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  • 1
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    Hot spot foraging depths of southern elephant seal males at the Filchner Trough outflow, Southern Weddell Sea (2010)
    In:  EPIC3SCAR XXXI & Open Science Conference, Buenos Aires, ArgentinaJul.- 06 Aug. 2010., 30
    Details
    Publication Date: 2019-07-16
    Description: The region around the sill of the Filchner Trough outflow (77°S, 36°W) is considered a hot spot, both in terms of biology and physical oceanography. The factors contributing to this oceanic area of enhanced food availability and its relation to physical processes are not yet understood. Animal-borne satellite telemetry of southern elephant seal males, instrumented at King George Island / Isla 25 de Mayo aims to describe the seals' preferred foraging depths around the Filchner Trough in order to elucidate the vertical distribution of prey in relation to the oceanographic features on-site. Recent deployments (2010) represent a follow-up study of an ARGOS satellite telemetry project on elephant seals in 2000. Adult males travelled deep into the winter pack ice of the Weddell Sea along the western continental shelf break until they reached the region of the sill of the Filchner Trough outflow, where they remained in a localized 100 km wide shelf-slope area for several months. The re-instrumentation aims to investigate if males continue to travel to similar areas. The trilateral, long-term observation study of scientists from South Africa, Argentina and Germany is based on a synoptic approach for Marion Island and King George Island / Isla 25 de Mayo.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 2
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    Photomodeller calibration files for images from southern elephant seals during JUB2010 campaign (2010)
    PANGAEA
    In:  EPIC3Bremerhaven, PANGAEA
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: PANGAEA Documentation , notRev
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  • 3
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    Environmental influences on the at-sea behaviour of elephant seals in changing environments (2013)
    SCAR
    In:  EPIC3XI SCAR Biology Symposium, Barcelona, Spain, 2013-07-15-2013-07-19Barcelona, SCAR
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 4
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    Foraging behaviour of Ross seals in King Haakon VII Sea: an opportunity lost? (2012)
    In:  EPIC3African Marine Mammal Colloquium, Kleinbaai, South Africa, 2012-05-21-2012-05-25
    Details
    Publication Date: 2019-07-17
    Description: A proposed study into the ranging and diving behaviour of Ross seals Ommatophoca rossii in an area of high relative abundance in the eastern Weddell Sea, and their diet through direct (stomach contents and scats) and indirect (dive behaviour, jaw activity recordings and stable isotope analyses) means was turned down for the SANAP research period 2012-2014. The aim was to improve knowledge of the way oceanographic conditions affect one of the four true Antarctic species of seal breeding off the Princess Martha Coast, Antarctica in the King Haakon VII Sea with a view to using Ross seals as bioindicators of environmental change under a scenario of ocean warming, progressive disintegration of the West Antarctic ice-sheet and decrease in sea-ice coverage. Designed to build on earlier SANAP seal research in this area of pack-ice in the late 1970’s and early 1990’s, using the new SA Agulhas II as the research platform, it would apply latest technology such as Conductivity, Temperature, Depth (CTD)-Satellite Relay Data Loggers (SRDLs), Mandible Accelerometers (MACs) and stable isotope analyses to characterise Ross seal distribution, diet and physical characteristics of the water column where they forage. Ross seals are ideal candidates as they made long foraging trips north of the pack-ice into pelagic areas of the Southern Ocean for most of the year (in 2001) and returned to the pack-ice only for short periods to breed and moult. The comprehensive analysis and synthesis of biological and physical data perceivably could make an important contribution to determining relationships between hydrographic features, ocean currents, sea floor characteristics, prey dynamics, and the distribution and abundance of marine top predators. A possible way forward in the use of a top predator as an oceanographic profiler to detailing the structure and function of the pack-ice ecosystem likely affected by global warming is presented.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 5
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    Winter foraging hot spots of southern elephant seal males from King George Island and oceanography (2012)
    In:  EPIC3SCAR XXXII & Open Science Conference, Portland, OR, USA, 2012-07-13-2012-07-25
    Details
    Publication Date: 2019-07-17
