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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Infection Dynamics of Herpesvirus in Gopher Tortoises

Saldanha, Joanne 01 January 2018 (has links)
Gopherus polyphemus, commonly known as the Gopher Tortoise, is a dryland reptile native to the southeastern United States. It is commonly a resident of longleaf pine and dry oak sand hill habitats. It is considered a keystone species because they dig deep burrows that provide shelter to them as well as many other animals. Habitat loss, fragmentation, and disease are major threats and have caused this species to be federally listed as a threatened species under the Endangered Species Act (ESA). Disease is a major threat to the gopher tortoise’s survival, and with declining populations, the need to investigate pathogens is crucial. Herpesvirus, is known to contribute to upper respiratory tract diseases (URTD) in G. polyphemus and is the primary focus of this project. Due to high mutation rates in the virus, a modified version of PCR, nested PCR, was conducted on eye and nose swabs and blood samples obtained from G. polyphemus to detect the presence of the alpha herpesvirus pathogen. The positive samples were then sent for genetic sequencing to confirm the occurrence of the pathogen. The detectability of Herpesvirus in eye and nose swabs was compared to blood and lymph samples and statistical tests concluded that both sample types had the same detectability.
42

Conservation and coexistence of a federally listed species within a landscape highly modified for commodity production: gopher tortoise (Gopherus polyphemus) and intensive pine (Pinus spp.) management

Duffie, Duston R 07 August 2020 (has links)
Gopher tortoise (Gopherus polyphemus; hereinafter, tortoise) is listed as threatened under the Endangered Species Act in the western portion of its range. Across the species’ range, approximately 70 % of potential habitat is privately owned, and these properties are often managed primarily for timber production. However, tortoise ecology on private, working forest landscapes remains poorly understood. To provide a better understanding of tortoise response to active forest management, I evaluated population demographics, movement ecology, and habitat selection of two tortoise populations: former Ben’s Creek Wildlife Management Area (BC) in Washington Parish, Louisiana and Perry County Gopher Tortoise Management Unit (PCGTMU) in Perry County, Mississippi. At BC, tortoises were generally clustered along utility rights-of- way and roadways. At PCGTMU, tortoises were clustered within forest stands with high quality soils. Low recruitment has been documented at BC for the last 25 years. However, PCGTMU appears to have a stable population with active recruitment.
43

An Investigation of Habitat Suitability Factors and their Interactions for Predicting Gopher Tortoise Habitat

Lavallin, Abigail V. 29 October 2018 (has links)
This thesis evaluates the interaction between four habitat factors vital to the gopher tortoise in Florida. Federally and state listed as threatened throughout its entire range, the gopher tortoise is vital to protect, not only for itself individually but its burrows provide an essential habitat to over 300 species making it a key stone species within its environment. Historic habitat modeling methods are reviewed for the gopher tortoise to highlight the gap on this topic. This research expanded on the methods utilized by Baskaran et al. (2006) evaluating the soil, landcover, percentage of canopy cover and the depth to water table habitat factors key to the gopher tortoise. Statistical analysis was used to establish the interactions using a regression type analysis of the presence/absence data relative to the four factors. A probability map for the study site was then computed from the results. The Analysis of Deviance results for the statistical model with land cover type as an independent variable and a 3-way interaction term for the other factors found that the land cover term was significant as an independent variable and the 3-way interaction of the other 3 habitat factors was significant. This result demonstrates that there is in fact an interaction between the habitat factors influencing the location of gopher tortoises. This finding is significant in future gopher tortoise research as it indicates that habitat factors evaluated individually may not be as important as the interactions between the factors. By understanding the interactions between the habitat factors, the FWC can work alongside other agencies to ‘increase and improve’ these key habitat areas preventing them from destruction. The map results also help pinpoint those fragmented potential habitat sites which are most at risk from full destruction and loss allowing agencies the work on protecting and expanding the suitable habitat landscape in order to ‘enhance and restore’ the gopher tortoise populations residing there, helping them to ‘maintain the gopher tortoise’s function as a keystone species’
44

