72 research outputs found
The relationship between loggerhead turtle (Caretta caretta) movement patterns and Mediterranean currents
No full textPrevious studies have shown that loggerhead sea turtles (Caretta caretta), monitored by satellite telemetry, complete long-distance migration between the western and eastern Mediterranean basins following a seasonal pattern. This study investigated if these migration routes may be influenced by surface currents by superimposing the tracks of three loggerhead turtles (curved carapace length >55 cm), migrating from the western to the eastern Mediterranean basin, on Lagrangian data of current developed into pseudo-eulerian speed fields. The average travel speed of the turtles was 1.6 km h-1 and did not depend on the current speed or direction. We observed a connection between surface currents and the turtles' migration routes, although not a conclusive one. These observations show that neritic stage loggerhead turtles conduct migration in two distinct alternate phases: the first characterized by high and constant speed of travel both when swimming with or against currents and the second typified by low travel speeds and a good concurrence between the trailed routes and the course of the currents. These two phases corresponded to two types of movements, one where the turtle migrates actively to reach a specific destination (either neritic foraging, wintering or nesting ground) and the other, where the turtle drifts with the mesoscale current and forages pelagically. It seemed thus, that the influence of currents on a turtle's movements depends on the turtle's momentary behaviour and location of residenc
Multidirectional migrations from a major nesting area in Turkey support the widespread distribution of foraging sites for loggerhead turtles in the Mediterranean
No full textSatellite tracking studies have identified some of the migratory corridors and foraging sites of Mediterranean loggerhead sea turtle (Caretta caretta) rookeries over the past few decades. However, due to a lack of information for breeding rookeries in Libya and Turkey, our understanding of the distribution and connectivity of adult loggerheads is limited. We satellite-tracked 17 female loggerhead turtles breeding in one of the main nesting areas in Turkey to identify (1) migratory pathways, and (2) their foraging areas. Females were tracked for 96-657 d (mean: 271 d), and followed 3 general migratory directions (southeast, southwest and northwest/west). While migrating, individuals alternated oceanic and neritic movements, generally travelling significantly slower when in neritic waters (average speed reduction: 20%). Five turtles stopped between 1 to 3 times in stopover sites for 6 d before resuming their migration. While 1 turtle resided in oceanic foraging areas, the remaining 16 loggerheads settled in 12 distinct neritic foraging grounds; 2 turtles shared one site and 4 turtles shared another site. The identified foraging grounds were widely distributed across the Eastern and Central basin, in locations known to be frequented by loggerhead turtles from other rookeries. The present findings reveal links between foraging areas and one of the main breeding sites in Turkey, providing useful information for species conservation.Turkish Ministry of Environment and Urbanization; RAC-SPA; Baku-Tbilisi-Ceyhan Pipeline Company; TUI Care Foundation; MAVA Foundation; US Fish and Wildlife Ser vice under the Marine Turtle Conservation Act [PL 108-266]; University of PisaWe thank Dr. Flegra Bentivegna, Dr. Fulvio Maffucci and all DEKAMER volunteers for their help during field activities. Dr. Cheryl Sanchez (Pisa, IT) kindly revised the English text. Funding was provided by the Turkish Ministry of Environment and Urbanization, RAC-SPA, Baku-Tbilisi-Ceyhan Pipeline Company, TUI Care Foundation, MAVA Foundation, the US Fish and Wildlife Ser vice under the Marine Turtle Conservation Act (award no. PL 108-266), and the University of Pisa
Normal ultrasonographic features of loggerhead (Caretta caretta) eyes
No full textThe Loggerhead sea turtle (Caretta caretta) is widely distributed in the Mediterranean Sea but, like other sea turtles, it is considered a threatened species. Improving anatomical knowledge on normal aspects of the species is important for correct diagnosis and proper therapy and, therefore, for improving the chances of a complete recovery and a fast reintroduction into the wild for a greater number of sea turtle bycatch and other mishaps. For this reason, 15 Loggerhead turtles, with clinically healthy eyes, were submitted to ocular ultrasonographic (US) examinations. The US exam was quick, non-invasive, and simple to perform and permitted researchers to assess all the ocular features. © 2020, Croatian Natural History Museum. All rights reserved
