Weddell seals have biological adaptations that allow them to dive deep–as much as of hundreds of meters–while hunting, but also an uncanny ability to find the breathing holes they need on the surface of the ice. Now, researchers supported by the National Science Foundation (NSF) believe they have figured out how they do it–by using the Earth's magnetic field as a natural GPS. "This animal, we think, may be highly evolved with an ability to navigate using magnetic sense in order to find ice holes some distance apart and get back to them safely," explained Randall Davis of the Department of Marine Biology at Texas A&M University. If the hypothesis turns out to be true, it would represent the first evidence of such a trait in a marine mammal.