SOUTHWOOD, A.L.*; HIGGINS, B.M.; BRILL, R.W.; SWIMMER, J.Y.; University of Hawaii; NOAA Fisheries; NOAA Fisheries; NOAA Fisheries: Aquatic chemoreception in loggerhead sea turtles: behavioral responses to food and a novel chemical

We developed an assay to investigate the behavioral responses of loggerhead sea turtles, Caretta caretta, to chemical stimuli presented underwater. Captive-reared juvenile loggerhead turtles from wild stock were placed in a rectangular choice tank in complete darkness and presented with either food homogenate or a novel chemical (2-phenylethanol, floral scent). Tank design and water flow within the tank were such that the chemical stimulus was present on one side of the tank and absent on the other. There was no significant difference in the amount of time spent on the side of the tank where food homogenate or 2-phenylethanol was delivered during chemical trials vs. control trials in which no chemical was present. However, turtles spent significantly more time in the section of the tank with high, turbulent water flow (i.e., near the drain grate) during food trials compared with control trials. This suggests that turtles attempt to use flow cues to locate the source of food chemicals in the absence of visual cues. During trials, the turtles displayed a behavior in which they put their nostrils to the tank floor and used rear flippers to paddle backwards or in circles around the same spot. Turtles displayed this �back-up� behavior with significantly greater frequency during food and 2-phenylethanol trials compared with control trials. The increase in frequency of this behavior during chemical trials likely indicates chemical detection by the turtle. The induction of detection and searching behavior in the presence of food homogenate shows that chemoreception may play an important role in the foraging ecology of loggerhead turtles.