The Role of Season, Tide, and Diel Period in the Presence of Harbor Seal (Phoca vitulina) Breeding Vocalizations in Glacier Bay National Park and Preserve, Alaska

Glacier Bay National Park and Preserve is marine protected area in southeastern Alaska that is home to one of the largest seasonal aggregations of harbor seals (Phoca vitulina) in the region. Harbor seals, like the majority of phocids, are an aquatically breeding pinniped species. During the breeding season, male harbor seals use acoustic signals to defend underwater territories from other males and possibly to attract females. We used a long-term passive acoustic dataset to examine the trends in harbor seal vocal behavior near a terrestrial haulout as a function of season, tides, and time, of day. Seasonality analyses indicated a sharp increase in vocal activity during the months of June and July, which correlates with the estimated timing of the breeding at this location. Contrary to previous studies, there was no effect of tidal height on the documented calling behavior of harbor seals at this location, perhaps because the recordings were made farther from shore, within 10 km of the major haul-out area. Diel analyses showed that harbor seal males call throughout the day, hut, similar to other populations, calling significantly increased at night when more seals are foraging. This analysis provides evidence that specific environmental parameters play a role in harbor seal acoustic behavior in Glacier Bay and allows for behavioral comparisons among different harbor seal populations across the globe to guide future research efforts working to protect harbor seals during the breeding season.