O. G. Dely szerk.: Vertebrata Hungarica 21. (Budapest, 1982)

Adler, Kr.: Sensory aspects of Amphibian navigation and compass orientation 7-18. o.

PHASE-SHIFT TESTS (Prüfung der Phasenverschiebung) EXPECTED DIRECTION ACTUAL RESULTS (Prüferwartung) (Prüfergebnis) DELAYED 6 HOURS (6 Std. Verzögerung) Fig. 2. Effect of clock-shifting on compass orientation in toads (

Bufo amerlcanu

s). Animals phaseshifted by 6 hours (one-quarter of a daily cycle) orient outdoors in expected directions approximately 90° (one-quarter of a circle) relative to controls if they are using a guidance mechanism that is time-based. These angular "errors" in movement would be expected to be clockwise in phase-delayed and counterclockwise in phase-advanced animals (in North Temperate regions; see text) Actual results strongly support the hypothesis that the compass mechanism is time-compensated. Data are displayed as if the test arena is viewed from above its center, each dot representing an individual toad (see Fig. 1). Statistical data are: m

v, mean vector for group; r, vector length (a measure of group variability ranging from 0 to 1); JJ, V-test statistic where concentration is in some expected direction; j), probability level. Note group variability and also the nonrandom distribution of toads scoring in the "wrong" semicircle. Original data