Abstract
The shifting climatic regime of maritime Antarctica is driving complex
changes across trophic levels that manifest differentially across
species and regions. Land-breeding pinnipeds have increased their
seasonal attendance near Palmer Station since earliest observations in
the mid-1900s, and Antarctic fur seals (Arctocephalus gazella)
now represent a significant but unstudied predator population in the
area during the austral summer. To characterize the timing of abundance
and 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 date and site
suitability. Estimated peak abundance occurred on March 11 (day 71) of
2020, and high habitat suitability was most associated with low-slope
and low-elevation inshore terrain, and relatively dry, sun-exposed, and
wind-sheltered locations. 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 and abundance of terrestrial occupancy
of Antarctic fur seals in this region—a critical first step in
understanding the phenology and ecological role of this largely
nonbreeding predator population. These findings establish a baseline
from which to estimate future changes in this seasonal population and
the potential pressures it exerts on sympatric terrestrial and marine
biota, as the physical environment and food chain of the western
Antarctic Peninsula transform under long-term climatic changes.