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, 1 (1), 82-6

First Records of Dive Durations for a Hibernating Sea Turtle

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First Records of Dive Durations for a Hibernating Sea Turtle

Sandra Hochscheid et al. Biol Lett.

Abstract

The first published record, from the early 1970s, of hibernation in sea turtles is based on the reports of the indigenous Indians and fishermen from Mexico, who hunted dormant green turtles (Chelonia mydas) in the Gulf of California. However, there were no successful attempts to investigate the biology of this particular behaviour further. Hence, data such as the exact duration and energetic requirements of dormant winter submergences are lacking. We used new satellite relay data loggers to obtain the first records of up to 7h long dives of a loggerhead turtle (Caretta caretta) overwintering in Greek waters. These represent the longest dives ever reported for a diving marine vertebrate. There is strong evidence that the dives were aerobic, because the turtle surfaced only for short intervals and before the calculated oxygen stores were depleted. This evidence suggests that the common belief that sea turtles hibernate underwater, as some freshwater turtles do, is incorrect.

Figures

Figure 1
Figure 1
(a) Migration route of a subadult loggerhead turtle (X represents release site; filled triangles represent positions determined via the ARGOS system). The bottom right rectangle encloses the Gulf of Laconia where the turtle overwintered. (b) Monthly average SST from 1970 to December 2002 for the overwintering site of the turtle in this study (Peloponnese), and for two further putative overwintering sites: the Gulf of Calfornia and Cape Canaveral. Note: the dataset for the Gulf of California area is not complete and does not cover all months.
Figure 2
Figure 2
(a) Dive durations (filled circles) of a loggerhead turtle recorded in different months during the tracking period. The monthly average aerobic dive limit (cADL; square) was calculated as detailed in §2. Open triangles represent the monthly average SST. (b) Dive profiles of an overwintering loggerhead turtle during December 2002 (top) and February 2003 (bottom). Two dive profiles were reconstructed from the five most significant points of inflection (filled diamonds). For the other dives only maximum dive depth (open diamonds), dive duration and surface duration were available. Black horizontal bars indicate hours of darkness and were derived from a sunrise/sunset table (Astronomical Applications Department, US Naval Observatory, http://aa.usno.navy.mil/data/docs/RS_OneYear.html) for the locations at which these dive data were received.

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