Incubation environment affects phenotype of naturally incubated green turtle hatchlings

A comparison of body size and flipper size was carried out on green turtle Chelonia mydas) hatchlings produced from natural nests at two beaches on Ascension Island, South Atlantic and one beach in northern Cyprus in the Mediterranean (N=18 nests; N=180 hatchlings). Hatchlings from Ascension Island were significantly larger and heavier than hatchlings in Cyprus, a likely consequence of maternal size effects. Incubation temperature appeared to influence body size of hatchlings on Ascension Island with higher temperatures producing smaller hatchlings. Both hind and fore-flipper area scaled positively with body size. In proportion to body size, hind-flipper area appears relatively consistent among the Atlantic populations but is smaller than hatchlings measured in Hawaii

Dive angles for a green turtle (Chelonia mydas)

The depth and swim speed of a green turtle (Chelonia mydas) were measured during the internesting period in Cyprus. For dives to the seabed (U-dives) we used these data to determine dive angles. Typically the turtle initially descended at a steep angle ([similar]60°) but as the dive continued this angle lessened until the turtle approached the seabed at an average angle of [similar]15°. This systematic change in descent angle is consistent with the prediction that the energetic implications of dive angle are most important at the start of the dive when the turtle is fighting to overcome its positive buoyancy. On leaving the seabed, the turtle often seemed to rise passively

Oceanic long-distance navigation : do experienced migrants use the earth\u27s magnetic field?

Albatrosses and sea turtles are known to perform extremely long-distance journeys between disparate feeding areas and breeding sites located on small, isolated, oceanic islands or at specific coastal sites. These oceanic journeys, performed mainly over or through apparently featureless mediums, indicate impressive navigational abilities, and the sensory mechanisms used are still largely unknown. This research used three different approaches to investigate whether bi-coordinate navigation based on magnetic field gradients is likely to explain the navigational performance of wandering albatrosses in the South Atlantic and Indian Oceans and of green turtles breeding on Ascension Island in the South Atlantic Ocean. The possibility that magnetic field parameters can potentially be used in a bi-coordinate magnetic map by wandering albatrosses in their foraging area was investigated by analysing satellite telemetry data published in the literature. The possibilities for using bi-coordinate magnetic navigation varied widely between different areas of the Southern Oceans, indicating that a common mechanism, based on a bi-coordinate geomagnetic map alone, was unlikely for navigation in these areas. In the second approach, satellite telemetry was used to investigate whether Ascension Island green turtles use magnetic information for navigation during migration from their breeding island to foraging areas in Brazilian coastal waters. Disturbing magnets were applied to the heads and carapaces of the turtles, but these appeared to have little effect on their ability to navigate. The only possible effect observed was that some of the turtles with magnets attached were heading for foraging areas slightly south of the control turtles along the Brazilian coast. In the third approach, breeding female green turtles were deliberately displaced in the waters around Ascension Island to investigate which cues these turtles might use to locate and return to the island; the results suggested that cues transported by wind might be involved in the final stages of navigation

Temperature-dependent sex determination of Ascension Island green turtles

We examined the role played by temperature in the duration of incubation and sex ratio of green turtle hatchlings at Ascension Island, one of the most important green turtle rookeries in the Atlantic. Temperature at control sites at nest depth and in 39 green turtle nests was measured using small temperature recording devices. The sex ratio of hatchlings was ascertained in a sub-sample of monitored nests allowing the description of the relationship between intranest temperature and hatchling sex ratio, demonstrating a pivotal incubation temperature of 28.8°C. The seasonal profile in sex ratio of hatchlings produced on all nesting beaches at Ascension Island was estimated, showing that a female-biased sex ratio would be expected with a female:male ratio of the order of 3:1. The use of nest temperature, air temperature, sand temperature at control sites, and incubation duration as proxies to estimate hatchling sex ratio are discussed

Reptilian diving: highly variable dive patterns in the green turtle (Chelonia Mydas)

