The southern elephant seal (SES), Mirounga leonina, was intensively harvested during the 18th and 19th centuries, though never reduced to the levels seen for the northern species (Mirounga angustirostris). Although a number of putative populations occurring within the species’ circumpolar distribution in the Southern Ocean have been genetically assessed, no data was previously available for the Marion Island population. This study integrates Marion Island into the broader database by genetically profiling individuals with 9 microsatellite DNA loci (n = 73) and a single mitochondrial DNA (mtDNA, n = 68) locus corresponding to hypervariable region I (HVRI) of the non-coding displacement loop (D-loop). These data were then combined with existing haplotype datasets from five island populations, namely Heard Island, Peninsula Valdés, Macquarie Island, South Georgia, Elephant Island, and Sea Lion Island breeding colonies, and with comparable microsatellite typing data from four populations, namely Peninsula Valdés, South Georgia, Elephant Island and Sea Lion island, respectively, permitting inter-population level comparisons. Genetic variation of the Marion Island population was high for both microsatellite and mtDNA and consistent with levels previously reported for the other populations, with the exception of Peninsula Valdés (Argentina) where diversity levels are low. Forty polymorphic sites defined 44 mtDNA haplotypes from 68 Marion Island individuals. Of the 44 sequence haplotypes, three were shared with Sea Lion Island, one with Elephant Island, two with Heard Island and one with Macquarie Island. From the microsatellite data, it was found that Marion Island, like most other SES populations, had no private alleles. The one exceptional population is that at Sea Lion Island which has several private alleles at two loci. Marion Island was significantly differentiated from each of the other breeding colonies included in the study based on FST analyses for both microsatellite and mtDNA data. The magnitude of genetic differentiation between Marion Island and the South Georgia, Sea Lion and Elephant Islands was somewhat higher than that previously reported when the latter three islands were compared, but considerably less than the differentiation found between Marion Island and either Peninsula Valdés or Macquarie Island. Though the two markers showed similar trends with respect to population structuring, the pairwise differentiation at microsatellite loci was an order of magnitude lower than that of mtDNA, suggesting more frequent male-mediated gene flow between putative populations than female-mediated gene flow. Higher male dispersal was also confirmed by migration rate estimates from the microsatellite data compared to estimates from the mtDNA locus. These data are consistent with the earlier interpretation that most putative island populations show moderate levels of differentiation not directly related to geographic distance, while the mainland population in Argentina and the population at Macquarie Island stand out as being highly differentiated from the rest. / Dissertation (MSc)--University of Pretoria, 2008. / Zoology and Entomology / unrestricted

While studies of dispersal note significant fidelity to natal site and to the site of first reproduction, few consider fidelity to other sites, and none have done so systematically. This study examined fidelity to all terrestrial sites within the study area during the course of its life, by a migratory marine predator, the southern elephant seal, Mirounga leonina. It also attempted to assess the role played by the winter haulout in terms of site fidelity. Finally it examined the influence of possible deterioration in spatial memory over time on site fidelity. The data used in this study were generated by a long-term mark-recapture programme conducted at subantarctic Marion Island. Although immature elephant seals of both sexes return to the vicinity of their natal sites, they appear to avoid popular breeding beaches, returning closest to the site previously used. At the first reproductive haulout, however, females return closer to their natal site than any other site, while males, although hauling out in the vicinity of their natal site, haul out closest to sites used in the year prior to the first breeding haulout. Subsequently, adults of both sexes breed closest to the breeding haulout of the previous year and moult closest to the moult haulout of the previous year. While males show greater site fidelity during the breeding season, there is no difference in site fidelity during the moult. Primiparous females show greater levels of site fidelity if recorded in the study site as an immature animal during either the winter or the moult haulouts. Also in female elephant seals, lower site fidelity is associated with an increase in the duration of period of absence from a site, and a lower number of visits to a site. Various factors related to site familiarity, social factors and anthropogenic disturbance may be responsible for the lack of strict site fidelity that is evident. Dispersal patterns may differ between the sexes due to differences in their life history. While purpose of the winter haulout by immature seals may be to increase familiarity with haulout sites, and thus site fidelity, the moult haulout also plays a role. / Thesis (PhD)--University of Pretoria, 2013. / Zoology and Entomology / Unrestricted

Thesis (PhD)--University of Pretoria, 1992. / gm2014 / Zoology and Entomology / unrestricted

Du fait de l’isolement géographique de l’océan austral et des conditions météorologiques qui y règnent, la collecte de données océanographiques par les moyens conventionnels est particulièrement couteuse dans cette région du globe. Pour pallier à ces difficultés, l’utilisation d’enregistreurs électroniques embarqués sur des prédateurs marins, et notamment sur les éléphants de mer austraux, s’est révélée être une approche intéressante. Les femelles éléphants de mer s’alimentent en grande partie de petits poissons méso-pélagiques bioluminescents, les myctophidés. Leur forte abondance et leur comportement de migration nycthémérale confèrent à ces organismes un rôle écologique de première importance dans l’océan austral. Cependant, la distribution spatiale des proies de l’éléphant de mer, et les processus physiques et biologiques qui influent sur la dynamique de cette distribution sont encore mal connus. Cette thèse se propose d’enquêter sur ces sujets à partir des données à haute fréquence d’échantillonnage collectées par des femelles éléphants de mer. L’analyse du comportement de plongée des femelles éléphants de mer, en relation avec les variations du taux de rencontre de proie dont les données d’accélération permettent d'avoir une estimation, est au cœur des différents travaux développés dans cette thèse. Les résultats obtenus suggèrent notamment, (1) une diminution de l’abondance des proies avec la profondeur ainsi qu’une homogénéisation de leur distribution, (2) une distribution en couches de cette ressource, (3) l’intervention de contraintes verticales délimitant l’étendue verticale de ces couches et ainsi capable de moduler leur densité, (4) au sein des couches, une dispersion relativement importante des proies en comparaison de la portée des capacités de perception du prédateur, et enfin (5) un rôle significatif des tourbillons méso-échelle et de leur bordure sur la structuration de la distribution des ressources alimentaires de l’éléphant de mer durant l’été austral. / Because of the remoteness and harsh meteorological conditions of the southern ocean, data sampling is more costly in this area. Use of electronic devices attached to marine predators (Bio-logging), such as southern elephant seals, has emerged as an interesting approach to cope with this problem. Female southern elephant seals primarily feed on small bioluminescent meso-pelagic fishes called myctophids. Because of their large abundance and of their diel vertical migration behaviour, these organisms have a major ecological importance in the southern ocean. However, the spatial distribution of the elephant seals prey, as well as the bio-physical processes affecting the dynamics of this distribution, are still poorly known. This thesis intends to investigate this issue using high sampling frequency bio-logging data collected by female southern elephant seals. This work is based on the analysis of elephant seals diving behaviour in relation to changes in the occurrence of prey encounter events detected from acceleration data. Our results suggest that (1) prey abundance decreases with depth and that their distribution tend to standardize, (2) prey are distributed into layers, (3) vertical constraints could modulate the prey density by acting on the vertical spread of these layers, (4) prey items are well dispersed in comparison to the perception range of elephant seals, and finally (5) that meso-scale eddies, notably their edges, play a structuring role in the prey distribution during the austral summer.

Please read the abstract in the section 00front of this document. / Dissertation (MSc)--University of Pretoria, 2010. / Zoology and Entomology / unrestricted