Are social attributes associated with alarm calling propensity?

Emitting alarm calls may directly benefit individuals if callers have an increased chance of surviving, if calling increases the caller’s status, or if calling functions through reciprocity. Although previous studies have examined the costs and benefits of alarm calling, few have examined how an individual’s social position can influence the propensity to emit calls. An individual’s position in its social network may vary and individuals differ in the strength and degree to which they are connected to others. We hypothesized that this variation could influence the rate at which individuals emit calls. We examined how various social attributes (degree centrality, closeness centrality, eigenvector centrality, strength, and embeddedness) were related to the likelihood that yellow-bellied marmots (Marmota flaviventris) emitted calls. To do so, we first defined 2 principle components—"popularity" and "relationship strength"—and used generalized linear mixed effects models to explain both the natural rate of alarm calling and the rate of trap-induced calling. We found that the natural rate of alarm calling increased for marmots that were less popular (i.e., involved in fewer connections with other marmots) and that the rate of trap-induced calling increased for marmots involved in weaker relationships. These findings refute the reciprocity hypothesis. However, less popular marmots could be seeking to enhance their social status by calling, or they could be deterring predators without the aid of others. Similarly, marmots in traps are faced with an imminent personal threat. Thus, marmots in weaker relationships that cannot rely on other marmots may call to deter predators.