Listening for behavior: Identifying common behavior-associated call types to improve acoustic monitoring of cryptic sound-producing species.

Passive acoustic monitoring has become crucial in detecting cryptic sound-producing animals over the past two decades, but the behavioral context of different call types and the insights this information conveys have not been as widely integrated. Here, we used acoustic data alongside behavioral observations to better characterize North Atlantic right whale (Eubalaena glacialis) call type production in the context of social surface active group (SAG) behavior. Verified right whale calls collected from both archival recorders and biologging tags were grouped into discrete call types, and the presence or absence of a SAG during call production was assessed based on visual observations and auxiliary tag data. We identified four discrete call types within the data, all of which showed significant differential use based on SAG presence (p ≤ 0.001, Wilcoxon rank sum tests): lower-frequency (100-250 Hz) "moans" and "upcalls" produced in SAG absence and higher-frequency (300-500 Hz) "downcalls" and "constant calls" produced during SAG events. The identification of call types associated with this social behavior provides a means for both general acoustic and aggregation detection of the species while building a framework to continue integrating behavioral ecology into passive acoustic monitoring studies.