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Life history and physiological ecology of the lizard, Cordylus Giganteus
Bibliography: pages 243-268.
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| Format: | Thesis |
| Language: | English |
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Department of Biological Sciences
2015
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| _version_ | 1867614480783900672 |
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| access_status_str | Open Access |
| author | Van Wyk, Johannes H |
| author2 | Louw, Gideon |
| author_browse | Louw, Gideon Van Wyk, Johannes H |
| author_facet | Louw, Gideon Van Wyk, Johannes H |
| author_sort | Van Wyk, Johannes H |
| collection | Thesis |
| description | Bibliography: pages 243-268. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/16002 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:52:43.272Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2015 |
| publishDateRange | 2015 |
| publishDateSort | 2015 |
| publisher | Department of Biological Sciences |
| publisherStr | Department of Biological Sciences |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/16002 Life history and physiological ecology of the lizard, Cordylus Giganteus Van Wyk, Johannes H Louw, Gideon Turner, Scott Nicolson, Sue W Zoology Bibliography: pages 243-268. Cordylus giganteus is a large, terrestrial, viviparous lizard, endemic to the Highveld grasslands of South Africa. Its distribution is limited and its conservation status is vulnerable. Autopsy and mark-recapture methods were used to study the seasonal aspects of its reproductive cycle, diet, energy reserves, growth, population dynamics, daily activity and thermoregulation. Reproduction is distinctly seasonal in both sexes. Females may reproduce biennially. Vitellogenesis commenced in autumn (March), and continued through hibernation with ovulation in spring (October). Two or three young are born in autumn. A functional placenta is implicated. Seasonal steroid hormone profiles are presented. Males exhibit a postnuptial spermatogenetic cycle. Spermatogenesis commences in spring with peak spermiogenesis in autumn and testicular regression following in late autumn. Spermatozoa are stored in the epididymis and ductus deferens for seven to eight months. A bimodal plasma testosterone profile is reported, consistent with spermiogenesis in autumn and mating behaviour in spring. C. giganteus feeds during 8 months of the year and prefer Coleoptera as prey. Fat bodies are utilized for winter maintenance and reproduction. Hatchlings grow 20-30mm during the first year and maximum growth rates occur in summer. Males and females attain sexual maturity at about 165 mm SVL in the fourth year. Seasonal affects on growth rate resulted in poor fit by either logistic-by-length or von Bertalanffy models and a seasonal oscillating model was introduced. Adult males are smaller than females; head sizes are the same but allometric slopes differed significantly. Population size and structure remained stable in the study area. Densities ranged from 9 - 11 lizards/ha. The age structure is marked by the low relative abundance of juveniles. Survivorship during the first year varied among years. Mortality was highest during summer months rather than winter months. Average annual survival of adults 'was high, but varied with sex and years (ranged from 58%-80%). A life table yielded a net reproductive rate (Ro= 1) sufficient to sustain the population, if the reproductive life of an adult female is at least 12 years. Lizards remain in their burrows during winter. In summer, activity was bimodal on sunshine days but unimodal on cool overcast days. Body temperature is regulated by behavioural means (postural and orientation changes) and by shuttling to the cool burrow microclimate. The life history strategy corresponds partially to that of K-selection. 2015-12-28T06:10:42Z 2015-12-28T06:10:42Z 1992 Doctoral Thesis Doctoral PhD http://hdl.handle.net/11427/16002 eng application/pdf Department of Biological Sciences Faculty of Science University of Cape Town |
| spellingShingle | Zoology Van Wyk, Johannes H Life history and physiological ecology of the lizard, Cordylus Giganteus |
| thesis_degree_str | Doctoral |
| title | Life history and physiological ecology of the lizard, Cordylus Giganteus |
| title_full | Life history and physiological ecology of the lizard, Cordylus Giganteus |
| title_fullStr | Life history and physiological ecology of the lizard, Cordylus Giganteus |
| title_full_unstemmed | Life history and physiological ecology of the lizard, Cordylus Giganteus |
| title_short | Life history and physiological ecology of the lizard, Cordylus Giganteus |
| title_sort | life history and physiological ecology of the lizard cordylus giganteus |
| topic | Zoology |
| url | http://hdl.handle.net/11427/16002 |
| work_keys_str_mv | AT vanwykjohannesh lifehistoryandphysiologicalecologyofthelizardcordylusgiganteus |