Crabeater seals exhibit extreme dietary specialization, feeding almost exclusively on Antarctic krill. This specialization has inextricably linked habitat use, life history and evolution of this pinniped species to the distribution of its prey. Therefore, the foraging habitat of crabeater seals can be used to infer the distribution of Antarctic krill. Here, we combined seal movements and diving behaviour with environmental variables to build a foraging habitat model for crabeater seals for the rapidly changing western Antarctic Peninsula (WAP). Our projections show that future crabeater seal foraging habitat and, by inference, krill distribution will expand towards offshore waters and the southern WAP in response to changes in circulation, water temperature and sea ice distribution. Antarctic krill biomass is projected to be negatively affected by the environmental changes, which are anticipated to manifest as a decrease in krill densities in coastal waters, with impacts on the land-/ice-based krill predator community, particularly in the northern WAP.
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We thank the National Science Foundation, United States Antarctic Program, Palmer Station, RV Laurence M. Gould crew and AGUNSA Chile for logistics support. Many people assisted with the fieldwork, particularly M. Hindell, N. Gales, A. Friedlaender, C. Kuhn, T. Goldstein, D. Shuman, M. Fedak, M. Goebel, P. Robinson, S. Villegas-Amtmann and S. Simmons. Animal handling was authorized by the University of California, Santa Cruz Institutional Animal Care and Use Committee and conducted under National Marine Fisheries Service permits 87-1593 and 87-1851-00. This study was part of LAH Doctoral studies, funded by CONICYT-Fulbright (Chile). The fieldwork was funded under National Science Foundation Office of Polar Programs grants ANT-0110687, 0840375, 0533332 and 0838937, the National Undersea Research Program and the National Oceanographic Partnership through the Office of Naval Research. L.A.H. was funded under JIP 00 07-23 from the E&P Sound and Marine Life Industry Project of the IAGOP. A.P. thanks CONICYT-PAI 79160077 and FONDAP 15150003.
The authors declare no competing interests.
Peer review information Nature Climate Change thanks Jessica Melbourne-Thomas, Dominik Nachtsheim and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
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Comparison between krill distribution and current crabeater seal foraging habitat. a, Sampling locations included in KRILLBASE between 2000 and 2016; b, krill densities (No. krill m-2) obtained from KRILLBASE between 2000 and 2016 (ref. 18); c, krill spawning habitat along the wAP22; d, crabeater foraging habitat (inferred krill distribution) as modeled in this study).
Projected future offshore expansion of the habitat of crabeater seals along the western Antarctic Peninsula (Linear regression model: Habitat width ~ Latitude * Period). Habitat width was defined as the mean distance between the coast and the 50% habitat importance contour for 50 km bins in the North coordinate. Error bars indicate the standard deviation of the habitat width for the bins. Colour dashed lines indicate the fitted linear regressions. Green indicates current habitat width. Yellow is projected habitat width under projected environmental changes.
Frequency distribution of the duration of continuous travel segments, as identified from satellite telemetry, for crabeater seals from the western Antarctic Peninsula.
Boosted Regression Tree (BRT). Partial dependence plots of the relationship between environmental covariates and presence/absence of crabeater seals along the western Antarctic Peninsula.
Boosted Regression Tree (BRT) Analysis. Receiver Operator Curve (ROC) shows a low performance of the final BRT model selected (Area Under the Curve, AUC = 0.64).
Boosted Regression Tree (BRT) Analysis. Relative influence of environmental variables used in the BRT models to predict foraging habitat of crabeater seals. The relative influence indicates the proportion of variation in the data explained by each variable with respect to the rest of the variables.
Receiver Operator Curve (ROC) to estimate the performance of the final Generalised Additive Mixed Model (GAMM) to predict the foraging habitat of crabeater seals from the western Antarctic Peninsula. The final selected model performance was estimated based on the Area Under the Curve (AUC) of 0.97.
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Hückstädt, L.A., Piñones, A., Palacios, D.M. et al. Projected shifts in the foraging habitat of crabeater seals along the Antarctic Peninsula. Nat. Clim. Chang. 10, 472–477 (2020). https://doi.org/10.1038/s41558-020-0745-9
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