Foundations of Deduction's Pedigree: A Non-Inferential Account

Seitz, Jeremy January 2009 (has links)
In this thesis I discuss the problems associated with the epistemological task of arriving at basic logical knowledge. This is knowledge that the primitive rules of inference we use in deductive reasoning are correct. Knowledge of correctness, like all knowledge, is available to us either as the product of inference, or it is available non-inferentially. Success in the campaign to justify the correctness of these rules is mired by opposing views on how to do this properly. Inferential justifications of rules of inference, which are based on reasons, lead to regressive or circular results. Non-inferential justifications, based on something other than reasons, at first do not seem to fare any better: without a basis for these justifications, they appear arbitrary and unfounded. The works of Boghossian and Dummett who argue for an inferentialist approach, and Hale who supports non-inferentialism are carefully examined in this thesis. I conclude by finding superiority in Hale's suggestion that a particular set of basic logical constants are indispensable to deductive reasoning. I suggest that we endorse a principle which states that rules are not premises, and are therefore to be excluded from expression as statements in a deductive argument. I argue that the quality of being indispensable is sufficient for a basic rule of deduction to be countenanced as default-justified, and therefore need not be expressed in argument. By a rule's evading expression in argument, it avoids circular reasoning in deductive arguments about its own correctness. Another important outcome that emerges from my research is the finding that non-inferential knowledge is ontologically prior to the inferential sort. This is because plausible inferential knowledge of basic logical constants shall always be justified by circular reasoning that already assumes the correctness of the rule to be vindicated. This initial assumption is tantamount to non-inferential knowledge, and therefore this latter is more primitive-in fact the only primitive-species of basic logical knowledge.
45

Foundations of Deduction's Pedigree: A Non-Inferential Account

Seitz, Jeremy January 2009 (has links)
In this thesis I discuss the problems associated with the epistemological task of arriving at basic logical knowledge. This is knowledge that the primitive rules of inference we use in deductive reasoning are correct. Knowledge of correctness, like all knowledge, is available to us either as the product of inference, or it is available non-inferentially. Success in the campaign to justify the correctness of these rules is mired by opposing views on how to do this properly. Inferential justifications of rules of inference, which are based on reasons, lead to regressive or circular results. Non-inferential justifications, based on something other than reasons, at first do not seem to fare any better: without a basis for these justifications, they appear arbitrary and unfounded. The works of Boghossian and Dummett who argue for an inferentialist approach, and Hale who supports non-inferentialism are carefully examined in this thesis. I conclude by finding superiority in Hale's suggestion that a particular set of basic logical constants are indispensable to deductive reasoning. I suggest that we endorse a principle which states that rules are not premises, and are therefore to be excluded from expression as statements in a deductive argument. I argue that the quality of being indispensable is sufficient for a basic rule of deduction to be countenanced as default-justified, and therefore need not be expressed in argument. By a rule's evading expression in argument, it avoids circular reasoning in deductive arguments about its own correctness. Another important outcome that emerges from my research is the finding that non-inferential knowledge is ontologically prior to the inferential sort. This is because plausible inferential knowledge of basic logical constants shall always be justified by circular reasoning that already assumes the correctness of the rule to be vindicated. This initial assumption is tantamount to non-inferential knowledge, and therefore this latter is more primitive-in fact the only primitive-species of basic logical knowledge.
46

Caracterização ultrassonográfica dos órgãos da cavidade celomática do jabuti-piranga (Chelonoidis carbonaria SPIX, 1824)

