McRae, T. R. (2020). A review of squirrel alarm-calling behavior: What we know and what we do not know about how predator attributes affect alarm calls. Animal Behavior and Cognition, 7(2), 168-191. doi: https://doi.org/10.26451/abc.07.02.11.2020

Forty years ago, vervet monkeys were shown to use three different predator-specific calls that elicit three different antipredator behaviors, jump-starting investigation into the information content of animal signals. Over the intervening years, our thinking about the nature of alarm calls has continued to mature. Based primarily on studies in primates, squirrels, and birds, our conceptualization of alarms has moved from a dichotomous view of calls as either referencing external stimuli or expressing emotional response, toward an increasingly nuanced view of emotional and external contexts interacting in sometimes nuanced ways to shape communication. Simultaneously, after vigorous debate, the fundamental role of information in alarm calls, as in other forms of communication, is largely accepted. However, many core phenomena in alarm-calling behaviors remain unresolved. Among these, the forces that give rise to generalized alarms versus specialized categorical or continuous variation in alarm call acoustic parameters are not well characterized, in part because most alarm calling systems are either not so simply categorized or are themselves not yet well-understood. To move the field forward, we must better understand the layered information content of alarms, and how that information does and does not affect the behavior of others. With the goal of encouraging additional research in these areas, I summarize what we know and what we do not know about the predator-related information in squirrels’ alarm calling systems across the five subfamilies of Sciuridae, in the context of their sociality and whether they are burrowing or arboreal.

Alarm calls, Sciuridae, Animal communication, Referential, Information