The homing pigeon's internal compass may lie in their liver, with its high concentration of iron. This is according to a team from the University of Bonn and the Max Planck Institute of Animal Behavior (MPIAB) in Germany, who have discovered that macrophages in the liver possess a quantum property called superparamagnetism, which may act as a compass 'needle'. The pigeons have all the machinery they'd need to 'read' this compass, with nerve fibers capable of carrying signals from the macrophages to the brain. The researchers tested this theory by taking 34 homing pigeons on a test run, 19 kilometers from their home, under overcast conditions. They found that pigeons treated with a drug that wipes out macrophages were unable to find their way back home, while those without the drug arrived within 70 minutes. This suggests that the internal compass in their liver may be most important when there's no Sun to guide the way. The research raises the question of whether other animals, such as sharks, migratory birds, nocturnal bats, and blind mole rats, are also guided by quantum immune cells with a direct cable to the brain. The study, published in Science, could fundamentally change how we understand navigation.