Meireles, Yara Silva 24 February 2014 (has links)
Submitted by Simone Souza (simonecgsouza@hotmail.com) on 2017-10-18T14:46:12Z No. of bitstreams: 1 DISS_2014_Yara Silva Meireles.pdf: 2036361 bytes, checksum: e2354a551bdb7659a6dce8b6fe10737f (MD5) / Approved for entry into archive by Jordan (jordanbiblio@gmail.com) on 2017-11-08T12:41:22Z (GMT) No. of bitstreams: 1 DISS_2014_Yara Silva Meireles.pdf: 2036361 bytes, checksum: e2354a551bdb7659a6dce8b6fe10737f (MD5) / Made available in DSpace on 2017-11-08T12:41:22Z (GMT). No. of bitstreams: 1 DISS_2014_Yara Silva Meireles.pdf: 2036361 bytes, checksum: e2354a551bdb7659a6dce8b6fe10737f (MD5) Previous issue date: 2014-02-24 / CAPES / Nesse estudo foram descritas a morfologia ultrassonográfica e sintopia das vísceras da cavidade celomática do jabuti-piranga. Trinta e oito animais hígidos, 19 machos e 19 fêmeas, foram anestesiados com cetamina e midazolan e contidos em decúbito ventral para realização de varredura ultrassonográfica da cavidade celomática através dos acessos cervicais e pré-femorais com transdutor setorial multifrequencial. Foram aferidas várias medidas corpóreas e frequência cardíaca e foram avaliadas a morfologia, ecogenicidade e a sintopia do coração, tireóide, fígado, vesícula biliar, estômago, intestinos, ovários, oviduto, testículos, rins e bexiga. O coração mostrou dois átrios e um ventrículo com parede trabecular e espessa. Na base cardíaca pode-se visibilizar a tireóide ovalada e ecogênica, cujas medidas mostraram correlação positiva com o peso do animal. O fígado, a vesícula biliar e o aparelho digestório foram semelhantes ao visto em mamíferos e quelônios, porém, a imagem do fígado dos jabutis apresentou aparência mais hiperecóica em relação aos dos mamíferos. Os rins foram vistos como estruturas triangulares, hipoecóicas, homogêneas e vascularizadas e a bexiga foi observada na maioria das vezes com forma alongada com conteúdo anecóico e sua parede foi vista como uma fina linha hiperecóica quando havia líquido livre. Os testículos foram observados como estruturas alongadas, homogêneas e hiperecóicas em relação aos rins. Os folículos ovarianos foram vistos como esferas ecogênicas a hiperecogênicas de tamanho e quantidade variável, o oviduto como uma estrutura tubular sigmoide. Os eram estruturas com finas linhas hiperecóicas com sombreamento acústico posterior. Em alguns animais, havia quantidade variável de líquido livre ao redor do coração e na cavidade celomática. / In this study we describe the sonographic morphology and sintopy of the coelomic cavity organs of red-footed tortoise. Thirty eight healthy animals, 19 males and 19 females, were anesthetized with ketamine and midazolam and contained in ventral decubitus position for scanning the coelomic cavity through the cervical and pre- femoral access with multifrequency sector transducer. Several body measurements and heart rate were measured and the morphology, echogenicity and sintopy of the heart, thyroid, liver, gallbladder, stomach, intestines, ovaries, oviduct, testis, kidney and bladder were evaluated. The heart showed two atria and one ventricle with trabecular thick wall. In cardiac basis was visualized the oval and echogenic thyroid, which showed a positive correlation with the weight of the animal. The liver, gallbladder and digestive system were similar to those seen in mammals and turtles. However, the tortoise liver was more hyperechoic relative to mammals. The kidneys were seen as triangular structures, hypoechoic, homogeneous and vascularized and the bladder was observed mostly as elongated with anechoic content and its wall was seen as a thin hyperechoic line when there was free fluid. The testes were observed as elongated, homogeneous and hyperechoic in relation to kidney structures. The ovarian follicles were seen as a hyperechoic echogenic balls of variable size and quantity, the oviduct as a sigmoid tubular structure and eggs as thin hyperechoic lines with posterior acoustic shadowing. In some animals, there was a variable amount of anechoic fluid around the heart and in the coelomic cavity.
47

Estudo comparativo entre anestesia espinhal com lidocaína e bupivacaína em Tartaruga-da-Amazonia (Podocnemis expansa Schweigger) (Testudines, Podocnemididae) / A comparative study of spinal anesthesia with lidocaine and bupivacaine in Podocnemis expansa Schweigger (Testudines, Podocnemididae)

