When something frightens grazing deer, they all suddenly bound away together in an apparently organized fashion. How does a stressed-out, possibly panicked group of animals manage to coordinate such a getaway without crashing into one another?
In an effort to find out, biologist Hynek Burda of the Czech University of Life Sciences Prague and his team turned to roe deer, European ungulates that often graze in open fields. As a favorite of hunters, the deer associate humans with danger and run away when approached. During the spring and summer of 2014 the researchers deliberately startled 188 groups of grazing deer in three different Czech hunting grounds.
It is reasonable to assume that the deer would run directly away from an approaching threat or toward the nearest cover. Instead the researchers discovered that the animals preferred heading toward magnetic north or south.
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To Burda, this observation suggests that roe deer might be able to detect the earth's magnetic field, as if they have an innate compass. “Magnetoreception is apparently a less exotic sense than usually assumed,” he says. It may allow individuals in the herd to escape without colliding (because they head in the same direction), as well as to rapidly reassemble as a group once the threat has passed. The findings were published in August in Behavioral Ecology and Sociobiology.
Matthew Kauffman, a zoologist at the University of Wyoming who was not involved in the study, says the results are intriguing because researchers seldom consider geomagnetism as a strategy to avoid predators. But he adds that more evidence is needed to confirm the explanation and that Burda and his group should repeat the experiment in different places during different seasons. “Lots of things in the natural environment could correlate with the cardinal directions,” Kauffman says.