We observed polar bear movement patterns that were associated with season, presence of daylight, wind speed, and bear speed. Seasons vary in food distribution and habitat conditions34,36,67. As food abundance and distribution change and as energetic cost of foraging change, different foraging behaviours may be optimal32,38,68. Within any season, wind speed can influence the effectiveness of olfactory search. Higher wind speeds increase turbulence and affect odour filament distribution and may be unfavourable for olfaction13,46,47. In addition, bear speed might reflect different behaviours, only some of which are cross-wind search19. Other behaviours such as travel between patches, migration, rest, or visual search likely exhibit different relationships with wind than cross-wind search.

Distinguishing between behaviours is complicated by the delineation of biologically meaningful seasons and by the resolution and accuracy of the wind estimation, ice drift estimation, and GPS tracking data. Although the modelled wind direction was a mean 10° left of wind measured at Churchill Airport (Supplementary Fig. S2), it falls within the bin sizes used in the χ2 tests (±25° or ±20°, depending on orientation), and would not cause misclassification of the predominant direction. The 4-hour resolution of the location data can only capture sustained movements, masking short-term responses to wind, such as upwind localization of a detected odour. Despite the inherent challenges and limitations of studying animals with vast and remote ranges, we observed several wind- and season-associated behaviours.

In Hudson Bay, terrestrial foraging by polar bears is limited to less energetically dense foods (e.g., berries, and seaweed)34,35,36,37, and the bears minimize unnecessary movement to conserve energy32,38,39. We found a weak (though significant) association between bear movement and wind during summer, suggesting that cross-wind search is either reduced or absent during this season (Fig. 3a). We found a similar bimodal distribution in movement relative to north, with bears tending to move north or south (Fig. 2a). Any movement during the summer would be confined by the shoreline, which extends north-south in western Hudson Bay (Fig. 1). Because of the predominantly northwesterly winds (Supplementary Fig. S3), random movement confined by the shoreline would tend to also be cross-wind. Thus, the cross-wind movement we observed during summer may be an artefact of the landscape rather than a response to wind.

Freeze-up begins in northwest Hudson Bay69 and, by moving northwards during the months leading up to freeze-up, bears are able to return to the sea ice sooner. The northward movement we observed during autumn (Fig. 3b) may be an example of polar bears’ migratory behaviour associated with freeze-up32.

Polar bears traveled predominantly downwind during freeze-up (Fig. 4a), which leads them east towards the centre of the Bay (Fig. 2c). In addition to following the southeastward advancing sea ice, we suggest the movement may be partly guided by wind. Because wind direction was variable (Supplementary Fig. S3), movement guided solely by celestial or global cues (such as solar position or global magnetisms)41 would have a stronger association relative to north than relative to wind, which was not the case (Fig. 2c vs Fig. 4a). As intraspecific competition affects distribution of female polar bears with cubs70, the focus of such bears during freeze-up may be to disperse throughout the Bay and away from conspecifics. The pattern of dispersal during freeze-up may be sex-specific as females avoid males due to the threat of infanticide33. However, we cannot draw conclusions regarding male movement, because only females with young were collared.

We observed cross-wind movement during freeze-up, however, only at low wind and high bear speeds (Fig. 4b). Because predominant cross-wind movement during freeze-up was found only at lower wind speeds (<21.6 km/h) compared to winter (<36 km/h), it suggests that some foraging during freeze-up may occur.

During winter, at high wind speeds or when polar bears were moving slowly movement was predominantly downwind (Fig. 5a) and was not predicted. Explanations for the downwind movement include that it may represent a default orientation that generally leads bears southeast and further into the Bay. Second, it may be a thermoregulatory response to high wind speeds; moving downwind minimises the surface area of a bear exposed to wind and shields the face. Thermoregulatory downwind orientation has been modelled and observed for several taxa71,72. Third, if wind direction fluctuates more than 30° from the mean, then upwind or downwind movement provide more information about the environment than cross-wind movement, a phenomenon described as the geometric pattern of scent dispersion8,13. However, the geometric pattern of scent dispersion alone cannot account for the low frequency of upwind movement observed. Finally, behaviours apart from cross-wind search, such as travel, still-hunting, movement following habitat features, or other olfactory search strategies may tend to be downwind. Non-olfactory behaviours occupy around 60% of polar bear time budgets19,25.

