Thesis (M.Sc. (Zoology & Entomology)) - Rhodes University, 2007.

Thesis (M.S.)--Oregon State University, 1998. / Typescript (photocopy). Includes bibliographical references (leaves 44-50). Also available on the World Wide Web.

Thesis (Ph. D.)--University of Western Australia, 2004. / Title from PDF t.p. (viewed Feb. 7, 2006). Includes bibliographical references.

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Arid and semi arid environments are characterised by extreme fluctuations in temperature and low rainfall which present significant challenges to the animals inhabiting these areas. Mammals, such as aardvarks (Orycteropus afer, Pallas 1766), excavate burrows in order to avoid predators and climatic extremes and are termed “ecosystem engineers” as they physically modify their environment and in doing so create new habitats and alter the availability of resources to other species. In this study I assessed the microhabitat conditions (maximum and minimum temperature, relative humidity and seed abundance) of aardvark burrows in relation to paired control sites. In addition, I evaluated the use of aardvark burrows by other vertebrate and invertebrate species and investigated the impact of aardvark burrow mounds on landscape scale floristic diversity. Maximum temperatures were significantly lower (p < 0.05) and minimum temperatures and midday humidity were significantly higher (p < 0.05) inside the burrows at the three study sites, Kwandwe Private Game Reserve (Kwandwe), Mountain Zebra National Park (MZNP) and Tswalu Kalahari Reserve (Tswalu). There were no significant differences between the concentration of seeds, the average numbers of unique individual small mammals, trap success or small mammal species richness recorded inside the burrows compared to outside (p > 0.05). At all three sites, small mammal species diversity was higher in the burrows but this result was also not significant (p > 0.05 for all). Trap success and the number of individuals captured was higher at Tswalu than the other two sites (p < 0.05 for both). The different methods used in this study revealed a total of 25 mammal, seven bird, one amphibian and six reptile species utilising aardvark burrows. There were significant differences in insect community assemblages between the burrows and open control areas at Kwandwe and Tswalu (p < 0.05 for both) but not at MZNP (p > 0.05). The parasitic guild was more prominent inside the burrows than outside but their abundance was not as high as anticipated, possibly due to the placement of traps closer to the burrow entrances than the sleeping chambers. The complex structure of the burrows prevented the placement of traps in close proximity to the sleeping chambers. As expected, the amount of bare earth was significantly higher on active and recently abandoned burrow mounds compared to the old burrow mounds and reference plots at all three sites (p < 0.05 for all), with the exception of the active burrows at Tswalu. Overall, the different plot types were characterised by significantly different plant communities during all the seasons at MZNP, during three of the seasons at Kwandwe and only during winter at Tswalu. The total species richness recorded on the reference plots was higher than on the burrow mounds at all three sites. However, species diversity on the reference plots was not significantly higher than the burrows at any of the sites (p > 0.05 for all sites). Although the results were not significant, the overall species diversity at a site level was greater than the reference patches at Kwandwe and Tswalu (p > 0.05 for both). Aardvarks fulfil the criteria of a significant ecosystem engineer and their presence in arid and semi-arid environments is likely to be critical to the survival of other individual organisms and species, particularly when alternative burrowing animals are either absent or restricted in their activities. Thus, aardvark populations should be considered a conservation priority in arid and semi-arid ecosystems.

