title: Influence of oceanographic structures on foraging strategies: Macaroni penguins at Crozet Islands.
abstract: BACKGROUND
  In the open ocean, eddies and associated structures (fronts, filaments) have strong influences on the foraging activities of top-predators through the enhancement and the distribution of marine productivity, zooplankton and fish communities. Investigating how central place foragers, such as penguins, find and use these physical structures is crucial to better understanding their at-sea distribution. In the present study, we compared the travel heading and speed of the world's most abundant penguin, the Macaroni penguin (Eudyptes chrysolophus), with the distribution of surface physical structures (large-scale fronts, eddies and filaments).
  
  
  RESULTS
  The study was performed during December 2012 in the Crozet Archipelago (46.42° S; 51.86° E), South Indian Ocean. Six males at incubation stage were equipped with GPS loggers to get their trajectories. We used Eulerian and Lagrangian methods to locate large-scale fronts, mesoscale eddies (10-100 km) and part of the sub-mesoscale structures (<10 km, filaments) at the surface of the ocean. By comparing the positions of birds and these structures, we show that Macaroni penguins: i) target the sub Antarctic Front; ii) increase their foraging activity within a highly dynamic area, composed of eddy fields and filamentary structures; and iii) travel in the same direction as the predominant currents.
  
  
  CONCLUSIONS
  We show that penguins adjust their travel speed and movement during their whole trips in relation with the oceanographic structures visited. At a large scale, we hypothesize that Macaroni penguins target the sub Antarctic Front to find profitable patches of their main prey. At finer scale, Macaroni penguin may adopt a horizontal drifting behavior in strong currents, which could be a way to minimize costs of displacement.
authors.affiliation: Centre d'Etudes Biologiques de Chizé, UMR 7372, CNRS - Université de La Rochelle, 79360 Villiers en Bois, France.
authors.forename: Cecile
authors.initials: C
authors.lastname: Bon
authors.affiliation: Sorbonne Universités, UPMC Université Paris 06, UMR 7159, LOCEAN-IPSL, F-75005, Paris, France/Université Paris-Diderot/CSIRO-UTAS Quantitative Marine Science Program, IMAS, Private Bag 129, Hobart, TAS 7001 Australia.
authors.forename: Alice
authors.initials: A
authors.lastname: Della Penna
authors.affiliation: Sorbonne Universités, UPMC Université Paris 06, UMR 7159, LOCEAN-IPSL, F-75005 Paris, France.
authors.forename: Francesco
authors.initials: F
authors.lastname: d'Ovidio
authors.affiliation: School of Life and Environmental Sciences, Faculty of Science, Engineering and the Built Environment, Deakin University, 221 Burwood Highway, Burwood, VIC 3125 Australia.
authors.forename: John
authors.initials: J
authors.lastname: Y P Arnould
authors.affiliation: Centre d'Etudes Biologiques de Chizé, UMR 7372, CNRS - Université de La Rochelle, 79360 Villiers en Bois, France.
authors.forename: Timothée
authors.initials: T
authors.lastname: Poupart
authors.affiliation: Centre d'Etudes Biologiques de Chizé, UMR 7372, CNRS - Université de La Rochelle, 79360 Villiers en Bois, France.
authors.forename: Charles-André
authors.initials: CA
authors.lastname: Bost