Weak electromagnetic waves interfere with European robins’ migratory orientation
A background buzz of electromagnetic waves from such ordinary sources as electronic equipment can interfere with a bird’s magnetic compass, according to a particularly careful set of experiments.
Normally, migratory birds held in captivity during their travel season tend to hop, face and fidget in the direction they would fly. But caged in huts at a German university, European robins (Erithacus rubecula) failed to orient in their usual migratory direction unless researchers screened out the campus’s background electromagnetic frequencies, says Henrik Mouritsen of the University of Oldenburg in Germany. Yet the robins oriented normally in a rural area with less electromagnetic background, he and colleagues report May 7 in Nature.
Previous claims that typical background levels of electromagnetic emissions affect biological processes have been outright debunked or questioned. But this set of experiments was unusual in its protocol, says Joseph Kirschvink of Caltech, who also studies the magnetic sense in animals and has criticized other papers for lack of rigor. He wants to see other researchers repeat the experiments, but, he says, Mouritsen’s team “did the best job so far, enough so that I think it needs to be considered seriously.”
The electromagnetic background he measured was not strong: Signals ranging in frequency up to 5 megahertz occurred at intensities well below the World Health Organization’s limits for human exposure. Kirschvink compares the exposure to standing five kilometers away from a 50-kilowatt AM radio station.
But just being within listening range of one AM station wasn’t a problem for bird orientation, Mouritsen found. Nor do cell phones or power lines explain the effect. He speculates it’s the sum total of the electronic equipment in use on the Oldenburg campus that accounted for the effect.
The effects disappeared when Mouritsen’s team moved the experiments to the countryside, which has much less intense electromagnetic background noise.
Asked whether these experiments have any implications for human health — a notoriously controversial question with a history of hard-to-replicate claims — Mouritsen just laughs. “I study birds,” he says.
Mouritsen acknowledges that conventional sensory processes in living cells would not be expected to jam at such weak levels of electromagnetic background noise. “It’s not the first time it’s been claimed,” he says, “but I hope it’s the first time it holds up.”
The results are “exciting and scary,” says John B. Phillips of Virginia Tech in Blacksburg. They suggest that experiments in labs all over the world may have missed finding animals’ magnetic compasses because background electromagnetic noise interfered. He recently demonstrated that mice could learn to navigate a maze using magnetic fields when he shielded the experiment’s apparatus from background frequencies.
Mouritsen’s work on background interference began with an experimental disaster. As a graduate student in Denmark, he had studied bird navigation using the standard test of looking at the direction of migratory birds’ fidgeting. But when he set up the same kinds of experiments at Oldenburg in 2004, they didn’t work. He kept trying for three years, but the birds couldn’t orient themselves. “We were desperate,” he says.
Normal orientation behavior returned only when he shielded the birds from electromagnetic noise with aluminum screens connected to the equivalent of a lightning rod. “I didn’t want to study this,” he remembers, because he was well aware of the zany claims and iffy experimental protocols that have littered the research on electromagnetic effects on biological processes.
Over seven years, however, he and collaborating research teams tweaked and repeated the experiments. To eliminate possible bias among students collecting data, he kept them from seeing whether the shielding device was actually connected to the lightning rod. The effect still showed up.
Researchers also found they could artificially create the disorienting effect by sending artificial “background” electromagnetic interference into shielded huts.
Animals have more than one way to sense magnetic information that can be used for orientation, Phillips says. Many have particles of magnetite in their bodies, but evidence suggests they may use something else for orienting to compass directions. That could be a quantum compass, one that depends on weird subatomic effects such as temporary differences between entangled electrons in a molecule such as cryptochrome (SN Online: 1/7/11).
Mouritsen says the low energies involved in his results suggest to him that something subtle, such as the proposed quantum compass, could be at work. Yet he found that a broad range of frequencies disrupted his birds, in contrast to a previous study and some theoretical predictions about bird quantum compasses. If his results hold up, the avian version of quantum weirdness may have gotten even weirder.
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