Site specialists, diet generalists? Isotopic variation, site fidelity, and foraging by loggerhead turtles in Shark Bay, Western Australia

Thomson, Jordan A.; Heithaus, Michael R.; Burkholder, Derek A.; Vaudo, Jeremy J.; Wirsing, Aaron J.; Dill, Lawrence M.

doi:10.3354/meps09637

Cited by 54 publications

(43 citation statements)

References 57 publications

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“…loggerheads at foraging grounds (adult and sub-adult loggerheads captured <5 km from original capture sites over time periods >1 year in Australia [64]) and have also observed little overlap in residence areas (49.0 km mean distance between individual core-use areas in the GoM [3]). …”

Section: Possible Residence Area Territoriesmentioning

confidence: 99%

Bahamas connection: residence areas selected by breeding female loggerheads tagged in Dry Tortugas National Park, USA

Hart

Sartain

Fujisaki

2015

Animal Biotelemetry

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Background: Delineation of home ranges, residence and foraging areas, and migration corridors is important for understanding the habitat needs for a given species. Recently, many population segments of Northwest Atlantic loggerhead sea turtles (Caretta caretta) were designated as endangered or threatened; the smallest subpopulation is in the Dry Tortugas. Foraging and residence areas for this subpopulation have not been defined outside the Gulf of Mexico. Here, for Dry Tortugas loggerheads that traveled to the Bahamas, we use a combination of switching state-space modeling (SSM) and home-range estimators to determine migration period, spatially delineate and describe residence areas, and examine inter-annual home-range repeatability.

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Section: Possible Residence Area Territoriesmentioning

confidence: 99%

Bahamas connection: residence areas selected by breeding female loggerheads tagged in Dry Tortugas National Park, USA

Hart

Sartain

Fujisaki

2015

Animal Biotelemetry

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“…This study builds upon a growing body of evidence that green turtles (Broderick et al 2007, Vander Zanden et al 2013, Shimada et al 2014 and other marine turtle species (Schofield et al 2010, Thomson et al 2012, Tucker et al 2014, Pajuelo et al 2016 show high levels of fidelity to non-breeding sites. The ability to isotopically track some individuals for up to 4 breeding seasons, with a temporal frame of ap proxi mately 2 to 8 yr, presented clear evidence for a high degree of fidelity to the pre-defined foraging areas.…”

Section: Ascertaining Foraging Site Fidelitymentioning

confidence: 99%

Satellite tracking and stable isotope analysis highlight differential recruitment among foraging areas in green turtles

Bradshaw¹,

Broderick²,

Carreras³

et al. 2017

Mar. Ecol. Prog. Ser.

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Identifying links between breeding and non-breeding sites in migratory animals is an important step in understanding their ecology. Recognising the relative importance of foraging areas and ascertaining site-specific levels of recruitment can provide fundamental and applied insights. Here, satellite telemetry and the stable isotope ratios (δ 13 C, δ 15 N and δ 34 S) of 230 green turtles Chelonia mydas from a regionally important rookery in northern Cyprus were employed to evaluate the relative importance of 4 foraging areas. A preliminary analysis of stable isotope ratios suggested that a major foraging area had been missed through satellite telemetry as a large proportion of turtles had isotope ratios that did not correspond to sites previously identified. Stable isotope ratios were then employed to select 5 turtles to be fitted with platform terminal transmitters in 2015. All 5 turtles were subsequently tracked to the same location, Lake Bardawil in Egypt. Serially collected tissue samples from 45 females, ranging over 2 to 4 breeding seasons, suggested that foraging site fidelity was very common, with 82% of females exhibiting extremely high temporal consistency in isotope ratios. Quantifying fidelity allowed an evaluation of foraging areaspecific contributions to each breeding cohort over the past 2 decades and demonstrated that recruitment was unequal among sites, and dynamic over time, with Egypt now currently the major contributor to the nesting aggregation. This work demonstrates the utility of stable isotope analysis to elucidate the spatial ecology of cryptic taxa and illustrates how more robust baselines can be assembled against which to measure the success of future marine conservation initiatives.

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“…Nesting loggerhead turtles can be assigned to their coastal foraging areas in the NWA using stable isotope values because NWA adult female turtles show fidelity to their foraging grounds both within and between years (Hawkes et al 2007a(Hawkes et al , 2011, as has been observed in other loggerhead populations (Broderick et al 2007, Schofield et al 2010, Thomson et al 2012). However, some NWA turtles have been found to occasionally use oceanic waters (Hawkes et al 2007a(Hawkes et al , 2011, which may result in unusual stable isotope values.…”

Section: Isotopic Characterization Of the Geographic Areas Used By Admentioning

confidence: 99%

Assignment of nesting loggerhead turtles to their foraging areas in the Northwest Atlantic using stable isotopes

et al. 2012

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Abstract. Differential foraging area use can affect population demographics of highly migratory fauna because of differential environmental changes and anthropogenic threats among those areas. Thus, identification of foraging areas is vital for the development of effective management strategies for endangered migratory species. In this study, we assigned 375 loggerhead turtles (Caretta caretta) nesting at six locations along the east coast of the United States to their foraging areas in the Northwest Atlantic (NWA) using carbon and nitrogen stable isotope values (d 15N values characterized three geographic areas-with distinct abiotic and biotic features-used by adult loggerheads in the NWA. Discriminant analysis assigned all 375 female loggerheads to one of the three foraging areas; 91% were assigned with probabilities of !80%. The proportion of nesting turtles using each foraging ground varied geographically; most turtles nesting in northern beaches (72-80%) tend to forage at higher latitudes while most turtles nesting in southern beaches (46-81%) tend to forage at lower latitudes. Stable isotopes can reveal the foraging location of loggerhead turtles in the NWA, which will allow robust analyses of foraging ground effects on demography and improve the design of management strategies for the conservation of loggerhead populations. The conclusions and methods developed in this study are also relevant for other populations of sea turtles and for other highly migratory species.

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Site specialists, diet generalists? Isotopic variation, site fidelity, and foraging by loggerhead turtles in Shark Bay, Western Australia

Cited by 54 publications

References 57 publications

Bahamas connection: residence areas selected by breeding female loggerheads tagged in Dry Tortugas National Park, USA

Bahamas connection: residence areas selected by breeding female loggerheads tagged in Dry Tortugas National Park, USA

Satellite tracking and stable isotope analysis highlight differential recruitment among foraging areas in green turtles

Assignment of nesting loggerhead turtles to their foraging areas in the Northwest Atlantic using stable isotopes

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