Habitat selection by a threatened lizard, the sungazer (Smaug giganteus): implications for conservation
| dc.contributor.author | Stanton-Jones, Wade | |
| dc.date.accessioned | 2024-02-06T08:20:27Z | |
| dc.date.available | 2024-02-06T08:20:27Z | |
| dc.date.issued | 2024 | |
| dc.description | A thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the Faculty of Science, School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, 2023 | |
| dc.description.abstract | Climate change and habitat transformation are some of the primary threats that reptiles face as a consequence of persisting in their selected habitats. Some species, such as habitat specialists, may be particularly vulnerable to these threats given their restricted geographic ranges, strict habitat requirements, and limited dispersal abilities. Knowledge of the factors that drive habitat and microhabitat selection by a species, the impact that habitat transformation may have on that species, and how the species is expected to respond to climate change is necessary for informing conservation management strategies. Smaug giganteus (the sungazer) is a threatened (Vulnerable), habitat specialist lizard that is endemic to the Highveld grasslands of South Africa. Unfortunately, suitable habitat exists in a landscape where anthropogenic activities (e.g., agriculture and mining) are prevalent, and a major threat that sungazers face is habitat transformation and fragmentation. Sungazers are unique within their family (Cordylidae) in that they rely on self-constructed burrows in specific microhabitats within the grassland matrix as long-term, often permanent, shelter and refuge sites. Because of this, aspects of their life history, and the current threats that they face, sungazers may be particularly vulnerable to the combined effects of climate change and habitat transformation. The primary aim of this thesis was to assess the consequences of habitat selection and use by sungazers by investigating the potential impact of climate change on habitat suitability for the species, the fine-scale impacts of habitat transformation, and to identify the microhabitat requirements by sungazers such that recommendations for future conservation management of the species could be made. The potential impact of climate change on habitat suitability for sungazers was assessed by projecting their current ecological niche envelope into the future, under different climate change scenarios. The models predicted that sungazers may experience minor range contractions under the moderate case scenario, but vulnerability to climate change increased under the worst-case scenario. At the broadscale level, the models predicted that sungazers would shift their geographic range to the southwest. However, given the species life history traits, limited dispersal capacity, and the fragmented habitat in which subpopulations exist, climate tracking is unlikely, and sungazers may be more vulnerable to the effects of climate change than predicted by niche models. An assessment of the demographics and dynamics of four sungazer subpopulations existing at sites with different habitat conditions revealed that the impact of habitat transformation on sungazers may be more devasting than what was previously reported. In this study, the sungazer subpopulations existing in habitats transformed by mining activities, and severe overgrazing have declined by more than 50% over a 16-year period. This assessment at the subpopulation level (colony level) suggests that the current size of the sungazer population is probably an overestimate. A comparison between the microhabitat characteristics surrounding sungazer burrows and random sites in the landscape revealed that sungazers use microhabitats comprised of low vegetation cover and short grasses in which to construct their burrows. Burrow construction in these microhabitats generally occurs on northerly facing slopes. When constructing their burrows, sungazers tend to orientate burrow entrances in the same direction as the aspect of the slope but northerly directions are preferred. This thesis provides the first insights into the potential effects that climate change may have on sungazers in the future and highlights the severity of impact that habitat transformation has on sungazers at fine spatial scales. The findings not only justify the importance of conservation management for sungazers but provide critical information to assist with future conservation protocols. | |
| dc.description.librarian | TL (2024) | |
| dc.description.sponsorship | Rufford Foundation University of the Witwatersrand Postgraduate Merit Award | |
| dc.faculty | Faculty of Science | |
| dc.identifier.uri | https://hdl.handle.net/10539/37511 | |
| dc.language.iso | en | |
| dc.phd.title | PhD | |
| dc.school | Animal, Plant and Environmental Sciences | |
| dc.subject | Sungazers | |
| dc.subject | Climate change | |
| dc.subject | Lizard | |
| dc.title | Habitat selection by a threatened lizard, the sungazer (Smaug giganteus): implications for conservation | |
| dc.type | Thesis |