Browsing by Author "Stanton-Jones, Wade"

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    The development and use of an automated cellular PIT tag reader system for assessing the activity patterns of the sungazer (smaug giganteus)
    (2018) Stanton-Jones, Wade
    The activities and movement patterns of animals have been of strong interest to researchers for decades. The technological growth over the last few decades has resulted in studies on animal activities presenting more accurate, reliable findings. As a result, very few studies still use the conventional, direct observation technique to monitor activity patterns. Additionally, there has been a growing interest in modern tracking equipment, especially the use of radiofrequency identification (RFID) technologies. Typically, RFID systems only comprise of two main components to monitor animal activities: the transponder tag which is fitted to an animal either externally or subdermally, and the interrogator (reader) which electromagnetically powers the transponder to read its unique identification code. The reader itself can be handheld or automated. However, the automated reader systems (ARS) are limited by storage capacity of the datalogger and still require a researcher to actively attend to the system to download the captured data. In light of this, the first aim of this study was to develop an automated cellular reader system (ACRS) that enables completely remote access to data at any given time, from any electronic device with internet connectivity. The second aim was to implement the newly designed system in an assessment of the activity patterns of Sungazers over two seasons, winter and spring. I followed the FDX-A protocol to develop an autonomous reader capable of reading 125 kHz passive integrated transponder tags (PITs), which were subdermally injected into 58 Sungazers (Smaug giganteus), a species known to be highly sedentary. I developed 12 ACRSs which were each fitted with a cellphone engine in which a SIM card was installed in each reader and loaded with data and airtime, monthly, for the 6-month duration of the study. The reading antennas were fitted around the circumferences of 12 Sungazer burrows and the activity patterns of the Sungazers were monitored. The ACRSs provided a 98.5% success rate in their ability to report on the emergence and retreating activities of Sungazers. The ACRSs recorded data from 10 Sungazers. Six Sungazers were active for 37.3% of the days during the winter months, displayed significantly less frequent shuttling behaviours, and showed higher variation in the proportion of the duration of daily activity above ground during this time compared to spring. Male Sungazers visited neighbour burrows significantly more frequently than did females but both sexes displayed high site fidelity. The findings of this study suggest that activity of a portion of the population of Sungazers during winter could be a behavioural response to infection. The increased movements of male Sungazers suggests that spring is the mating season of Sungazers. Finally, the development of the ACRSs have provided insightful information on the activity patterns of Sungazers and the results suggest that Sungazers display seasonal variation in terms of activity. The ACRSs were able to function maintenance free for the duration of the study period and can easily be adapted to studies on other animals.
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    Habitat selection by a threatened lizard, the sungazer (Smaug giganteus): implications for conservation
    (2024) Stanton-Jones, Wade
    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.