Behavioral context of male fin whale Balaenoptera physalus call production on a western North Atlantic summer foraging ground

Acoustic behavior of fin whales in the endangered western North Atlantic stock, outside of singing behavior, remains poorly understood. Over 2 summers, 29 suction cup multisensor acoustic biologging tags were deployed on fin whales in southern New England, USA, collecting 137.5 h of data (mean: 6.3 h; range: 0.17-19 h). In total, 22 males and 1 female were identified through photo identification and genetic analysis, demonstrating a sex bias in sampled whales. Males tagged in associated dyads (n = 3) displayed moderate dive synchrony. Individuals called infrequently (0.8 ± 2.0 calls h -1 ), and the longest period without calls exceeded 15 h. Kinematic patterns in movement data were used to identify 5 behavioral states (feeding, exploratory foraging, travel, rest, and unknown). Call rates were highest during nighttime feeding. Nine of the 22 males produced calls during the recording period (mean for subset: 20 calls; range: 1-132 calls). One broadband, 4 low frequency (20 Hz), and 3 higher frequency (>40 Hz) call types were identified. Three individuals produced short, irregular call bouts. High frequency downsweeps were a significantly larger proportion of the traveling call repertoire (24%) than all states combined (8.8%). These results support the hypothesis that sounds are used for feeding coordination in this species. As fin whale presence is monitored acoustically offshore of the US East Coast, these findings show the potential for missed detections of individuals outside of the breeding season due to low call rates and detection of a small percentage of highly vocal individuals during mid-summer in this habitat.