ON THE morning of 26 December 2004, villagers from Bang Koey in Thailand noticed something strange. A herd of buffalo grazing on the beach lifted their heads, pricked their ears and looked out to sea, then turned and stampeded to the top of a nearby hill. For the baffled villagers who chose to follow them, it was a live-saving move. Minutes later, the tsunami struck.
Since then, there have been hundreds of reports of animals seemingly foretelling the catastrophe – not just minutes, but sometimes hours and even days before it occurred. These include tales of bizarre behaviour across a menagerie of wild beasts including elephants, antelopes, bats, rats and flamingos, plus stories of dogs refusing to go for their usual morning walk along the beach. Could these creatures have been sensing early warning signs of the massive earthquake that triggered the Asian tsunami? It is an outlandish assertion, given that seismologists have so far failed to come up with any sign that might be used to predict that a quake is imminent. Yet, for that same reason, the possibility that animals might hold the answer cannot be ignored. After all, an advance warning system could save thousands or even millions of human lives.
The idea that animals can predict earthquakes has ancient origins. Way back in 373 BC the Greek historian Thucydides recorded descriptions of rats, dogs, snakes and weasels deserting the city of Helice in droves just days before an earthquake of catastrophic proportions hit. It was the first in a long line of such anecdotes. There is also no shortage of theories about what might be going on. What has been lacking, however, is any real scientific data linking strange animal behaviour with earthquakes. Now at last we have some, and from a most unusual quarter. Last November, a psychologist looking for signs of depression in dogs announced that he had stumbled upon this illusive evidence.
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The story begins in late 2000, when Stanley Coren from the University of British Columbia started a study to address the question of whether dogs, like some humans, suffer from “seasonal affective disorder”, commonly known as the wintertime blues. Twice a week, he would email 200 dog owners in Vancouver, asking them to rate their pets’ activity and anxiety levels using a nine-point scale. The results were disappointing. In general there was little daily variability, and Coren’s initial analysis of many months’ worth of information strongly refuted his suspicion that dogs can become depressed during winter. “I just assumed that the data wasn’t going anywhere and put the project on the backburner,” he says. So it was some time before Coren even noticed what he had unknowingly recorded.
“When I finally did go through the figures in detail a couple of years later, I noticed this strange point of data just floating there.” The anomaly occurred on 27 February 2001. Of the 193 dogs recorded that day, 47 per cent (91) were well above their usual baseline for activity and 49 per cent (95) – mostly the same dogs – were well above their usual baseline for anxiety. Both measures were statistically significant, and the likelihood of a difference this big happening by chance was less than 1 in 1000.
At first Coren thought that severe weather, perhaps a thunderstorm, might have driven the dogs berserk. Flicking through the newspaper archives proved him wrong. Instead, he noticed the earthquake. On 28 February a quake of magnitude 6.8 shook the Pacific north-west, with an epicentre at Nisqually, Washington, about 240 kilometres south of Vancouver.
Coren was fascinated by his chance discovery and started to wonder what the dogs could possibly have sensed. There were few clues in the standard literature. Seismologists looking for signals foretelling a major earthquake have failed miserably to find any. Even the famed Parkfield experiment in California, the most comprehensive long-term earthquake research project in the world, has so far drawn a blank. Since 1985, researchers from the US Geological Survey (USGS) and the State of California have exhaustively monitored a section of the San Andreas fault near the town of Parkfield. They have analysed every tremor, measured tiny movements of the fault, known as creep, at 10-minute intervals, and even looked for changes in water levels in local wells to see if seismic activity might raise or lower them. To date, the project has revealed nothing that would reliably indicate that a quake is imminent.
Despite this, the mass of anecdotal evidence about animals predicting earthquakes has attracted much speculation about what they might be sensing. One idea is that some animals detect changes in the Earth’s electrical field – although the very existence of electromagnetic changes associated with earthquakes is disputed. Another theory is that animals are responding to subterranean gases such as radon and hydrogen released from rocks before a quake – despite the fact that few experts accept that such gases are in fact produced.
