Animals such as butterflies, turtles, and birds are given the ability to perceive the Earth’s magnetic field and navigate themselves accordingly. Migratory species also benefit from the sun, stars, and even scents in nature as they from one place to another.

Magnetic fields and poles

Modern studies have focused on how animals perceive the Earth’s magnetic field and act accordingly. We need to look closer at the Earth’s “magnetic polar points” to understand how magnetic fields work exactly.

It is important not to confuse geographic and magnetic poles. There is a layer called the “inner core” in the center of our Earth where all substances are in a fluid state, similar to those seen in volcanic eruptions. Volatile and molten elements such as nickel and iron form a magnetic electric field above the Earth. This is also the force that is responsible for causing our compasses to point north. At the center, the Earth’s magnetic field changes due to these fluid substances. That is, our compass does not always show the “true north,” i.e. the exact geographical north.

As of the last decade, the Earth’s magnetic pole has kept moving at a rate of about 55 km per year. The magnetic north pole, found in Canada in 1831, has now shifted 2300 km and approached Siberia. Scientists say that about 780 thousand years ago, today’s southern and northern magnetic poles were exactly the opposite. Although the magnetic poles shift, the Earth’s magnetic field continues to function properly. This is imperative for protecting all life on Earth, as a balanced magnetic field protects our planet from the magnetic effects of solar flares and solar winds.

Effects of polar shift

A new magnetic map of our planet is released every five years due to the fact that our magnetic poles are constantly shifting. This does not affect most people on a daily basis, however it does present a challenge for people and vehicles that rely on a compass. Due to the shift, a difference called “magnetic declination angle” occurs between the magnetic north pole and the geographic north pole. This angle varies according to the location. For example, in Canada the magnetic deflection angle is 13 degrees whereas in Brazil it is 20 degrees. In order to determine their exact location, military and civilian aircraft and ships manually or automatically calculate their location based on the angle of deviation and navigate accordingly. Even if we are not aware, our mobile phones are automatically updated according to this calibration. In physics, the formula known as Lenz’s Law, or a tool called a gaussmeter, can be used to calculate the Earth’s magnetic field.

Cryptochromes

This complex and intricate system affects most animal life on Earth, including birds, insects, and fruit flies. So, if these magnetic poles keep changing how do animals find their way? Most creatures utilize cryptochromes, a type of flavoprotein that affects their body clock.

Cryptochrome (CRY) [1] is found to play a leading role in this regard. Cryptochrome-2, one of the two cryptochrome photoreceptors, has been proven to be instrumental in regulating the daily life rhythm of beings by fine-tuning their body clocks and assisting certain animals such as migratory birds, king butterflies, and fruit flies to navigate their migratory paths accurately.

Years of research conducted by Steven Reppert and his team at the University of Massachusett’s School of Medicine on fruit flies and butterflies revealed the function of cryptochrome-2.

According to the research published in Nature magazine in 2009 [2], Dr. Reppert and his team found that flies could not adjust themselves to a new magnetic field without any form of cryptochrome, but that they could regain their sensitivity to a magnetic field only after cryptochrome-2 production.

During the study, the genetic structure of fruit flies was examined and it was ensured that they produced cryptochrome-2.

Speaking to the BBC, Dr. Reppert emphasized that they developed a system to understand how the perception of the magnetic field works in fruit flies. They sought the answer to the question, if cryptochrome-2 was to be transferred from animals to flies, can these proteins act like magnetic sensors in other forms? They have found out that human beings were the most effective option among all vertebrates to yield cryptochrome for this purpose. Their experiment with butterflies yielded the same results. They observed that flies without cryptochromes did not show any signs of magnetic field detection only until their genetic structure was intervened to produce a human version of the molecule.

In another experiment carried out by scientists, a group of migratory birds had iron nuggets, some of which were magnetized to scramble the Earth’s magnetic field, attached to their feet. It was observed that the birds with magnetized nuggets lost their migration path and the birds with unmagnetized nuggets could navigate as easily as usual.

Of course, birds could not know these exact calculations that many people do not even know. Pathfinding skills are “programmed” into birds before they are born so that even if the magnetic field shifts this wonderful mechanism in animals always delivers them to the right location.

The loggerhead sea turtles

As soon as they hatch on the east coast of Florida, the loggerhead sea turtles, Caretta Carettas, swim into Sargasso Sea, migrate into the North Atlantic Circle, and then subsequently into the Atlantic Ocean. The turtles first swim to the northeast towards Europe, then to the south, and return to North America after spending 5-10 years in this hot and nutrient-rich migratory loop.

