Familiarity with a partner facilitates the movement of drift foraging juvenile grayling (Thymallus thymallus) into a new habitat area
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Preferring one social partner over another can enhance fitness. This paper reports that juvenile grayling were significantly more likely to enter and forage in new, upstream habitats when paired with familiar versus unfamiliar social partners. Fish paired with unfamiliar partners or when alone were more reluctant to enter the new area. The entry times for both fish in a familiar pair were significantly correlated, but uncorrelated for unfamiliar fish. These differences between familiars and unfamiliars were consistent over a 2-week period. Fish with familiar partners spent more time within three body lengths of each other than did those with unfamiliars. The results are discussed in relation to optimality models of drift foraging, which do not included sociality. It is suggested that the social dimension creates a more dynamic foraging response to variable environmental conditions and could have consequences for growth.
KeywordsSocial context Exploration Drift foraging Familiar Grayling
Paul Hart thanks the University of Leicester for granting him study leave and the University of Karlstad for inviting him to visit and for financial support. We thank Ashley Ward and Mike Webster for instructive comments on an earlier draft. The experiment was approved by Sveriges Djurförsöksetiska nämnd (Swedish Experimental Animal’s Ethical Committee, Reference Number: 278-2010).
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