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The Mexico Earthquakes and Rats

Rats and earthquakes
21 Sep

Should we look to rats and other animals to predict earthquakes?

Mexico has suffered two devastating earthquakes in the last 2 weeks. This is not surprising, considering that Mexico sits within the Pacific Ring of Fire.rats on the march

This is a horseshoe shaped area of the planet encompassing New Zealand through to Japan, The Bering Strait and round to the tip of South America, and 80% of earthquakes strike here.  In this area, five tectonic plates collide, making central and Southern Mexico one of the most unstable regions in the world. 

Coupled with this, Mexico City is built on a dry lakebed, which is soft and wet, and amplifies shaking.  Neither is it surprising that two earthquakes occurred within weeks of each other, because it is common for seismic activity to move along fault lines in a chain reaction.

Earthquakes happen when energy that is built up deep inside the Earth is released.  This energy builds up because the huge amount of heat from within the Earth keeps its tectonic plates in constant motion, and the friction created where two collide causes even more energy to build up.  The resulting shaking on the earth’s surface has a devastating effect on populations and infrastructure, and seismologists have been trying to predict where a quake might strike for many years. The trouble is that warning systems give very little notice, because earthquakes move fast, 50 times faster than a category 5 hurricane.

Case Studies

Maybe these seismologists should be turning their attention instead to the planet’s wildlife as it is staggering to note how certain animals behave in the days and weeks before an earthquake.

Rachel Grant, a lecturer from Anglia Ruskin University in the UK, in collaboration with NASA scientists has been studying this with surprising results. 

  • L’Aquila, Italy April 6 2009. A colony of toads abandoned its pond, inexplicably, 3 days before the earthquake struck
  • Haicheng, China Feb 4 1975. Snakes evacuated their burrows during winter hibernation and risked suicidally low temperatures for no apparent reason. In December 1974, rats and snakes appeared ‘frozen’ on the road, rats seemed to be ‘drunk’ , cows and horses were increasingly agitated.  The authorities took heed and as a result, this was one of the few earthquakes in history to be successfully predicted. The resulting evacuation reduced the death toll from an estimated 150,000 to just over 2,000.
  • Contamana, Peru August 24 2011. Most of the wildlife in the Yanachaga-Chenillen National Park had fled 5 days before.

Rodents are burrowing animals, they spend time underground and are found in close proximity to water. So, it stands to reason that they would be able to note subtle changes before we do, and react accordingly.

There are two explanations as to why these animals could predict future strikes.earthquake damaged road

Changes in the environment

When rocks are under extreme stress, as they would be during such immense seismic activity before an earthquake, they shift around and release charged particles, which flow out to the surrounding rocks. Eventually these particles find their way to the surface where they react with the air, converting air molecules to charged particles called ions.  We already know that such airborne ions cause nausea and headaches in humans and interestingly, increased levels of the stress hormone serotonin in animals.  Could this explain why certain animals get extremely agitated before an earthquake?

These charged particles also react with water, turning it to hydrogen peroxide, which would be toxic to any aquatic or semi-aquatic animal.  It’s not surprising that they would flee.

Seismic Waves

The energy generated by an earthquake travels in waves. There are two types

  • P-Waves (primary) are longitudinal, which means the vibrations run in the same direction as the direction of travel. These are the waves that seismologists see first when monitoring earthquake activity, and interestingly, the waves that rodents feel way before humans do.  These waves can travel to the other side of the earth because they pass through both solids and water.  When rodents and other animals start taking evasive action, it is no doubt because they feel these subtle vibrations
  • S-Waves (secondary) are transverse, which means the vibrations run at right angles to the direction of travel. These waves will only travel through solids.


Nobody likes to have rats invading our homes or businesses and we all take steps to control them when they occur.  However even the most unwelcome visitor can be useful in the right environment and if we successfully interpret their actions.

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