Tracking leatherback turtles (Dermochelys coriacea) during consecutive inter-nesting intervals: Further support for direct transmitter attachment

Over recent years there have been substantial efforts to record and interpret the post-nesting movements of leatherback turtles (Dermochelys coriacea) breeding in tropical regions. Less well documented are the movements undertaken by individual turtles during the breeding season itself, or more specifically between sequential nesting events. Such movements are of interest for two reasons: (1) gravid female leatherbacks may range extensively into the territorial waters and nesting beaches of neighbouring countries, raising questions for conservationists and population ecologists; and (2) the magnitude of movements themselves help elucidate underlying reproductive strategies (e.g. whether to rest near to the nesting or forage extensively). Here, satellite relay data loggers are used (SRDLs) to detail the movements and behaviour of two female leatherback turtles throughout three consecutive inter-nesting intervals in the Commonwealth of Dominica, West Indies. Both near-shore residence and extensive inter-nesting movements were recorded, contrasting previous studies, with movements away from the nesting beach increasing towards the end of the nesting season. Using this behavioural study as a backdrop, the suitability of attaching satellite transmitters directly to the carapace was additionally explored as an alternative approach to conventional harness deployments. Specifically, the principal aims were to (1) gather empirical data on speed of travel and (2) assess dive performance (aerobic dive limit) to enable comparisons with turtles previously fitted with harnesses elsewhere in the Caribbean (n = 6 turtles; Grenada, WI). This produced mixed results with animals bearing directly attached transmitters travelling significantly faster (55.21 km day(-1): SD 6.68) than harnessed individuals (39.80 km day(-1); SD 6.19); whilst no discernable difference in dive performance could be found between the two groups of study animals. (C) 2009 Elsevier B.V. All rights reserved.

The role of infrequent and extraordinary deep dives in leatherback turtles (Dermochelys coriacea)

Infrequent and exceptional behaviours can provide insight into the ecology and physiology of a particular species. Here we examined extraordinarily deep (300-1250 m) and protracted (>1h) dives made by critically endangered leatherback turtles (Dermochelys coriacea) in the context of three previously suggested hypotheses: predator evasion, thermoregulation and exploration for gelatinous prey. Data were obtained via satellite relay data loggers attached to adult turtles at nesting beaches (N=11) and temperate foraging grounds (N=2), constituting a combined tracking period of 9.6 years (N=26,146 dives) and spanning the entire North Atlantic Ocean. Of the dives, 99.6% (N=26,051) were to depths <300 m with only 0.4% (N=95) extending to greater depths (subsequently termed 'deep dives'). Analysis suggested that deep dives: (1) were normally distributed around midday; (2) may exceed the inferred aerobic dive limit for the species; (3) displayed slow vertical descent rates and protracted durations; (4) were much deeper than the thermocline; and (5) occurred predominantly during transit, yet ceased once seasonal residence on foraging grounds began. These findings support the hypothesis that deep dives are periodically employed to survey the water column for diurnally descending gelatinous prey. If a suitable patch is encountered then the turtle may cease transit and remain within that area, waiting for prey to approach the surface at night. If unsuccessful, then migration may continue until a more suitable site is encountered. Additional studies using a meta-analytical approach are nonetheless recommended to further resolve this matter.

Protracted rainfall decreases temperature within leatherback turtle (Dermochelys coriacea) clutches in Grenada, West Indies: Ecological implications for a species displaying temperature dependent sex determination

Protracted or intense rainfall may affect the reproductive success of reptilian species on a number of levels ranging from the availability of prey, the integrity of the nesting site and the subsequent survivability of offspring. For sea turtles (a species displaying temperature sex determination) nesting throughout the tropics and subtropics, rainfall has previously been shown to influence the development environment of clutches; in its extreme resulting in high levels of egg or hatchling mortality. Yet when compared to other abiotic variables affecting clutch success, rainfall has received relatively little attention. We therefore examined how fluctuations in local rainfall at a tropical nesting site for leatherback turtles (Dermochelys coriacea) affected the nest environment. Temperature data loggers placed within clutches (n = 8) revealed that protracted rainfall had a marked cooling effect on nests, so that seasonally improbable male-producing temperatures (

First records of oceanic dive profiles for leatherback turtles, Dermochelys coriacea, indicate behavioural plasticity associated with long-distance migration