Diving reptiles, unlike most diving birds and mammals, return infrequently to the surface to breathe. Spending the bulk of their lives underwater, they are likely to have developed a large variety of specific behavioural patterns different from those of their warm-blooded counterparts. However, for technical reasons, underwater behaviour of these aquatic reptiles remains poorly understood. In this study green turtles Chelonia mydas nesting on Cyprus (Eastern Mediterranean) were equipped with multi-channel data loggers monitoring diving behaviour and activity (via a logger-integrated 3-D compass which served as an activity sensor) during the inter-nesting interval. Data from 2 turtles for 2 consecutive inter-nesting intervals were available for detailed dive analysis. Both turtles showed highly variable dive patterns ranging from travelling subsurface dives to specific dive types such as U- (mainly resting and foraging dives), S- (a form of energy saving swimming) and V-dives. The green turtles stayed near the coast throughout the study, dived no deeper than ca 25 m, but remained underwater for up to ca 40 min. The recordings of the activity sensor revealed high activity levels (less than 20% resting d-1) during the whole inter-nesting period which was attributed to extensive foraging. The combination of both the activity data and the dive data showed that the turtles were engaged in travelling movements for 46% of the inter-nesting time spent underwater, foraged for 34% and rested for 12% of the time. We discuss the physiological, ecological and conservation implications of these results

Reproductive seasonality and sexual dimorphism in green turtles

The temporal distribution of nesting and mating in green turtles Chelonia mydas at Ascension Island (7°57¹S, 14°22¹W) in the South Atlantic is described. Mathematical description of the seasonal pattern of nesting showed extreme similarity between seasons, and evidence is presented to support the hypothesis that observed patterns are driven by prevailing environmental temperature. Mating was observed to begin before nesting and follow a pattern consistent with a modelled seasonal influx of suitable females into the annual breeding population. When available data on male size are compared with that of females from the same population (n = 12 populations), a pronounced and consistent sexual dimorphism, with males being smaller than females, is highlighted in all populations. The possible mechanisms behind the evolution of such a pattern are discussed

Movement patterns of green turtles in Brazilian coastal waters described by satellite tracking and flipper tagging

The movements of 8 green turtles Chelonia mydas in Brazilian coastal waters were tracked using transmitters linked to the Argos system for periods of between 1 and 197 d. These were the first tracking data gathered on juveniles of this species in this important foraging ground. Information was integrated with that collected over a decade using traditional flipper-tagging methods at the same site. Both satellite telemetry and flipper tagging suggested that turtles undertook 1 of 3 general patterns of behaviour: pronounced long range movements (>100 km), moderate range movements (<100 km) or extended residence very close to the capture/release site. There seemed to be a general tendency for the turtles recaptured/tracked further afield to have been among the larger turtles captured. Satellite tracking of 5 turtles which moved from the release site showed that they moved through coastal waters; a factor which is likely to predispose migrating turtles to incidental capture as a result of the prevailing fishing methods in the region. The movements of the 3 turtles who travelled less than 100 km from the release site challenge previous ideas relating to home range in green turtles feeding in sea grass pastures. We hypothesise that there may be a fundamental difference in the pattern of habitat utilisation by larger green turtles depending on whether they are feeding on seagrass or macroalgae. Extended tracking of 2 small turtles which stayed near the release point showed that small juvenile turtles, whilst in residence in a particular feeding ground, can also exhibit high levels of site-fidelity with home ranges of the order of several square kilometers

Spatio-temporal genetic tagging of a cosmopolitan planktivorous shark provides insight to gene flow, temporal variation and site-specific re-encounters