Nascimento, Liliane Rangel 12 March 2013 (has links)
Was aimed at evaluating the effects of lidocaine and bupivacaine via the spine in turtles of the species Podocnemis expansa in promoting motor and sensitive blockages in the tail/cloaca and pelvic members, as well as the existence of significant differences in the effects produced by the two drugs. Was used 20 animals with average weights of 1.15 kg, which were divided into two anesthetic protocols: 4.6 mg/kg of lidocaine 2% and 1.15 mg/kg of bupivacaine 0.5% deposited in the spinal region in the sacro-coccigeal area. Was evaluated the latency period, the reasonable period for anesthesia and the recovery period. For the latency period of the tail/cloaca we obtained (Lca) 54±34.05 seconds (sec) and 54±18.97sec as mean values for lidocaine and bupivacaine respectively. The latency period of the pelvic member (LMp) was in average 264±75.89 seconds for lidocaine and 180±126.49 sec for bupivacaine. Then the reasonable period for anesthesia on the tail/cloaca (Hca) was 36±9.43 minutes (min) and 60.8±32.10 min for the anesthetics in the same sequence. The averages for the reasonable period in pelvic members (HMp) were 24.6±10.83 min and 58.7±33.82 min for the respective drugs. Finally, the recovery period (Rec) was 33.5±16.33 min for lidocaine and 77.5±33.27 min for bupivacaine. The average times found for bupivacaine were significantly higher except during periods of latency of the tail/cloaca and pelvic members. The heart rate remained within the range considered normal for the testudines. Was conclude that the use of lidocaine and bupivacaine via the spine is safe and effective in the promotion of anesthesia in the region of the tail/cloaca and in pelvic limbs, and that the reasonable times for anesthesia are enough to perform simple and ordinary surgical procedures. / Objetivou-se avaliar os efeitos da lidocaína e bupivacaína por via espinhal em cágados da espécie Podocnemis expansa na promoção de bloqueios motor e sensitivo nas regiões da cauda/cloaca e membros pelvinos, bem como a existência de diferenças nos efeitos produzidos pelos dois fármacos. Foram utilizados 20 animais com massa corporal média de 1,15 kg de ambos os gêneros, estes foram distribuidos em dois protocolos anestésicos: 4,6 mg/kg de lidocaína 2% e 1,15 mg/kg de bupivacaína 0,5%, depositadas na região espinhal no espaço interarcual sacro-coccígeo. Foram avaliados o período de latência, período hábil de anestesia e o período de recuperação. Foram obtidos, para período de latência da cauda/cloaca (Lca) 54±34,05 segundos (seg) e 54±18,97 seg como valores médios para lidocaína e bupivacaína respectivamente. O período de latência do membro pelvino (LMp) teve como média 264±75,89 seg para lidocaína e 180±126,49 seg para bupivacaína. Já o período hábil de anestesia em cauda/cloaca (Hca) foi de 36±9,43 minutos (min) e 60,8±32,10 min para os anestésicos na mesma sequencia. As médias para o período hábil nos membros pelvinos (HMp) foram de 24,6±10,83 min e 58,7±33,82 min para os respectivos fármacos. Por fim, o período de recuperação (Rec) foi de 33,5±16,33 min para lidocaína e 77,5±33,27 min para bupivacaína. As médias de tempo encontradas para bupivacaína foram significativamente maiores exceto nos períodos de latência de cauda/cloaca e de membros pelvinos. A freqüência cardíaca permaneceu dentro do intervalo considerado normal para os testudines. Conclui-se que a utilização de lidocaína e bupivacaína por via espinhal é segura e eficaz na promoção de anestesia na região de cauda/cloaca e nos membros pelvinos, e que os tempos hábeis de anestesia são suficientes para execução de procedimentos cirúrgicos mais simples e rotineiros. / Mestre em Ciências Veterinárias
48

Seasonal effects on the feeding ecology and habitat of Chersina Angulata in the South Western Cape