A more exotic explanation comes from perhaps the most outspoken and controversial champion of the idea that animals can predict earthquakes, Rupert Sheldrake, a biologist and director of the Perrott-Warrick Project in London, which researches unexplained human and animal abilities. “People notice unusual animal behaviour before all sorts of disasters ranging from earthquakes to air raids,” he says. “I think animals are picking up on something that we are not. It could be electromagnetic, or perhaps even a sixth sense.”
Coren’s attention, however, was drawn to a more down-to-earth idea. He suspected the dogs in his study might simply be hearing vibrations. “I had read a number of reports stating that people working in avalanche search and rescue operations believed their dogs could hear victims buried deep beneath the snow, and started wondering if dogs could hear something before an earthquake.” So back he went to his data to see whether there was any evidence to support this.
“Could dogs be hearing something before an earthquake?”
Sure enough, Coren discovered that of the 14 dogs in his study that had hearing impairments, only one had shown any significant increase in anxiety that day, and it was living with a hearing dog that had also become anxious. Encouraged by this finding, he went on to look for factors that might explain why some dogs became agitated on 27 February and others did not. He found that dogs with floppy ears showed only half the change in activity and one-third the change in anxiety levels of dogs with pricked ears. Not only would an ear flap reduce the amount of sound reaching the inner ear, Coren also realised that it would attenuate high-frequency sounds more than low-frequency ones. What’s more, dogs with smaller heads were significantly more likely to behave strangely before the earthquake than those with larger heads, with nearly double the increase in anxiety and activity. This was particularly interesting given that dogs with smaller heads tend to be more sensitive to high frequencies than those with larger heads.
Taken together, Coren’s results present an alluring hypothesis. He suggests that the kind of high-frequency sounds that many dogs can hear are emitted before an impending earthquake, perhaps from rocks scraping or breaking underground.
Admittedly this is only one study. Even if Coren is right about dogs, it is still possible that other animals may be able to predict quakes in different ways. Still, his findings will appeal to anyone interested in putting the phenomenon on a more scientific footing. One of these is Eric Wikramanayake, a conservation scientist with WWF, who happened to be studying elephants in Sri Lanka when the Asian tsunami struck. “There were all these reports of elephants fleeing beaches hours and even days before, due to a sense of impending danger, which people attribute to a sixth sense,” he says. “Our data just do not show any of this.”
Elephants take cover
Like Coren, Wikramanayake had not set out to investigate earthquake prediction. He was interested in how elephants use their habitats and how they range over them, so had radio collared animals in two different herds to monitor their movements. This gave him information about all the elephants’ comings and goings both before the massive earthquake that caused the tsunami – which was 1000 kilometres out to sea – and during the time it took for the tsunami to hit Sri Lanka. What he found was precisely nothing. One herd was only 100 metres away from the beach when the tsunami arrived and all they did was take cover behind a large sand dune when the wave came within sight. The other herd was safely located about 5 kilometres inland and did not show any unusual movements before, during or after the event.
That is at least consistent with Coren’s idea that dogs are detecting high-frequency sounds. Elephant hearing is geared towards low frequencies, and they only reacted once they could see they were in danger. “Based upon what we observed, I don’t think there is a need for us to invoke a sixth sense to explain the elephant behaviour,” Wikramanayake says. “As far as I can tell, the evidence from dogs and elephants is strongly suggesting that we need not look any further than the five senses we already know about.”
If Coren’s idea is correct, however, that raises the question of why the extensive Parkfield experiment has detected nothing. The answer may lie in finances and logistics. “We expected to see an earthquake of 6.0 or more at Parkfield within seven years of the project start date, and it didn’t happen,” says seismologist Peggy Hellweg from the University of California, Berkeley. The expected earthquake eventually struck in 2004, but by that time inaccessible instruments had started to fail, and some researchers were leaving to put their efforts into other research projects. “[The acoustic detection] system was funded and run by IBM but they had pulled out of the experiment by 1991,” says USGS seismologist Andy Michael.
