Abstract
Harbor seals ( Phoca vitulina ) exhibit sex‐specific differences in diet and spatial distribution. Previous studies have documented consistent variation in sexual composition among haul‐out sites, but the proximate factors underlying this spatial segmentation remain poorly understood. We examined whether variation in haul‐out site sex composition is associated with proximity to anthropogenic disturbance or prey availability across 14 sites in the Salish Sea. Using site‐specific sex composition estimates derived from molecular analyses, we quantified the distance via marine waterways of each haul‐out relative to marinas (used as a proxy for human disturbance) and Pacific salmon ( Oncorhynchus spp.) runs. We also evaluated spatial patterns of marinas and salmon runs using GIS‐based density metrics. All male‐dominated sites were located closer to marinas than all but one female‐dominated and even sex composition sites, whereas no clear relationship was found between haul‐out sex compositions and sizes of marinas and proximity to or density of salmon runs. Multinomial logistic regression supported the association between haul‐out sex composition and distance to the nearest marina, but not salmon run proximity or density. These findings suggest that spatial patterns by harbor seals are associated with anthropogenic disturbance in the Salish Sea—which has implications for pinniped monitoring and management in human‐dominated coastal systems.