Pigeons' livers may enable magnetic navigation when the sun doesn't shine, study finds
A research team in Germany has published new data on how pigeons use magnetic fields as a navigation method when visibility is limited. A key
A research team in Germany has published new data on how pigeons use magnetic fields as a navigation method when visibility is limited. A key part of the long-sought answer could lie in an unexpected organ, their livers. Day or night, rain or shine, wherever they're released, trained pigeons can find their way home over distances as high as almost 1,000 kilometers (around 600 miles). It's a skill humans have made use of since time immemorial. And for around a century, scientists have known that magnetoreception plays a part in the birds' navigational cocktail. A research team from the University of Bonn and the Max Planck Institute of Animal Behavior wrote in the journal Science this week that a core part of the secret to homing using magnetic fields may lie in the birds' livers. India: Meet the woman passionate about pigeon racing To view this video please enable JavaScript, and consider upgrading to a web browser that supports HTML5 video What did the study find? The study notes how the "mechanisms underlying" the reception of magnetic information in the rock dove — or Columba livia — "appear to be numerous and are still being discovered." Some physical connections in more intuitive locations — like the beak, eyes and brain — have already been identified. "Here, we used physical, morphological, functional, and genomic assays to identify the presence of superparamagnetic macrophages in the liver," the researchers write.
Macrophages are immune cells that break down old red blood cells. As part of this process, they accumulate iron, which may allow them to respond to magnetic fields. "We found that after macrophage depletion, pigeons flying under overcast conditions lacked their usual orientation capabilities," they said. When the sun was visible, the birds' orientation was unimpaired, suggesting that visual and solar-based cues were another of the pigeons' navigation methods. But given the birds' inability to navigate magnetically without the assistance from their livers, the researchers concluded: "We propose that in homing pigeons, superparamagnetic macrophages in the liver are required for finding magnetic direction." What did the researchers say? Martin Wikelski, Director at the Max Planck Institute of Animal Behavior said that "what looks like a 'gut feeling' in bird navigation may actually have a physical basis." The immune cells in question are located near nerve cells in the liver. The researchers postulate that this may be how they can transmit data to the pigeons' brains. "We didn't expect immune cells to act like sensors for magnetic fields at all. Our results reveal a previously unknown mechanism for magnetic perception in animals," said co-senior author of the study Christian Kurts, Director at the Institute of Molecular Medicine and Experimental Immunology at the University Hospital Bonn. Despite their surprise about the answer apparently lying in macrophages, the scientists knew ahead of the study that some organs were particularly worthy of study.
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