- Historically, scientists have dismissed accounts of animals acting strangely before earthquakes, mostly due to the anecdotal nature of the accounts and a lack of reliable sources.
- By examining camera-trap photos, researchers were able to observe changes in animal behavior in the time leading up to a magnitude 7.0 earthquake in Yanachaga National Park.
- The present study appears to validate a longstanding belief that animals can sense earthquakes coming and that they react more as the earthquakes approach.
Twenty-three days before a major earthquake in 2011 animals began disappearing from part of Yanachaga National Park in Peru. By 24 hours before the quake they had completely vacated the area. A recent study documenting the animals’ retreat with camera-trap data suggests that animals may have an uncanny ability to sense and flee from irritating portents of seismic activity.
Historically, scientists have dismissed accounts of animals acting strangely before earthquakes, mostly due to the anecdotal nature of the accounts and a lack of reliable sources. “[T]he infrequency and unpredictability of earthquakes means that most relevant pre-earthquake studies suffer, of necessity, from small sample sizes and from difficulties with reproducibility under comparable conditions,” states the recent study, published in the journal Physics and Chemistry of the Earth.
However, a few credible observations of odd animal behavior do exist. For instance, before a magnitude 6.3 earthquake in L’Aquila, Italy, in 2009, researchers detected unusual toad behavior in areas where they also detected atmospheric disturbances that typically occur before earthquakes.
The present study relied on images from motion-capture cameras set up in Yanachaga National Park by the Virginia-based conservation group Tropical Ecology and Assessment and Monitoring Network. For 30 days leading up to the earthquake — and one day after — the cameras operated round the clock in nine separate locations throughout the park, capturing animal movements. Zoologist Rachel Grant of Hartpury College in Gloucester, England, and her colleagues geophysicist Jean Pierre Raulin of McKenzie University in São Paulo, Brazil, and solid-state physicist Friedemann Freund of the SETI institute in California obtained photographic evidence from these camera traps through an online database.
Examining the camera-trap photos, the researchers were able to observe changes in animal behavior in the time leading up to the magnitude 7.0 earthquake in Yanachaga National Park, some 323 kilometers (200 miles) from the quake’s epicenter. Grant and her team noticed that the number of animals visible in the photos started to decrease 23 days before the earthquake, and rapidly declined in the days leading up to the shock.
“I was amazed to see animal numbers reducing dramatically before the earthquake and the 24 hours preceding the earthquake, no animal movements were recorded by any camera trap in the national park. This made my hair stand on end!” Grant told Mongabay.
She described this finding as “thrilling.”
Of particular interest to the researchers was the activity of rodents, the most abundant animals in the park, which “almost completely” disappeared as the earthquake approached, according to the paper. This observation may not come as a surprise since there have been documented cases of sensitivity in laboratory rodents during large earthquakes such as the ones in Kobe, Japan, in 1995 and Wenchuan, China, in 2008.
The present study appears to validate a longstanding belief that animals can sense earthquakes coming and that they react more as the earthquakes approach. “From looking at other studies including our own, there seem to be two broad thresholds within which animals are affected; 8-10 days and then 24-48 hours before the quake; however, many more studies are required before we can be certain of this,” Grant said.
The researchers believe the animals in Peru were reacting to the same seismic phenomenon that the toads in Italy reacted to in 2009: positive ionization of air molecules that results from the shifting of the earth’s crust. Grant and her colleagues think the Peruvian animals retreated to a lower elevation within the park to escape the ions’ irritating effects.
“[P]ositive air ionization is a rather common process in nature in seismically active regions, and the medical community has known since the 1960s that positive airborne ions are ‘bad for you’,” Freund told Mongabay. “They create discomfort, headaches, nausea. People get sick. Animals can be expected to react by trying to move away, if they can. If there are animals in captivity or domesticated, they may get restless, even panicky,” he said.
The team did not measure positive air ions in Yanachaga National Park in Peru, although they are currently seeking funding to do so. However, Freund has measured them in a laboratory setting at the NASA Ames Research Center in Mountain View, California, as well as in field stations in other parts of the world. He described his work confirming that tremors in the earth before and during earthquakes result in positive air ionization in a 2009 paper. Freund mentioned that California currently has over 100 field stations recording air ionization, and parts of Peru and Alaska host such stations as well.
Freund said it has been a challenge to get the scientific community interested in the effect of positive ions on animals. “As I learned more about stresses waxing and waning in the Earth’s crust, all the time and in particular in tectonically active regions and before major earthquakes, I was certain the scientific community, in particular, the meteorologists, would jump at it,” he said. “However, nobody paid attention.”
Freund added that in addition to the positive airborne ions, the animals might also be reacting to very low-frequency radio waves that come out of the ground prior to earthquakes.
The authors acknowledge that more work needs to be done to confirm what drives animals away from earthquake zones, but they hope their study proves provocative enough to generate more research. “If this correlation can be substantiated by systematically monitoring a wider range of reported pre-earthquake phenomena, this would lead to a better understanding of the premonitory abilities of animals,” they conclude.
Freund, F.T., Kulahci, I.G., Cyr, G., Ling, J., Winnick, M., Tregloan-Reed, J. et al. (2009). Air ionization at rock surfaces & pre-earthquake signals. Journal of Atmospheric and Solar-Terrestrial Physics 71: 1824-1834.
Grant, R.A., Raulin, J.P., Freund, F.T. (2015). Changes in Animal Activity Prior to a Major (M=7) Earthquake in the Peruvian Andes. Physics and Chemistry of the Earth. doi: http://dx.doi.org/10.1016/j.pce. 2015.02.012
Grant, R.A. and Halliday, T. (2010). Predicting the unpredictable; evidence of pre‐seismic anticipatory behaviour in the common toad. Journal of Zoology 281: 263-271.