Magnetic Remanence in Bats

Abstract

Evidence which has been accumulating over the past 40 years shows that many species of temperate zone bats migrate and accurately locate their summer roost sites and winter hibernacula. They also home reasonably well when artificially displaced (Griffin, 1970; Baker, 1978). Despite abundant documentation of these behaviors, we still have no acceptable explanation for how they are accomplished. It is clear that echolocation alone is not sufficient. The visual capabilities of bats are much more refined than is generally believed (Childs and Buchler, 1981; Buchler and Childs, 1982). However, it seems likely that still other orientation cues must be available to them because a disconcerting number of displaced, blinded bats still have been able to home effectively (e.g., Mueller, 1966, 1968; Davis and Barbour, 1970). Encouraged in particular by recent research with homing pigeons (reviewed elsewhere in this volume), we were interested in determining ultimately if bats might also use the earth’s magnetic field as a cue during homing or migration. Because of the expected complexity and duration of the necessary experiments to test for the perception of a magnetic field by bats, we chose instead to first search for the presence of magnetic material.