Foraging behaviour of King Penguins (Aptenodytes patagonicus) in relation to predictable mesoscale oceanographic features in the Polar Front Zone to the north of South Georgia Annette Scheffer * , Philip N. Trathan, Martin Collins British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge, UK article info Article history: Received 13 March 2008 Received in revised form 1 December 2009 Accepted 10 April 2010 Available online 8 May 2010 abstract Marine predators are thought to utilise oceanic features adjusting their foraging strategy in a scale- dependent manner. Thus, they are thought to dynamically alter their foraging behaviour in response to environmental conditions encountered. In this study, we examined the foraging behaviour of King Pen- guins (Aptenodytes patagonicus) breeding at South Georgia in relation to predictable and stable oceano- graphic features. We studied penguins during their long post-laying foraging trips during December 2005 and January 2006. For this investigation, we undertook a simultaneous analysis of ARGOS satel- lite-tracking data and Mk 7 WildLife Computers Time Depth Recorder (TDR) dive data. To investigate cor- relations between foraging behaviour and oceanographic conditions, we used SST data from January 2006 from MODIS satellite AQUA. To determine changes in search effort, first passage time (FPT) was calcu- lated; for analysis of dive behaviour, we used several dive parameters that are thought to be reliable indi- cators of changes in foraging behaviour. King Penguins appeared to target predictable mesoscale features in the Polar Front Zone (PFZ), either a warm-core eddy in the PFZ or regions of strong temperature gra- dients at oceanic fronts. Two different trip types could be distinguished: direct trips with a straight path to one foraging area at the edge of an eddy or at a thermal front, and circular trips where birds foraged along strong thermal gradients at the northern limit of the PFZ. It is likely that both trip types were a direct consequence of prey encounter rates and distributions, both of which are likely to be associated with these oceanographic features. Circular trips often included passages across the centre of an eddy where birds made deep foraging dives, but remained only a short time in the eddy, possibly because prey were too deep. All birds showed Area Restricted Search (ARS) at scales of <10 km. The two trip types had different ARS patterns, with clear ARS hotspots for direct trips and several ARS hotspots over the whole duration of the trip for circular trips. Dive behaviour had clear relationships with the changing water temperature and the time of day, presumably in response to different prey distribution. Especially for direct trips, dive behaviour showed significant differences within and outside of ARS hotspots. Thus, King Penguins appear to target predictable mesoscale features in the PFZ. They use ARS in different patterns to exploit the environment and adjust their foraging strategy and diving behaviour depending upon condi- tions they encountered. Diving behaviour showed correlations to ARS patterns, especially for direct trips, which may represent a favourable foraging strategy. The presence of predictable oceanic features allows King Penguins to focus their foraging effort, presumably allowing them to increase their foraging success and decrease their diving effort. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction The survival and breeding success of seabirds and other marine predators critically depends upon the spatial and temporal distri- bution of their prey; indeed, their foraging behaviour is strongly related to the abundance, distribution and predictability of these resources (Rodhouse et al., 1996; Hull et al., 1997; Weimerskirch et al., 1997; Fauchald et al., 2000; Weimerskirch, 2007). Physical and biological processes in the ocean control the distri- bution and abundance of plankton and nekton, which affects the distribution of higher trophic levels such as seabirds and marine mammals (Pakhomov and McQuaid, 1996). Heterogeneity in the marine environment results in patchiness and aggregated distribu- tions of marine resources over several different scales (Croxall et al., 1984; Fauchald, 1999). Foragers in patchy systems are known to adjust their search pattern in order to assess the system at different scales (Fauchald, 1999). Marine predators feeding on such prey patches should concentrate their foraging efforts in areas where resources are most predictable and therefore adjust their 0079-6611/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.pocean.2010.04.008 * Corresponding author. Tel.: +44 (0)1223 221547; fax: +44 (0)1223 362616. E-mail address: annhef@bas.ac.uk (A. Scheffer). Progress in Oceanography 86 (2010) 232–245 Contents lists available at ScienceDirect Progress in Oceanography journal homepage: www.elsevier.com/locate/pocean