We used Satellite Relay Data Loggers to obtain the first dive profiles for critically endangered leatherback turtles outside the nesting season. As individuals moved from the Caribbean out into the Atlantic, key aspects of their diving behaviour changed markedly, in line with theoretical predictions for how dive duration should vary with foraging success. In particular, in the Atlantic, where foraging success is expected to be higher, dives became much longer than in the Caribbean. The deepest-ever dive profile recorded for a reptile was obtained in the oceanic Atlantic, with a 54-min dive to 626 m on 26 August 2002. However, dives were typically much shallower (generally

Measuring the state of consciousness in a free-living diving sea turtle

We report on results from two types of data-logger attached to hawksbill turtles (Eretmochelys coriacea) in the breeding season at the Seychelles, Indian Ocean. Conventional time-depth recorders (TDRs) showed prolonged bouts of long dives to the seabed, consistent with benthic resting. This behaviour has been widely reported in sea turtles and appears to be a common feature for energy conservation. An Inter-Mandibular Angle Sensor (IMASEN) recorded mouth opening and buccal pumping by one turtle for 2.5 days. Buccal pumping occurred widely while the turtle was submerged, consistent with a function of olfactory sensory perception of the turtle's environment. However, buccal pumping stopped during the middle of long benthic dives consistent with the turtle entering a phase of sleep. It therefore appears that by recording buccal oscillations, it is possible to assess the state of consciousness of turtles allowing the eco-physiology of diving to be more fully explored. (C) 2007 Elsevier B.V. All rights reserved.

The ocean sunfish Mola mola: insights into distribution, abundance and behaviour in the Irish and Celtic Seas

Here we provide baseline data on the distribution and abundance of Mola mola within the Irish and Celtic Seas, made during aerial surveys from June to October during 2003-2005. These data were considered in conjunction with concurrent observations of three potential jellyfish prey species found throughout the region: Rhizostoma octopus, Chrysaora hysoscella and Cyanea capillata. A total area of 7850 km(2) was surveyed over the three years with an observed abundance of 68 sunfish giving a density of 0.98 ind/100 km(2). Although modest, these findings highlight that the species is more common than once thought around Britain and Ireland and an order of magnitude greater than the other apex jellyfish predator found in the region, the leatherback turtle (Dermochelys coriacea). furthermore, the distribution of sunfish sightings was inconsistent with the extensive aggregations of Rhizostoma octopus found throughout the study area. The modelled distributions of predator-prey co-occurrence (using data for all three jellyfish species) was less than the observed co-occurrence with the implication that neither jellyfish nor sunfish were randomly distributed but co-occurred more in the same areas than expected by chance. Finally, observed sunfish were typically small (similar to 1 in or less) and seen to either bask or actively swim at the surface.

Jellyfish aggregations and leatherback turtle foraging patterns in a temperate coastal environment

Leatherback turtles (Dermochelys coriacea) are obligate predators of gelatinous zooplankton. However, the spatial relationship between predator and prey remains poorly understood beyond sporadic and localized reports. To examine how jellyfish (Phylum Cnidaria: Orders Semaeostomeae and Rhizostomeae) might drive the broad-scale distribution of this wide ranging species, we employed aerial surveys to map jellyfish throughout a temperate coastal shelf area bordering the northeast Atlantic. Previously unknown, consistent aggregations of Rhizostoma octopus extending over tens of square kilometers were identified in distinct coastal

Animal-borne sensors successfully capture the real-time thermal properties of ocean basins

Climate change is perhaps the most pressing and urgent environmental issue facing the world today. However our ability to predict and quantify the consequences of this change is severely limited by the paucity of in situ oceanographic measurements. Marine animals equipped with sophisticated oceanographic data loggers to study their behavior offer one solution to this problem because marine animals range widely across the world's ocean basins and visit remote and often inaccessible locations. However, unlike the information being collected from conventional oceanographic sensing equipment, which has been validated, the data collected from instruments deployed on marine animals over long periods has not. This is the first long-term study to validate in situ oceanographic data collected by animal oceanographers. We compared the ocean temperatures collected by leatherback turtles (Dermochelys coriacea) in the Atlantic Ocean with the ARGO network of ocean floats and could find no systematic errors that could be ascribed to sensor instability. Animal-borne sensors allowed water temperature to be monitored across a range of depths, over entire ocean basins, and, importantly, over long periods and so will play a key role in assessing global climate change through improved monitoring of global temperatures. This finding is especially pertinent given recent international calls for the development and implementation of a comprehensive Earth observation system ( see http://iwgeo.ssc.nasa.gov/documents.asp?s=review) that includes the use of novel techniques for monitoring and understanding ocean and climate interactions to address strategic environmental and societal needs.