Joshua,Quinton Ignatius January 2008 (has links)
<p>Nearly one-third of the world&rsquo / s tortoises live in South Africa, but little is known about their habitat requirements and feeding ecology. Chersina angulata, the angulate tortoise, is endemic to&nbsp / southern Africa, with a wide distribution along the western and southern coasts. Because this tortoise occupies a number of different habitat types, it has always been considered a generalist&nbsp / herbivore, although little is known about its&nbsp / diet and other needs. This study evaluates the habitat characteristics and feeding ecology of C. angulata at two study sites in the southwestern&nbsp / &nbsp / &nbsp / Cape, the West Coast National Park (WCNP) and Dassen Island (DI). The WCNP is a large conserved area in the Fynbos biome, along the southwestern coast of South Africa, whereas DI is a&nbsp / small offshore island with low floral and faunal diversity, just south of the WCNP. The efficacy of three methods used to study the feeding ecology of herbivores, focal observations, macroscopic faecal analysis and histological analysis of scats, was evaluated. Plant cover, species diversity, and the variety of growth forms were substantially larger at the WCNP than on DI.&nbsp / In the WCNP, shrubs and grasses were the dominant growth forms but the vegetation also included herbs, succulents, restios, sedges and parasitic plants. A few perennial species such as&nbsp / the grass Ehrharta villosa, shrubs such as Helichrysum niveum, Nylandtia spinosa and Rhus spp., and succulents such as Carpobrotus edulis and Ruschia spp., provided most of the plant&nbsp / cover. DI had a depauperate flora, consisting of succulents and herbs, and ephemeral plants contributed more than perennials did to plant cover throughout the year. The succulents Mesembryanthemum crystallinum and Tetragonia fruticosa provided most of the cover on DI. Angulate tortoises are herbivores and 72 diet plants in 32 plant families were identified to the&nbsp / species or genus level. Several diet species, however, could not be identified. In&nbsp / addition to angiosperms, the tortoises&rsquo / diet included mosses, mushrooms, insects,snails and animal faeces.&nbsp / The most important growth forms in the diet were herbs and grasses. The diet of the WCNP tortoises was more diverse than the diet of DI tortoises, but the number of principal food items in&nbsp / the diet did not differ between the two sites. Over an annual cycle, WCNP tortoises had four principal food plants while DI tortoises had five principal food plants. At both sites, principal food&nbsp / &nbsp / plants changed with the season and few plants remained principal food items in more than one season. Cynodon dactylon was a principal food item in three of the four seasons in the WCNP, whereas Trachyandra divaricata was a principal food plant each season on DI. Most principal food plants were grass or herb species but the sedge Ficinia nigrescens, and a succulent that&nbsp / could be identified only to the family level (Aizoaceae), featured strongly in the spring diets of DI and WCNP tortoises, respectively.&nbsp / The three study methods did not provide the same type or quality of information about the feeding ecology of angulate tortoises. The small size and wary nature of angulate tortoises compromised focal studies because it was often not possible to see&nbsp / what the tortoises ate. This method, however, provided the interesting observation that rabbit&nbsp / faecal pellets contributed nearly 30% to summer and autumn diets on DI when food was scarce.&nbsp / Rabbit faeces may not only provide a source of nutrients but may also supplement the microflora, required to digest cellulose, in the tortoises&rsquo / guts. Macroscopic evaluation of the tortoises&rsquo / &nbsp / scats appeared to be an ineffective method to identify diet plants, and the bulk of the scat mass could not be identified. This indicates&nbsp / that angulate tortoises either selected food low in fibrous&nbsp / content or that the digestive system of the tortoises dealt efficiently with tough plant material. The macroscopic method was the only method that highlighted the large contribution of&nbsp / fruits / seeds to the diet of angulate tortoises. Since the tortoises digested many seeds only partially, or not at all, C. angulata is potentially an important agent of seed dispersal in the southwestern Cape. The macroscopic study showed that on DI, sand made up 28% of the scat mass in spring, whereas sand never made a substantial contribution to the scat composition of WCNP tortoises. Lithophagy may be an important strategy in a depauperate habitat, such as DI, because the abrasive action of sand may help with the digestion of tough plants, or the sand may&nbsp / provide the tortoises with important minerals that are deficient in their food plants.The histological analysis of scats provided the most comprehensive diet list for C. angulata. Selection indices&nbsp / based on data from the histological analysis indicated that angulate tortoises were highly selective in their food choice. Most of the principal food items were selected out of proportion to their&nbsp / availability and the tortoises avoided the most abundant plants in their habitats. Several factors, such as palatability, accessibility and profitability, may have influenced their food choice. The proportional similarity indices for WCNP and DI tortoises, respectively, were 0.31 and 0.16, confirming that C. angulata is a food specialist and not a food generalist as was previously thought. This factor should be considered in the management of this species and in future conservation planning of its habitat.&nbsp / &nbsp / </p>
49

Seasonal effects on the feeding ecology and habitat of Chersina Angulata in the South Western Cape

