Mice Use Built-In Compass Only mole rats and bats, who live almost entirely in the dark, are known to use specialized navigation tools. Both types of mammals have an inner compass that helps them utilize the Earth’s magnetic field to tell where they are, and where they are going. But little research of this type has been conducted on other mammals – until now. A zoologist at Germany’s University of Duisberg-Essen, Pascal Malkemper, spent months in the remote Czech Republic forests catching and studying wild mice. He learned that wild mice nest consistently in a north-south configuration, demonstrating their use of magnetic fields for orientation. The finding is consistent with studies done on lab mice. Malkemper trapped 45 mice, one at a time, and set them up in their own cylindrical containers. They made nests and, after releasing them the next day, the researcher measured the orientation of the nests. The result was always the same: materials piled up at the walls in north-south arrangements relative to the cylinder’s circular floor area. Speculation on how this occurs relates to what is known about “inner compasses” that some creatures carry, which rely on spinning electrons. The theoretical model postulates that light enters the eye, which then activates certain proteins in the retina, temporarily separating a pair of electrons within the proteins. The electrons, now apart, become more sensitive to magnetic fields, which begins a chemical reaction similar to a switch. The exact way the mice “see” the traces of the electronic field is not fully understood.