Student Projects

 

Dahné du Toit (Ph.D.): Morphological and behavioural correlates of melanism

There is a distinct clustering of melanistic ectotherms in the southwestern corner of southern Africa, including at least eight melanistic (black) cordylid lizard species. These species occur as isolated populations at coastal or montane localities where there is a high incidence of fog or cloud cover. Of the eight melanistic cordylid species occurring in the southwest, the Graceful Crag Lizard, Pseudocordylus capensis, has by far the largest distribution range. Unlike most other cordylids, the Graceful Crag Lizard has well-developed hind-limbs and are able to scale vertical surfaces. The association with vertical rock faces and/or large boulders, may, through the range of microclimate the latter offer, allow P. capensis to survive in lowland situations, normally inhospitable for melanistic species. If this is indeed the case, various aspects of the general biology of this species may be compromised in lowland situations. Project coordinator and Ph.D. student, Dahné du Toit, is looking at the morphological characters of melanistic cordylids and how this relates to distribution range size and habitat selection. She is also investigating how this impacts on foraging behaviour, social structure, and predator-prey relationships. Understanding the habitat requirements and thermal biology of the Graceful Crag Lizard seems central in understanding the evolutionary future of specific populations in this species and in deriving specific conservation targets for the species in the Greater Cederberg Biodiversity Corridor.

The public is invited to help with this study by reporting localities where they have spotted this lizard. Please remember to also submit a photograph of the lizard, as this is required for positive identification of the species. For more information on this project, please contact Dahné at dadutoit@sun.ac.za.

 

Jenny Jackson (Ph.D.): Chameleon Reproduction Studies

Eight species of dwarf chameleons occur in the Cape Floristic Region (CFR). Ph.D. student, Jenny Jackson, is investigating the highly unusual reproduction strategies in these chameleons. It is thought that dwarf chameleons are capable of producing 17 live young in a single clutch and up to four clutches per year. This is a huge reproductive output for such a small animal. Jenny's project concentrates specifically on the timing of reproduction, clutch size and how many clutches a single female can bear in a year.

The public is invited to become involved in Jenny's project by completing the attached datasheet when they observe chameleons in the field or in their gardens. For more information, please contact Jenny at jjackson@sun.ac.za.

 

Cindy Shuttleworth (M.Sc.): Armadillo lizards and termites

Permanent group-living is a rare phenomenon among lizards. The armadillo girdled lizard, Cordylus cataphractus, is found to naturally occur in groups. The species is well known for its tail-biting behaviour. When threatened, it rolls into a tight ball and firmly grasps its tail in its mouth, thereby protecting its soft underparts. This is the reason why this lizard has received the common name, “armadillo lizard”. Locally, it is often referred to as ‘skurwejantjie' or ‘blinkogie'. The Greater Cederberg area is a well known ecotourist destination, with the armadillo lizard occurring at several of these localities. Due to its many interesting characteristics, the armadillo lizard has high potential for ecotourism, especially in the Greater Cederberg Biodiversity Corridor (GCBC).

It has been suggested that dependence on termites as a food source, has been a key factor in the evolution of group-living behaviour in the armadillo lizard. Colonies of social insects (termites, ants, bees and wasps), represent a concentrated source of energy, and therefore serve as a potentially rewarding food item for predators. It has been found in previous studies that the southern harvester termite, Microhodotermes viator, is possibly the most important source of prey in the diet of Cordylus cataphractus. M.Sc. student Cindy Shuttleworth, is looking at the role that termitophagy plays in the group-living behaviour displayed by the armadillo lizard. Her study will be conducted in the GCBC, and she will be looking at range overlap between the armadillo lizard and the southern harvester termite. In her study she will also search for correlations between the density of the lizards and the termites. Cindy will also determine whether the southern harvester termite is an essential dietary item of the group-living armadillo lizard.

