An attempt to demonstrate magnetic compass orientation in two species of mammals

An attempt was made to train two species of small mammals (the bush opossum,Monodelphis domesticus, and the Djungarian hamster,Phodopus sungorus) to search for food in the direction indicated by an earth-strength magnetic field. Five opossums and 4 hamsters were tested in a cross-shaped arena whose four arms faced geographic north, south, east, and west. A set of coils generated a magnetic field whose north pole could be randomly pointed toward any arm. A subject was given a food reward if it entered the arm indicated by the north direction of the field. In 12 series of 73 to 1,127 trials each, the subjects were unable to select the appropriate arm with a frequency greater than random. This result contrasts strongly with a variety of published studies on mammals, birds, and other vertebrates that have indicated good ability to determine direction from the earth’s magnetic field.