ambiente subterrâneo oferece rotas de deslocamento entre pontos de forrageamento ou local de estoque de alimentos e abrigo contra predadores e frio ou calor intensos. Dentre os roedores, cerca de 250 espécies usam o espaço subterrâneo (11%). Algumas dessas espécies são \"subterrâneas estritas\", mas a maioria são \"fossoriais\" em diferentes graus de dependência do subterrâneo, como o Clyomys bishopi que forrageia sobre a terra. O objetivo deste trabalho foi caracterizar o sistema subterrâneo dessa espécie endêmica do cerrado paulista, e correlacionar com aspectos distais e proximais do comportamento de escavação. No primeiro capítulo, são descritos os sistemas subterrâneos e verificadas suas relações com variáveis ambientais. No segundo, o uso do espaço pela espécie é investigado a partir da dinâmica de abertura das bocas de tocas de sistemas ao longo de dois anos. No terceiro capítulo, a temperatura interna dos sistemas é caracterizada e investigada quanto à sua relação com variáveis ambientais. Finalmente o último capítulo apresenta uma revisão sistemática sobre o uso de sistemas subterrâneos em Rodentia. Os sistemas subterrâneos de C. bishopi são complexos, com diversos túneis, bocas e câmaras de estocagem de sementes e com material de ninho. Os sistemas são maiores e mais profundos na estação seca do que na chuvosa. A espécie abre e fecha as bocas de seus sistemas ao longo do ano, e o maior número de abertura de bocas foi encontrado na estação seca em paisagem aberta, apoiando a hipótese de que os sistemas subterrâneos para a espécie funcionam principalmente como rotas de deslocamento entre áreas de forrageamento, protegidos de predadores. A temperatura apresenta um ciclo circadiano com acrofase após o pôr do sol sem distinção entre as estações climáticas, têm relações com a paisagem em que estão inseridas, sendo menores nas paisagens fechadas e mais elevadas na chuva, com temperatura mais elevada dentro da toca durante a noite e início da manhã. Os hábitos subterrâneos carregam sinais filogenéticos e tem relação com hábitos sociais, interações com o ambiente e a disponibilidade de alimento nos dois sentidos, seja no ganho ou na perda da socialidade. A manutenção da vida social numa espécie e a complexidade dos sistemas relacionam-se também com a maior compactação do solo. A hipótese das relações evolutivas entre a formação de colônias de sistemas subterrâneos, com seus usos e a vida social pode ser testada em trabalhos futuros / The subterranean environment provides displacement routes between foraging points or food storage locations and shelter from predators and intense heat or cold. Among rodents, about 250 species use underground space (11%). Some of these species are strictly subterranean, but most of them are \"fossorial\" in varying degrees of subterranean dependence, such as the Clyomys bishopi that forages above ground. The aim of this study was to characterize the burrow system of this species (that is endemic to cerrado of São Paulo) and to correlate with distal and proximal aspects of the burrowing behavior. In the first chapter, the burrow systems are described and their relationships with environmental variables are verified. In the second, the use of space by the species is investigated from the dynamics of opening and closing burrow systems entrances over two years. In the third chapter, the internal burrow\'s temperature is characterized and it is investigated in relation to the environmental variables. Finally, the last chapter presents a systematic review about the use of burrow systems in Rodentia. Burrow systems of C. bishopi are complex, with several tunnels, entrances and chambers of food storage and nest material. The systems are larger and deeper in the dry season than in the rainy one. The species opens and closes the entrances of its systems throughout the year, and the largest number of entrance openings was found in the dry season that are in open landscape, supporting the hypothesis that this species uses the burrow systems mainly as displacement routes between foraging areas, protected from predators. Temperature exhibits a circadian rhythm with acrophase after sunset without distinction between climatic seasons. This rhythm has relations with the landscape in which they are inserted: smaller in the closed landscapes and more elevated in the rain with higher temperature inside the burrow during night and early in the morning. Subterranean lifestyle carries phylogenetic signals and is related to social habits with interactions between the aridity and the availability of food and sociality on both directions: gain or loss of sociality. Also there are relations soil hardness, burrow\'s complexity and the maintenance of sociality among species. The hypothesis of the evolutionary relationships between the formation of burrow systems colonies with their uses and sociality can be tested in future studies

[Truncated abstract] Ecosystem engineers are organisms that physically modify habitat in a manner that modulate resource flows and species within ecosystems. Ecosystem engineering is distinct from classical interactions (competition, predation, parasitism and mutualism) in that it does not involve direct trophic exchange between organisms. The term ‘ecosystem engineer’ is a recently adopted one, and we are just beginning to investigate the occurrence and impact of engineers in ecosystems. My thesis explores the ecosystem engineering actions of Wedge-tailed Shearwaters, Puffinus pacificus, in a Mediterranean island, heathland ecosystem. I have approached this by (1) describing and quantifying the physical impact of these engineers, and (2) describing and quantifying the effects that these actions have on three major ecosystem components: the soil, the vascular plants, and the vertebrate fauna. Wedge-tailed Shearwaters are procellariid seabirds that excavate nesting burrows on offshore islands. The birds are colonial nesters, and on Rottnest Island, 17 km off the mainland coast of south-western Western Australia, their colonies have expanded considerably in recent decades. The expansion fits the trend observed in other tropicalorigin seabirds that breed in south-western Australia. In the last ten years, two new colonies have appeared (in a total of six) and the number of burrows on the island has almost doubled, to 11 745 ± 1320SE. In the same period the area occupied by the birds has increased by almost half ...