Seasonal and sex-related variation in the activity patterns of common seals (Phoca vitulina)

Around Orkney, both males and females hauled-out regularly during summer, showing a marked diurnal pattern. At the beginning of moult, males hauled-out every day; consequently, male behaviour became more synchronous. Females showed no sign of a similar change in behaviour at the beginning of moult, but appeared to spend more of their time at sea after lactation. During winter, seals appeared to spend more time in offshore waters, although they regularly returned to the inshore study area to haul-out. At this time of year there was no marked diurnal haul-out pattern. There was a high degree of individual variation in the effect of the tidal cycle on activity patterns, which appeared to be related to tide-related changes in food and habitat availability. Overall, however, the tidal cycle had less effect on haul-out behaviour in summer, when strong circadian patterns were more important. -from Authors