ESR 31:61-73 (2016)  -  DOI: https://doi.org/10.3354/esr00750

Trading shallow safety for deep sleep: juvenile green turtles select deeper resting sites as they grow

Kristen M. Hart1,*, Connor F. White2, Autumn R. Iverson3, Nick Whitney2

1US Geological Survey, Wetland and Aquatic Research Center, 3321 College Avenue, Davie, FL 33314, USA
2Behavioral Ecology and Physiology Program, Mote Marine Laboratory, 1600 Ken Thompson Parkway, Sarasota, FL 34236, USA
3US Geological Survey (contracted by Cherokee Nation Technologies), Wetland and Aquatic Research Center, 3321 College Avenue, Davie, FL 33314, USA
*Corresponding author:

ABSTRACT: To better protect endangered green sea turtles Chelonia mydas, a more thorough understanding of the behaviors of each life stage is needed. Although dive profile analyses obtained using time-depth loggers have provided some insights into habitat use, recent work has shown that more fine-scale monitoring of body movements is needed to elucidate physical activity patterns. We monitored 11 juvenile green sea turtles with tri-axial acceleration data loggers in their foraging grounds in Dry Tortugas National Park, Florida, USA, for periods ranging from 43 to 118 h (mean ± SD: 72.8 ± 27.3 h). Approximately half of the individuals (n = 5) remained in shallow (overall mean depth <2 m) water throughout the experiment, whereas the remaining individuals (n = 6) made excursions to deeper (4 to 27 m) waters, often at night. Despite these differences in depth use, acceleration data revealed a consistent pattern of diurnal activity and nocturnal resting in most individuals. Nocturnal depth differences thus do not appear to represent differences in behavior, but rather different strategies to achieve the same behavior: rest. We calculated overall dynamic body acceleration (ODBA) to assess the relative energetic cost of each behavioral strategy in an attempt to explain the differences between them. Animals in deeper water experienced longer resting dives, more time resting per hour, and lower mean hourly ODBA. These results suggest that resting in deeper water provides energetic benefits that outweigh the costs of transiting to deep water and a potential increased risk of predation.


KEY WORDS: Chelonia mydas · Dry Tortugas · Accelerometers · Dive profile · Green turtle


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Cite this article as: Hart KM, White CF, Iverson AR, Whitney N (2016) Trading shallow safety for deep sleep: juvenile green turtles select deeper resting sites as they grow. Endang Species Res 31:61-73. https://doi.org/10.3354/esr00750

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