A Critical Review of the Sun-Azimuth Hypothesis

The ability to find compass directions with the help of the sun, and to keep the same compass direction despite the (apparent) movement of the sun during the day, has been known since 1950 [1, 2, 3]. During the last ten years this sun compass has been found to exist in many birds [3–7], several arthropods [8–14], in fishes [15, 16] of three families, and very recently in reptiles [17, 18]. In analyzing this behavior we encounter several interesting problems of modern biology. (Orientation, daily rhythm, seasonal periodicity, evolution.)