Cordylus cataphractus is listed as Vulnerable in the South African Red Data Book for Amphibians and Reptiles. It is very popular as a pet and the illegal pet trade poses a serious threat to this species. Because it lives in groups and is sluggish in nature, it is easily collected. Through the help of civil society alerting the authorities about illegal collection a negative impact on this species can be prevented. The public is invited to help with this study by reporting localities where they have spotted this lizard. Please remember to also submit a photograph of the lizard, as this is required for positive identification of the species. For more information on this project, please contact Cindy at co@sun.ac.za.

 

Jeannie Hayward (M.Sc.): Armadillo lizards and group dynamics

The group-living lizard, Cordylus cataphractus, commonly known as the armadillo girdled lizard, is a rock-dwelling lizard endemic to the dry western regions of SA. It has been established that C. cataphractus groups do not represent family units, owing to the high degree of intergroup movement observed between different groups.

Cordylus cataphractus feeds on termites at termite ports considerable distances away from the home crevice. Individuals also venture out in the open when moving between groups. The species developed heavy dermal armour and a unique tail-biting anti-predator mechanism to protect them against terrestrial predators it encounters when away from the crevice. Their spines and dermal plates also make it difficult to extract them from a crevice once they are inside. But this heavy armour also renders them relatively slow and sluggish, and therefore extremely vulnerable to birds of prey. As a result, during general maintenance behaviour such as basking, individuals spend most of their time in very close proximity to the crevice opening.

Following this argument, it seems probable that C. cataphractus 's group-living lifestyle may possibly also confer some anti-predatory advantages against avian predators. In numerous studies of mammals and birds, it has been established that one advantage of grouping or flocking behaviour is that group membership can reduce individual risk from predators through the “dilution effect” and the “many-eyes hypothesis”. This “safety in numbers” effect has very rarely been investigated in lizards, because very few previously studied lizard species form permanent social aggregations. The group-living C. cataphractus presents us with an ideal opportunity to determine whether group-living may also have anti-predatory advantages in reptiles.

As mentioned, the great majority of groups are of small and medium size (<20 individuals), but very large groups (>30) are also encountered quite regularly. An interesting, and also very important academic question is why this is so? Why do we find so many groups of 2-6 individuals, but also groups of 60 individuals? Therefore, in addition to the issue regarding anti-predatory benefits, this study will also address two other key questions, namely: “What are the factors influencing group size?”, and “How does a group “grow”, i.e. expand from a single-male into a multi-male group?” For more information on this project, please contact Jeannie at 13808869@sun.ac.za.

 

Anita Meyer (M.Sc.): The GCBC, the Tankwa and Herpetofauna Conservation

The Greater Cederberg Biodiversity Corridor (GCBC) was mainly delineated on the basis of floristic importance and diversity with the general assumption that a significant portion of faunal diversity will inevitably be included and thus protected within the specified area. Anita's study explores just how relevant the GCBC is to particularly the herpetofauna of the Western Cape. This will be done by conducting a large-scale analysis of the distribution patterns of the lizards, snakes and tortoises which occur in the region spanning the southwestern part of the Western and Northern Cape provinces of South Africa.
Records from various scientific institutions across South Africa will be pooled to create an extensive data base of presence/absence data of the herpetofauna in the region. This will then analyzed, in conjunction with various other data layers such as climate, topography and vegetation, with GIS software – ESRI ArcView. Various diversity components - species richness, species turnover and endemism - will subsequently be determined for the lizards, snakes and tortoises in the study area, according to the distributions obtained for each species. It will then be possible to interpret these diversity patterns in terms of the climatic, topographic and vegetation data.
From a reptile perspective the Tankwa-Karoo is grossly undersampled. This leaves a major gap in the knowledge (and understanding) of the true distribution ranges of many species occurring in the larger study area. The Tankwa-Karoo may represent an important dispersal barrier to a relatively immobile guild such as reptiles and it is therefore important to study it in terms of its biogeographical importance. Anita aims to conduct a systematic survey of the reptilian fauna of the Tankwa-Karoo. A number of strategically selected locations, representative of the different habitats within the region, will be sampled extensively to ensure that a maximum number of species will be encountered. This will allow the description and mapping of the species distribution ranges within the region. For more information on this project, please contact Anita at 13810766@sun.ac.za.

 

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