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Title: The behaviour of free-living marine turtles : underwater activities, migrations and seasonal occurrences
Author: Martin, C. S.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2003
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Time-Depth-Recorders (TDRs) and satellite transmitters were deployed onto five Green turtles, Chelonia mydas. The attachment of these devices was to examine their mid-water diving behaviour, as they travelled back to Ascension Island after being experimentally displaced. The functions of two types of mid-water dives were examined, by investigating their patterns of occurrence, profiles and relationship with the speed of travel. The high-resolution pressure information was then used to investigate the descent and ascent tactics during these two types of mid-water dives. Short-term variations in the rtes of vertical movement were shown to reflect behavioural adaptations to deal with changes in lung volume and buoyancy with depth. Satellite-Relay-Data-Loggers (SRDLs) were deployed onto four Green turtles in order to study their diving behaviour and movements during the inter-nesting period at Ascension Island. The data obtained from the SRDLs allowed the reconstruction of complete dive profiles. Swim speed (N = 1 turtle), depth utilisation and the role of U-shaped dives to the sea bed were reported. Lung volumes were modelled in order to estimate aerobic dive limits of turtles resting at different depths. The routine swimming depth of Green turtle hatchlings was estimated, by direct observation, during their swimming frenzy. In agreement with predictions on the optimisation of swimming depth with regards to wave drag, it was found that hatchlings tended to swim at about 3.5 times their body thickness below the surface. This behavioural adaptation was thought to increase survival rtes. Information on the temporal occurrence of Leatherback turtles, Dermochelys coriacea, in the Bay of Biscay (French Atlantic coast) was presented for the period 1979-2000. The seasonal distributions of strandings and sightings were reported. The results indicated that ecological requirements (such as presence/absence of foraging material) were probably major factors driving the seasonal patterns of Leatherback turtle occurrences in temperate waters.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available