Authors

Bethany Holtz '16, Gettysburg College

Location

CUB Ballroom

Session

Poster Presentations

Start Time

4-29-2016 4:30 PM

End Time

4-29-2016 6:15 PM

Supervising Faculty Member

Wendy Piniak

Department

Environmental Studies

Description

Although the visual and geologic orientation cues utilized by sea turtle hatchlings during seafinding, when they move from the nest to the sea after hatching, have been well studied, the potential for auditory stimuli to act as an orientation cue has not been well explored. Over the past several decades our knowledge of the auditory capacity of sea turtles has increased greatly, yet little is known about the biological significance of this sensory ability. To investigate whether hatchlings can use ocean sounds during seafinding, we measured the behavioral responses of hatchling loggerhead sea turtles (Caretta caretta) collected from nesting beaches in North Carolina to the presence of beach wave sound recorded on a nesting beach during the summer of 2015. The highest sound energy of beach waves occursHz, which overlaps with the most sensitive hearing range of loggerhead hatchlings (range of frequency detection: 50-1600 Hz, maximum sensitivity: 50-400 Hz). In our experiment, we placed turtles in a V-maze that isolated them from visual, vibratory, and chemical cues. One end of the V held a speaker producing beach wave sounds recorded from nesting beaches, while the other end held sound-reducing foam. We examined the phonotaxic behaviors of the hatchlings at two sound pressure levels (68 dB re: 20μPa and 64 dB re: 20μPa measured directly in front of the speaker). In the presence of the higher sound pressure level (68 dB re: 20μPa), hatchlings exhibited no phonotaxic response (p=1.0); yet, at the reduced sound pressure level (64 dB re: 20μPa), hatchlings exhibited a negative phonotaxic response (p=0.005). In control trials, hatchlings oriented to the two sides of the V-maze equally (p=0.701), suggesting the hatchlings in the lower volume treatment group were responding negatively to the sound. These results indicate the need for further auditory orientation experiments to better understand hatchling behavioral responses to environmental acoustic cues and to address possible impacts of anthropogenic beach sounds that have the potential to disorient hatchlings during seafinding.

Comments

Environmental Studies Senior Honors Thesis

Attached is the full research thesis, which the poster presentation was based on.

Document Type

Student Research Paper

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Apr 29th, 4:30 PM Apr 29th, 6:15 PM

Now Hear This! Orientation and Behavioral Responses of Hatchling Loggerhead Sea Turtles, Caretta caretta, to Environmental Acoustic Cues

CUB Ballroom

Although the visual and geologic orientation cues utilized by sea turtle hatchlings during seafinding, when they move from the nest to the sea after hatching, have been well studied, the potential for auditory stimuli to act as an orientation cue has not been well explored. Over the past several decades our knowledge of the auditory capacity of sea turtles has increased greatly, yet little is known about the biological significance of this sensory ability. To investigate whether hatchlings can use ocean sounds during seafinding, we measured the behavioral responses of hatchling loggerhead sea turtles (Caretta caretta) collected from nesting beaches in North Carolina to the presence of beach wave sound recorded on a nesting beach during the summer of 2015. The highest sound energy of beach waves occursHz, which overlaps with the most sensitive hearing range of loggerhead hatchlings (range of frequency detection: 50-1600 Hz, maximum sensitivity: 50-400 Hz). In our experiment, we placed turtles in a V-maze that isolated them from visual, vibratory, and chemical cues. One end of the V held a speaker producing beach wave sounds recorded from nesting beaches, while the other end held sound-reducing foam. We examined the phonotaxic behaviors of the hatchlings at two sound pressure levels (68 dB re: 20μPa and 64 dB re: 20μPa measured directly in front of the speaker). In the presence of the higher sound pressure level (68 dB re: 20μPa), hatchlings exhibited no phonotaxic response (p=1.0); yet, at the reduced sound pressure level (64 dB re: 20μPa), hatchlings exhibited a negative phonotaxic response (p=0.005). In control trials, hatchlings oriented to the two sides of the V-maze equally (p=0.701), suggesting the hatchlings in the lower volume treatment group were responding negatively to the sound. These results indicate the need for further auditory orientation experiments to better understand hatchling behavioral responses to environmental acoustic cues and to address possible impacts of anthropogenic beach sounds that have the potential to disorient hatchlings during seafinding.