Andrew E. Myers

Health Evaluation of Leatherback Turtles (Dermochelys coriacea) in the Northwestern Atlantic During Direct Capture and Fisheries Gear Disentanglement

Abstract Health evaluations were conducted in the northwestern Atlantic for 19 leatherback turtles, which included 12 turtles directly captured as part of a satellite telemetry study and 7 turtles entangled in fishing gear. Assessment included physical examination; determination of heart rate and respiratory rate; and hematologic, plasma biochemical, nutritional, toxicologic, parasitologic, and microbiological investigations. Significant differences were found between directly captured and entangled turtles for curved carapace length, curved carapace width, blood urea nitrogen, chloride, sodium, triglycerides, relative heterophil count, relative monocyte count, relative and absolute eosinophil count, pH, bicarbonate, lead, and beta-hydroxybutyrate. Directly captured turtles showed evidence of mild respiratory acidosis. Significant differences were found between sexes for curved carapace length, curved carapace width, total protein, globulin, sodium, relative monocyte count, gamma-globulin, and anion gap. Relatively high blood concentrations of selenium and cadmium were found in all turtles.

Tools for studying animal behaviour : validation of dive profiles relayed via the Argos satellite system

Central to many behavioural and ecological studies is the need to record the movements and performance of freeliving animals. The challenge of making such measurements is particularly acute in marine settings where animals are often submerged and/or far from shore, making direct observations difficult. Consequently, animal-borne electronic devices now play a crucial role in studies of marine vertebrates. However, there is currently a marked dichotomy in the types of behavioural data that can be collected using these devices. On the one hand, data loggers have expanded massively in memory and the range of parameters they can measure. For example, data are now routinely being collected on depth (Laidre et al. 2003), water temperature (Metcalfe & Arnold 1997), animal swim speed, acceleration/flipper beat frequency (Williams et al. 2000; Wilson et al. 2002) and compass heading (Davis et al. 2003). Furthermore, a range of logging visual-imaging systems provide a view of an animal’s behaviour in relation to its immediate environment (e.g. Takahashi et al. 2004; Reina et al. 2005). A key limitation of these archival devices is that they must be recovered in order to obtain data. This makes them suitable for studies on species that will return to predictable locations (e.g. during the breeding season, seals and penguins return to provision offspring) or if used in conjunction with other devices to facilitate recovery (e.g. popoff systems and VHF transmitters). On the other hand, to obtain information from animals that move large distances and where instrument recovery is not possible, the standard technique is to use the Argos satellite system (http://www.argosinc.com). Behavioural data relayed remotely via the Argos satellite system are constrained by the limited bandwidth available, with

Behaviour and buoyancy regulation in the deepest-diving reptile : the leatherback turtle

SUMMARY In the face of the physical and physiological challenges of performing breath-hold deep dives, marine vertebrates have evolved different strategies. Although behavioural strategies in marine mammals and seabirds have been investigated in detail, little is known about the deepest-diving reptile – the leatherback turtle (Dermochelys coriacea). Here, we deployed tri-axial accelerometers on female leatherbacks nesting on St Croix, US Virgin Islands, to explore their diving strategy. Our results show a consistent behavioural pattern within dives among individuals, with an initial period of active swimming at relatively steep descent angles (∼–40 deg), with a stroke frequency of 0.32 Hz, followed by a gliding phase. The depth at which the gliding phase began increased with the maximum depth of the dives. In addition, descent body angles and vertical velocities were higher during deeper dives. Leatherbacks might thus regulate their inspired air-volume according to the intended dive depth, similar to hard-shelled turtles and penguins. During the ascent, turtles actively swam with a stroke frequency of 0.30 Hz but with a low vertical velocity (∼0.40 ms–1) and a low pitch angle (∼+26 deg). Turtles might avoid succumbing to decompression sickness (‘the bends’) by ascending slowly to the surface. In addition, we suggest that the low body temperature of this marine ectotherm compared with that of endotherms might help reduce the risk of bubble formation by increasing the solubility of nitrogen in the blood. This physiological advantage, coupled with several behavioural and physical adaptations, might explain the particular ecological niche the leatherback turtle occupies among marine reptiles.