When navigating a new town, state or country the first thing we pull out is our cell phones. Unfortunately, animals do not have the luxury of GPS. Not only do our cell phones tell us where to go, it tells us where the nearest Starbucks is, the nearest mall and much more.
However, in animals, a variety of species possess magnetic senses that are attracted to the Earth’s magnetic fields. Birds, fish, turtles and foxes all use the Earth’s magnetic field for specific uses such as navigation and hunting. Migrating animals are believed to use the Earth’s magnetic field to navigate. Homing pigeons have miniature particles of magnetite in their upper beaks which has allowed them to see the Earth’s magnetic fields and be responsible for their extraordinary navigation abilities. Magnetite is known as the strongest naturally magnetic material on Earth.
What Creates the Earth’s Magnetic Fields?
Earth’s magnetic fields behave the same way as a bar magnet. The Earth’s magnetic field is caused by a dynamo effect. This works due to the flowing liquid metal in the outer core of the planet which then generates electric currents to form a magnetic field that extends around Earth. In addition, in the Earth’s core the magnetic field has sources in the crust and in the ionosphere and magnetosphere. The geometric field variates on different scales and frequency vibrations which is what helps animals navigate around the globe.
Humpback Whales
The Humpback whale holds the record for the longest migration on Earth. Humpbacks have been tracked making a journey over 9,500 kilometres from breeding areas in Brazil all the way to Madagascar. In Winter, these ocean giants leave foraging grounds and travel to breed in warmer waters. Humpbacks exhibit high route fidelity, meaning year after year they travel in near-straight lines using the exact same route with outstanding accuracy. Whales are known to have a small quantity of magnetite in their skull which is believed to use the Earth’s magnetic field for navigation.
Ridley Sea Turtles
As hatchling turtles make their way to the ocean, they are in geographic learning mode, sensing the Earth’s magnetic fields and feeling the ocean currents which, they store in their brains until instinct brings them back years later. Ridley Sea Turtles make one of the greatest fleets amongst the animal kingdom with most species swimming thousands of kilometres to lay their eggs in the same sand where they were born. When turtles migrate to their breeding grounds, they use an internal compass which operates of that to a normal compass. The needle on a compass always points at the Earth’s magnetic North Pole. If the compass is moved the needle will always stay focused and aimed towards the magnetic field of the North Pole. At the magnetic North Pole, the magnetic field lines are perpendicular to the surface, near the equator they are parallel, meaning the compass will point sideways (West – East). Turtles and other animals can sense different angles of inclination and declination. In term they are sensing there X and Y co-ordinates.
Salmon
Salmon are known for hatching in freshwater streams and swimming towards the ocean. After hatching, salmon cover thousands of miles before eventually laying eggs in natural streams. Years later salmon head back to the freshwater streams that they call ‘home’. A study published by Current Biology discovered salmon use the Earth’s magnetic field like a map, similar to that of hatchling turtles. Salmon appear to inherit this map through genetic hand-me-downs which helps them use magnetism to leave an imprint of the Earth’s magnetic field at the mouth of their native river.
Foxes
For hunting, foxes use a technique known as a mouse pounce. When foxes face in a North Eastern direction they have a much higher success rate of catching prey than any other direction. Foxes align their pounces to the Earth’s magnetic field. The fox can detect the magnetism through fine tuning it’s to match to the angel of the Earth’s magnetic field. As it finds this, the fox can determine the distance of the prey and calculate how far it must jump to land directly on top of the prey. Foxes use a protein in their eyes known as cryptochrome which is sensitive to the Earth’s magnetism. This has been known to allow them to see the Earth’s magnetic field as a patch within their vision.
As new discoveries are being made daily, it is still hugely unknown how animals can use the Earth’s magnetic field to navigate and hunt. Either way, various animals are utilising the Earth’s magnetism to allow them to return to breeding grounds and hunting for prey using the magnetic fields.