Caller identification and characterization of individual humpback whale acoustic behavior

Acoustic recording tags provide fine scale data linking acoustic signaling with individual behavior; however, when an animal is in a group, it is challenging to tease apart calls of conspecifics and identify which individuals produce each call. This, in turn, prohibits robust assessment of individual acoustic behavior including call rates and silent periods, call bout production within and between individuals, and caller location. To overcome this challenge, we simultaneously instrumented small groups of humpback whales on a western North Atlantic feeding ground with sound and movement recording tags. This approach enabled comparison of relative amplitude of each call across individuals to infer caller identity for 97% of calls. We found that humpback whale individual call rates are highly variable across individuals and groups (0-89 calls/h), with calls produced throughout dives and in bouts with short inter-call intervals (ICI = 2.2s). Most calls received a likely response from a conspecific within 100s. These results have important implications for acoustic monitoring and density estimation. Future studies can expand on these caller identification methods and further investigate the nature of sequence production and counter-calling in humpback whale social calls. Finally, this approach is useful for understanding intra-group communication in social groups across taxa.