Science

  • Issue 119 / September - October 2017



    Animals That Sense Earthquakes

    Atif Yorulmaz

    In 1975, Chinese scientists successfully predicted a major earthquake. How did they do it? By paying attention to animal behavior. Might careful observation of animals be the key to predicting future quakes?


    Certain phenomena can be known after deliberation, as they occur within the limits of our current knowledge. Other phenomena may be known eventually, although we cannot yet penetrate them with our present knowledge and technology. Certain things can be known partially by employing guesswork about, say, the parameters that impact changing climate and environmental conditions. Other phenomena, such as the blossoming of trees or predicting the route of a hurricane using satellite photographs, can be predicted with great precision. However, there are still many other things that we cannot predict precisely. Earthquake is one of them.


    It is not difficult to predict the possibility of a future earthquake, which can be done by measuring the stress and plasticity of rocks or monitoring micromovements in faults. In countries located between active tectonic continental plates, an earthquake might strike at any moment – yet it is impossible to say when and where. Although it is possible to measure stress, pressure, and vibrations using devices like seismographs, it is not possible to predict which plate will break when and with what force. We may not know when it will strike, but still we can be prepared for it and minimize the destruction. Erecting high-rise buildings on a ground which is not solid enough and with insufficient construction techniques is certainly not a good preparation for earthquakes.


    Although humans cannot predict earthquakes in advance, there has been an increase in the number of laboratory studies into animals predicting earthquakes. This isn’t a new phenomenon: former generations are known to have made extensive observations about the matter, yet none were presented as scientific evidence that could withstand scrutiny. Evaluated objectively, these conclusions are not completely irrelevant or groundless; however, they never confidently predict the time, place, and force of an earthquake.


    Numerous sources include observations about strange pre-earthquake behavior of many domestic animals such as dogs, cats, cattle, chickens, and rabbits, as well as non-domesticated animals like insects, birds, and various sea creatures. But such behavior could well stem from other factors such as hunger, inter-group competition, and other adverse conditions.


    Ants and snakes


    Ants and snakes deserve special emphasis thanks to their anatomical and physiological features. Although both species are somewhat deaf to the sounds coming from the air, evidence suggests that they might be able to detect sounds, electromagnetic radiation, and gas emissions coming from the depths of the Earth. In a remarkable story in the Qur’an (chapter al-Naml), an ant detects Solomon’s approaching armies and warn other ants not to be crushed. One may think here of an allusion to the ant’s skill to detect the vibrations generated by the clopping of the horses.


    Monitoring ant behavior closely could help with earthquake preparations. If there is a significant increase in the number of ants at one location; if they have left their nests and move differently; or if there is an increase in the number of dead ants for no obvious reason, then an earthquake might be imminent.


    A body like an electronic communication center


    Despite its tiny body, the ant has a variety of sensory organs. It’s almost as if it were a fully-equipped center for picking up and evaluating pulses. The ant has three small eyes on its head that enable it to detect the intensity and polarization of light, as well as compound eyes on the sides of its head, each with multiple lenses providing 180 degrees of vision. The pair of antennae on its head, filled with receptors for taste, smell, and humidity, make it possible to detect all types of chemicals in the environment and are more important than the ant’s eyes. Some types of ants are almost blind and rely completely on their antennae.


    Desert ants have about one thousand lenses in their eyes, while we humans have one in each eye. Rüdiger Wehner and his colleagues at the University of Zurich discovered that each ant eye has 80 lenses specialized in detecting polarized light across the ultraviolet range of the spectrum. Each lens focuses on a different point in the sky. One lens, for example, receives light from 180 degrees, another from 270 degrees, and so on. Even if they cannot see the sun, they can locate it thanks to the specialized cells in their eyes. This enables them to find the right compass direction and to determine the distance they have covered.


    Sensory hairs


    Especially mind-boggling about ants is the keenness of the special sensory hairs in various regions of their exoskeleton (Figure 1). The hairs on the antennae and the underside of the legs are particularly sensitive. Each hair is attached to the exoskeleton through a delicate joint and moves with the slightest vibration. The sensory cell under the hair is connected to a nerve fiber, and even a slight vibration of the hair causes a chemical exchange signal by which the ant “feels.” Some of these hairs respond to sound waves. These hairs group in certain regions (Figure 2). Considering the complex sensory organs on their head, the fact that they can perceive more than a million chemical and light signals, that the sensory hairs under their mouth and on their legs can send signals, and that they have a brain with as much as 500,000 nerve cells, it seems reasonable to assume that ants can detect an earthquake before it strikes.



    A group of scientists from the University of Duisburg-Essen led by Gabriela Berberich studied more than 15,000 red wood ant mounds that lay along some of Germany's biggest and most active earthquake fault lines, between 2009 and 2012. They monitored the insects’ movements with video cameras, entered the movements into a special software, and kept track of any deviation from the ants’ normal behavior patterns. The ants typically scooted around actively all day and went back to their mounds to rest at night. Yet, right before an earthquake they did not enter their mounds but loitered outside throughout the night. Once the earthquake was over, the ants would relax and go back to their regular routine. Even more interesting was that they did not change their behavior for tiny tremors below 2.0.