    Description: Deployments of ARGOS satellite transmitters on adult southern elephant seal males at King George Island in 2010 represent a follow-up study of an earlier project in 2000/2001. Males had either moved along the Bransfield Strait and around the tip of the Antarctic Peninsula or deep into the winter pack ice of the southern Weddell Sea. The latter finding could not be reproduced, though seals travelled on comparably extended latitudinal gradients between King George Island / Isla 25 de Mayo and South Georgia or the southern Bellingshausen Sea. The recent movements seem to contradict patterns of sexual segregation interpreted from earlier studies, suggesting more overlap between foraging grounds of adult males and females then previously assumed. As far as we could track individuals, most post-moult movements were oriented to South Georgia towards the breeding season and back thereafter. The seals' long and straight line movements at distances of more than 1500 km allowed for cross sectional analyses of hydrographic features and revealed information on the temperature and salinity regime during winter. All seals showed extended residence times at specific circumscribed at-sea locations, considered as foraging hot spots. These spots were widely distributed within the Bellingshausen and northern Weddell Seas and seem to be linked to bathymetric features, such as slopes, seamounts or plateaus. The study involves scientists from South Africa (MRI), Argentina (IAA) and Germany (AWI) in a synoptic approach of the investigation of the movement behaviour of southern elephant seals from King George Island and Marion Island, and highlights our long-time collaboration within the "Year of Science" of South Africa and Germany in 2012/13.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 6
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    Tiletamine/zolazepam immobilization of adult post-moult southern elephant seal males (2013)
    SPRINGER
    In:  EPIC3Polar Biology, SPRINGER, ISSN: 0722-4060
    Details
    Publication Date: 2019-07-17
    Description: Immobilization and anaesthesia of adult male southern elephant seals (Mirounga leonina) is potentially risky for animals and scientists. A tiletamine/zolazepam injection is considered the most appropriate drug combination for field application in this species. Since appropriate dosages are difficult to assess due to uncertainties in weight estimation, we used photogrammetry-derived weight estimates to ensure precise post hoc calculations of dosages. We report on 15 intramuscular tiletamine/zolazepam immobilizations of post-moult males of the upper weight class at King George Island/Isla 25 de Mayo, in April 2010. Initial injections were made using blowpipe syringes. Mean tiletamine/zolazepam combined dosages of 0.71 mg kg-1 (SD ± 0.16) ranged between 0.46 and 1.01 mg kg-1. In four cases, ketamine was added in dosages between 0.96 and 2.61 mg kg-1. Mean induction period was 23 min (± 15), and the mean duration of the procedures from first injection to release of the animals required 96 min (± 51). Four seals exhibited periods of apnoea, and one case of an extended, repetitive, and potentially critical apnoea (〉25 and 8 min) required intervention in order to successfully re-initiate spontaneous respiration. All procedures resulted in proper immobilizations allowing for the deployment of the satellite tags on the seals’ heads. The fact that even substantial deviations between the initial weight estimates and the photogrammetry-derived weight estimates had no apparent effect on the course of the immobilization underlines the drugs’ wide safety margin in this species.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 7
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    Post-moult movements of adult female southern elephant seals from Marion Island (2009)
    In:  EPIC318th Biennial Conference on the Biology of Marine Mammals, Québec City, QC, Canada 16 October 2009., 12
    Details
    Publication Date: 2019-07-17
    Description: Adult female southern elephant seals are predominantly pelagic, coming ashore biannually solely to breed and to moult. The success of the post-moult foraging trip has direct implications for female breeding success and the final weaning weight and future survival of the pup and may impact population fluctuations. In 2007 and 2008, a total of 13 post-moult adult female southern elephant seals from sub-Antarctic Marion Island were tracked via satellite transmitters. Ten of the resulting tracks were completed by recurrence of the female to Marion Island, with mean track durations of 250 days. The total trip distances ranged between 22 810.6 km and 13 169.7 km (mean = 18 980.9 km). Seals tracked in 2008 displayed longer total trip distances (20 450.6 km ± 5362.5 km) than seals tracked in 2007 (16 776.3 km ± 6106.5 km). The mean maximum distance attained was 2 793.9 km ± 845.6 km and did not vary between years. In contrast to southern elephant seals tracked from Kerguelen Island in 2003/2004, adult female seals (this study) travelled extensive distances due west of Marion Island. Only three individuals travelled to and within the Antarctic sea ice during the study period. The remaining animals travelled extensively along the South West Indian Ridge, often resulting in overlap of large portions of the tracks. Tracks displayed areas of restricted movement, which either coincided with areas of higher chlorophyll concentrations, anomalous sea-surface temperatures or mesoscale sea-surface height anomalies. An understanding of the relationships between southern elephant seal female movements and the variability of oceanographic features may help to identify driving forces of Marion Island southern elephant seal population fluctuations. Quantification of heterogeneity within marine habitats is thus necessary in order to further our understanding of such relationships.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 8
