Experimentally seeded social cues in the wild: costs to bearers and potential benefits to receivers

Conspecifics can provide social cues about the presence of key features of the surrounding environment, such as food or predators. Attending to social cues may therefore potentially benefit receivers, or at least be worth following. Yet, bearing social cues could also be costly, particularly if it increases the likelihood of close-range interaction with non-kin. Here, we experimentally seeded social cues in the wild onto focal individuals of the social hermit crab (Coenobita compressus), testing (1) the “potential benefits to receivers” hypothesis, which predicts that receivers will follow social cues to orient toward valuable resources, and (2) the “costs to bearers” hypothesis, which predicts that bearers of social cues will experience direct (physical) costs or indirect (constrained movement) costs due to interaction with receivers. Consistent with hypothesis (1), in natural encounters, conspecifics that crossed paths frequently made antennal contact, potentially gathering social information at close range. In experiments, naive conspecifics followed focal individuals bearing “positive” social cues (about a valuable food resource) significantly more often than they followed individuals bearing less attractive (“neutral” or “ambivalent”) social cues, pointing to a potential benefit. Consistent with hypothesis (2), individuals bearing positive social cues incurred greater direct and indirect costs, being physically flipped more often and achieving shorter displacements compared to individuals bearing other social cues. We conclude that experimentally seeded social cues in the wild can confer costs to bearers and potentially benefit receivers. Broadly, the costs of bearing social cues, revealed here, underscore the importance of not overlooking that social cues may be costly.