Migratory movements in response to seasonal resources often influence population structure and dynamics. Yet in mobile marine predators, population genetic consequences of such repetitious behaviour remain inaccessible without comprehensive sampling strategies. Temporal genetic sampling of seasonally recurring aggregations of planktivorous basking sharks, Cetorhinus maximus, in the Northeast Atlantic (NEA) affords an opportunity to resolve individual re-encounters at key sites with population connectivity and patterns of relatedness. Genetic tagging (19 microsatellites) revealed 18% of re-sampled individuals in the NEA demonstrated inter/multi-annual site-specific re-encounters. High genetic connectivity and migration between aggregation sites indicate the Irish Sea as an important movement corridor, with a contemporary effective population estimate (Ne) of 382 (CI = 241–830). We contrast the prevailing view of high gene flow across oceanic regions with evidence of population structure within the NEA, with early-season sharks off southwest Ireland possibly representing genetically distinct migrants. Finally, we found basking sharks surfacing together in the NEA are on average more related than expected by chance, suggesting a genetic consequence of, or a potential mechanism maintaining, site-specific re-encounters. Long-term temporal genetic monitoring is paramount in determining future viability of cosmopolitan marine species, identifying genetic units for conservation management, and for understanding aggregation structure and dynamics

Investigating differences in population recovery rates of two sympatrically nesting sea turtle species

This is the final version. Available on open access from Wiley via the DOI in this recordData Availability Statement: Data are available from corresponding author upon reasonable request.Estimating life‐history traits and understanding their variation underpins the management of long‐lived, migratory animals, while knowledge of recovery dynamics can inform the management of conservation‐dependent species. Using a combination of nest counts and individual‐based life‐history data collected since 1993, we explore the drivers underlying contrasting population recovery rates of sympatrically nesting loggerhead (Caretta caretta) and green (Chelonia mydas) turtles in North Cyprus. We found that nest counts of loggerhead and green turtles from 28 beaches across the island increased by 46% and 162%, respectively over the past 27 years. A Bayesian state‐space model revealed that, at our individual‐based monitoring site, nesting of green turtles increased annually at four times the rate of that of loggerhead turtles. Furthermore, we found that loggerhead turtles nesting at the individual‐based monitoring site had stable reproductive parameters and average adult survival for the species and are the smallest breeding adults globally. Based on results from multiple matrix model scenarios, we propose that higher mortality rates of individuals in all age classes (likely driven by differences in life history and interaction with fisheries), rather than low reproductive output, are impeding the recovery of this species. While the increase in green turtles is encouraging, the Mediterranean population is estimated to have around 3,400 adults and is restricted to the Eastern Basin. The recovery of loggerhead turtles is likely to be compromised until mortality rates in the region are adequately quantified and mitigated. As survival of immature individuals is a powerful driver for sea turtle population numbers, additional efforts should target management at pelagic and neritic foraging areas. Understanding threats faced by immature life stages is crucial to accurately parameterise population models and to target conservation actions for long‐lived marine vertebrates

A global horizon scan of issues impacting marine and coastal biodiversity conservation

The biodiversity of marine and coastal habitats is experiencing unprecedented change. While there are well-known drivers of these changes, such as overexploitation, climate change and pollution, there are also relatively unknown emerging issues that are poorly understood or recognized that have potentially positive or negative impacts on marine and coastal ecosystems. In this inaugural Marine and Coastal Horizon Scan, we brought together 30 scientists, policymakers and practitioners with transdisciplinary expertise in marine and coastal systems to identify new issues that are likely to have a significant impact on the functioning and conservation of marine and coastal biodiversity over the next 5–10 years. Based on a modified Delphi voting process, the final 15 issues presented were distilled from a list of 75 submitted by participants at the start of the process. These issues are grouped into three categories: ecosystem impacts, for example the impact of wildfires and the effect of poleward migration on equatorial biodiversity; resource exploitation, including an increase in the trade of fish swim bladders and increased exploitation of marine collagens; and new technologies, such as soft robotics and new biodegradable products. Our early identification of these issues and their potential impacts on marine and coastal biodiversity will support scientists, conservationists, resource managers and policymakers to address the challenges facing marine ecosystems