Is it feasible that the carrier pigeon “carries” an internal compass?
Extensive research has been conducted in the past few decades in an attempt to uncover the secret of nature’s navigators; pigeons, sharks, bees, trout, turtles, whales, bats and rats are all exceptional navigators, often covering vast distances to reach their precise destination.
Experiments have already concluded that these animals hold the key to tune in the Earth’s magnetic field, but up until recently, the exact biological mechanism they use to do this, puzzled scientists around the world.
However, as it is not just one animal or type of animal that possess this navigational expertise, scientists believed there had to be a common variable, there had to be a biological explanation.
A Magnetic Protein Compass
Dr Can Xie, a molecular biophysicist at Peking University, believes to have made progress in highlighting a pair of proteins in the eye, which, together with sunlight creates a natural compass.
One of the proteins, crytochrome (Cry) had already been highlighted in previous research as a light-sensitive protein that plays a key role in magnetic sensing. However, alone, it didn’t provide enough evidence.
The second protein, referred to as “magneto-receptor” (MagR) contains iron, so acts just like a compass needle, connecting with external magnetic fields, whilst also needing to team-up with Cry to function.
These proteins run from the retina nerve in the eye to the brain, forming a rod-like polymer, just like a compass needle, that can orientate itself in the direction of a given magnetic field, differentiating between north and south and sending information to the nervous system that enables accurate navigation by tapping into the Earth’s magnetic pulse.
Initially, the genome of fruit flies were tested to discover this protein combination, however further biochemical and biophysical experiments demonstrated that the same Cry/MagR complex is stable in the retinas of pigeons, as well as butterflies, rats, whale and even human cells, although, it appears that the proteins are in less quantities in the human eye.
The First Animal Compass Was Discovered in Worms
Earlier in 2015, scientists from The University of Texas discovered the first animal-magnetic sensor in worms.
Interestingly, worms in the United States when hungry, moved down, deeper into the Earth to search for food, however, when the scientists conducted the same experiment in labs in Australia and other parts of the world, the worms didn’t necessarily move downward.
Instead, they moved at a specific angle to the Earth’s magnetic field. This was counter-tested by reversing the electro-magnetic field in the US lab and results provided evidence that worms in fact have a sense of magnetic field.
Despite the discovery of this protein-duo being breaking news for scientists, particularly for Dr Xie and his team, his theory is met with some controversy.
Professor Michael Walker, an expert in magnetic sensing, from the University of Auckland, prefers the hypothesis that animals navigate using their nose, instead of the eyes. Previous theory supports a crystal containing iron oxide being present in nose cells, which acts as a similar magnet.
Experiments where pigeons have had their noses anesthetised showed navigation became a problem for them.
Either way, nature never ceases to amaze! With natural selection though, it is likely that animals only have one biological compass – which is the most feasible theory to you?