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dc.contributor.advisorKok, O. B.
dc.contributor.advisorSmith, V. R.
dc.contributor.authorAvanant, Nico Loubser
dc.date.accessioned2016-06-08T16:27:04Z
dc.date.available2016-06-08T16:27:04Z
dc.date.issued1999
dc.identifier.urihttp://hdl.handle.net/11660/2720
dc.description.abstractEnglish: This thesis presents the results of a studv of the biotic and abiotic conditions experienced by house mice on Marion Island, their morphological and reproductional adaptations to island conditions, the seasonal changes in their diet. and of the densities and biomasses of their prey items. By establishing burrow systems and sheltered aboveground runways nuce experience a microelimate that is far less harsh than the macroelimatie regime. In terms of warmth, this extends the season of mouse activity significantly compared with what would be allowed by the macroclimate. House mice are opportunistic feeders and this plays a major role in their survival under the harsh conditions on Marion Island. The mice are primarily carnivores and impact severely on soil macroinvertebrate populations, annually removing up to several times the average instantaneous standing crop of some macroinvertebrate populations. Since macroinvertebrates are cardinal agents of ecosystem functioning by being the main mediators of nutrient cycling on the island, their predation by mice has severe ecological implications. Between 1979/80 and 1992/93 the densities and biomasses of the mouse's major invertebrate prey species have decreased. The percentage composition of the various prey types in the macroinvertebrate population has also changed. These changes have caused changes in the composition of the mouse's diet. Seasonal changes in reproductive status, sex ratio, age structure, body mass and length, kidney- and adrenal mass, and length and shape of intestines were determined, in order to provide information concerning the house mouse's response to fluctuating environmental parameters and to assess the levels of stress experienced by mice at different times of the year. Stress levels are influenced by population density, sex, reproductive status, temperature and availability of food. In 1992/93 mice had significantly larger body to tail length ratios than in 1979/80, despite the fact that the island warmed considerably in the interim. This warming has allowed a significantly longer breeding season, perhaps by as much as two months. It is suggested that this is the reason that end of season densities are now considerably higher than in 1979/80.en_ZA
dc.description.abstractAfrikaans: Hierdie tesis toon die resultate van 'n studie van die biotiese en abiotiese toestande wat deur die huismuis op Marioneiland (46°54' S, 37°45' E) ondervind word - hulle morfologiese en voortplantings-aanpassings by eiland toestande, die seisoenale veranderinge in die dieët, asook die digtheid en biomassas van hulle prooi. Deur die daarstelling van 'n tonnelsisteem en beskutte bogrondse gange, ondervind die muise 'n mikroklimaat wat baie minder vel is as die mikroklimaat regime. In terme van hitte laat dit die seisoen, sover muisaktiwiteite aangaan, toe om baie langer te wees as wat deur die mikroklimaat toegelaat word. Muise is opportunistiese voeders en dit speel 'n groot rol in hulle oorlewing onder die uiterste toestande op Marioneiland. Muise is hoofsaaklik karnivore en het 'n geweldige impak op die grond mikro-invertebraatbevolkings en verwyder jaarliks tot verskeie kere die onmiddelike opbrengs van sekere van die mikro-invertebraatbevolkings. Aangesien mikro-invertebrata van kardinale belang is in die funksionering van die ekosisteem deurdat hulle die beskikbaarstelIers van voedingstof-sirkulering op die eiland is, het die feit dat hulle die prooi van muise is, geweldige ekologiese implikasies. Tussen 1979/80 en 1992/3 het die digthede en biomassas van die invertebraatspesies wat hoofsaaklik die muis se prooi is, verminder. Die persentasie samestelling van die verskeie prooitipes in die mikro-invertebraatbevolkings het ook verander. Hierdie veranderinge het veranderinge in die muis se dieët tot gevolg gehad. Seisoenale veranderinge in geslagtelike status, geslagsverhoudings, ouderdomstruktuur, liggaamsmassa en -lengte, nier- en adrenaalgewig en lengte en die mates van die ingewande is bepaal om inligting ten opsigte van die muis se reaksie op wisselende omgewingsparameters te verkry, asook die stresvlakke deur die muis ondervind op verskeie tye van die jaar. Stresvlakke word beinvloed deur bevolkingsdigtheid, geslag, voortplantingstatus, temperatuur en beskikbaarheid van voedsel. In 1992/93 is betekenisvolle groter liggaam-tot stertlengte verhoudings bepaal as in 1979/80, ten spyte van die feit dat die eiland intussen aansienlike hoër temperature ondervind. Hierdie verwarming het 'n aansienlike langer broeiseisoen tot gevolg, omtrent tot soveel as twee maande. Dit is waarom die veronderstelling daar is dat die digthede aan die einde van die teelseisoen nou aansienlik hoër is as die in 1979/80.af
dc.language.isoenen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectMice -- Environmental aspects -- Marion Island (Prince Edward Islands)en_ZA
dc.subjectThesis (D.Phil. (Zoology and Entomology))--University of the Orange Free State, 1999en_ZA
dc.titleThe ecology and ecophysiology of Marion Island house mice, Mus Musculus L.en_ZA
dc.typeThesisen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


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