Magnetic Birds Attract Poles, while Lobsters and Turtles Ask for Directions;

How Birds and Other Animals Navigate their Environment with the Use of Earth's Magnetic Field
Introduction to Migratory Flights of Birds
For many years, scientists have known that migratory birds use Earth’s magnetic field to help them navigate on their long journeys. Scientists are still unsure how birds sense this magnetic field, but in more recent years researchers have done experiments on migratory birds, in order to find out how birds sense the magnetic field. Scientists have come up with two theories. One is that birds are able to sense the magnetic field because of a magnetic receptor in their beaks; the other theory is that the birds have special chemicals in their eyes that allow them to actually see the magnetic field.

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A flock of migrating birds.

Magnetic Beaks
Researchers believe some migratory birds can sense the magnetic field through their upper beak because there is a magnetite receptor there, which is made up of iron-based magnetic crystals. This senses the strength of the magnetic field, which is strongest at the poles, and it measures the angle of the field compared to the ground. The beak is similar to a compass. According to the experiment done by Max Plank Institute in Germany, they found that when they re-magnetized the iron particles in the beaks of migratory birds like robins and red warblers, it suggested that the beaks do act as a type of compass or navigational device. It partially allowed the birds to decide in what direction to go in. (Re-magnetization is similar to when you rub a magnet with a piece of metal allowing for the metal to become magnetized, by doing this you can change the direction of magnetism by rubbing it in the other direction.) The research shows that migratory birds may have sensory systems linked to their beaks that use iron to detect the Earth’s magnetic field.

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The Earth's magnetic fields are at the north and south magnetic poles,
which are close to but not at the geographic north and south poles.

Magnetized Eyes
New and recent evidence now claims that birds can actually see the Earth’s magnetic field and that is how many birds navigate on their long journeys. Dominik Heyers and other German researchers did a study on the brains of garden warblers and their migratory habits. They found a link between the neurons in the eye and regions of the brain involved in migration. In the experiment, Heyers and his colleagues injected a dye into the birds’ brains called, cluster N, which is the region of their brain most associated with migration. This got the birds into “a migratory mood,” as Heyers put it. Then they injected another dye into the birds’ eyes to show the path of the neurons. The dyes followed the path of the neurons and ended up in the thalamus (pit stop for visual information in the brain). The data showed that birds could sense the magnetic field due to receptors in the eye. Some scientists believe that the chemical that allows for this to happen is cryptochrome because it generates free electrons when it absorbs light. When earth spins, this affects the free electrons, which allows birds to detect the field. Researchers believe that the birds see the North as a dark spot and gradients of light as the other directions.

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The struture of cryptochrome.

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A picture of the Garden Warbler perching on a tree.

Spiny Lobsters
Much like birds, the Caribbean spiny lobsters navigate their way using small variations of earth’s magnetic field. A current issue in the journal Nature provides evidence that the spiny lobsters can find their way home at night just by using earth’s magnetism. Larry Boles, an author of the study says that the spiny lobster is the one of the few animals that demonstrates the clearest example of true navigation. Even in complete darkness, the lobsters are able to guide themselves home by using the earth’s magnetic system. Numerous test and experiments show that the lobsters could find their direction even in strange places that they did not know and with their eyes covered. There were no useful visual or chemical cues, and regardless of that the spiny lobsters still found their way. Not only do the lobsters have directional or compass sense they use the earth’s magnetic field to find out where they are geographically. This ability is called true navigation which is much like the G.P.S. system. This true navigation was unexpected in lobsters because researchers and scientist never expected this quality in invertebrates. These lobsters have this ability due to magnetite, which are the same mineral used in compasses. This G.P.S. like ability is most evident in spinal lobsters out of all the animals that posses this unique quality.

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Picture of a Spiny Lobster crawling around underwater.

Sea Turtles
Sea turtles are of the few animals that posses an extraordinary navigation sense. Sea turtles are among the long distance migratory animals. It is amazing how much distance the turtles have to travel in order to reproduce in their home areas. As hatchlings sea turtles have never seen the ocean and yet they are able to find their path to the ocean. These turtles follow a migratory path which allows them to travel extensive distance in the featureless ocean. These turtles use their navigation senses to exploit the earth’s magnetic field to reach their navigational goals. Sea turtles posses a positional or map sense and a compass sense to determine their position. Evidence from recent experiments prove that sea turtles use the earth’s magnetic field in order to guide themselves. An incident was recorded in which some turtle fisherman captured a few turtles and because of a storm they had escaped from the ship. Some moths later the same fishermen went to the same location in which they had initially captured the turtles and they found out that the turtles they caught were the same ones that had escaped during the storm. The turtles had successfully found their way home using there navigation senses.

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A picture describing the location of the sea turtles that were able to escape.

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Baby sea turtles find their way into the ocean.

Fooled By Nature: Turtle Navigators

Works Cited (sites and photos credited):