Abstract
Blanding's turtle hatchlings emerge from their natal nests naïve to environmental stimuli and primarily sense visual cues on the horizon as a dispersal target. During a period of hours or days, hatchlings develop a compass mechanism that allows them to maintain a direction of travel, even when the target is not visible. We examined the dispersal directions of Blanding's turtle hatchlings captured during dispersal by translocating them into a circular arena in a field of corn in order to measure their dispersal direction guided by a compass mechanism. To test for use of a sun compass, a magnetic compass, or both, we observed dispersal direction of hatchlings released at the center of the arena. Hatchlings were released in an initial trial, treated with normal (no-shift) or 6-hr clock-shifted photoperiods for 4 to 10 days, and released into the arena for a second trial with magnets (or non-magnetic controls) adhered to their carapaces. We predicted that clock-shifting would reduce dispersal angle 90° and disruption of magneto-reception would disorient hatchlings. All four treatment groups dispersed directionally during first trials (Rayleigh's Z-tests; all p < 0.001) and in second trials dispersal angles were unchanged in hatchlings with magnets (Watson's U2; both p > 0.50); they were not using a geo-magnetic compass. Hatchlings that were not clock-shifted maintained their initial heading but clock-shifted hatchlings reduced dispersal angle a mean of 111°, not significantly different than the experimental prediction of 90° (Rayleigh's Z = 22.217, p < 0.001, no-shift; Rayleigh's Z = 19.286, p < 0.001, shift; Watson's U255,58 p < 0.001). An analysis of dispersal angles using only daily means of groups of turtles each released on different days also showed significant directionality, no magnet effect, and a significant clock-shift effect (two-sample Hotelling test, p < 0.002). Hatchlings were using a sun compass exclusively.
Advisor
John D. Krenz
Committee Member
Christopher Ruhland
Committee Member
Robert Sorensen
Date of Degree
2015
Language
english
Document Type
Thesis
Degree
Master of Science (MS)
Department
Biological Sciences
College
Science, Engineering and Technology
Recommended Citation
Schlenner, M. A. (2015). Sun-Compass Orientation During Natal Dispersal in Hatchling Blanding's Turtles (Emydoidea blandingii) [Master’s thesis, Minnesota State University, Mankato]. Cornerstone: A Collection of Scholarly and Creative Works for Minnesota State University, Mankato. https://cornerstone.lib.mnsu.edu/etds/394/
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