Responses of a polar predator to a glacier calving event
Adélie Antoine, Jean-Benoît Charrassin, Virginia Louise Andrews-Goff, Christophe Barbraud, Théodore Bloch, Karine Delord, Alexander Fraser, Robert Harcourt, Karine Heerah, Mark Hindell, Clive R. McMahon, David Nerini, Baptiste Picard, Michael Sumner, Simon Targowla, Esther Tarszisz, Sara LabrousseAbstract
Extreme episodic changes in Antarctic continental shelf regions, such as glacier calving or iceberg grounding, can fundamentally reshape regional sea-ice conditions. Weddell seals are obligate sea-ice predators and so may reflect ecosystem change around the Antarctic shoreline. From 2006 to 2024, the movements and diving behaviour of 35 female Weddell seals were studied using biotelemetry. Following the calving of the Mertz Glacier Tongue in February 2010, five females expanded into the previously unused Commonwealth Bay, where they undertook between 0.05 and 65.3% of their dives. This shift coincided with the establishment of persistent land-fast ice in the region (2019–2024), absent prior to calving (2006–2009). Residency times were positively associated with land-fast ice persistence. Although generalized additive mixed models detected no significant overall effect of calving on dive depth, dive duration, hunting time or hunting depth when averaged across the study area, all behavioural variables displayed pronounced spatial heterogeneity. This suggests that calving primarily altered the spatial distribution of diving and foraging behaviour rather than inducing uniform behavioural shifts. By contrast, this glacier calving event caused catastrophic breeding failures in seabirds, whereas even the resulting drastic sea-ice changes remained within the behavioural and spatial flexibility of Weddell seals.