Seabird satellite tracking validates the use of latitudinal isoscapes to depict predators' foraging areas in the Southern Ocean

Abstract

Stable isotopes are increasingly being used to trace wildlife movements. A fundamental prerequisite of animal isotopic tracking is a good knowledge of spatial isotopic variations in the environment. Few accessible reference maps of the isotopic landscape ("isoscapes") are available for marine predators. Here, we validate for the first time an isotopic gradient for higher trophic levels by using a unique combination of a large number of satellite-tracks and subsequent blood plasma isotopic signatures from a wide-ranging oceanic predator. The plasma δ(13)C and δ(15)N values of wandering albatrosses (n = 45) were highly and positively correlated to the Southern Ocean latitudes at which the satellite-tracked individuals foraged. The well-defined latitudinal baseline carbon isoscapes in the Southern Ocean is thus reflected in the tissue of consumers, but with a positive shift due to the cumulative effect of a slight (13)C-enrichment at each trophic level. The data allowed us to estimate the carbon isotopic position of the main oceanic fronts in the area, and thus to delineate robust isoscapes of the main foraging zones for top predators. The plasma δ(13)C and δ(15)N values were positively and linearly correlated, thus suggesting that latitudinal isoscapes also occur for δ(15)N at the base of the food web in oceanic waters of the Southern Ocean. The combination of device deployments with sampling of relevant tissues for isotopic analysis appears to be a powerful tool for investigating consumers' isoscapes at various spatio-temporal scales.

Spatial and isotopic niche partitioning during winter in chinstrap and Adélie penguins from the South Shetland Islands

“…The observed differences within and between species indicates that isotope signatures from penguin tail feathers may be a useful tracer for identifying large-scale movement patterns of Adélie and chinstrap penguins, similar to other Southern Ocean seabirds (e.g., Cherel and Hobson 2007, Phillips et al 2009, Jaeger et al 2010. However, it is important to note that consumer stable isotope values can change over time due to shifts in dietary composition or movement between geographic location with differing isotopic baselines (e.g., Cherel and Hobson 2007, Brasso and Polito 2013, McMahon et al 2013).…”

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

“…Other speciesspecific isoscapes on marine predators have been developed for albatrosses equipped with tracking devices (n ¼ 45) in the Southern Ocean (Jaeger et al 2010) and for untracked bigeye (n ¼ 196) and yellowfin (n ¼ 387) tuna that were sampled in conjunction with fishery operations in the Pacific Ocean (Graham et al 2010). However, with tuna the isotopic values were assumed to reflect the signature of the capture location, although they may have been in transit (i.e., sampled during migration).…”

“…Satellite-tracked individuals often constitute training data for the development of models to geographically assign individuals of unknown origin (e.g., Jaeger et al 2010, Ceriani et al 2012, Seminoff et al 2012. However, to apply telemetry assignment models with confidence, it is critical to assess their performance by conducting external validation.…”

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

“…5A). Recent studies have integrated telemetry data to validate marine geographic patterns in d 13 C or d 15 N values of highly migratory animals such as seabirds (Jaeger et al 2010) and sea turtles (Seminoff et al 2012) over broad spatial scales (e.g., within ocean basins). Here, we present the combined d 13 C and d 15 N spatial characterization for a highly migratory animal at a regional scale in the NWA.…”