A statistical investigation of the behavioural responses of a deep diving predator to mesoscale oceanographic features

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dc.contributor.advisorAnsorge, Isabelle Janeen_ZA
dc.contributor.advisorMcintyre, Trevoren_ZA
dc.contributor.advisorRyan, Peter Gen_ZA
dc.contributor.authorMassie, Philipen_ZA
dc.date.accessioned2014-11-05T03:56:10Z
dc.date.available2014-11-05T03:56:10Z
dc.date.issued2014en_ZA
dc.descriptionIncludes bibliographical references.en_ZA
dc.description.abstractMarion Island lies directly in the path of the ACC and to the south-west of the island is an extensive region of high sea level anomaly variability (eddy field). Previous research has shown how southern elephant seals from Kerguelen Island and Peninsula Valdés have targeted eddies for foraging. These findings combined with the observed post-moult migrations of tagged female southern elephant seals from Marion Island which traverse the nearby eddy field suggest that they may exploit the eddy field for foraging. Overall the seals undertook significantly more of their dives (18.5) within the eddy field than predicted (p < 0.01). Eleven of the 16 seals dived within the eddy field region significantly more often than predicted. Dives were generally shallower and shorter within the eddy field. Mixed models estimated that a maximum depth reduction of 53.03 ± 5.30 m (LME: t=10.00, DF=24986, p < 0.01) and a dive duration reduction of 6.17 ± 0.58 min (LME: t=10.70, DF=24986, p < 0.01) could be attributed to diving within the eddy field. Within the eddy field U-dives increased by 6.97, W dives decreased by 7.18 and O-dives increased by 0.21. Seven individuals’ maximum dive depths were shallower and nine individuals dive durations were shorter as a result of diving within the eddy field. Ten individuals showed significant changes in the types of dives which they undertook inside of the eddy field with eight seals undertaking more Uand fewer W-dives and two seals undertaking more W- and fewer U-dives. Overall the effect of diving within the eddy field appeared to be biologically important to ten seals. While dive durations were significantly affected by changing sea level anomaly (SLA) (LME: 0.15 ± 0.01 min, t=11.72, DF=12372, p < 0.01), maximum depths were not. The log-odds of switching from U- to W-dives within the eddy field were significantly affected by changing SLA (Multinomial: 0.00 ± 0.00, z=2.97, p < 0.01). However all significant effects of SLA on dive parameters within the eddy field were very small in comparison to those of day-stage. The low magnitudes of the effects of SLA were similar for all individuals.en_ZA
dc.identifier.apacitationMassie, P. (2014). <i>A statistical investigation of the behavioural responses of a deep diving predator to mesoscale oceanographic features</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Biological Sciences. Retrieved from http://hdl.handle.net/11427/9194en_ZA
dc.identifier.chicagocitationMassie, Philip. <i>"A statistical investigation of the behavioural responses of a deep diving predator to mesoscale oceanographic features."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 2014. http://hdl.handle.net/11427/9194en_ZA
dc.identifier.citationMassie, P. 2014. A statistical investigation of the behavioural responses of a deep diving predator to mesoscale oceanographic features. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Massie, Philip AB - Marion Island lies directly in the path of the ACC and to the south-west of the island is an extensive region of high sea level anomaly variability (eddy field). Previous research has shown how southern elephant seals from Kerguelen Island and Peninsula Valdés have targeted eddies for foraging. These findings combined with the observed post-moult migrations of tagged female southern elephant seals from Marion Island which traverse the nearby eddy field suggest that they may exploit the eddy field for foraging. Overall the seals undertook significantly more of their dives (18.5) within the eddy field than predicted (p < 0.01). Eleven of the 16 seals dived within the eddy field region significantly more often than predicted. Dives were generally shallower and shorter within the eddy field. Mixed models estimated that a maximum depth reduction of 53.03 ± 5.30 m (LME: t=10.00, DF=24986, p < 0.01) and a dive duration reduction of 6.17 ± 0.58 min (LME: t=10.70, DF=24986, p < 0.01) could be attributed to diving within the eddy field. Within the eddy field U-dives increased by 6.97, W dives decreased by 7.18 and O-dives increased by 0.21. Seven individuals’ maximum dive depths were shallower and nine individuals dive durations were shorter as a result of diving within the eddy field. Ten individuals showed significant changes in the types of dives which they undertook inside of the eddy field with eight seals undertaking more Uand fewer W-dives and two seals undertaking more W- and fewer U-dives. Overall the effect of diving within the eddy field appeared to be biologically important to ten seals. While dive durations were significantly affected by changing sea level anomaly (SLA) (LME: 0.15 ± 0.01 min, t=11.72, DF=12372, p < 0.01), maximum depths were not. The log-odds of switching from U- to W-dives within the eddy field were significantly affected by changing SLA (Multinomial: 0.00 ± 0.00, z=2.97, p < 0.01). However all significant effects of SLA on dive parameters within the eddy field were very small in comparison to those of day-stage. The low magnitudes of the effects of SLA were similar for all individuals. DA - 2014 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2014 T1 - A statistical investigation of the behavioural responses of a deep diving predator to mesoscale oceanographic features TI - A statistical investigation of the behavioural responses of a deep diving predator to mesoscale oceanographic features UR - http://hdl.handle.net/11427/9194 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/9194
dc.identifier.vancouvercitationMassie P. A statistical investigation of the behavioural responses of a deep diving predator to mesoscale oceanographic features. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 2014 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/9194en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Biological Sciencesen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.titleA statistical investigation of the behavioural responses of a deep diving predator to mesoscale oceanographic featuresen_ZA
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationnameMScen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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