Habitat use by critically endangered North Pacific right whales linked to sea ice dynamics at varying spatial scales.

Documenting distributional shifts in populations is critical for understanding ecosystem function and developing effective conservation strategies, particularly for rare and understudied species. The Critically Endangered eastern population of North Pacific right whale (NPRW) was driven to near extinction by commercial whaling and has not recovered (N < 35). We analyzed passive acoustic data from seven sites along the eastern Bering Sea shelf (2012-2019) to investigate spatial and environmental associations of NPRW calling patterns on a rapidly warming primary foraging ground. Generalized additive models were used to relate acoustic metrics summarized by ecological year (March-February) to environmental conditions at two scales: (1) cold pool extent (CPE), a shelf-scale hydrographic feature derived from seasonal sea ice meltwater that structures right whale prey, and (2) site-specific mean fall bottom temperature (BT), a local thermal expression of cold pool conditions and fall mixing. NPRW phenology, specifically spring arrival and fall departure, was modeled against sea ice retreat and formation dates. NPRW calls occurred at all sites but were most consistently detected within Critical Habitat in the southeastern Bering Sea (SEBS). Calling activity expanded northward during consecutive years of lower CPE (2014-2016), whereas overall few detections occurred during record-low CPE years (2018 and 2019), suggesting a redistribution associated with environmental conditions. While spatial structure explained much of the observed variation, models incorporating CPE and BT received greater and comparable support, suggesting that NPRW calling patterns are associated with habitat conditions generated by cold pool processes rather than single metrics. The strength of environmental effects implied greater sensitivity of calling intensity to environmental variability than calling occurrence. Significant environmental relationships were restricted to the SEBS, where detections increased with CPE and decreased with warming BTs, consistent with known prey-temperature associations. These results, combined with no significant trends between whale phenology and sea ice timing, suggest that NPRW calling patterns are associated with trophically mediated effects of sea-ice-driven oceanography rather than direct responses to ice timing. More broadly, this study demonstrates how long-term passive acoustic monitoring can reveal climate-associated changes in marine predator calling patterns and link detected calling to ecosystem processes operating across spatial scales.