Despite freezing temperatures, scores of snakes slithered out of their hibernation dens in the weeks before a magnitude 7.3 earthquake struck the Chinese city of Haicheng on February 4, 1975. The reptiles’ behavior, along with other incidents, helped persuade authorities to evacuate the city hours before the massive quake.
For centuries, people have described unusual animal behavior just ahead of seismic events: dogs barking incessantly, cows halting their milk, toads leaping from ponds. A few researchers have tried to substantiate a link. In a 2013 study, Germany scientists videotaped red wood ants that nested along a fault line and found they changed their usual routine before a quake, becoming more active at night and less active during the day. But most such attempts have relied largely on anecdotal evidence and single observations, according to a 2018 Bulletin of the Seismological Society of America review that examined 180 previous studies.