History

• In the early 1980s, the U.S. Geological Survey studied captive rats and asked people to contact them if they saw any unusual pet behavior before an earthquake. The study turned up nothing. "What we're faced with is a lot of anecdotes. Animals react to so many things, so it's hard to have a controlled study to get that advanced warning signal," said Andy Michael of the USGS.
  
  

Early Research

• According to the U.S. Geological Survey, most of the studies about unusual animal behavior prior to earthquakes are taking place in China and Japan. A 2003 study in Japan concluded that excessive barking and biting by dogs are possible predictors of earthquakes. In China, unusual animal behavior prompted officials to evacuate the city of Haicheng before an earthquake.
  
  

Recent Studies

• In 2009, researcher Rachel Grant was studying a population of toads during breeding season. Without explanation, they disappeared. Confused, Grant tried to find an explanation. Five days later, a 6.3 earthquake struck the area. Researching, she discovered that a migration of toads was also seen in 2008 in Szechuan, China, before a quake. According to Grant, more study is needed to discover what earthquake precursors the animals are sensing.