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Extreme weather events influence dispersal of naive northern fur seals


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Lea, M-A, Johnson, D, Ream, R, Sterling, JT, Melin, S and Gelatt, T 2009 , 'Extreme weather events influence dispersal of naive northern fur seals' , Biology Letters, vol. 5, no. 2 , pp. 252-257 , doi: 10.1098/rsbl.2008.0643.

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Since 1975, northern fur seal (Callorhinus
ursinus) numbers at the Pribilof Islands (PI) in
the Bering Sea have declined rapidly for
unknown reasons. Migratory dispersal and
habitat choice may affect first-year survivorship,
thereby contributing to this decline. We
compared migratory behaviour of 166 naive
pups during 2 years from islands with disparate
population trends (increasing: Bogoslof and San
Miguel Islands; declining: PI), hypothesizing
that climatic conditions at weaning may
differentially affect dispersal and survival.
Atmospheric conditions (Bering Sea) in autumn
2005–2006 were anomalously cold, while
2006–2007 was considerably warmer and less
stormy. In 2005, pups departed earlier at all
sites, and the majority of PI pups (68–85%)
departed within 1 day of Arctic storms and
dispersed quickly, travelling southwards through
the Aleutian Islands. Tailwinds enabled faster
rates of travel than headwinds, a trend not
previously shown for marine mammals. Weather
effects were less pronounced at Bogoslof Island
(approx. 400 km further south), and, at San
Miguel Island, (California) departures were
more gradual, and only influenced by wind and
air pressure in 2005. We suggest that increasingly
variable climatic conditions at weaning,
particularly timing, frequency and intensity of
autumnal storms in the Bering Sea, may alter
timing, direction of dispersal and potentially
survival of pups.

Item Type: Article
Authors/Creators:Lea, M-A and Johnson, D and Ream, R and Sterling, JT and Melin, S and Gelatt, T
Keywords: migration; Alaska; storms; Bering Sea
Journal or Publication Title: Biology Letters
ISSN: 1744-9561
DOI / ID Number: 10.1098/rsbl.2008.0643
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