During winter, at low wind speeds and while polar bear speeds were high, movement was predominantly cross-wind (Fig. 5b) and matched our predicted movement for cross-wind olfactory search. If the cross-wind movement during freeze-up and winter is reflective of cross-wind olfactory search, the greater frequency at lower wind speeds aligns with findings that polar bear hunting success increases with decreasing wind speed73. Cross-wind movement was also more common at night than during the day (Fig. 5b), supporting our hypothesis that movement is primarily guided by olfaction during periods of darkness, while movement during the day may rely, in part, on visual cues. We observed cross-wind movement more frequently among bears wearing collars that had 30-minute fix rates than those wearing collars with 4-hour fix rates (Fig. 5b vs. d). Additionally, the proportion of 30-minute data in the slow wind and fast bear category was 2.6 times greater than among 4-hour collars, suggesting that directionalities observed among the lower resolution collars underestimated the proportion of cross-wind movement. Additionally, the 30-minute data that was subsampled at 4-hour intervals revealed the same patterns as non-subset 30-minute data and 4-hour data, where movement was downwind while winds were fast or bears were slow, and movement was cross-wind while winds were slow and bears were fast (Supplementary Fig. S5), suggesting that the observed patterns were not an artefact of sampling rate.

An alternative explanation for cross-wind movement is that it is a response to environmental features that are associated with the predominant winds, such as pressure ridges74. However, environmental features cannot account for the association between bear orientation and wind speed or presence of daylight, as was exhibited during freeze-up and winter. Specifically, the presence of pressure ridges is independent of wind speed and presence of daylight, while cross-wind movement was dependent on these factors. Additionally, because of the counter-clockwise gyre in Hudson Bay and changing winds, pressure ridges in the Bay are not uniformly cross-wind.

During break-up, mean polar bear movement was 34° relative to the wind (Fig. 6). With the predominant northwesterly winds, this would take the bears southeast towards shore and following the retreating ice. The movement relative to north shows a large component of northwestward movement (Fig. 2e), which may reflect bears compensating for ice drift41,42 before returning to land as hunting conditions deteriorate. As the season progresses and sea ice melts, polar bears may spend increasingly more time swimming, during which collars cannot transmit locations75,76. As such, limiting analysis to only 4-hour collars does capture the complete range of behaviours, especially during break-up.

We predicted that polar bears employ cross-wind olfactory search and predicted that this would occur more frequently during winter, when they enter hyperphagia54, under moderate wind speeds, when conditions are conducive for olfaction 73,77,78, at higher bear speeds, when they are more likely engaged in active search, and at night, when olfaction may be more effective than visual search45. The observed cross-wind movement during winter generally supports our hypotheses and predictions. Olfactory foraging may vary across populations due to patterns of sea ice distribution and raises additional research questions. Does maintenance of relative position on drifting ice41,42 come at the expense of prolonged olfactory search? Polar bears on more stable ice may be less active than bears on drifting ice38 - what is the role of olfaction in more stable habitats? Arctic wind speeds are projected to increase due to climate change79 and could impede polar bear hunting success73. Further studies using higher temporal resolution location data, in combination with direct observation of hunting bears, would further our understanding of olfactory predation. Additionally, given its influence on behaviour, wind could be incorporated as a characteristic in habitat selection modelling of olfactory predators, as the quality of a habitat may be dependent on windscapes. In practice, windscapes could be used as modifiers to the available habitat (e.g., fast winds invoke downwind movement, while cross-wind movement would be favoured under moderate winds). To our knowledge, this is the first such evidence of cross-wind orientation for olfactory search for any wild, non-avian carnivore. The methods presented here are widely applicable and can provide insight on olfactory search among predators across taxa (e.g., canids, felids, and mustelids) and on prey using olfaction to avoid predators.