Joshua,Quinton Ignatius January 2008 (has links)
<p>Nearly one-third of the world&rsquo / s tortoises live in South Africa, but little is known about their habitat requirements and feeding ecology. Chersina angulata, the angulate tortoise, is endemic to&nbsp / southern Africa, with a wide distribution along the western and southern coasts. Because this tortoise occupies a number of different habitat types, it has always been considered a generalist&nbsp / herbivore, although little is known about its&nbsp / diet and other needs. This study evaluates the habitat characteristics and feeding ecology of C. angulata at two study sites in the southwestern&nbsp / &nbsp / &nbsp / Cape, the West Coast National Park (WCNP) and Dassen Island (DI). The WCNP is a large conserved area in the Fynbos biome, along the southwestern coast of South Africa, whereas DI is a&nbsp / small offshore island with low floral and faunal diversity, just south of the WCNP. The efficacy of three methods used to study the feeding ecology of herbivores, focal observations, macroscopic faecal analysis and histological analysis of scats, was evaluated. Plant cover, species diversity, and the variety of growth forms were substantially larger at the WCNP than on DI.&nbsp / In the WCNP, shrubs and grasses were the dominant growth forms but the vegetation also included herbs, succulents, restios, sedges and parasitic plants. A few perennial species such as&nbsp / the grass Ehrharta villosa, shrubs such as Helichrysum niveum, Nylandtia spinosa and Rhus spp., and succulents such as Carpobrotus edulis and Ruschia spp., provided most of the plant&nbsp / cover. DI had a depauperate flora, consisting of succulents and herbs, and ephemeral plants contributed more than perennials did to plant cover throughout the year. The succulents Mesembryanthemum crystallinum and Tetragonia fruticosa provided most of the cover on DI. Angulate tortoises are herbivores and 72 diet plants in 32 plant families were identified to the&nbsp / species or genus level. Several diet species, however, could not be identified. In&nbsp / addition to angiosperms, the tortoises&rsquo / diet included mosses, mushrooms, insects,snails and animal faeces.&nbsp / The most important growth forms in the diet were herbs and grasses. The diet of the WCNP tortoises was more diverse than the diet of DI tortoises, but the number of principal food items in&nbsp / the diet did not differ between the two sites. Over an annual cycle, WCNP tortoises had four principal food plants while DI tortoises had five principal food plants. At both sites, principal food&nbsp / &nbsp / plants changed with the season and few plants remained principal food items in more than one season. Cynodon dactylon was a principal food item in three of the four seasons in the WCNP, whereas Trachyandra divaricata was a principal food plant each season on DI. Most principal food plants were grass or herb species but the sedge Ficinia nigrescens, and a succulent that&nbsp / could be identified only to the family level (Aizoaceae), featured strongly in the spring diets of DI and WCNP tortoises, respectively.&nbsp / The three study methods did not provide the same type or quality of information about the feeding ecology of angulate tortoises. The small size and wary nature of angulate tortoises compromised focal studies because it was often not possible to see&nbsp / what the tortoises ate. This method, however, provided the interesting observation that rabbit&nbsp / faecal pellets contributed nearly 30% to summer and autumn diets on DI when food was scarce.&nbsp / Rabbit faeces may not only provide a source of nutrients but may also supplement the microflora, required to digest cellulose, in the tortoises&rsquo / guts. Macroscopic evaluation of the tortoises&rsquo / &nbsp / scats appeared to be an ineffective method to identify diet plants, and the bulk of the scat mass could not be identified. This indicates&nbsp / that angulate tortoises either selected food low in fibrous&nbsp / content or that the digestive system of the tortoises dealt efficiently with tough plant material. The macroscopic method was the only method that highlighted the large contribution of&nbsp / fruits / seeds to the diet of angulate tortoises. Since the tortoises digested many seeds only partially, or not at all, C. angulata is potentially an important agent of seed dispersal in the southwestern Cape. The macroscopic study showed that on DI, sand made up 28% of the scat mass in spring, whereas sand never made a substantial contribution to the scat composition of WCNP tortoises. Lithophagy may be an important strategy in a depauperate habitat, such as DI, because the abrasive action of sand may help with the digestion of tough plants, or the sand may&nbsp / provide the tortoises with important minerals that are deficient in their food plants.The histological analysis of scats provided the most comprehensive diet list for C. angulata. Selection indices&nbsp / based on data from the histological analysis indicated that angulate tortoises were highly selective in their food choice. Most of the principal food items were selected out of proportion to their&nbsp / availability and the tortoises avoided the most abundant plants in their habitats. Several factors, such as palatability, accessibility and profitability, may have influenced their food choice. The proportional similarity indices for WCNP and DI tortoises, respectively, were 0.31 and 0.16, confirming that C. angulata is a food specialist and not a food generalist as was previously thought. This factor should be considered in the management of this species and in future conservation planning of its habitat.&nbsp / &nbsp / </p>
50

Seasonal effects on the feeding ecology and habitat of Chersina Angulata in the South Western Cape

