behavior of the Mongolian gerbil l Mongolian gerbils and albino rats were observed individually in an open field. The rats exhibited their normal tendency to remain in the peripheral areas of the field. However. the gerbils did not show such thigmotactic tendencies. Gerbils demonstrated more frequent central area occupancy, greater duration of central area occupancy, and greater locomotion in the field. The greater alertness and activity of the gerbil, in combination with its apparent relative preference for an open field, may have important implications in maze running situations. This note points out an unusual aspect of the open field running behavior of the Mongolian gerbil, Mer ion e s unguiculatus.