1307 How a simple adaptive foraging strategy can lead to emergent home ranges and increased food intake Jacob Nabe-Nielsen, Jakob Tougaard, Jonas Teilmann, Klaus Lucke and Mads C. Forchhammer J. Nabe-Nielsen (nabe@dmu.dk), J. Tougaard, J. Teilmann and M. C. Forchhammer, Dept of Bioscience, Aarhus Univ., Frederiksborgvej 399, DK-4000 Roskilde, Denmark. JNN and MCF also at: Greenland Climate Research Centre, Greenland Inst. of Natural Resources, PO Box 570, DK-3900 Nuuk Greenland. – K. Lucke, Inst. for Terrestrial and Aquatic Wildlife Research, Univ. of Veterinary Medicine, Hannover, Germany. Animals often alternate between searching for food locally and moving over larger distances depending on the amount of food they ind. his ability to switch between movement modes can have large implications on the fate of individuals and populations, and a mechanism that allows animals to ind the optimal balance between alternative movement strategies is therefore selectively advantageous. Recent theory suggests that animals are capable of switching movement mode depend- ing on heterogeneities in the landscape, and that diferent modes may predominate at diferent temporal scales. Here we develop a conceptual model that enables animals to use either an area-concentrated food search behavior or undirected random movements. he model builds on the animals’ ability to remember the proitability and location of previously visited areas. In contrast to classical optimal foraging models, our model does not assume food to be distributed in large, well-deined patches, and our focus is on animal movement rather than on how animals choose between foraging patches with known locations and value. After parameterizing the ine-scale movements to resemble those of the harbor porpoise Phocoena phocoena we investigate whether the model is capable of producing emergent home ranges and use pattern-oriented modeling to evaluate whether it can reproduce the large-scale movement patterns observed for porpoises in nature. Finally we investigate whether the model enables animals to forage optimally. We found that the model was indeed able to produce either stable home ranges or movement patterns that resembled those of real porpoises. It enabled animals to maximize their food intake when ine-tuning the memory parameters that controlled the relative contribution of area concentrated and random movements. What enables animals to respond optimally to the plethora of environmental conditions that they are exposed to during their lives? he answer to this question is partly linked to their selection of foraging strategies, which is one of the central topics in behavioral ecology (Schoener 1971, Krebs and Davies 1984). Recent studies suggest that animals are capable of switching among diferent canonical move- ment modes depending on their internal state, environmen- tal factors and physiological constraints on their movement (Fryxell et al. 2008, Nathan et al. 2008). Diferent move- ment modes tend to characterize behavior at diferent spatial and temporal scales (Morales et al. 2004, Fryxell et al. 2008, Owen-Smith et al. 2010), but the mechanisms that control the behavioral shifts are poorly understood. Much of the theory of animal movement is based on the premises that individuals attempt to optimize their for- aging behavior by selecting among alternative resource patches (Bartumeus and Catalan 2009). Several studies have discussed how foraging is inluenced by cognitive processes, and particularly how an individual’s behavior relects its ability to remember favorable patches from previous visits and to navigate back to them (Tan et al. 2002, Gautestad and Mysterud 2005, Van Moorter et al. 2009). he cost of moving to diferent food patches has also been incorporated in numerous optimal foraging models (Griiths 1980, Mitchell and Powell 2004, Matsumura et al. 2010). In addition it is increasingly recognized that landscape compo- sition afects animal movement (Bowne and Bowers 2004, Hengeveld et al. 2009, McNamara and Houston 2009, Humphries et al. 2010). he present study extends existing theory of optimal foraging by shifting the focus from which patches animals should select in order to forage opti- mally. Instead we discuss how food intake can be increased through the choice of ine-scale movement mode for animals that continuously move through a landscape comprising a large number of small food patches. Which movement mode is optimal depends on the spatial distribution and amount of food found in the patches. Animal movement has frequently been modeled using correlated random walk (CRW) models (Turchin 1998, Morales et al. 2004, Bartumeus et al. 2005, Getz and Saltz 2008) where turning angles are correlated. Such models have been used to faithfully reproduce the ine scale movements for a large number of species, particularly in homogeneous environments (Turchin 1998, Morales et al. 2004), and CRW behavior has sometimes been interpreted Oikos 122: 1307–1316, 2013 doi: 10.1111/j.1600-0706.2013.00069.x © 2013 he Authors. Oikos © 2013 Nordic Society Oikos Subject Editor: horsten Wiegand. Accepted 8 January 2013