The relationship between loggerhead turtle (Caretta caretta) movement patterns and Mediterranean currents
No full textPrevious studies have shown that loggerhead sea turtles (Caretta caretta), monitored by satellite telemetry, complete long-distance migration between the western and eastern Mediterranean basins following a seasonal pattern. This study investigated if these migration routes may be influenced by surface currents by superimposing the tracks of three loggerhead turtles (curved carapace length >55 cm), migrating from the western to the eastern Mediterranean basin, on Lagrangian data of current developed into pseudo-eulerian speed fields. The average travel speed of the turtles was 1.6 km h-1 and did not depend on the current speed or direction. We observed a connection between surface currents and the turtles' migration routes, although not a conclusive one. These observations show that neritic stage loggerhead turtles conduct migration in two distinct alternate phases: the first characterized by high and constant speed of travel both when swimming with or against currents and the second typified by low travel speeds and a good concurrence between the trailed routes and the course of the currents. These two phases corresponded to two types of movements, one where the turtle migrates actively to reach a specific destination (either neritic foraging, wintering or nesting ground) and the other, where the turtle drifts with the mesoscale current and forages pelagically. It seemed thus, that the influence of currents on a turtle's movements depends on the turtle's momentary behaviour and location of residenc
Gastrointestinal investigation of parasites and Enterobacteriaceae in loggerhead sea turtles from Italian coasts
No full textBACKGROUND: Caretta caretta is the most abundant sea turtle species in the Mediterranean, and studies on this species have vastly expanded during recent years, including those investigating gut bacterial and parasitic communities. Members of these communities have been reported with variable prevalence and pathogenicity, mainly depending on their host and environment (e.g. lifespan, distribution, habitat, diet, health status and stressors). Indeed, many species commonly inhabiting the sea turtle gastrointestinal tract exhibit an opportunistic behaviour. This study aimed to provide baseline data on enterobacterial and parasitic composition, through bacteriological culture-based methods and the FLOTAC parasitological technique, in cloacal and faecal samples of 30 live Caretta caretta, examined upon their arrival at the Marine Turtle Research Centre (Portici, Italy). RESULTS: Enterobacteriaceae were isolated in 18/23 cloacal samples (78.3%), with Citrobacter and Morganella as the most common genera, followed by Proteus, Enterobacter, Providencia, and Hafnia. Parasitic elements were detected in 11/30 faecal samples (36.7%), with Enodiotrema, Rhytidodes, and Eimeria as most common genera, followed by Pachypsolus and Cymatocarpus. Additionally, Angiodyctium is reported for the first time in this host. The majority (47.8%) of sea turtles hosted exclusively Enterobacteriaceae, whereas 30.4% hosted both parasites and Enterobacteriaceae; the remaining 21.8% hosted neither of the agents. CONCLUSIONS: Bacteria and parasites evaluated in the present study are common in Mediterranean loggerhead sea turtles, with slight differences between the western and eastern basin. Although naturally present in the gastrointestinal system of free-living sea turtles, their relationship with these hosts might range from mutualism to parasitism. Indeed, members of the gut community might express their pathogenic potential in immune-compromised animals, such as those in rehabilitation facilities. Therefore, it is advisable to include in the standard work-up of rescued sea turtles a screening procedure for such opportunistic agents, in order to better evaluate the animal's health status and achieve timely intervention with appropriate treatment, thus improving rehabilitation. Furthermore, data collected from free-living sea turtles represent a starting point for investigating wild populations. However, further studies are needed to clarify the differences between sea turtle's normal gut microbiome and pathobiome
Adult sex ratios of loggerhead sea turtles (Caretta caretta) in two Mediterranean foraging grounds
