MEPS 386:275-286 (2009)  -  doi:10.3354/meps08084

Changes in flipper beat frequency, body angle and swimming speed of female green turtles Chelonia mydas

Tohya Yasuda1,2,*, Nobuaki Arai1

1Department of Social Informatics, Graduate school of Informatics, Kyoto University, Yoshidahonmachi, Sakyo-ku, Kyoto 606-8501, Japan
2Present address: School of Agriculture, Kinki University, Nakamachi 3327-204, Nara 631-8505, Japan

ABSTRACT: Data loggers were utilized to record depth, temperature, biaxial motion and swimming speed for female green turtles Chelonia mydas between nesting events in Thailand. The present study demonstrated clear alternations in swimming effort with depth. Both resident and maximum dive depths significantly affected flipper beat frequency, suggesting that turtles change flipper beat frequency with current buoyancy in ways similar to other diving mammals and birds. Body angles became steepest during the initial phases of descent and ascent, but were <60°. Swimming speeds were related to flipper beat frequency and current buoyancy. Swimming speeds based on the dominant stroke frequency during the inter-nesting period (0.18 to 0.21 Hz) were estimated at 0.52 to 0.60 curved carapace lengths s–1. These values are similar to the modal speeds of the leatherback turtles Dermochelys coriacea and the mean speeds during the initial descent of the loggerhead turtles Caretta caretta. We calculated the dynamic body acceleration (DBA) as the index of activity during the descent and ascent phases and found a relationship between maximum dive depth and DBA. Although active stroking during deeper dives may result in a shorter dive duration, daytime dives (ca. 16 to 26 m) were deeper than those observed during the night (ca. 9 to 13 m). This result suggests a beneficial reproductive strategy for females that involves changes in vertical space, for example, to obtain refuge from energy-consuming encounters with males or predators.

KEY WORDS: Diving behaviour · Chelonia mydas · Sea turtles · Flipper beat frequency · Swimming speed · Body angle

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Cite this article as: Yasuda T, Arai N (2009) Changes in flipper beat frequency, body angle and swimming speed of female green turtles Chelonia mydas. Mar Ecol Prog Ser 386:275-286

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