The distribution and timing of bearded seal (<italic>Erignathus barbatus</italic>) vocalizations reflect changing environmental conditions in the Bering, Chukchi, and Beaufort Seas

Abstract

The Arctic is experiencing dramatic shifts in climate that have led to changes in sea ice distribution, extent, and timing that pose adaptability challenges for Arctic species. Ice obligate species, such as the bearded seal,<italic>Erignathus barbatus</italic>, are inherently vulnerable to Arctic warming due to their reliance on seasonal sea ice as a platform for pupping and molting. Bearded seals are a highly vocal pan-Arctic species, in which males produce underwater vocal displays as part of courtship behavior during mating season. Bearded seal vocalizations were once believed to be a spring phenomenon, but results of this study have revealed year-round acoustic activity by bearded seals in the Bering, Chukchi, and Beaufort Seas (BCB). This new insight suggests that passive acoustic monitoring can be employed as an effective method to examine bearded seal distribution, migration patterns, and population structure year-round. This study provides a more complete understanding of bearded seal behavior and ecology through the analysis of year-round passive acoustic data collected in the BCB between 2008 and 2011. The BCB comprises three ecologically distinct bodies of water connected by the currents that flow northward from the Pacific Ocean through the Bering Strait and into the Arctic. The fine- and broad-scale oceanographic and physiographic variability that exists among the BCB may directly or indirectly (through sea ice conditions) affect bearded seal distributions. Analysis of seal vocal presence relative to sea ice distribution helped to clarify the relationships between bearded seal vocal behavior, habitat preferences and sea ice conditions. Regional and recording-site variability in call activity was largely related to sea ice conditions and geography, however oceanographic variability may contribute to the fine-scale variability in call activity that was present between closely located sites. This research provides a contemporary baseline of bearded seal distributions needed for detecting future population fluctuations as a result of sea ice variability in the disrupted polar climate. Results of this study revealed a positive correlation between bearded seal call activity and sea ice conditions. This tight coupling of sea ice and call activity provide evidence that variability in sea ice conditions may have major implications for the success of the bearded seal population in the BCB as the climate continues to change.