Gray seals (Halichoerus grypus) are acoustically active marine mammals that use vocalizations for intra-specific communication year-round. While vocal behavior during the breeding season is well documented, less is known about acoustic activity at seasonal ephemeral haul out sites outside of the breeding season. Using land-based passive acoustic monitoring and boat-based focal observations, this study examines gray seal vocalizations at two summer haul out locations within Cape Cod National Seashore, focusing on call types, call rates, and the effects of herd demographics on these acoustic patterns. Recordings from 2024–2025 from Long Point and Lobster Cove in Provincetown, Massachusetts reveal three discrete call types: low-frequency yodels and higher-pitched moans and growls. Call rates varied across sites and sampling days, with individuals producing between 0–61 calls per 15-min focal session (Median = 0; Mean = 1.5; SD = 7.70; n = 68). Ongoing analyses further suggests changes in vocal activity with herd size and sex ratio indicating potential roles in spacing, low-level agonistic behavior, or social cohesion. Establishing this acoustic baseline contributes to understanding the function and variability of gray seal communication in dynamic haul out environments and aims to inform future monitoring efforts amid rising anthropogenic and environmental pressures.
Lacio et al. (2025) studied this question.