Dr. Kenneth Lohmann and his team at the University of North Carolina wanted to observe whether loggerhead sea turtles used regional magnetic fields to find their migration paths. They set up a mechanism in a large water tank that was installed with coils in order to form multiple magnetic fields. 79 newly hatched turtles were then clad in cloth vests with wires connected to a computerized monitoring system and left in the same tank. Juvenile turtles were subjected to magnetic fields equivalent to those that exist at critical points of the North Atlantic Cycle, such as in the north of Florida, off the coast of Portugal, and at the southern end of the cycle. As a result, it was observed that in every magnetic field simulated in the experiment, the turtles begin to swim in the opposite direction. For instance, when the magnetic field in the northeastern part of the loop was applied, the animals headed south. In a real ocean setting, this direction keeps them on the right track and prevents them from entering icy waters and dying of hypothermia.

How do animals do it?

There are several research works documenting that not only birds, but also bats, ants, foxes, deer, and even cows feel magnetic fields.

Animals generally migrate to find more suitable reproductive, feeding and living areas for themselves. It is amazing how they know which way to go as soon as they are born. How do they decide that a place they’ve never been to is most suitable for them? How did they learn those navigational skills?

It is amazing to observe this intricate and interlinked system between the Sun, the Earth, and all the living things in it: while the rays of the Sun are needed for life, the harmful ones among them need to be shielded away from the Earth with a magnetic field, a field which is detected by a protein in animals so they can travel to places to continue their lives.

Human cryptochrome

Cryptochrome proteins are also present in the human body [3]. Cryptochrome-2 is especially functional and is linked more to adjusting biological rhythm rather than perceiving the Earth’s magnetic field.

Dr. Aziz Sancar, Chemistry professor and Nobel Prize winner, observed in his experiments of circadian clocks [4] that the cryptochrome pigment located in the eye, skin, and part of the brain regulated the circadian rhythm of mammals.

Currently, many theories are proposed and experiments are conducted on discovering the extent that human beings can perceive the Earth’s magnetic field.

Meanwhile, the wisdom behind the constant shift in the Earth’s magnetic pole awaits to be revealed.

Notes

1. https://en.wikipedia.org/wiki/Cryptochrome
2. Buchen, Lizzie. “Butterflies’ Migrational Timekeeper Found.” Nature, September 24, 2009.
3. Discovered between 1996 and 1998 in humans by Aziz Sancar and his colleagues, cryptochrome is one of the four genes that set the circadian clock in mice. This protein is also a member of a family of proteins including photolyase, DNA’s repair enzyme, on which Prof. Aziz Sancar has worked throughout his scientific career.
4. Rhythmic behavior and physiological changes that have a 24-hour cycle and regulate the day and night cycles of living beings. 

Further reading

Attenborough, David. 1998. The Life of Birds, Princeton University Press Princeton, New Jersey.

Let us imagine the earth as a small sphere before us. If we throw an object from the North Pole toward point A on the equator line, the object follows a curved line towards the right side and reaches point B, not point A. Likewise, an object thrown from the South Pole towards the same point A will follow a similar line curved in the opposite direction. These cases have a common point. An object rolling on a rotating ground moves on a curved line. This curved line, instead of a straight one, is explained with reference to the force of acceleration. This force is named after the French engineer, Coriolis who explained it in 1835. If this force-which is generated by the earth rotating around its own axis-did not exist, then air movements and ocean currents, and consequently the climate conditions of our world, would be different than they are. The objects in our example, thrown from the two poles, go in different directions, because the world rotates counter-clockwise when looked from the North Pole, and clockwise from the South Pole.

The air over the equator receives the sun’s rays at a broad angle. It rises up after gaining heat and is replaced by colder air coming from distant latitudes. Air convection begins in connection with these heat changes. So if the world did not rotate, the air on the Poles would get heavier with cold air and come down. Then, it would be replaced by hot air from lower latitudes. The air at the equator would rise up with gaining heat and would move until reaching the Poles where it would come down after losing heat. Then, it would return to the equator, this time very close to the ground. In this case, the world would probably be an uninhabitable place with cold and fierce winds blowing all around. And of course, the side facing the sun would be very hot and the other side would be very cold.

Instead, the Coriolis effect makes these great atmospheric air masses move over our rotating earth. The hot air rising up from the equator moves towards the poles with a curved course thanks to the Coriolis effect (Figure 4). As this air current approaches the latitudes around 30 degrees, it loses heat and descends. A part of the descending air begins to move back toward the equator, but it follows a curved line again owing to the Coriolis effect. So this last curving forms the “trade winds.” In the past, sailing ships traveled from Europe to America for the purpose of trade; thus, these winds were named as trade winds. This air circulation between the equator and the 30-degree meridians is known as Hadley circulation. These air currents cause heavy rainfall in the equatorial region and the consequent formation of rain forests, which are considered as the lungs of our planet, and also they cause the formation of deserts around the region where the dry and hot weather are pure blessings for us. They are a blessing because the airborne dust rising from the desert fertilizes the rainclouds and plays a critical role for rainfall.

