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The Influence of Personality on a Group-Level Process: Shy Hermit Crabs Make Longer Vacancy Chains



Mark Briffa, Marine Biology & Ecology Research Centre, Plymouth University, Drake Circus, Plymouth PL3 8AA, UK.



Animal personality has been investigated in a variety of contexts but few studies have investigated the effects of individual-level traits on processes that occur at the group or population level. Vacancy chains describe sequences of linked vacancy moves in systems where individuals use discrete and reuseable resource units. When a new resource unit becomes available, this can cause a cascade of moves between resource units, beyond the first individual that encounters the new unit. Thus, vacancy chains can drive the distribution of resources through a population. Here, I investigate the effect of variation in boldness on movements between vacant gastropod shells in the hermit crab Pagurus bernhardus. Boldness was quantified using the duration of a startle response, which varied consistently between individuals. In groups of five crabs, introduction of a single new shell led to aggregate benefits, in terms of improving shell quality, across all group members. Boldness did not influence the extent of these benefits or the extent to which they were distributed between crabs of different sizes. Initially, vacancy chains were longer, indicating that more individuals moved between shells, for bold groups compared with shy groups. After 24 h, however, the chain length was longer for shy groups. Thus, although participation in a vacancy chain may lead to similar benefits, these could be more widespread for groups comprising shy individuals that show long startle responses, low inquisitiveness and low aggression. Similar effects on resource acquisition could be present in other examples of animals that utilise reusable resource units and show consistent between-individual differences in behaviour.