Credit: Suriya Silsaksom/Alamy
Pigeons can sense Earth’s magnetic field by detecting tiny electrical currents in their inner ears, researchers suggest. Such an inner compass could help to explain how certain animals can achieve astonishing feats of long-distance navigation.
The team performed advanced brain mapping as well single-cell RNA sequencing of pigeon inner-ear cells. Both lines of evidence point to the inner ear as the birds’ ‘magnetoreception’ organ. The results appeared in the Science on 20 November 1.
“This is probably the clearest demonstration of the neural pathways responsible for magnetic processing in any animal,” says Eric Warrant, a sensory biology researcher at the University of Lund in Sweden. Studies have suggested that various animals, including turtles, trout and robins, can sense the direction and strength of magnetic fields, although the evidence has sometimes been contested — and the mechanisms have remained controversial.
Bird-brained navigation
Two leading hypotheses have led the research into how birds sense magnetic fields. One is a quantum-physics effect in retina cells where birds ‘see’ magnetic fields. Another is that microscopic iron oxide particles in the beak could act as tiny compass needles. However, it’s largely unknown where magnetic information is sensed in animals’ brains and how sensory neurons confer sensitivity to electromagnetic changes.
In 2011, researchers found hints that magnetic fields triggered pigeons’ vestibular system, the organ that enables vertebrates to sense accelerations (including gravity) and helps them to stay balanced2. The structure is made of three fluid-filled loops which are mutually perpendicular, so they can communicate to the brain the direction of an acceleration by breaking it down into three ‘x, y, z’ components.
Compass protein attracts heap of criticism
David Keays, a neuroscientist at Ludwig-Maximilian University of Munich in Germany, designed an experiment that could reveal how pigeons’ brains respond to magnetic fields.
Keays’ team exposed six pigeons to a magnetic field slightly stronger than Earth’s for just over an hour. The birds’ heads were immobilized and the magnetic field was continually rotated to simulate the heads’ motions with respect to Earth’s geomagnetic field.
... continue reading