Joshua, Quinton Ignatius January 2008 (has links)
Philosophiae Doctor - PhD (Biodiversity and Conservation Biology) / Nearly one-third of the world’s tortoises live in South Africa, but little is known about their habitat requirements and feeding ecology. Chersina angulata, the angulate tortoise, is endemic to southern Africa, with a wide distribution along the western and southern coasts. Because this tortoise occupies a number of different habitat types, it has always been considered a generalist herbivore, although little is known about its diet and other needs. This study evaluates the habitat characteristics and feeding ecology of C. angulata at two study sites in the southwestern Cape, the West Coast National Park (WCNP) and Dassen Island (DI). The WCNP is a large conserved area in the Fynbos biome, along the southwestern coast of South Africa, whereas DI is a small offshore island with low floral and faunal diversity, just south of the WCNP. The efficacy of three methods used to study the feeding ecology of herbivores, focal observations, macroscopic faecal analysis and histological analysis of scats, was evaluated. Plant cover, species diversity, and the variety of growth forms were substantially larger at the WCNP than on DI. In the WCNP, shrubs and grasses were the dominant growth forms but the vegetation also included herbs, succulents, restios, sedges and parasitic plants. A few perennial species such as the grass Ehrharta villosa, shrubs such as Helichrysum niveum, Nylandtia spinosa and Rhus spp., and succulents such as Carpobrotus edulis and Ruschia spp., provided most of the plant cover. DI had a depauperate flora, consisting of succulents and herbs, and ephemeral plants contributed more than perennials did to plant cover throughout the year. The succulents Mesembryanthemum crystallinum and Tetragonia fruticosa provided most of the cover on DI. Angulate tortoises are herbivores and 72 diet plants in 32 plant families were identified to the species or genus level. Several diet species, however, could not be identified. In addition to angiosperms, the tortoises’ diet included mosses, mushrooms, insects,snails and animal faeces. The most important growth forms in the diet were herbs and grasses. The diet of the WCNP tortoises was more diverse than the diet of DI tortoises, but the number of principal food items in the diet did not differ between the two sites. Over an annual cycle, WCNP tortoises had four principal food plants while DI tortoises had five principal food plants. At both sites, principal food plants changed with the season and few plants remained principal food items in more than one season. Cynodon dactylon was a principal food item in three of the four seasons in the WCNP, whereas Trachyandra divaricata was a principal food plant each season on DI. Most principal food plants were grass or herb species but the sedge Ficinia nigrescens, and a succulent that could be identified only to the family level (Aizoaceae), featured strongly in the spring diets of DI and WCNP tortoises, respectively. The three study methods did not provide the same type or quality of information about the feeding ecology of angulate tortoises. The small size and wary nature of angulate tortoises compromised focal studies because it was often not possible to see what the tortoises ate. This method, however, provided the interesting observation that rabbit faecal pellets contributed nearly 30% to summer and autumn diets on DI when food was scarce. Rabbit faeces may not only provide a source of nutrients but may also supplement the microflora, required to digest cellulose, in the tortoises’ guts. Macroscopic evaluation of the tortoises’ scats appeared to be an ineffective method to identify diet plants, and the bulk of the scat mass could not be identified. This indicates that angulate tortoises either selected food low in fibrous content or that the digestive system of the tortoises dealt efficiently with tough plant material. The macroscopic method was the only method that highlighted the large contribution of fruits / seeds to the diet of angulate tortoises. Since the tortoises digested many seeds only partially, or not at all, C. angulata is potentially an important agent of seed dispersal in the southwestern Cape. The macroscopic study showed that on DI, sand made up 28% of the scat mass in spring, whereas sand never made a substantial contribution to the scat composition of WCNP tortoises. Lithophagy may be an important strategy in a depauperate habitat, such as DI, because the abrasive action of sand may help with the digestion of tough plants, or the sand may provide the tortoises with important minerals that are deficient in their food plants.The histological analysis of scats provided the most comprehensive diet list for C. angulata. Selection indices based on data from the histological analysis indicated that angulate tortoises were highly selective in their food choice. Most of the principal food items were selected out of proportion to their availability and the tortoises avoided the most abundant plants in their habitats. Several factors, such as palatability, accessibility and profitability, may have influenced their food choice. The proportional similarity indices for WCNP and DI tortoises, respectively, were 0.31 and 0.16, confirming that C. angulata is a food specialist and not a food generalist as was previously thought. This factor should be considered in the management of this species and in future conservation planning of its habitat. / South Africa

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