| Summary: | Northern fur seal pups, Callorhinus ursinus , from declining populationsin the Bering Sea contend with extreme and highly variable oceanicconditions during their first winter migrations. Understanding how naiveanimals from increasing and decreasing populations respond to changeableenvironmental cues is fundamental to disentangling possible mechanismsdriving observed, large-scale declines. We tracked 166 newly-weaned pupsfrom four North American populations, both increasing and decreasing,to determine the influence of wind conditions, sea surface height andtemperature and proximity to productive frontal features on the foragingstate of individual pups. Pups conducted far-ranging migrations across theNorth Pacific Ocean, triggered by the onset of autumnal storms. At-seaconditions differed markedly between the two years as did pup movements.Alaskan pups travelled faster when 'assisted' by tailwinds and spent moretime in northern latitudes in less stormy years. The migration patterns ofpups were more random than those published for adults also indicating thatyoung animals undergo a period of learning at sea. We provide examples andspeculate on how storms may impact survival of naive pups, particularly inyears when pup weaning mass is low. We conclude that increasing intensityand frequency of storm events in the North Pacific Ocean could haverepercussions on pup behaviour and population demographics of Northernfur seals across their range.
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