No full textSea turtles show temperature-dependent sex determination (TSD) and information on sex ratios at different life stages is necessary both for population dynamics models for conservation and to shed light on the possible adaptive value of TSD. Adults represent the less abundant class of sea turtle populations and adult sex ratios at foraging grounds are very difficult to obtain. We first analysed biometric data of 460 juvenile and adult loggerhead sea turtles ranging from 60 to 97.5 cm curved carapace length (CCL), in which a clear bimodal distribution of tail length (the main secondary sexual character of adult males) was observed in the size class >75 cm CCL. We then sexed 142 adult turtles in this size class collected from the Tunisian shelf and from the southeastern Tyrrhenian Sea, observing a proportion of females of 51.5% (95% CI: 41.2-61.8%; n=97) and 40.0% (95% CI: 25.7-55.7%; n=45) respectively. Our results complement previous studies and support their findings of similar and more balanced sex ratios in adult and juvenile loggerhead turtles in the Mediterranean, in contrast with highly female-biased sex ratios of hatchlings. © 2014 CSIC
Loggerhead Turtle (Caretta caretta) Nests at High Latitudes in Italy: A Call for Vigilance in the Western Mediterranean
No full textFour new loggerhead turtle nest sites were discovered in July 2006 and July 2008 on Italian beaches in the regions of Puglia, Sardinia, and Campania. Previously, no nesting has been reported on those beaches. All nests were protected by a fence and a surveillance team and nest temperatures were monitored throughout the incubation period. The 2006 nests experienced low incubation temperatures, which lead to long incubation conditions and two of the nests had to be rescued and transferred into an artificial incubator. Both nests failed to hatch after >100 days of incubation, but for different reasons: in Puglia the entire clutch (47 eggs) contained only eggs with yolk, and hence, if the eggs were fertilized then embryonic death occurred early and could not be determined; in Sardinia all but two of the embryos (clutch size 92) developed until the pre-pipping stage but did not hatch, probably due to a lack of gas-exchange caused by a disrupted chorioallantoic membrane. The Campania nest in 2006 (93 eggs) hatched with a low success (33.3%) after a prolonged incubation period (72 days) and also contained many undeveloped eggs (60%). In 2008 instead, another nest in Campania incubated at very high temperatures (mean 33.2°C) and hatched after 46 days with a 92.2% success (clutch size was 115 eggs). The four nests reported here occurred contemporaneously with other nine unusual loggerhead turtle nesting events in the Western Mediterranean over the last decade. The possibility that turtles with relaxed philopatry explore new nest sites is discussed, but since no historical data on nesting in this region are available, organised monitoring of potential new nest sites is required to evaluate this behaviour
Connectivity and stock composition of loggerhead turtles foraging on the North African continental shelf (Central Mediterranean): implications for conservation and management
No full textThe loggerhead turtle, Caretta caretta, is a highly migratory species with a complex life cycle that involves a series of ontogenetic habitat shifts and migrations. Understanding the links amongst nesting populations and foraging habitats is
essential for the effective management of the species. Here we used mixed stock analysis to examine the natal origin of loggerhead turtles foraging on the North African continental shelf off Tunisia, one of the most important Mediterranean
neritic habitats. An 815-bp fragment of the mitochondrial DNA control region was sequenced from 107 individuals sampled from 2007 to 2009. No temporal variation in haplotype frequencies was detected. Juveniles (n = 87) and adults (n = 23) exhibited weak but significant genetic differentiation that resulted in different stock compositions. Libya was the main source population but the proportion of turtles from this rookery was higher in adults (median = 80%) than in juveniles (median = 35%). Western Greece was the second most important contributing population. Juvenile stock composition derived from mixed stock analysis and the estimates produced by numerical simulation of hatchling dispersion in the Mediterranean Sea were significantly correlated, supporting the recent theory that loggerheads imprint on possible future neritic habitats during the initial phase of their life. This association was not significant for adults, suggesting that other factors contribute to shaping their distribution. Overall, our results show that human activities on the South Tunisian continental shelf pose an immediate threat to the survival of the Libyan rookery
Bone density in the loggerhead turtle: functional implications for stage specific aquatic habits
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