In any event, it is debatable whether the Parkfield project would have detected any acoustic early warning signals even if a quake had come sooner. Hellweg points out that the activity associated with different earthquakes is highly variable. “We don’t understand earthquakes well enough to say why each quake gives off different signals.”
Even if some quakes are preceded by high-frequency vibrations, is it feasible that dogs in Vancouver could detect sounds emitted near Nisqually? Michael is extremely sceptical. He points out that the epicentre of the quake was over 240 kilometres south of Vancouver. “It is physically implausible for seismic waves in the kilohertz range to travel that far and be above the background noise level,” he says. “After all if they have trouble getting through a dog’s ear flap, how will they get through hundreds of kilometres of rock?” Normally, he adds, seismic waves at such high frequencies are only detectable at most a few tens of metres away from their source.
Although Michael is unconvinced by Coren’s ideas, he is intrigued by the blip in the data. “I am inclined to believe that this is just an extraordinary coincidence,” he says. But he adds a cautionary tale. “When Alfred Wegener presented his theory of continental drift he proposed mechanisms for continental movement that were easily disproved. His core ideas about tectonics were right but nobody was listening because the mechanisms were wrong.”
Besides, if animals such as dogs really are able to foretell earthquakes, does it really matter how? Given the potential to save human lives, Sheldrake thinks not. “We know that before at least some earthquakes animals behave strangely. That should be a powerful incentive for us to develop some sort of prototype warning system.” The idea is not so far-fetched. While western society has been reluctant to use animals as earthquake predictors, China has embraced the idea (see “Quake alert”). At the Nanning earthquake bureau in south central China, experts use a video link to keep a 24-hour watch on snakes in farms across the country. If animals in any of the farms begin making desperate and concerted attempts to escape from their enclosure, the observers raise a warning.
Other governments may not be willing to go that far just yet, but Coren believes they should at least explore the possibility of animal quake prediction. “A centre that people could call in to when they see unusual things would be useful,” he says. “We would be able to collect much more data – and if that proves useful we could begin considering giving warnings when we suddenly get hundreds of calls from a single area.” It could cost little more than the price of setting up a phone line. Put that way, what have we got to lose?
Quake alert
It is a tale of two earthquakes. Both were similar in magnitude, both hit cities with populations of about a million. One killed 25 per cent of the city’s inhabitants, the other killed fewer than 3 per cent. The reason? One was predicted, the other was not.
In the winter of 1974/75, scientists began to notice widespread changes in land elevation and ground water levels around the Chinese city of Haicheng in the north-eastern province of Liaoning. With these clear signs of seismic activity, the authorities faced an age-old dilemma: evacuate and risk an expensive false alarm, or sit tight and hope for the best. At first they issued a low-level alert, but as the months passed, locals became increasingly disconcerted by tremors. They also started to report incidence of animals behaving strangely: snakes freezing in the streets, dogs baying and cattle becoming agitated. Finally, convinced that something terrible was about to happen, officials issued an earthquake alert. Thousands of people either fled the city or built huts in the streets to avoid falling masonry. Days later, on 4 February 1975, a magnitude-7.3 quake struck. Just 2041 people died.
It was a coup. An earthquake that would normally have killed hundreds of thousands had been predicted with enough accuracy to allow people to move out of harm’s way. It was hailed as the birth of the modern era of earthquake prediction – but the optimism did not last long. The following year, on 28 July, a magnitude-7.6 earthquake struck another Chinese city, Tangshan in Hebei province, south of Beijing. This time nobody noticed any of the warning signs that had averted a disaster in Haicheng. The earthquake killed an estimated 250,000 people.
When US seismologists visited China in 1976 to investigate the success at Haicheng, they put it down to a pronounced sequence of foreshocks, and noted that many earthquakes do not follow this pattern of seismic activity. In the decades since, earthquake prediction has made few advances. Scientists still know of no sure-fire signal of imminent disaster, but some places such as Japan, Turkey and Mexico City now have early-warning systems that aim to detect a quake quickly enough to send out an alert to people living away from the epicentre. China has gone one step further. Its system also includes a facility to monitor strange behaviour in snakes at farms across the country.
