Differences in acoustic presence and vocal behavior of Spitsbergen's bowhead whales under ice-covered and open-water conditions.

Arctic-endemic bowhead whales (Balaena mysticetus) are facing extreme habitat changes, particularly due to ongoing sea-ice loss. This study compares acoustic presence and vocal behavior of bowhead whales at two ecologically distinct locations: (1) northwest of Svalbard at 81.5° N, a region that remains nearly ice-covered year-round, and (2) eastern Fram Strait at around 79° N, which is mostly ice-free throughout the year. To detect vocalizations in multi-year acoustic records, two Convolutional Neural Networks were trained. Acoustic presence periods were similar at both locations (October to April), but markedly higher and more continuous acoustic presence northwest of Svalbard indicates increased animal abundance. The frequent detection of song at this site further suggests that it serves as a winter breeding ground. Song diversity peaked in February, possibly reflecting animals arriving from north of Svalbard where sea ice retreated at that time. Regular acoustic detections between 2012 and 2023 in eastern Fram Strait show consistent seasonal presence of bowhead whales in this area. Our study contributes to assessing impacts of ongoing sea-ice decline on the Spitsbergen population and allows for more accurate predictions of future occurrence patterns. We provide new insights into intra-seasonal occurrence, thus support a holistic understanding of ecological characteristics of this population.