Isotopic Tracking of Migrant Wildlife

Hobson, Keith A.

doi:10.1002/9780470691854.ch6

Cited by 41 publications

(56 citation statements)

References 85 publications

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“…Subplots represent within individual absolute differences among serially collected samples using the first sample as a re ference. Filled circles: Bomba; triangles: Egypt; squares: TurkeyCyprus; diamonds: West Libya; open circles: unassigned not find discrete isotopic differences among all nonbreeding sites at a regional level given that the 2 most geographically separated foraging areas (Turkey-Cyprus and West Libya) were the most similar for δ 13 C and δ 15 N. The predictable increase of δ 13 C to wards the lower latitudes (Hobson 2007, Koch 2007) was confounded as our foraging areas were located on the north and south continental faces. Without the addition of the sulphur isotope ratios, we could not have reliably predicted the foraging area for a large proportion of turtles within this population.…”

Section: Selecting the Elements For Stable Isotope Analysismentioning

confidence: 99%

“…multiple geographically distinct areas share a similar isotopic profile), as discrete isotopic differences may not exist (Hobson 2007). In these circumstances, an additional isotope or trace element can be incorporated to supplement the carbon and nitrogen isotopes and possibly establish discrete differences among sites.…”

Section: Introductionmentioning

confidence: 99%

“…More specifically to the marine environment, δ 13 C can exhibit several strong spatial gradients relating to mean temperature and salinity because these factors influence primary production. In general, δ 13 C values increase from higher to lower latitudes, as well as from oceanic to neritic ecosystems, and from pelagic to benthic food sources (Hobson 2007, Koch 2007. The δ 15 N of a primary producer can be strongly influenced by the mode of nitrogen cycling , and substantial trophic discrimination (~3.4 ‰) (DeNiro & Epstein 1981) enables assumptions to be drawn concerning the consumer's trophic level (Hobson & Welch 1992, Godley et al 1998.…”

Section: Introductionmentioning

confidence: 99%

“…Nevertheless, satellite telemetry is expensive and can entail direct costs to the study animals, and therefore, sample size is often limited (Wilson & McMahon 2006, Godley et al 2008. However, the satellite data from a few individuals can be scaled-up to infer habitat use at a population level through the use of forensic chemical techniques such as stable isotope analysis (Hobson 2007, Jaeger et al 2010, Zbinden et al 2011, Robinson et al 2016.…”

Section: Introductionmentioning

confidence: 99%

“…The isotopic composition of a consumer's tissue reflects that of its diet after undergoing a predictable trophic enrichment (Graham et al 2010), providing a natural intrinsic tag that can link an animal to a location (Hobson 2007). The time period over which the diet is assimilated depends on the tissue-specific turn-over rates, and meta bolically active tissues can be selected dependent upon the time frame to be studied .…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

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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Section: Selecting the Elements For Stable Isotope Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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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Mitochondrial DNA short tandem repeats unveil hidden population structuring and migration routes of an endangered marine turtle

Tikochinski

Bradshaw

Mastrogiacomo³

et al. 2018

Aquatic Conservation

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The assessment of the composition and dynamics of endangered populations is crucial for management and conservation, and appropriate genetic markers are critical. The genetic structuring of the Mediterranean green turtle (Chelonia mydas) populations and the origin of the stranded animals found along the Israeli coast was investigated using new highly polymorphic short tandem repeat (STR) markers. The structuring of nesting populations was studied using pairwise genetic distances and a principal coordinates analysis (PCoA). The contribution of the different nesting populations to the stranded sample was assessed by using a mixed‐stock analysis. A clear population genetic structure, not detected before, has been revealed. The four nesting populations are genetically well differentiated, and thus should be considered as different management units. The populations from Turkey and Israel showed higher resemblance, despite residing at opposite ends of the Mediterranean distribution. The Turkish nesting population is the main source of the stranded turtles sampled along the Israeli shore, confirming that individuals from this population migrate from north to south along the eastern shore of the Mediterranean, as previously shown by telemetry studies. The use of a highly polymorphic haplotyping method enabled the detection of a clear genetic structuring of the green turtle populations in the eastern Mediterranean Sea that was not revealed in previous studies, demonstrating the importance of marker selection in population genetics. The analysis of the genetic composition of the stranded turtles allowed us to investigate the migration patterns from nesting to foraging areas, supporting previous satellite‐tracking and stable‐isotope results. These results will help to delineate conservation management units for the species in the Mediterranean, and reveal connectivity among beaches and mixed aggregations.

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Incorporating breeding abundance into spatial assignments on continuous surfaces

Rushing

Marra

Studds

2017

Ecology and Evolution

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Determining the geographic connections between breeding and nonbreeding populations, termed migratory connectivity, is critical to advancing our understanding of the ecology and conservation of migratory species. Assignment models based on stable isotopes historically have been an important tool for studying migratory connectivity of small‐bodied species, but the low resolution of these assignments has generated interest into combining isotopes with other sources in information. Abundance is one of the most appealing data sources to include in isotope‐based assignments, but there are currently no statistical methods or guidelines for optimizing the contribution of stable isotopes and abundance for inferring migratory connectivity. Using known‐origin stable‐hydrogen isotope samples of six Neotropical migratory bird species, we rigorously assessed the performance of assignment models that differentially weight the contribution of the isotope and abundance data. For two species with adequate sample sizes, we used Pareto optimality to determine the set of models that simultaneously minimized both assignment error rate and assignment area. We then assessed the ability of the top models from these two species to improve assignments of the remaining four species compared to assignments based on isotopes alone. We show that the increased precision of models that include abundance is often offset by a large increase in assignment error. However, models that optimally weigh the abundance data relative to the isotope data can result in higher precision and, in some cases, lower error than models based on isotopes alone. The top models, however, depended on the distribution of relative breeding abundance, with patchier distributions requiring stronger downweighting of abundance, and we present general guidelines for future studies. These results confirm that breeding abundance can be an important source of information for studies investigating broad‐scale movements of migratory birds and potentially other taxa.

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Isotopic Tracking of Migrant Wildlife

Cited by 41 publications

References 85 publications

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

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

Mitochondrial DNA short tandem repeats unveil hidden population structuring and migration routes of an endangered marine turtle

Incorporating breeding abundance into spatial assignments on continuous surfaces

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