Haul-out Behavior of Harbor Seals (Phoca vitulina) in Summer on Yellow Island: Diel Patterns Contrasting Females with Pups and Solitary Seals

Abstract

Knowledge of harbor seal distribution, abundance, and site fidelity is essential for conservation, as is knowledge of female-pup behavior. I focused on these elements in this study by assessing haul-out tendencies of a local population of harbor seals on Yellow Island, Washington, and contrasting these characteristics between female-pup pairs and solitary seals. I found that seal abundance varied with temperature, tidal height, and time of day, although these factors were not independent and worked simultaneously to determine haul-out abundance. Female-pup pairs hauled out in proportion to the number of female-pup pairs at the study site, suggesting these pairs were not more likely to haul-out than solitary seals under any conditions. It is possible that due to the unique adaptations of harbor seals during the pupping season, including a maternal foraging cycle and comparatively precocial pups, females and their young did not have different haul-out needs than other seals. However, females with young remained in the study site for a longer period of time, even as haul-out sites decreased. This finding was consistent with other studies demonstrating the increased site fidelity and decreased length of foraging trips of females with pups during the pupping season. Aggregating in haul-out areas may also be a predator avoidance mechanism.