Thesis (M.S.)--Oregon State University, 1997. / Typescript (photocopy). Includes bibliographical references (leaves 35-40). Also available on the World Wide Web.

Thesis (Ph. D.)--Oregon State University, 1999. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

Thesis (M.S.)--University of Guelph, 1998. / Includes bibliographical references (leaves 74-84).

Magister Scientiae - MSc / There have been many cases reported of amphibian populations declining. These are often due to anthropogenic factors such as habitat destruction and pollution. However, some eclines have not had an obvious cause and many of these have been investigated and found to be due to pathogenic disease. Batrachochytrium dendrobatidis is a recently described pathogen of frogs. The population declines that have been associated with chytridiomycosis have occurred in relatively undisturbed areas such as national parks. The declines tend to occur at higher altitudes or in colder climates. This is thought to be because of the frog immune system being slower at lower temperatures. This project gives an overview of chytrid infection in the Western Cape and at a small number of sites in the Northern Cape and Eastern Cape. / South Africa

No description available.

The purpose of this investigation was to analyze the distribution of amphibians and reptiles in Texas by means of the methods of Webb and Hagmeier and Stults. An additional graphical analysis was made, including range and range limits which provides a cross-section of faunal change along selected base lines across the state.

The purpose of this research was to compile a presence list of reptiles and amphibians that occur in Palo Pinto County, Texas, and to investigate the ecological distributions and zoogeographic affinities of these herpetiles. The study area was chosen primarily because of its location in North Central Texas and its rugged topography, which sets it apart from the surrounding area.

The purpose of this study was to make a preliminary study of the herpetofauna of Montague County in relation to ecological distribution. Also taken into consideration were the zoogeographic relationships of the various species.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, 2015. / Land transformation and associated habitat loss has been identified as one of the biggest global factors affecting decreases in frog biodiversity. Gauteng Province is South Africa’s economic hub and much of the Highveld grassland, characteristic of the region, has been transformed for urban and agricultural purposes. Large, isolated depressions underlain by impervious soils – known as pans – are typical wetland systems of the Highveld region which form habitat for many frog species. I undertook a coarse assessment of amphibian habitat in eleven pans (six representing urban and five representing agricultural areas) by measuring water quality at one point in time (electro-conductivity, temperature, pH, and concentration of sulphates, ortho-phosphates, ammonia, nitrates + nitrites and metals (Na, Mg, K, Ca)), and pan metrics, such as distance to tarred road, area of available terrestrial habitat and pan area. A frog survey using the pitfall-trap method of capture was also conducted at each of the sample sites for the purposes of evaluating frog biodiversity and spatial habitat utilisation. Evidence of acid mine drainage contamination, extensive dumping of household and building waste, nutrient enrichment and close proximity to roads with heavy traffic were found at urban sites. Agricultural sites were located significantly further away from tarred roads compared to urban sites but some were affected by deposition of eroded material from nearby cropland. A Pearson’s Correlation found a strong correlation between NO2 + NO3-N concentration and Amietophrynus gutturalis abundance across sites. Correlation matrices detected a strong, positive correlation between available terrestrial habitat adjacent to pans and pan proximity to tarred road with abundance of Cacosternum boettgeri, Pyxicephalus adspersus and Tomopterna cryptotis. At least six of the eight recorded frog species were captured at 80 m from the pan shoreline. Based on potential sensitivity of some species to available terrestrial habitat area, I recommend that buffer zones around pans should be between 100 and 500 m to ensure species persistence.

Chytridiomycosis, a disease of amphibians caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), is an ideal system for studying how temperature influences the host-pathogen relationship because both the host and the pathogen are ectothermic. In this dissertation, I employ a three-pronged approach to investigate the relationship between temperature and the prevalence, severity, and outcome of Bd infections in Northern cricket frogs (Acris crepitans) using both laboratory experiments and field studies. In Chapter One, I conducted a Bd exposure study to determine whether constant temperatures affect Bd pathogenesis differently in live hosts than in culture. Exposure frogs were inoculated weekly with 100 million zoospores of a virulent strain of Bd and frogs were incubated at one of six temperatures: 11, 14, 17, 20, 23, or 26°C. Infection prevalence and pathogen load in Bd-exposed frogs were highest at 14°C while survival was lowest at 11˚C. These results demonstrate that Bd pathogenicity peaks at different temperatures in live hosts than Bd growth peaks at in culture. In Chapter Two, I combine a field study that assesses the effect of microhabitat choice, seasonality and latitude on Bd prevalence and severity in wild amphibian populations with a laboratory study that investigates how temperatures that fluctuate during diurnal and nocturnal cycles influence Bd pathogenicity. Across all states, I found that year was the only significant predictor of infection prevalence, but probability of infection was predicted by year, month, and latitude, and pathogen load was predicted by month and body temperature. In my experimental study, I found infection prevalence and pathogen load to be highest, and survival lowest, in the Louisiana winter group (7˚-17˚C). In my third chapter, I used a biophysical model, Niche Mapper, to predict probability of survival and infection prevalence in Northern cricket frogs by modelling host body temperature. I found that the probability of an infected frog surviving thirty days in May was highest in Southern Louisiana and lowest in Northern Michigan. These studies demonstrate that temperature is an important influence on infection outcome in live hosts. / 1 / Julia Madeleine Sonn