Magnetoreception Abilities in Juvenile Loggerhead Sea Turtles

• Main Author: Hanover, Joshua Frazier
• Other Authors: College of Arts and Sciences, Department of Biology, Lohmann, Catherine
• Format: Thesis
• Language: English
• Published: University of North Carolina at Chapel Hill 2017
• Subjects: turtle; navigation; orientation; biology; magnetoreception; caretta; sea turtle; North Atlantic
• Online Access: https://doi.org/10.17615/dnk3-jy72; https://cdr.lib.unc.edu/downloads/4m90f027z?file=thumbnail; https://cdr.lib.unc.edu/downloads/4m90f027z

Loggerhead sea turtles (Caretta caretta) complete extensive, open-ocean migrations around the North Atlantic subtropical gyre current system over the course of many years. Evidence suggests that magnetoreception, or the ability to detect the Earth’s magnetic field, plays a role in their ability to navigate large, open areas lacking obvious cues. One possibility is that sea turtles use geographically predictable differences in the Earth’s magnetic field in order to guide themselves. In order to exploit these geographical differences, turtles must be able to monitor changes in the ambient magnetic field. Two experimental methods were used to assess how juvenile sea turtles react to a changing magnetic field. The first, an orientation experiment, was designed to test whether juvenile loggerhead sea turtles can detect and respond to changes in the inclination (angle at which the field intersects the Earth’s surface) and intensity (strength of the field) in a simulated environment. The second, an activity experiment, was performed to develop a laboratory-based behavioral assay to quantify changes in the activity level of juvenile sea turtles when exposed to a rapidly-changing magnetic field. This information could be valuable to future studies addressing the mechanisms underlying magnetoreception in migratory animals. In both experiments, a similar approach was taken in which juvenile turtles were placed into an aquatic arena with a changing magnetic field. For the orientation investigation, the field changed in accordance with the turtle’s own movement and an orientation vector was calculated. For the activity investigation, the field changed in a predetermined manner and activity was quantified by comparing the number of flipper strokes in the absence or presence of the change. Orientation trial results were inconclusive in that animals did not respond to the applied magnetic fields, unlike the animals in previous experiments. Activity trials failed to demonstrate that turtles have an activity response to a ...