Understanding the mechanisms behind animal movement decisions is fundamental in identifying what makes a movement strategy successful and in predicting how an individual will respond to environmental change. The unprecedented physical changes occurring on Earth can have profound consequences for animal movements, which have evolved to be finely tuned to environmental cues or rely on specific conditions at certain sites. This is especially true in the Arctic, where elevated water temperatures and reduced sea ice pose stressors to cryophilic species, which have movement strategies tied to the extreme but predictable seasonality of the environment. In this thesis, I use satellite tag data from male beluga whales of the Eastern Beaufort Sea (EBS) population to develop a comprehensive understanding of their movements and the relationship between these movements and the environment, from small-scale decisions related to foraging to large-scale seasonal redistribution. I also consider the functional traits of belugas to frame my research in the broader field of movement ecology such that the findings can be applied to other marine predators. Much of this thesis centres around beluga dive behaviour, where I characterised and inferred likely functions behind individual dives over an annual cycle, used this to infer seasonal changes in behaviour, and answer further questions about the environmental drivers of movement, activity cycles, foraging ecology, and question our understanding of migration in highly mobile marine predators. An overriding theme revealed by these analyses is the complexity and diversity of the movements and dive behaviour exhibited by EBS belugas. This population forages nearly continuously over the annual cycle, including in their winter habitat and during so-called migrations, but they use a range of strategies depending on environmental conditions. They exhibit traits during long-distance movements characteristic of migration and nomadism, but conform wholly to the classical views of neither. We identified that EBS belugas occupy and forage over a range of sea ice conditions, from open water to areas approaching 100% ice cover, and even with a small sample size we found individual variability in the routes taken and dive behaviour. The flexibility in strategies at the individual level and the diversity of traits at the population level may provide resilience for EBS belugas in the face of environmental change.