German researchers from the Universities of Bonn and Duisburg-Essen have elucidated the mechanism by which pigeons navigate using Earth’s magnetic field. For years, the precise workings of this “internal compass” remained elusive, but a piece of the puzzle has now been found in an unexpected area: the birds’ immune system.
It turns out that macrophages, a type of immune cell found in pigeon livers, play a fundamental role. As these cells process old red blood cells, iron accumulates within them, imparting superparamagnetic properties. This allows them to respond to the planet’s magnetic field, aiding the birds in their navigation. The study’s authors explain that during flight, these nanoparticles align with the magnetic field, becoming magnetized, which enables pigeons to sense Earth’s magnetism.
To test this hypothesis, scientists conducted an experiment with pigeons, training them to return to their coop from over 20 kilometers away. The results showed that pigeons whose macrophages were removed lost their directional sense during overcast weather but could still successfully find their way home on clear days by using the sun as a reference.
These findings suggest that pigeons employ a dual navigation strategy, utilizing both the magnetic field and the sun’s position. The iron-rich macrophages are situated close to nerve fibers, facilitating the transmission of magnetic information to the brain.
This discovery holds significance not only for understanding animal navigation but also for immunology, paving the way for new research into “immunosensing”—the capability of the immune system to perceive external stimuli, including magnetic fields.
About the Author
