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  • Marion Island  (1)
  • genetics, ecology  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Survivorship of a declining population of southern elephant seals, Mirounga leonina, in relation to age, sex and cohort (1999)
    Springer
    Oecologia 121 (1999), S. 201-211 
    Details
    ISSN: 1432-1939
    Keywords: Key words Survival ; Decline ; Mark-recapture ; Elephant seals ; Marion Island
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study quantified both the age- and sex-specific survival rates of juveniles and adults, and tested for interannual differences in age-specific survival rates of the southern elephant seal population at Marion Island. Pups were tagged on an annual basis from 1983 onwards at Marion Island, and a consistent recapture program yielded data that was analysed using the software package MARK to obtain maximum-likelihood estimates of survival and capture probability. On average, 1st-year survival was 0.58 and 0.62, and survival rate averaged over the first 3 years of life, 0.69 and 0.74 for males and females, respectively. From years 4 to 9, the average survival rate was 0.66 and 0.75 for males and females, respectively. Survival estimates for elephant seals in their 10th–13th year are also presented, although these are based on very small sample sizes. Averages of age-specific survival estimates from the earlier (mostly 1983–1987 cohorts) and later (mostly 1988–1992 cohorts) periods were compared and considerable reductions were observed in 4th- and 5th-year male survival, and 4th-year female survival. The comparatively low adult survival is suggested as the proximate cause, and food limitation as deduced from the decline in survival of elephant seals with comparatively high energetic demands as the ultimate cause behind the population decline at Marion Island. Although not tied in with the decline of the population, 1987, 1990 and 1993 were identified as high-mortality years.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050922
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    Paper (German National Licenses)
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  • 2
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    A global cline in a colour polymorphism suggests a limited contribution of gene flow towards the recovery of a heavily exploited marine mammal (2018)
    Royal Society
    Details
    Publication Date: 2018-10-18
    Description: Evaluating how populations are connected by migration is important for understanding species resilience because gene flow can facilitate recovery from demographic declines. We therefore investigated the extent to which migration may have contributed to the global recovery of the Antarctic fur seal ( Arctocephalus gazella ), a circumpolar distributed marine mammal that was brought to the brink of extinction by the sealing industry in the eighteenth and nineteenth centuries. It is widely believed that animals emigrating from South Georgia, where a relict population escaped sealing, contributed to the re-establishment of formerly occupied breeding colonies across the geographical range of the species. To investigate this, we interrogated a genetic polymorphism (S291F) in the melanocortin 1 receptor gene, which is responsible for a cream-coloured phenotype that is relatively abundant at South Georgia and which appears to have recently spread to localities as far afield as Marion Island in the sub-Antarctic Indian Ocean. By sequencing a short region of this gene in 1492 pups from eight breeding colonies, we showed that S291F frequency rapidly declines with increasing geographical distance from South Georgia, consistent with locally restricted gene flow from South Georgia mainly to the South Shetland Islands and Bouvetøya. The S291F allele was not detected farther afield, suggesting that although emigrants from South Georgia may have been locally important, they are unlikely to have played a major role in the recovery of geographically more distant populations.
    Keywords: genetics, ecology
    Electronic ISSN: 2054-5703
    Topics: Natural Sciences in General
    Published by Royal Society
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