When surfacers do not dive : multiple significance of extended surface times in marine turtles

Hochscheid, S., Bentivegna, F., Hamza, A. and Hays, G.C. 2010, When surfacers do not dive : multiple significance of extended surface times in marine turtles, Journal of experimental biology, vol. 213, no. 8, pp. 1328-1337, doi: 10.1242/jeb.037184.

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Title When surfacers do not dive : multiple significance of extended surface times in marine turtles
Author(s) Hochscheid, S.
Bentivegna, F.
Hamza, A.
Hays, G.C.ORCID iD for Hays, G.C. orcid.org/0000-0002-3314-8189
Journal name Journal of experimental biology
Volume number 213
Issue number 8
Start page 1328
End page 1337
Total pages 10
Publisher Company of Biologists
Place of publication Cambridge, England
Publication date 2010-04-15
ISSN 0022-0949
1477-9145
Keyword(s) dive behaviour
marine turtle
behavioural thermoregulation
aerobic dive limit
surface time
vessel strike
Summary Marine turtles spend more than 90% of their life underwater and have been termed surfacers as opposed to divers. Nonetheless turtles have been reported occasionally to float motionless at the surface but the reasons for this behaviour are not clear. We investigated the location, timing and duration of extended surface times (ESTs) in 10 free-ranging loggerhead turtles (Caretta caretta) and the possible relationship to water temperature and diving activity recorded via satellite relay data loggers for 101–450 days. For one turtle that dived only in offshore areas, ESTs contributed 12% of the time whereas for the other turtles ESTs contributed 0.4–1.8% of the time. ESTs lasted on average 90 min but were mostly infrequent and irregular, excluding the involvement of a fundamental regulatory function. However, 82% of the ESTs occurred during daylight, mostly around noon, suggesting a dependence on solar radiation. For three turtles, there was an appreciable (7°C to 10.5°C) temperature decrease with depth for dives during periods when ESTs occurred frequently, suggesting a re-warming function of EST to compensate for decreased body temperatures, possibly to enhance digestive efficiency. A positive correlation between body mass and EST duration supported this explanation. By contrast, night-active turtles that exceeded their calculated aerobic dive limits in 7.6–16% of the dives engaged in nocturnal ESTs, probably for lactate clearance. This is the first evidence that loggerhead turtles may refrain from diving for at least two reasons, either to absorb solar radiation or to recover from anaerobic activity.
Language eng
DOI 10.1242/jeb.037184
Field of Research 069999 Biological Sciences not elsewhere classified
Socio Economic Objective 970106 Expanding Knowledge in the Biological Sciences
HERDC Research category C1.1 Refereed article in a scholarly journal
Copyright notice ©2010, Company of Biologists
Persistent URL http://hdl.handle.net/10536/DRO/DU:30058317

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