Artigo sobre aves e outros animais sentem sismos
The belief that animals can predict earthquakes has been around for centuries.
In 373 B.C., historians recorded that animals, including rats, snakes and weasels, deserted the Greek city of Helice in droves just days before a quake devastated the place.
Accounts of similar animal anticipation of earthquakes have surfaced across the centuries since. Catfish moving violently, chickens that stop laying eggs and bees leaving their hive in a panic have been reported. Countless pet owners claimed to have witnessed their cats and dogs acting strangely before the ground shook—barking or whining for no apparent reason, or showing signs of nervousness and restlessness.
But precisely what animals sense, if they feel anything at all, is a mystery. One theory is that wild and domestic creatures feel the Earth vibrate before humans. Other ideas suggest they detect electrical changes in the air or gas released from the Earth.
Earthquakes are a sudden phenomenon. Seismologists have no way of knowing exactly when or where the next one will hit. An estimated 500,000 detectable quakes occur in the world each year. Of those, 100,000 can be felt by humans, and 100 cause damage.
One of the world's most earthquake-prone countries is Japan, where devastation has taken countless lives and caused enormous damage to property. Researchers there have long studied animals in hopes of discovering what they hear or feel before the Earth shakes in order to use that sense as a prediction tool.
American seismologists, on the other hand, are skeptical. Even though there have been documented cases of strange animal behavior prior to earthquakes, the United States Geological Survey, a government agency that provides scientific information about the Earth, says a reproducible connection between a specific behavior and the occurrence of a quake has never been made.
"What we're faced with is a lot of anecdotes," said Andy Michael, a geophysicist at USGS. "Animals react to so many things—being hungry, defending their territories, mating, predators—so it's hard to have a controlled study to get that advanced warning signal."
In the 1970s, a few studies on animal prediction were done by the USGS "but nothing concrete came out of it," said Michael. Since that time the agency has made no further investigations into the theory.
In 373 B.C., historians recorded that animals, including rats, snakes and weasels, deserted the Greek city of Helice in droves just days before a quake devastated the place.
Accounts of similar animal anticipation of earthquakes have surfaced across the centuries since. Catfish moving violently, chickens that stop laying eggs and bees leaving their hive in a panic have been reported. Countless pet owners claimed to have witnessed their cats and dogs acting strangely before the ground shook—barking or whining for no apparent reason, or showing signs of nervousness and restlessness.
But precisely what animals sense, if they feel anything at all, is a mystery. One theory is that wild and domestic creatures feel the Earth vibrate before humans. Other ideas suggest they detect electrical changes in the air or gas released from the Earth.
Earthquakes are a sudden phenomenon. Seismologists have no way of knowing exactly when or where the next one will hit. An estimated 500,000 detectable quakes occur in the world each year. Of those, 100,000 can be felt by humans, and 100 cause damage.
One of the world's most earthquake-prone countries is Japan, where devastation has taken countless lives and caused enormous damage to property. Researchers there have long studied animals in hopes of discovering what they hear or feel before the Earth shakes in order to use that sense as a prediction tool.
American seismologists, on the other hand, are skeptical. Even though there have been documented cases of strange animal behavior prior to earthquakes, the United States Geological Survey, a government agency that provides scientific information about the Earth, says a reproducible connection between a specific behavior and the occurrence of a quake has never been made.
"What we're faced with is a lot of anecdotes," said Andy Michael, a geophysicist at USGS. "Animals react to so many things—being hungry, defending their territories, mating, predators—so it's hard to have a controlled study to get that advanced warning signal."
In the 1970s, a few studies on animal prediction were done by the USGS "but nothing concrete came out of it," said Michael. Since that time the agency has made no further investigations into the theory.
Erratic Behavior in Dogs
Researchers around the world continue to pursue the idea, however. In September 2003 a medical doctor in Japan made headlines with a study that indicated erratic behavior in dogs, such as excessive barking or biting, could be used to forecast quakes.
There have also been examples where authorities have forecast successfully a major earthquake, based in part on the observation of the strange antics of animals. For example, in 1975 Chinese officials ordered the evacuation of Haicheng, a city with one million people, just days before a 7.3-magnitude quake. Only a small portion of the population was hurt or killed. If the city had not been evacuated, it is estimated that the number of fatalities and injuries could have exceeded 150,000.
Researchers around the world continue to pursue the idea, however. In September 2003 a medical doctor in Japan made headlines with a study that indicated erratic behavior in dogs, such as excessive barking or biting, could be used to forecast quakes.
There have also been examples where authorities have forecast successfully a major earthquake, based in part on the observation of the strange antics of animals. For example, in 1975 Chinese officials ordered the evacuation of Haicheng, a city with one million people, just days before a 7.3-magnitude quake. Only a small portion of the population was hurt or killed. If the city had not been evacuated, it is estimated that the number of fatalities and injuries could have exceeded 150,000.
The Haicheng incident is what gave people hope that earthquakes might be predictable, says Michael, and what prompted the animal behavior studies by the USGS.
It was later discovered, though, that a rare series of small tremors, called foreshocks, occurred before the large quake hit the city.
It was the foreshock sequence that gave (Chinese officials) the solid prediction," Michael said.
Still, the Chinese have continued to look at animal behavior as an aid to earthquake prediction. They have had several notable successes and also a few false alarms, said Rupert Sheldrake, a biologist and author of the books, Dogs that Know When Their Owners Are Coming Home and The Sense of Being Stared At.
A reproducible connection between animal behavior and earthquakes could be made, he said, but "as the Chinese have discovered, not all earthquakes cause unusual animal behavior while others do. Only through research could we find out why there might be such differences."
Sheldrake did his own study looking at animal reactions before major tremors, including the Northridge, California, quake in 1994, and the Greek and Turkish quakes in 1999.
In all cases, he said, there were reports of peculiar behavior beforehand, including dogs howling in the night mysteriously, caged birds becoming restless, and nervous cats hiding.
Geologists, however, dismiss these kinds of reports, saying it's "the psychological focusing effect," where people remember strange behaviors only after an earthquake or other catastrophe has taken place. If nothing had happened, they contend, people would not have remembered the strange behavior.
It was later discovered, though, that a rare series of small tremors, called foreshocks, occurred before the large quake hit the city.
It was the foreshock sequence that gave (Chinese officials) the solid prediction," Michael said.
Still, the Chinese have continued to look at animal behavior as an aid to earthquake prediction. They have had several notable successes and also a few false alarms, said Rupert Sheldrake, a biologist and author of the books, Dogs that Know When Their Owners Are Coming Home and The Sense of Being Stared At.
A reproducible connection between animal behavior and earthquakes could be made, he said, but "as the Chinese have discovered, not all earthquakes cause unusual animal behavior while others do. Only through research could we find out why there might be such differences."
Sheldrake did his own study looking at animal reactions before major tremors, including the Northridge, California, quake in 1994, and the Greek and Turkish quakes in 1999.
In all cases, he said, there were reports of peculiar behavior beforehand, including dogs howling in the night mysteriously, caged birds becoming restless, and nervous cats hiding.
Geologists, however, dismiss these kinds of reports, saying it's "the psychological focusing effect," where people remember strange behaviors only after an earthquake or other catastrophe has taken place. If nothing had happened, they contend, people would not have remembered the strange behavior.
Maryann Mottfor National Geographic News
November 11, 2003
November 11, 2003
