82.4 Friday, Jan. 6 A two-method approach for investigating the underwater hearing capabilities of loggerhead sea turtles (Caretta caretta) LAVENDER, A. L.*; BARTOL, S. M.; BARTOL, I. K.; Old Dominion University, Norfolk, VA; Virginia Wesleyan College, Norfolk; Old Dominion University, Norfolk, VA firstname.lastname@example.org
Sea turtles are one group of protected marine animals potentially impacted by rising levels of anthropogenic sound. According to a limited number of morphological and electrophysiological studies, sea turtles appear to be low frequency specialists. Previous electrophysiological studies have not been correlated with behavioral responses, an important step for hearing assessment, as AEP-audiograms have been found to underestimate the auditory threshold. We collected underwater AEPs and behavioral responses from loggerhead sea turtles (Caretta caretta) to low frequency tone bursts (50-1300 Hz) using a J9 underwater speaker. To collect electrophysiological responses to sound, each turtle was positioned below the air-water interface, and a Tucker Davis Technologies (TDT) system was used to collect averaged AEPs during signal presentation. Responses were processed using MATLAB routines to yield time and frequency domain waveforms for threshold determination. Behavioral audiograms were recorded using a two-response, forced-choice approach. Individuals were subjected to a multi-step conditioning procedure to establish associations between experimental apparatus and signal presence/absence. Threshold analyses were based on the percentage of correct responses and response time calculations for each block of trials. Our AEP and behavioral audiograms demonstrate sea turtles respond to low frequency sounds (<1000 Hz) and as hypothesized, the behavioral data indicate a lower threshold for each tested frequency. These data provide two independent measures of hearing frequency range and threshold and promise to serve as an integral component of future assessment plans that address impacts of sound on sea turtles.