Stable isotopes confirm a foraging dichotomy in juvenile loggerhead sea turtles

McClellan, Catherine M.; Braun-McNeill, Joanne; Avens, Larisa; Wallace, Bryan P.; Read, Andrew J.

doi:10.1016/j.jembe.2010.02.020

Cited by 108 publications

(120 citation statements)

References 68 publications

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“…This pattern too is in general accordance with recent findings obtained elsewhere showing how loggerhead spatial behaviour is actually characterised by a considerable complexity (Hatase et al 2002;Hawkes et al 2006Hawkes et al , 2007Rees et al 2010). This variability is likely linked to the loggerhead's plastic and opportunistic foraging habits (McClellan et al 2010;Reich et al 2010;Narazaki et al 2013), which allow them to exploit both neritic and oceanic foraging grounds.…”

Section: General Considerationsmentioning

confidence: 99%

Movement patterns of marine turtles in the Mediterranean Sea: a review

Luschi

Casale

2014

Italian Journal of Zoology

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Understanding the at-sea spatial behaviour of sea turtles is a priority for their conservation. In the present paper, the current information on the distribution and movement patterns of the two species breeding in the Mediterranean, the loggerhead and the green turtle, is reviewed, focusing mainly on the 195 published routes of satellite-tracked turtles. A satisfactory level of knowledge about adults' migrations and other movements is reached only for loggerheads breeding at Zakynthos Island, Greece, and for green and loggerhead females nesting in Cyprus, while studies at foraging grounds are limited to loggerheads in the western and central parts of the basin. Adult males and females mostly show quite uniform post-breeding migratory patterns, typically moving towards individually specific neritic foraging grounds. A much higher variability is shown by loggerhead juveniles, which is probably associated with differences in their spatial behaviour while in oceanic or neritic waters. Evidence of seasonal migrations driven by lower temperatures in winter is available only for adult and juvenile loggerheads frequenting the two northernmost parts of the basin, i.e. the Ligurian and the northern Adriatic Sea. Current knowledge gaps and priorities for further research in the Mediterranean are discussed.

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Section: General Considerationsmentioning

confidence: 99%

Movement patterns of marine turtles in the Mediterranean Sea: a review

Luschi

Casale

2014

Italian Journal of Zoology

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“…The loggerhead population off Canaveral consists of a mix of year-round residents and seasonal (winter) residents: in spring and summer, this area hosts a major breeding aggregation (Henwood 1987 Reich et al 2008) but RBC and epidermis are estimated to reflect foraging habits at least 4 months prior to sampling (Brace and Altland 1955, Seminoff et al 2007. Thus, RBC and skin samples are assumed to represent the foraging area used by females during the non-breeding season (Caut et al 2008, Ceriani et al 2012, Pajuelo et al 2012, Seminoff et al 2012 and by juveniles and sub-adults that migrate between summer foraging grounds and overwintering areas (Wallace et al 2009, McClellan et al 2010.…”

Section: Study Sites and Tissue Collectionmentioning

confidence: 99%

“…Samples were prepared for stable isotope analysis following standard procedures. All samples with the exception of the 18 RBC from loggerheads captured in North Carolina estuaries (McClellan et al 2010) were prepared at the University of Central Florida. RBC samples were either dried at 608C (McClellan et al 2010) or freeze-dried for 48 h before being homogenized with mortar and pestle.…”

Section: Study Sites and Tissue Collectionmentioning

confidence: 99%

“…Epidermis samples were then dried at 608C for 48 h. Lipids were removed from all the samples (except those from North Carolina estuaries) using a Soxhlet apparatus with petroleum ether as solvent for 12 and 24 h (RBC and epidermis, respectively). A post hoc lipid correction factor (Post et al 2007) was applied to carbon isotope ratios of the RBC samples collected in North Carolina (see McClellan et al 2010). Sub-samples of prepared tissues (0.4-0.7 mg) were weighed with a microbalance and sealed in tin capsules.…”

