“How animals manage to find their way home time and again remains an enduring mystery, and not just to laypeople. How do sea turtles find their home beach after years at sea? How does a cuckoo from the Rhine floodplain find its summer territory in the African rainforest? Or how does a homing pigeon manage to return to its loft every time?
It is clear that they orient themselves not only using their senses of sight and smell but also by perceiving magnetic fields. However, the sensory organ responsible for this has by no means been clearly identified.
Much research on this subject has been conducted on birds. In the 1970s, for instance, Wolfgang Wiltschko was the first to demonstrate that robins possess a magnetic sense; they are able to find their migratory route even at night and under overcast skies. In an experiment using a cage where he manipulated the magnetic field, Wiltschko steered birds in different directions. It became evident that birds do not rely solely on the position of the sun and stars for orientation but also possess a magnetic compass. Later research revealed the presence of receptors in birds' beaks that detect changes in magnetic flux, as well as receptors in their eyes that register changes in the direction of the magnetic field.
Regarding pigeons—which are easy to keep and train, making them arguably the best model organisms for studying the magnetic sense—debate has centered on whether they "see" magnetic fields via light-sensitive molecules in their eyes or whether magnetic particles in their beaks guide them. While the relevant cells and particles have been identified, researchers have so far failed to prove that they are the actual seat of the magnetic sense.
Scientists led by Christian Kurts and Clivia Lisowski of the University of Bonn and Martin Wikelski of the Max Planck Institute of Animal Behavior in Radolfzell have now reported a new discovery in the journal *Science*. They hypothesize that these animals are able to navigate using their livers.
Using magnetic cell separation techniques, researchers screened organs suspected of playing a role in the magnetic sense—specifically the eyes, beak, and brain—for cells with high iron content. The liver and spleen were also processed through the apparatus. Indeed, the researchers discovered what they were looking for in the liver.
While this might initially sound odd, it can be explained through cell biology: the liver contains specialized immune cells known as macrophages, which break down aging red blood cells. These cells contain hemoglobin—and thus iron—which accumulates within the macrophages over time. In fact, an analysis of various pigeon tissues revealed that the liver holds the highest iron levels, making it the site that reacts most strongly to magnetism. Electron microscopy of the liver macrophages subsequently showed that these cells are located near nerve fibers. This could be the pathway by which information regarding the magnetic field travels from the liver macrophages to the brain.
The researchers also found evidence suggesting that the pigeons' magnetic sense might indeed be rooted in their liver macrophages: birds with impaired macrophages failed to find their way home on cloudy days. They only managed to reach their loft—located about 20 kilometers away—when the sun was shining. This provides a second crucial clue: clearly, the magnetic sense is not the pigeons' only means of orientation. Like other birds, they also rely on their vision, likely perceiving landmarks remembered from previous flights. This implies a redundant navigation system. It remains unclear, however, how the magnetic field information—transmitted from the macrophages to the brain via nerve cells—is processed once it arrives there.” [1]
1. Immer der Leber nach: Sitzt der Magnetsinn in Immunzellen? Frankfurter Allgemeine Zeitung; Frankfurt. 03 June 2026: N1. PIA HEINEMANN
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