ORIENTATION IN BOX TURTLES, TERRAPENE c. CAROLINA (LINNAEUS)

1. An investigation was made to test the hypothesis that box turtles [Terrapene c. carolina (Linnaeus)] employ a means of sun orientation similar to that found in birds. Box turtles from different localities were taken in closed containers to unfamiliar territory and released in large open fields 0.28 to 5.80 miles from their homes. (According to Stickel the home range is about 300 feet in diameter.) They were then observed over periods varying from ten minutes to two hours, and with the aid of a compass their headings during that period were plotted, and the distances traveled were paced off. After the observation they were again placed in closed containers and returned to a pit where they were kept until the next release.

2. Of forty-three turtles released and observed in this manner, twenty-two headed toward home; seventeen of the latter were released under sunny and overcast skies and in most cases this was done from at least two different release areas. Homeward headings were observed in sunny weather, but under overcast skies orientation broke down (Fig. 3). Twelve examples, two turtles each, of situations in which sixteen turtles with opposite homeward directions headed toward their respective homes at the same time from the same place, demonstrated that the heading was not dependent on some local environmental factor at the release point (Fig. 2).

3. Of sixteen turtles released from several completely different homeward directions, four showed definite ability to orient correctly (Fig. 4).

4. There were ten releases under sunny skies more than 150 miles from home. Nine turtles were used in these experiments. In seven of these headings the turtles went in a direction which seemed to correspond to the direction last chosen when close to home, regardless of the actual homeward direction. At short distances of a mile or less from home several turtles also headed in consistent directions regardless of the homeward direction.

5. Ten turtles in twenty experiments were first observed for directional heading in natural sunlight, and then observed in the shade while the sun's image was reflected upon them with a mirror. The direction of heading was altered in all cases and usually resulted in the turtles' heading for the mirror.

6. While walking, turtles stopped frequently and turned their heads as though looking at the sun.

7. These findings seem to support the hypothesis that turtle orientation resembles the type of orientation found in birds; however, more data are necessary to clarify numerous factors which may bring to light conflicting differences and close resemblances. Work is continuing and new developments will be reported as they are observed.