Section: Study Sites and Tissue Collectionmentioning

confidence: 99%

“…Loggerheads are generalist carnivores feeding mainly on benthos when on the continental shelf (Hopkins-Murphy et al 2003 but see McClellan et al 2010); therefore, variations in d 13 C in loggerhead tissues are due to a combination of low/high latitudes, nearshore/offshore, benthic/pelagic, and seagrass/phytoplankton-based food webs gradients.…”

Section: Isoscape Patternsmentioning

confidence: 99%

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Modeling and mapping isotopic patterns in the Northwest Atlantic derived from loggerhead sea turtles

et al. 2014

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Abstract. Stable isotope analysis can be used to infer geospatial linkages of highly migratory species.Identifying foraging grounds of marine organisms from their isotopic signatures is becoming de rigueur as it has been with terrestrial organisms. Sea turtles are being increasingly studied using a combination of satellite telemetry and stable isotope analysis; these studies along with those from other charismatic, highly vagile, and widely distributed species (e.g., tuna, billfish, sharks, dolphins, whales) have the potential to yield large datasets to develop methodologies to decipher migratory pathways in the marine realm. We collected tissue samples (epidermis and red blood cells) for carbon (d 13 C) and nitrogen (d 15 N) stable isotope analysis from 214 individual loggerheads (Caretta caretta) in the Northwest Atlantic Ocean (NWA). We used discriminant function analysis (DFA) to examine how well d 13 C and d 15 N classify loggerhead foraging areas. The DFA model was derived from isotopic signatures of 58 loggerheads equipped with satellite tags to identify foraging locations. We assessed model accuracy with the remaining 156 untracked loggerheads that were captured at their foraging locations. The DFA model correctly identified the foraging ground of 93.0% of individuals with a probability greater than 66.7%. The results of the external validation (1) confirm that assignment models based on tracked loggerheads in the NWA are robust and (2) provide the first independent evidence supporting the use of these models for migratory marine organisms. Additionally, we used these data to generate loggerhead-specific d 13 C and d 15 N isoscapes, the first for a predator in the Atlantic Ocean. We found a latitudinal trend of

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Conservation implications of isotopic variation in nails and blood with wetland quality in three species of Australian freshwater turtle

Francis,

Brandis,

Chessman

et al. 2024

Aquatic Conservation

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Australian freshwater turtles are declining, reflecting global turtle trends. Understanding variation in turtle diets and habitat requirements can guide protection and restoration of ecosystems. Diet and niche overlap were investigated in three co‐existing species of turtle—the broad‐shelled turtle Chelodina expansa, the eastern long‐necked turtle C. longicollis and the Macquarie turtle Emydura macquarii, in three rivers in the Murray–Darling Basin, Australia, in relation to environmental variables. Dietary variation in relation to water quality (salinity) and macrophyte cover was investigated using stable isotope analyses (δ15N and δ13C) of turtle tissues (plasma, red blood cell, whole blood and nail) representing food assimilation over different antecedent periods. These stable isotope results were consistent with current dietary understanding based on stomach flushing, indicating that isotope analyses are a non‐invasive method for obtaining dietary information. There were temporal dietary differences, with strong shifts between spring and summer sampling periods, particularly in the blood plasma. Intraspecific variation in diets reflected in δ15N and δ13C related to body size. There was evidence of high dietary overlap among the three species, potentially creating competition, particularly when they co‐occur or resources might be limited. Continued degradation of turtle habitats and water quality affects turtle diet and reduces habitat availability, forcing the three species of turtle to co‐exist in diminishing refugia, increasing interspecific competition for food. Protecting and restoring freshwater ecosystems, including maintaining freshwater refugia, is essential to conserve already declining populations of the three Australian freshwater turtle species.

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Stable isotopes confirm a foraging dichotomy in juvenile loggerhead sea turtles

Cited by 108 publications

References 68 publications

Movement patterns of marine turtles in the Mediterranean Sea: a review

Movement patterns of marine turtles in the Mediterranean Sea: a review

Modeling and mapping isotopic patterns in the Northwest Atlantic derived from loggerhead sea turtles

Conservation implications of isotopic variation in nails and blood with wetland quality in three species of Australian freshwater turtle

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