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    A lifetime at depth: vertical distribution of southern elephant seals in the water column (2010)
    In:  EPIC3Polar Biology, ISBN: Print 0179-1613 Onli
    Details
    Publication Date: 2019-07-17
    Description: Although numerous studies have addressed the migration and dive behaviour of southern elephant seals (Mirounga leonina), questions remain about their habita use in the marine environment. We report on the vertical use of the water column in the species and the potential lifetime implications for southern elephant seals from Marion Island. Long-term mark-resight data were used to complement vertical habitat use for 35 known individuals tagged with satellite-relay data loggers, resulting in cumulative depth use extrapolated for each individual over its estimated lifespan. Seals spent on average 77.59% of their lives diving at sea, 7.06% at the sea surface, and 15.35% hauled out on land. Some segregation was observed in maximum dive depths and depth use between male and female animalsmales evidently being physiologically more capable of exploiting increased depths. Females and males spent 86.98 and 80.89% of their lives at sea, respectively. While at sea, all animals spent more time between 300 and 400 m depth, than any other depth category. Males and females spent comparable percentages of
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 9
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    Temporal variation of cephalopods in the diet of Cape fur seals in Namibia (2003)
    Southern African Wildlife Management Association
    In:  South African Journal of Wildlife Research, 33 (2). pp. 85-96.
    Details
    Publication Date: 2021-08-03
    Description: Cape fur seal (Arctocephalus pusillus pusillus) scats were sampled over a period of eight years (1994-2001) at Atlas and Wolf Bay seal colonies in order to assess the cephalopod component of the diet of these seals and cephalopod diversity off the coast of Namibia. The temporal variation within the cephalopod component was investigated. A low diversity of cephalopods, only six species, are preyed upon, with Todarodes angolensis being the most important component both in numbers and wet weight in all years. Its lowered weight contribution during winter coincided with a greater diversity of other cephalopod species in the diet, which showed higher proportional weight contribution relative to Todarodes angolensis. Scat sampling was found to be an unreliable method of providing estimates of total prey weight consumption by seals, but was considered an acceptable method for proportional comparisons, especially given the ease of scat collection over extended periods.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
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    Killer Whale Nuclear Genome and mtDNA Reveal Widespread Population Bottleneck during the Last Glacial Maximum (2014)
    Oxford University Press
    Details
    Publication Date: 2014-04-23
    Description: Ecosystem function and resilience is determined by the interactions and independent contributions of individual species. Apex predators play a disproportionately determinant role through their influence and dependence on the dynamics of prey species. Their demographic fluctuations are thus likely to reflect changes in their respective ecological communities and habitat. Here, we investigate the historical population dynamics of the killer whale based on draft nuclear genome data for the Northern Hemisphere and mtDNA data worldwide. We infer a relatively stable population size throughout most of the Pleistocene, followed by an order of magnitude decline and bottleneck during the Weichselian glacial period. Global mtDNA data indicate that while most populations declined, at least one population retained diversity in a stable, productive ecosystem off southern Africa. We conclude that environmental changes during the last glacial period promoted the decline of a top ocean predator, that these events contributed to the pattern of diversity among extant populations, and that the relatively high diversity of a population currently in productive, stable habitat off South Africa suggests a role for ocean productivity in the widespread decline.
    Print ISSN: 0737-4038
    Electronic ISSN: 1537-1719
    Topics: Biology
    Published by Oxford University Press
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