A description of a rhythm or beat needs to include a description of its goodness of fit, meaning how well the rhythm describes a sequence. We present three independent ideas to further expand the applicability of rhythm analysis for isochronous, that is, metronome-like, rhythms. The temporal structure of animals' acoustic signals can inform about context, urgency, species, individual identity, or geographical origin. 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. 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. 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. However, many core phenomena in alarm-calling behaviors remain unresolved. Simultaneously, after vigorous debate, the fundamental role of information in alarm calls, as in other forms of communication, is largely accepted.

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. Over the intervening years, our thinking about the nature of alarm calls has continued to mature. 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.

Squirrel call