hays-whensurfacers-2010.pdf (950.04 kB)
When surfacers do not dive : multiple significance of extended surface times in marine turtles
journal contribution
posted on 2010-04-15, 00:00 authored by S Hochscheid, F Bentivegna, A Hamza, Graeme HaysGraeme HaysMarine 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.
History
Journal
Journal of experimental biologyVolume
213Issue
8Pagination
1328 - 1337Publisher
Company of BiologistsLocation
Cambridge, EnglandPublisher DOI
Link to full text
ISSN
0022-0949eISSN
1477-9145Language
engPublication classification
C1.1 Refereed article in a scholarly journalCopyright notice
2010, Company of BiologistsUsage metrics
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No categories selectedKeywords
dive behaviourmarine turtlebehavioural thermoregulationaerobic dive limitsurface timevessel strikeScience & TechnologyLife Sciences & BiomedicineBiologyLife Sciences & Biomedicine - Other TopicsRANGING LOGGERHEAD TURTLESDIVING BEHAVIORGREEN TURTLESSEA-TURTLESCARETTA-CARETTARESPIRATORY PHYSIOLOGYBASKING BEHAVIORBODY-TEMPERATURESOLAR-RADIATIONPASSAGE TIME
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