Humans have been using pigeons to send messages across long distances for thousands of years, thanks to their remarkable sense of direction. According to new research published in the journal Science, we may have been looking for the source of that ability in the wrong organ. There was a simple logic to scientists assuming the answer had something to do with their brains or eyes or even their inner ears. The answer was much lower: their liver.
It all has to do with how pigeons, or any animal really, detect the Earth’s magnetic field. The leading theories were all based on the idea that they “see” magnetic fields with some kind of light-sensitive molecules in their eyes, or maybe they detect them using magnetic particles and their beaks. All very fanciful, almost magical explanations, none of which ever explained the mystery.
Now, a team of researchers from Germany’s Max Planck Institute of Animal Behavior and the University of Bonn, among others, started to look elsewhere around birds’ bodies for evidence of magnetic activity. They wound up finding the strongest magnetic signal coming from the liver.
Is a Pigeon’s Internal Compass in Its Liver?
It sounds ridiculous, but it might all be thanks to something called macrophages, immune cells that break down old red blood cells and hold on to iron. Researchers found that these cells, rich in iron, are highly responsive to magnetic fields. So, when the researchers temporarily removed macrophages from trained homing pigeons, the birds had no idea how to navigate anymore on overcast days. When the sun was visible, they could still find their way home using the position of the sun, indicating that it’s not solely a liver-based ability.
All this suggests that the liver cells might function as a kind of internal organic compass. When viewed under an electron microscope, images revealed the macrophages sitting right alongside nerve fibers, potentially providing a pathway for magnetic information to reach the brain.
The researchers caution that none of this means they found a definitive answer to the question of how pigeons are such expert navigators, and it still may be the case that they rely on several navigation systems at once, as their ability to navigate using the position of the sun when macrophages were removed seems to indicate.
Regardless, it’s a remarkable ability that we’ve been taking advantage of for centuries, yet we’re only just beginning to understand.
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