How pigeons exploit magnetic fields for navigation

Pigeons in a control group returned to the aviary, while pigeons receiving injections lost directional sense and did not return until the next day when the sun was out. A follow-up test with clodronate-treated pigeons under sunny conditions showed no impairment because solar cues supported navigation. The findings indicate pigeons use both sun orientation and magnetic sensing, with magnetic perception involving a previously unsuspected mechanism. The results may help explain magnetoreception in bats and blind mole rats that lack functioning cryptochromes or live in low-light environments. The findings could also relate to long-distance orientation in certain sharks that use geomagnetic anomalies associated with seamounts. Tissue-resident macrophages may act as peripheral sensory cells providing biologically meaningful feedback to the brain.

"All the pigeons in the control group successfully navigated their way back to the aviary; those that received the injections lost their sense of direction and did not return home until the following day, when the sun was out. A follow-up experiment with the clodronate-treated pigeons under sunny conditions did not affect their homing ability because they were able to use solar cues."

"This suggests that pigeons use a combination of the sun's orientation and magnetic sensing to navigate-and the latter is a previously unsuspected mechanism for magnetic perception in animals. The authors think these results could also explain magnetoreception in bats and blind mole rats, which don't have functioning cryptochromes or live in environments with little to no light."

"They might also apply to certain species of shark capable of swimming in straight lines over long distances-such as scalloped hammerhead sharks, which seem to orient themselves using seamounts found to have geomagnetic anomalies. "Beyond magneto reception, our findings contribute to a broader emerging concept: tissue-resident macrophages can function as peripheral sensory cells, providing direct, biologically meaningful feedback to the brain," the authors concluded."

"Spiro and Drakesmith noted some caveats. For instance, the iron-rich cells in the liver could have been due to the diet of captive pigeons, given that many zoo-housed animals have iron overloads. They also don't think it's yet clear that the liver is the best and most likely organ for sensing magnetic fields. It's possible that doping the pigeons with clodronate also depleted macrophages located elsewhere in the body, skewing the histological results."

Read at Ars Technica