Habitat loss is the greatest contributor to the decline of species globally and thus understanding habitat use and the consequences fragmentation has on biodiversity is a fundamental step towards management and recovery. I conducted a radio-telemetry study to examine the spatial ecology and the effects of roads on Eastern Hognose Snakes (Heterodon platirhinos), a species at risk, in the Long Point Region of Ontario, Canada. I tested habitat selection at multiple spatial scales and I found that within the home range, snakes avoided agricultural land and selected open sand barrens, particularly for nesting. At the local scale, snakes avoided mature overstory trees and used younger patches of forest. Used locations had more woody debris, logs and low-vegetative coverage than locations selected at random. Eastern Hognose Snakes also showed avoidance of paved road crossings in their seasonal movements, but readily crossed unpaved roads. Management efforts for this species at risk should be placed on the conservation of sand barrens and on the construction of road underpasses to prevent genetic isolation of populations.

<p>Rapid urbanization threatens the survival of native wildlife species worldwide. In order to fully grasp the implications of the ongoing growth of urban areas on biodiversity, conservationists need to be able to quantify the response patterns of a wide range of different species to the expansion of urban and suburban land use. In this study, we set up two road-based transects across gradients of urbanization and habitat loss in the diverse longleaf pine forests of the Sandhills region of North Carolina, USA. With funding provided by the NC Wildlife Resources Commission, we drove the transects repeatedly at night in the field seasons of 2006-2008, tallying all vertebrate animals encountered (live or dead). The first transect (driven in all three years; 75 km long) ran from the urban areas of Southern Pines and Pinehurst down to the remote and relatively pristine habitats associated with the state-owned Sandhills Gamelands. The second transect (driven in 2007 and partially in 2008; 69 km long) began at the terminus of the first transect in the Gamelands, and then stretched down to the urban zones of Hamlet and Rockingham. </p><p> A total of 4900 vertebrate animals representing 69 species were observed on or near the road routes after driving a total of 16,625 km. This total includes 592 nightjars (ground-nesting nocturnal birds; e.g. whip-poor-wills) that we heard while driving the transects. In addition, in 2007 we surveyed for the nightjars and for quail (a high-priority game species that also nests on the ground) using 75 point count locations evenly distributed along the northern road route. </p><p> Regression tree analysis (a robust, nonparametric technique with minimal assumptions) was used to model the animal observation rates for a given 1 km road segment or point count as a function of various habitat variables measured within corresponding buffer zones for each segment. We also modeled snake and bird encounter rates as a function of mesopredator mammal observations. </p><p> Our results reveal that amphibian, snake, and ground-nesting bird observation rates are negatively associated with increasing levels of traffic and impervious surface. Conversely, mesopredator mammals (and domestic cats in particular) responded slightly positively to increasing urbanization, and negatively to protected area coverage. Both ground-nesting birds and snakes showed signs of negative correlations with mesopredator encounter rates, although these trends were not always significant due to high variability in the mesopredator data. </p><p> In order to try and confirm the results of the regression tree analyses, we also used a multivariate ordination approach (non-metric multidimensional scaling) to visualize the integrated community structure of all of the major vertebrate groups we observed in the Sandhills. The ordinations revealed that while the snake, ground-nesting bird, and amphibian groups were similar to each other in terms of their avoidance of urban conditions, the cats and native mesopredator species actually seemed to define widely divergent axes of community variation. Cats in particular were separated from the other groups on 2 out of 3 axes of the species-space ordination. Still, as we noted above for the regression tree models, it is difficult to sort out with our correlative data set whether cats and other mesopredators truly played an independent role in structuring and/or depleting the other wildlife guilds along our route. More experimental approaches are recommended for trying to resolve whether overabundant predators or road mortality and inappropriate habitat are more to blame for the much reduced encounter rates we observed for the snakes, birds, and amphibians in urban areas. Future studies will also be needed to confirm the logical assumption that road encounter rates provide a reasonably accurate index of the relative abundance of the different animal groups along the survey routes.</p> / Dissertation

We introduce a new way to accurately segment the 3D femur from pelvic CT scans. The femur is a difficult target for segmentation due to its proximity to the acetabulum, irregular shape and the varying thickness of its hardened outer shell. Atypical bone morphologies, such as the ones present in hips suffering from Femoral Acetabular Impingements (FAIs) can also provide additional challenges to segmentation. We overcome these difficulties by (a) dividing the femur into the femur head and body regions (b) analysis of the femur-head and neighbouring acetabulum’s composition (c) segmentations with two levels of detail – rough and fine contours. Segmentations of the CT volume are performed iteratively, on a slice-by-slice basis and contours are extracted using the morphological snake algorithm. Our methodology was designed to require little initialization from the user and to deftly handle the large variation in femur shapes, most notably from deformations attributed to cam-type FAIs. Our efforts are to provide physicians with a new tool that creates patient-specific and high-quality 3D femur models while requiring much less time and effort. We tested our methodology on a database of 20 CT volumes acquired at the Ottawa General Hospital during a study into FAIs. We selected 6 CT scans from the database, for a total of 12 femurs, considering wide inter-patient variations. Of the 6 patients, 4 had unilateral cam-type FAIs, 1 had a bilateral cam-type FAI and the last was from a control group. The femurs segmented with our method achieved an average volume overlap error of 2.71 ± 0.44% and an average symmetric surface distance of 0.28 ± 0.04 mm compared against the same, manually segmented femurs. These results are better than all comparable literature and accurate enough to be used to in the creation of patient-specific 3D models.

