UC Santa Cruz

The shifting climatic regime of maritime Antarctica is driving complex changes across trophic levels that are manifesting differentially across its resident species and regions. Land-breeding pinnipeds have increased their seasonal attendance near Palmer Station since the earliest observations in the mid-1900s, and Antarctic fur seals (Arctocephalus gazella) now represent a significant but unstudied predator population in the region during the austral summer. To characterize the timing of abundance and the fine-scale distribution of this seasonal attendance, we carried out regular drone surveys of terrestrial habitats near Palmer Station in the austral summer of 2020. Using repeat animal counts and photogrammetric data products, we modeled fur seal abundance at survey sites over the period of observation, modeled habitat suitability based on fine-scale topographic habitat characteristics, and estimated abundance across terrestrial habitats near Palmer Station as a function of these products. High habitat suitability was most associated with low-slope and low-elevation inshore terrain and with relatively dry, sun-exposed, and wind-sheltered locations, and estimated peak abundance occurred on March 11 (day 71) of 2020. Models estimated 2289-5544 (95% confidence interval) fur seals on land across all potential terrestrial habitats (41 discrete sites) near Palmer Station and Wylie Bay on the south coast of Anvers Island during peak abundance. This constitutes a first estimate of the aggregate timing, abundance, and distribution of Antarctic fur seals in the terrestrial habitats of this region-a critical first step in understanding the phenology and ecological role of this largely nonbreeding predator population. These findings additionally establish a baseline from which to estimate future changes in this seasonal population and its effects on sympatric terrestrial and marine biota, as the physical environment and food chain of the western Antarctic Peninsula transform under long-term climatic changes.