The ongoing mystery of the magnetosensing cows

Back in 2008, a team of German researchers published a paper in Proceedings of the National Academy of Sciences that claimed to demonstrate that cattle, when resting or grazing, actually align their bodies along the Earth's magnetic fields.

The team's results — which were based on satellite imagery of over 8,500 cattle from different regions around the globe — were compelling, but a recent attempt to replicate the researchers' findings has failed, inciting some pretty serious scientific squabble. So where does the great magnetic cow debate stand today?

The original findings, presented by a research team led by zoologist Hynek Burda, used images acquired from Google Earth to demonstrate the cows' magneto-reception capabilities.

"Amazingly," wrote the researchers, "this ubiquitous phenomenon does not seem to have been noticed by herdsmen, ranchers, or hunters. Because wind and light conditions could be excluded as a common denominator determining the body axis orientation, magnetic alignment is the most parsimonious explanation."

At the time, the team's findings garnered quite a bit of media attention — something that apparently rubbed some researchers the wrong way.

"When in 2008 [Burda and his colleagues] started to announce their surprising findings in [the] mass media, we got the impression that this is not the way science should be made and we took a closer look," says Lukas Jelinek, an electromagnetic-field researcher and one of the authors of the recent replication study. "We found out that it is not as fantastic as it was presented."

Using a new set of Google Maps imagery of around 3400 cattle, Jelinek and his colleagues concluded that the cows simply weren't lining up, and chalked the first team's findings up to things like poor quality of Google satellite photographs, lack of blinding in their evaluations, and subconscious bias.

But according to Burda and his colleagues, Jelinik and his team have been looking at the satellite imagery all wrong. Burda says that half of Jelinek's data has to be thrown out, because it features cows near high-voltage power lines, which his team hypothesizes can disrupt magneto-sensing capabilities in cattle. What's more, Burda's team investigated the behavior of cattle in herds, while Jelinek's team analyzed individual cows. By the time Burda and his colleagues got finished cleaning up the Jelinek data, they found that it actually supported their original findings that cattle can, in fact, magneto-sense.

So where does this leave us? When Nature News asked Sönke Johnsen (who studies magneto-reception at Duke University but was unaffiliated with either group's investigation) for his opinion, he sided with Burda and his team's initial findings:

[Johnsen] says that at least some of the images in question should probably not have been analysed. He also suggests that the proper unit of evaluation is probably the herd, as the alignment of individual cows in herds is unlikely to be independent. Overall, he says that the original results, "while mysterious, still stand".

[PNAS and Comparative Physiology via Nature News]