Natural history is a cornerstone of both theoretical and applied ecology, and provides the context for comparative and experimental studies. I studied the natural history of the Plains Garter Snake (Thamnophis radix) near the northern limit of its range in Miquelon Lake Provincial Park. Alberta, Canada. As is typical of garter snakes, T. radix at Miquelon were sexually dimorphic as adults - females grew faster, reached larger sizes and had relatively shorter tails than males. Mating occurred in spring and females gave birth in August; litter size ranged from 8-50 and was correlated with size of female. These snakes were generalist predators, but fed mainly on anurans when small, adding mammals and other prey as they grew. Despite sexual size dimorphism, I found no difference in diet between adult males and females. Feeding frequency was low overall (22%). especially in gravid females. In summer, snakes were found mainly near cover on south-facing field edges or in marshes, but not in forests, and moved relatively little. However, movement distances increased in fall as snakes sought hibernating sites. Snakes hibernated for up to eight months, either individually or in pairs, in rodent burrows. This study also revealed the importance of radiotelemetry when studying movements of small, secretive animals, as there were significant differences between the results obtained through opportunistic captures versus telemetry: habitat descriptions from opportunistic captures therefore were biased, although they still captured some elements of microhabitat use by T. radix. The data from this study will be important for comparative studies of the ecology of garter snakes and for the management of this species on the human-altered landscape surrounding Miquelon Lake.

Habitat loss is the greatest contributor to the decline of species globally and thus understanding habitat use and the consequences fragmentation has on biodiversity is a fundamental step towards management and recovery. I conducted a radio-telemetry study to examine the spatial ecology and the effects of roads on Eastern Hognose Snakes (Heterodon platirhinos), a species at risk, in the Long Point Region of Ontario, Canada. I tested habitat selection at multiple spatial scales and I found that within the home range, snakes avoided agricultural land and selected open sand barrens, particularly for nesting. At the local scale, snakes avoided mature overstory trees and used younger patches of forest. Used locations had more woody debris, logs and low-vegetative coverage than locations selected at random. Eastern Hognose Snakes also showed avoidance of paved road crossings in their seasonal movements, but readily crossed unpaved roads. Management efforts for this species at risk should be placed on the conservation of sand barrens and on the construction of road underpasses to prevent genetic isolation of populations.

Thesis (Ph.D) -- McMaster University, 1999. / Includes bibliographical references [leaves 52-53]. Also available via World Wide Web.

Thesis (M.S.)--Missouri State University, 2008. / "December 2008." Includes bibliographical references (leaves 33-37). Also available online.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2010.

Made available in DSpace on 2014-10-09T12:50:45Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:58:07Z (GMT). No. of bitstreams: 1 00738.pdf: 1846124 bytes, checksum: 6d5b678407c4a946c4b55ef4b823c2f4 (MD5) / Tese (Doutoramento) / IEA/T / Instituto de Quimica, Universidade de Sao Paulo - IQ/USP

Orientador: Otavio Augusto Vuolo Marques / Banca: Marcio Roberto Martins / Banca: Selma Maria de Almeida Santos / Resumo: A atividade diária é um aspecto pouco estudado entre as serpentes neotropicais. Essa região abriga grande riqueza de espécies com ecologia extremamente diversificada. Nesse contexto, este estudo buscou fornecer informações sobre padrões de atividade de várias espécies de dipsadídeos, o grupo de serpente mais diversificado da região neotropical. Foram observados 49 indivíduos de nove espécies, pertencentes a diferentes linhagens: Atractus pantostictus, Sibynomorphus mikanii, Apostolepis assimilis, Erythrolamprus aesculapii, Liophis miliaris, Oxyrhopus guibei, Philodryas patagoniensis, Thamnodynastes strigatus e Tomodon dorsatus. Os espécimes foram mantidos em cativeiro e monitorados por dez dias consecutivos por sistema de circuito interno. As espécies apresentaram atividade predominantemente diurna, com exceção de A. pantostictus, S. mikanii e O. guibei. Apostolepis assimilis, L. miliaris e O. guibei apresentaram padrão de atividade bimodal, além de E. aesculapii, que individualmente apresentou dois picos de atividade diários, embora o horário de tais picos tenha diferido entre os indivíduos. A análise de similaridade sugere que o padrão de atividade seja conservado em alguns grupos (E. aesculapii e L. miliaris, da tribo Xenodontini, e os dipsadíneos A. pantostictus e S. mikanii). Disponibilidade de alimento no ambiente natural e fatores climáticos também parecem influenciar a atividade, além do estado reprodutivo e variação ontogenética / Abstract: Daily activity is an understudied aspect among Neotropical snakes. This region possesses high species richness, and bears an extremely diverse ecology. In this context, the present study sought to provide information on activity patterns of several species of dipsadids, which is the most diverse group of snakes at the neotropical region. A total of 49 individuals were observed, comprising nine species, from different lineages: Atractus pantostictus and Sibynomorphus mikanii, Apostolepis assimilis, Erythrolamprus aesculapii, and Liophis miliaris, Oxyrhopus guibei, Philodryas patagoniensis, and Tomodon dorsatus and Thamnodynastes strigatus. The specimens were housed in captivity for 10 consecutive days and monitored by CCTV system. Most species presented predominantly diurnal activity, except A. pantostictus, S. mikanii and O. guibei. Apostolepis assimilis, L. miliaris and O. guibei showed bimodal activity pattern, as specimens of E. aesculapii individually presented two daily peaks of activity, even so the time of such peaks has differed among the individuals. The analysis of similarity suggests that the pattern of activity is preserved in some groups (E. aesculapii and L. miliaris, tribe Xenodontini, and the Dipsadini A. pantostictus and S. mikanii). Availability of food in the natural environment and climatic factors also seem to influence activity, beyond the reproductive state, and ontogenetic variation / Mestre