Seasonal, meteorological, tidal and diurnal effects on haul-out patterns of harbour seals (Phoca vitulina) in Iceland

Abstract

It is of critical importance to identify factors that affect harbour seal haul-out patterns to improve the accuracy of harbour seal censuses. In this study, haul-out patterns of harbour seals (Phoca vitulina) were investigated during different conditions at several major haul-out sites on Vatnsnes peninsula, NW Iceland (65°40′N and 20°48′W), over the 2008–2011 period. A seasonal haul-out pattern was detected among the seals, with the maximum number of seals on land found in July for most of the sites. Analyses of data for harbour seals on Vatnsnes indicate that the main pupping period occurs during late May to the beginning of June and moulting during late July to early August. Abundance at the sites increased with rising air temperature and decreased with increased windspeed and rising tides. However, no evidence that precipitation or cloud cover affected haul-out behaviour of the seals was detected. The diel haul-out pattern was investigated thoroughly in one of the haul-out sites and the results underlined the effect of tidal flucturation, air temperature and wind direction on the haul-out behaviour of harbour seals in the area. Results from this study can be used to improve the survey design when estimating the population size of harbour seals in Iceland and applied more broadly to the study of haul-out behaviour of harbour seals.