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Population dynamics of Southern Elephant Seals at Marion Island
Southern elephant seal populations have declined dramatically throughout their circum-polar distribution range during the last century. The leading hypotheses explaining the declines are environmental change and food limitation. Population trends in the 1990's favoured extinction of the population in the 21st century. Have those trends continued, and what is the population size and structure up to 2008?
Data from population counts additionally include both untagged and tagged seals, in contrast to the ongoing mark-recapture study utilizing tagged individuals only. I will investigate two possible sources of untagged individuals: immigration and tag loss.
Immigration will be quantified using anecdotal and foreign tag resight data.
Animals which loose their marks cannot be identified any more, and appear 1) 'dead' to the observer, 2) as immigrants to the population. New tag loss estimates, a statistic that is then used to correct survival rates of cohort, age and sex classes, will be computed from tag resight data.
Recent Publications
2009
de Bruyn, P.J.N., Tosh, C.A., Oosthuizen, W.H., Bester, M.N., Arnould, J.P.Y. (2009) Bathymetry and frontal system interactions influence seasonal foraging movements of lactating subantarctic fur seals from Marion Island. Marine Ecology-Progress Series.394:263-276
de Bruyn, P.J.N., Bester, M.N., Carlini, A.R., Oosthuizen, W.C. (2009) How to weigh an elephant seal with one finger: a simple three-dimensional photogrammetric application. Aquatic Biology.5(1):31-39
Oosthuizen, W.C., de Bruyn, P.J.N. (2009) King penguin brooding and defending a sub-Antarctic skua chick. Polar Biology.32(2):303-305
Oosthuizen, W.C., Cross, P.C., Bowers, J.A., Hay, C., Ebinger, M.R., Buss, P., Hofmeyr, M., Cameron, E.Z. (2009) Effects of Chemical Immobilization on Survival of African Buffalo in the Kruger National Park. Journal of Wildlife Management.73(1):149-153
2008
de Bruyn, P.J.N., Tosh, C.A., Oosthuizen, W.C., Phalanndwa, M.V., Bester, M.N. (2008) Temporary marking of unweaned southern elephant seal (Mirounga leonina L.) pups. South African Journal of Wildlife Research.38(2):133-137
Southern elephant seal populations have declined dramatically throughout their circum-polar distribution range during the last century. The leading hypotheses explaining the declines are environmental change and food limitation. Population trends in the 1990's favoured extinction of the population in the 21st century. Have those trends continued, and what is the population size and structure up to 2008?
Data from population counts additionally include both untagged and tagged seals, in contrast to the ongoing mark-recapture study utilizing tagged individuals only. I will investigate two possible sources of untagged individuals: immigration and tag loss.
Immigration will be quantified using anecdotal and foreign tag resight data.
Animals which loose their marks cannot be identified any more, and appear 1) 'dead' to the observer, 2) as immigrants to the population. New tag loss estimates, a statistic that is then used to correct survival rates of cohort, age and sex classes, will be computed from tag resight data. 
