Weddell seals are polar predators that must partition their time between many behaviours,
including hunting prey at depth and breathing at the surface. Although they have been well studied, little
is known about how foraging behaviour changes when access to breathing holes is restricted, such as in
the isolated-hole paradigm. The current study took advantage of previously gathered data for seals
diving at an isolated hole to compare with foraging behaviour of free-ranging seals that had access to
multiple holes. We examined dive structure, hunting tactics, and allocation of time, locomotor activity
and energy based on three-dimensional dive profiles and video imagery of prey encounters for
two free-ranging and six isolated-hole seals. Midsummer foraging dives of free-ranging seals were
remarkably similar to those of seals diving at an isolated hole, but there were differences in two
behavioural states and the frequency of several behavioural transitions. Results indicate that seals
employ an energetically more conservative foraging strategy when access to breathing holes is limited
and prey are less abundant. These results highlight the importance of understanding the complex
interactions between breathing hole access, prey abundance and other factors that may result in different
Weddell seal foraging strategies under changing future conditions.
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