Social security: individuals in socially reciprocal groups may perceive security from predators.

Abstract

One of the most explored factors mediating antipredator behavior is group size, which generally predicts individuals in larger social groups allocate less time to antipredator vigilance while foraging. However, group size alone does not capture the full complexity of sociality. An individual's 'sense of security', or their perceived risk of predation, is also influenced by an individual's social connections. Further, group social structure - the pattern of all social interactions in a group - could explain additional variation in perceptions of security for the individuals that reside in the group. Using the time allocated to vigilance during foraging and flight initiation distance (FID) to quantify individuals' social security, we explored whether individual yellow-bellied marmots (Marmota flaviventer) in tightly connected social groups looked less while foraging and had shorter FIDs. Using linear mixed effect models, we found modest support for the Social Security Hypothesis; individuals in more socially reciprocal groups may spend less time looking for predators while foraging. No measure of group social structure explained variation in FID. Measures of the immediate environment (the number of individuals within 10 m for vigilance and the distance from burrow and alert distance for FID) had effect sizes an order of magnitude greater than measures of social structure, suggesting an individual's immediate environment has more of an impact on their antipredator behavior than the structure of their social group.