Resource selection studies in ecology are commonly undertaken at a population-level, yet long-term individual-level studies are undoubtedly important. We compared the travelling- and dive behaviour characteristics of 22 adult male southern elephant seals (Mirounga leonina) tracked from King George Island / Isla 25 de Mayo (KGI) at the Antarctic Peninsula, with data obtained from 28 migrations performed by 17 adult males tracked from sub-Antarctic Marion Island (MI). The population-level home ranges of seals were similar in size for their two-dimensional home ranges (95% kernel density estimate: MI = 2.19 million km²; KGI = 2.1 million km²). However, Marion Island elephant seals typically performed deeper dives (MI = 605 ± 427 m; KGI = 444 ± 282 m), resulting in substantial differences between the total water volumes used when incorporating dive depths into population-level home range estimates (three-dimensional 95% kernel density estimate: MI = 1.4 million km³; KGI = 0.67 million km³). We further investigated the relative influences of population of origin, individual-level behavioural variability, estimated seafloor depths and migration type (i.e. post-moulting vs post-breeding migrations) on the three-dimensional home ranges of study animals. We found no statistically significant support for consistent individual-level differences in three-dimensional home range sizes between populations, but rather that individual-level variability explained most of the data variance, followed by other drivers (e.g. migration time and seafloor depth). These results highlight the need for continued broad-scale long-term individual-level monitoring in this species to inform population-level resource use and habitat requirements.