The air over the poles becomes cold, and it causes another air current as it becomes heavier and starts to descend. As the lowered air moves toward the equator, it changes course with the Coriolis effect. At the same time it begins to gain heat and ascend. At the latitudes where water ascends by gaining heat, a rain climate prevails. This polar air cycle is seen between latitudes of 60-90 degrees.

Some part of the air current, which descends down around 30 degrees of latitude, moves toward the poles at a low level. Also, some part of the air which comes from the poles and ascends begins to move towards the equator. So a third air cycling begins between the altitudes between 30-60 degrees. The “western winds” are brought forth from this third cycle. During the time of sailing ships, these winds were used to traveling from America to Europe (Figure 4).

In order for these air cycles to happen, the earth’s rotation around its own axis is not sufficient; its speed and atmospheric mass also play an important role. If the earth rotated slower, the Coriolis Effect would be too weak to give way to a triple air cycle. For example, since Venus rotates too slowly, there is only a single air cycle in its atmosphere. Another factor, as we mentioned, is the mass of the atmosphere. Since the atmosphere of Mars is thin and its mass is relatively less, the Coriolis Effect is too weak and there is only a single air cycle.

Coriolis Effect prevents the air current from following a straight course and the isobars form twisters as they proceed. Therefore, hurricanes in the Northern hemisphere move counter-clockwise, and those in the south move clockwise (Figure 5). Naturally, these main atmospheric movements are not the only ones. A region’s climate is dependent on several factors such as landscape, night-day heat differences, and the like. Therefore, the climatic conditions on the earth have a very complex structure. Even when we consider just these few factors discussed here, it is evident that there are countless parameters that make human life possible in our planet, and each one is finely adjusted. Even slight changes in rotation and the mass of the atmosphere would result in a dramatically different planet Earth.

The ocean currents

Movement of air masses affects the water on the ocean surface as well. Thus, wind-generated surface currents are born. These currents are parallel with the relevant winds. It is a well-known fact that these huge bodies of water change the climate of the regions they pass. Therefore, two places at 54 degrees of latitude show a surprising difference: there can be a polar bears’ park in Ontario, whereas palm trees and tropical fruits can grow in Belfast thanks to the Gulf Stream. There are other warm ocean currents that pass from Brazil, and the north and south of the equator. Some of major cold surface currents pass from Labrador, Canada, the Falkland Islands, and Peru. Warm currents soften the climate of the regions they pass, while cold currents provide sea creatures with rich food, and they are important areas of fishing.

The impact of the wind on ocean water normally reaches as deep as 100-200 meters, and even 1,000 meters in some cases. The Coriolis effect has a determining role on the direction of the currents. These currents on the move make a turn when their way is blocked by land. Thus, the succession of ocean currents becomes a cycle, and they form the great current cycles named as “gyre.” They turn clockwise in the Northern Hemisphere and counter-clockwise in the south.

There are five main ocean circulations on earth and each of them consists of four streams. These currents are at the north and south of the Atlantic Ocean, the north and south of the Pacific Ocean, and one in the Indian Ocean. The North Atlantic circulation is made up of the Northern Equator Current, the Gulf Stream, North Atlantic Current, and the Canary Current.

With the Coriolis effect, a blessing of wondrous scale, food chains are brought to life in the ocean and around coastal regions. The ocean waters are set in motion by the winds generated by the Coriolis effect, but they do not strictly follow the winds that activated them. With a deflection of nearly 45 degrees they move right in the Northern Hemisphere and to left in the Southern Hemisphere.

The effect of the winds weakens in the deeper ocean waters, and then the Coriolis effect becomes dominant. Thus the direction of ocean water carried in the Northern Hemisphere is vertical to the wind direction and towards the right. This condition causes ocean waters to be pushed towards the circulatory center, and the water level there rises about 2 meters.

As rising waters move down with the effect of gravity, the Coriolis effect comes to the stage again to give way to another current in the same direction within that current. The waters that were rising toward the center begin to sink, and they form a new vertical current. For the same reason, the separation of the water current to the right and left directions around the equatorial regions gives way to the waters at the bottom which then come to the surface. At these places, the water level decreases a little. This “upwelling” phenomenon has very important results. Dead organisms sinking down are broken down by bacteria in the deep waters. When this nutrient-rich water returns to the surface, it is a great blessing for so many sea creatures. It is a striking fact that the rotating of the earth is a means for providing many living beings with sustenance. All of these finely adjusted balances on our planet, which we mostly take for granted, provide reflecting minds with food for thought.