    To Berberich, red wood ants (Formica pratensis and F. polyctena) can detect shifts in gas emissions with the chemoreceptors in their antennae and shifts in the Earth’s magnetic field with the magnetoreceptors in some of their sensory hairs. It is also possible that ants possess sensory organs that can respond to short-lived thermal anomalies or radioactivity.


    Haicheng earthquake


    Animal responses to earthquakes has been a topic of interest in China. It has led to survey and research studies. A network of experimental stations has been set up in areas with high seismic activity in order to evaluate extraordinary phenomena and other abnormal behaviors. The majority of the Chinese population lives in agricultural areas, so their proximity to animals makes them close observers. They have reported a great number of abnormal incidences preceding earthquakes, especially in the last 24 hours before a quake. It was found that the irregular behaviors of rats, fish, and snakes started three days before big earthquakes and continued until a few hours or even minutes beforehand.


    Snakes came out of hibernation for two months in December 1974 and January 1975. It was as if they were committing suicide. Rats emerged from their dens and started to loiter in groups. These were both unexpected behaviors. The experts who evaluated the situation stated that a big earthquake was imminent.


    There was first a series of small tremors. Snakes continued emerging from under the snow; bigger creatures such as cattle, horses, pigs, and dogs displayed restlessness. Thousands of such abnormal animal behavior were reported in the following month. Finally, on February 4, 1975, an earthquake of magnitude 7.3 struck the Haicheng County of Liaoning Province in northeast China. Far fewer people perished because they were warned of the quake thanks to the extensive observations of animals. Officials ordered the evacuation of one million residents of Haicheng a day before the earthquake, so there were only about 2,000 casualties. If the county had not been evacuated, fatalities and injuries would have been expected to exceed 150,000. The Haicheng earthquake is believed to be the only big earthquake that has ever been successfully predicted.


    Geophysicist Friedmann Freund from NASA states that rocks under extreme tectonic stresses release electrically charged particles into the atmosphere before an earthquake. The particles react with air or water when they reach the Earth’s surface; they cause the formation of new molecules, like hydrogen peroxide, when they react with water. This chemical chain of events is believed to affect the organic material dissolved in the pond water, turning it into toxic substances for many aquatic animals.


    Although there are supporting observations about the abnormal behavior of eels and toads, the findings are inconclusive. Still, there are considerable records of abnormal toad and snake behavior before earthquakes.


    Snakes can perceive tremors and infrared radiation, which might help them detect possible weak shock waves or shifts in electromagnetic fields in a region before a powerful earthquake. Because rocks under stress emit infrared radiation – the anomalies of which were recorded by the NASA Terra satellite before a magnitude 7.9 earthquake that hit Bhuj, India, on January 21, 2001 – it is believed that snakes – nighttime hunters that possess a thermal camera for scanning the body temperature of their prey – can detect the infrared radiation that builds up before an earthquake. This infrared thermal “camera” is located inside a cavity between a snake’s nose and eyes.


    It was once believed that snakes were unable to hear because they did not respond to loud noises. Snakes do not have external ears, and there is only one bone in their middle ear (columella aurii). However, they should be able to sense incoming vibrations, as they have inner ears. Indeed, a study at Princeton showed that snakes have a very keen sense of hearing. Voltmeter measurements of neural activity indicated that the vibrations from the air reached the inner ear through the jaw bone and had an effect on the brain. It seemed that the sense of hearing in snakes was tuned to the sounds and vibrations made by larger animals.


    Studies have shown that snakes can detect sound by using sound pressure and sound-based mechanical vibrations. Experiments that measured the electrical responses of snakes’ head neurons and brain stems found that snakes can hear sounds of very high frequency. Snakes were found to hear sounds 10,000 times lower than is possible for human ears to hear. But how were the sounds transmitted to the inner ear of the snake, which was sensitive to vibrations? As low frequency sounds can be carried through solid substances, the research team wondered whether sound vibrations were transmitted from the ground to the snake’s body.


    Subsequent research showed that skull vibrations had the same intensity as the minimum mechanical vibrations snakes could perceive. They directly responded to the vibrations that came from the air to the skeleton, rather than to sound pressure. A snake cannot possibly hear sounds from the air, but they can perceive the sound in a way that is unfamiliar to us. Snakes do not just hear what we perceive to be a sound: their entire body acts like a single organ designed for receiving vibrations, and their brains can perceive these vibrations as if they were sounds. It’s likely that the ribs and spines, covered with keratin scales, play a role in this transmission.


    As research develops, we will be able to better understand what other creatures are equipped with troves of wisdom. It could open new windows into our world, allowing us to build safer cities and to appreciate the incredible intelligence of animals we consider to be “simple.”

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