Determinants of group splitting: an examination of environmental, demographic, genealogical and state-dependent factors of matrilineal fission in a threatened population of fish-eating killer whales (Orcinus orca)

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dc.contributor.authorStredulinsky, Eva Helene
dc.contributor.supervisorDarimont, Chris T.
dc.date.accessioned2016-10-12T19:51:57Z
dc.date.available2016-10-12T19:51:57Z
dc.date.copyright2016en_US
dc.date.issued2016-10-12
dc.degree.departmentDepartment of Geographyen_US
dc.degree.levelMaster of Science M.Sc.en_US
dc.description.abstractGroup living is a social strategy adopted by many species, where individuals can exhibit long-term social affiliation with others, strengthened through cooperative behaviour and often kinship. For highly social mammals, changes in group membership may have significant consequences for the long-term viability and functioning of a population. Detecting significant social events is essential for monitoring the social dynamics of such populations and is crucial to determining the factors underlying these events. Detecting when changes in social organization occur, especially with incomplete data, poses significant analytical challenges. To resolve this issue, I developed and assessed a straightforward, multi-stage and generalizable method with broad utility for ecologists interested in detecting and subsequently investigating causes of changes in social organization. My approach illustrates the frequency and ecological relevance of group fission and fusion events in a population of fish-eating ‘Resident’ killer whales (Orcinus orca). Group fission is a process commonly found in social mammals, yet is poorly described in many taxa, and has never been formally described in killer whales. To address this gap, I provided the first description of matrilineal fission in killer whales, from a threatened but growing Northern Resident killer whale population in which matrilineal fission has been observed for the past three decades. I also undertook the first comprehensive assessment of how killer whale intragroup cohesion is influenced by group structure, demography and resource abundance. Fission in Northern Resident killer whales occurred both along and across maternal lines, where animals dispersed in parallel with their closest maternal kin. I show that fission in this population is driven primarily by population growth and the demographic conditions of groups, particularly those dictating the nutritional requirements of the group. I posit that intragroup food competition is the most likely explanation for group fission in this population, where prey abundance also has ancillary effects. As group fission can have a direct impact on the fitness of group members and the long-term viability of a population, my findings underscore the importance of incorporating studies of sociality into the management of threatened populations of social mammals.en_US
dc.description.proquestcode0329en_US
dc.description.proquestcode0472en_US
dc.description.scholarlevelGraduateen_US
dc.identifier.urihttp://hdl.handle.net/1828/7603
dc.languageEnglisheng
dc.language.isoenen_US
dc.rightsAvailable to the World Wide Weben_US
dc.subjectgroup splittingen_US
dc.subjectgroup fissionen_US
dc.subjectmatrilinealityen_US
dc.subjectkiller whaleen_US
dc.subjectOrcinus orcaen_US
dc.subjectfood competitionen_US
dc.subjectkinshipen_US
dc.subjectdemographyen_US
dc.subjectsocialityen_US
dc.subjectgroup livingen_US
dc.titleDeterminants of group splitting: an examination of environmental, demographic, genealogical and state-dependent factors of matrilineal fission in a threatened population of fish-eating killer whales (Orcinus orca)en_US
dc.typeThesisen_US

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