Benfield, a researcher at Louisiana State University, told LiveScience in an earlier interview. [Video - ROV Captures Bizarre Deep-Sea Oarfish]
The oarfish is known in Japan as ryugu no tsukai or "messenger from the sea god's palace," according to the Japan Times. Dozens of the deep-sea denizens were discovered by Japanese fishermen around the time a powerful 8.8-magnitude earthquake struck Chile in March 2010.
Kiyoshi Wadatsumi, a specialist in ecological seismology, told the Japan Times, "Deep-sea fish living near the sea bottom are more sensitive to the movements of active faults than those near the surface of the sea."
Animals sensing earthquakes
These weren't the first times researchers suggested links between animal behavior and earthquakes. Indeed, there's a long history of anecdotal reports of pets, zoo animals and wildlife acting very strangely in the days or minutes before a tremor is felt by humans.
One famous instance is recorded in the history of Helike, an ancient Greek city. During the winter of 373 B.C., "all the mice and martens and snakes and centipedes and beetles and every other creature of that kind in the city left," wrote the Roman author Aelianus. "After these creatures had departed, an earthquake occurred in the night; the city subsided; an immense wave flooded and Helike disappeared."
In February 1975, a 7.3-magnitude earthquake struck Haicheng, a city of 1 million people located in China's Liaoning province. But one day earlier, city officials ordered an evacuation based in part on reports of strange animal behavior: Hibernating snakes in the area, for example, abandoned their winter hideouts months before normal. The early evacuation of Haicheng is credited with saving thousands of human lives. [The 10 Biggest Earthquakes in History]
Zoo officials at the Smithsonian's National Zoological Park in Washington, D.C., reported that many of their animals sought shelter or made distress calls in the minutes before a 5.8-magnitude quake struck the region on the afternoon of Aug. 23, 2010. Nocturnal snakes like copperheads came out of hiding, apes moved into the treetops and flamingos huddled tightly moments before the temblor was felt by zookeepers.
Toads moving uphill
Among the first scientific studies to document animal behavior before an earthquake comes from Italy, where a team of scientists spent a month investigating the breeding behavior of common toads (Bufo bufo) in April 2009. The toads typically breed in a shallow pool on a lakebed.
But at one point, most of the site's toads suddenly disappeared — and five days later, a strong earthquake struck the region. The toads returned to the pool once the quake's last aftershocks occurred. The researchers published their findings in the Journal of Zoology.
"It's the first time that any study has really documented unusual behavior before an earthquake in a scientific and methodical way," lead study author Rachel Grant, a zoologist from The Open University in the U.K., told LiveScience in an earlier interview. "We did it properly and scientifically, and consistently looked at behavior."
What could animals detect?
If animals can sense earthquakes before they occur, what could they be experiencing? There's no agreement on what — or if — animals can sense quakes, but there are some intriguing hypotheses.
In the study involving toads, researchers noticed that "toad activity coincides with pre-seismic perturbations in the ionosphere, detected by very-low frequency (VLF) radio sounding," they wrote. Nonetheless, the scientists weren't able to draw any conclusions from their research about what might have triggered the unusual toad behavior.
In research published in the International Journal of Environmental Research and Public Health in 2011, Grant and a research team found that tectonic stresses in the Earth's crust send "massive amounts of primarily positive air ions into the lower atmosphere."
When these ions reach a body of water, they oxidize "water to [create] hydrogen peroxide. Other reactions at the rock-water interface include the oxidation or partial oxidation of dissolved organic compounds," the authors wrote. The resulting compounds "may be irritants or toxins to certain species of animals," possibly resulting in the toads' migration from an otherwise welcoming pond.
No early-warning system
A group of physicists at the University of Virginia — investigating reports of animal behavior before earthquakes — discovered that rocks, when crushed under high pressure that mimicked the force of an earthquake, emitted high levels of ozone gas.
"Even the smallest rock fracture produced ozone," researcher Catherine Dukes told LiveScience in an earlier interview. "The question is, can we detect it in the environment?" And can animals detect a sudden rise in atmospheric ozone?
None of these hypotheses, however, is ready to be developed into an animal-based, early-warning system for earth tremors.
"This is not a way to predict earthquakes," Dukes said. "It's just a way to warn that the Earth is moving and something — an earthquake, or a landslide or something else — might follow."
Follow Marc Lallanilla on Twitter and Google+. Follow us @livescience, Facebook & Google+. Original article on LiveScience.