Animal Navigation Through Magnetoception

Magnetoception is the ability for certain animals to orient themselves based on the earth’s magnetic field. Magnetoception is used for navigational, altitude and location purposes by animals like fruit flies, bats, and other creatures.

Magnetoception is an extraordinary ability that allows certain animals like honeybees create a map of the world they live in by magnet perception. This allows animals to know where to find food, where they live in addition to other facts about the world around them.

Researchers have studied animals with perceived magnetoception abilities including fruit flies, lobsters, and certain bacteria. Vertebrates with magnetoception include many species of birds, turtles, sharks, and some types of stingrays.

Magnetotaxis

The use of magnetic fields to navigate is found in a certain type of bacteria, called magnetotactic bacteria. These bacteria are crucial for understanding other forms of magnetoception in animals; these bacteria orient themselves based on Earth’s magnetic field in a process called magnetotaxis. Magnetosomes, particles of magnetite or iron sulfide within the miniscule boundaries of the magnetotactic bacteria, give the bacteria its ability to find the magnetic fields because of a magnetic dipole effect. Magnetotactic bacteria are essentially permanent magnets, as the magnetosomes align with each other to maintain sensitivity towards Earth’s magnetic forces.

How Can Animals and Insects Navigate Using Magnetoception?

While the study of magnetotactic bacteria has been fairly well established, but the ways in which animals are able to orient themselves based on Earth’s magnetic fields are more uncertain. Two hypotheses have been put forward to explain the phenomena. The first is the Cryptochrome hypothesis, which states that cryptochrome, when exposed to blue light, is activated and forms a pair of radicals which can be parallel or anti-parallel. The power of the magnetic field around the animal affects the amount of time the cryptochrome stays active. The cryptochrome’s activation is thought to increase light sensitivity which would allow the animal (like a bird) to essentially see the magnetic field and respond to its directional pull. This theory is faulted, however, by the weak magnetic field surrounding Earth and is therefore thought to affect an animal’s sensitivity to light more so than their ability to sense a magnetic field.

The second hypothesis is that the existence of iron oxide or magnetite in certain levels in an animal’s body would have a physical effect on the animal’s ability to detect a magnetic field. If these elements are present in an animal’s body at high enough levels and are exposed to magnetism, they become permanently magnetized and could help steer the animal by the magnetic fields for the rest of its life. This is called the Magnetoreception hypothesis.

Inductive Sensing

The type of magnetoception present in sea creatures like sharks, stingrays and chimaeras is called inductive sensing. Ampullae of Loensini are a kind of electroreceptive organ that is present on the animal’s skin and are filled with a special kind of mucus. These ampullae allow the creature to detect direct electric currents such as those in the water around them from other predators and prey. The ampullae could also therefore be used to detect Earth’s magnetic field and assist with location, catching prey, and navigation.

One animal that has been extensively studied for its magnetoception qualities is the mollusk Tochuina tetraquetra. These creatures have been found to orient themselves between magnetic north and east before a full moon. The neural impulses in the mollusk were unchanged when studied for magnetoreceptive impulses which makes proving their magnetoception difficult. Various experiments involving magnetic fields and mazes have been conducted on Tochuina tetraquetra to try and uncover the mystery behind magnetoception.

Studies have shown that homing pigeons use magnetic fields to navigate under certain conditions. Homing pigeons are able to detect magnetic fields used by compasses and are able to use magnetic fields on overcast days to make their way back to their destination. Researchers hypothesize that a magnetite in the beak of pigeons accounts for their ability to navigate using magnetoception.

Some animals, when deprived of visual or olfactory cues, are able to navigate using magnetoception. These animals include bats, mice and mole rats. These animals, when given the use of their eyes, ears and noses, are still able to navigate their way home. This means that although these animals have magnetoception qualities they do not always use them as their primary navigation tools.

Magnetoception has been studied for many years but researchers have been unable to accurately pinpoint the sensory receptor that governs magnetoception in different animals. The continued study of the neural effects in animals might be able to shed more light on animals’ ability to navigate using magnetoception.

Cows face north using magnetoreception

Google Earth has a new function: determining the preferred orientation of cows.  Sabine Begall and Hynek Burda of the University of Duisburg-Essen looked at over 8,500 cattle and almost 3,000 resting red and roe deer from around the world using imagery from Google Earth and discovered that cattle grazing or resting tend to orient their bodies towards the north using magnetoreception

The exact benefit for cattle isn’t understood and the authors note that “ubiquitous phenomenon does not seem to have been noticed by herdsmen, ranchers, or hunters.”

References

Begall, S., Červený, J., Neef, J., Vojtěch, O., & Burda, H. (2008). Magnetic alignment in grazing and resting cattle and deer. Proceedings of the National Academy of Sciences, 105(36), 13451-13455.

Theoretical and Computational Physics Group. University of Illinois. NIH Center for Macromolecular Modeling and Bioinformatics. Animal Magnetoreception. 2014. http://www.ks.uiuc.edu/Research/cryptochrome/