Meeting Abstract
Animals must make decisions about how to categorize continuous variation in the world. An example of this is the recognition of familiar individuals. Because signal properties often vary within and among individuals, animals must group perceived variation into individual-specific perceptual categories and discriminate between variation that falls inside and outside of these categories. Such decision rules place boundaries around perceptual categories and are called “just-meaningful differences” (JMDs). To investigate signal variation and JMDs, we examined call variation and decision rules for discriminating between neighbors and strangers in a territorial frog. Male golden rocket frogs (Anomaloglossus beebei) learn to recognize neighbors’ calls and show less aggression towards neighbors compared with strangers. We quantified among- and within-individual variation in acoustic properties of calls and predicted an optimal JMD of 6% change for pulse rate and pulse duration, the most individually distinctive properties. We then empirically determined the JMD for pulse rate and pulse duration by testing territorial males in the field with habituation-discrimination playbacks. Males responded aggressively to synthetic calls but eventually habituated. Following habituation, we changed the pulse rate and pulse duration of the stimulus by 0%, 3%, 6%, 9%, and 12%. A 9% change elicited some recovery of aggression, but the largest recovery was observed in response to a 12% change, indicating a JMD at around 9%. These results confirm that male A. beebei can use temporal properties of advertisement calls to differentiate individuals. However, our predicted JMD did not match our empirically determined JMD, highlighting the limitations of analyses of signal variation for inferring receiver behavior.
