Density dependence is a common phenomenon in nature, and the intensity of density dependence is driven by competition over depletable resources. Habitat selection patterns are often density-dependent, and are driven by decreasing population mean fitness in a habitat as population density increases in that habitat. Yet not all resources are depletable, and non-depletable resources may sometimes be most important in dictating patterns of habitat selection. Ectotherms, for example, are defined by their dependence on environmental temperature to regulate body temperature, and temperature is often the most important resource for ectotherms. Is density dependence an important mechanism in ectotherms, especially when temperature is a limiting factor? In this thesis, I examine density dependence of fitness and habitat selection by ectotherms using red flour beetles and common gartersnakes. In chapter one and three, I test whether density-dependent habitat selection occurs when habitats differ in both temperature and food availability with red flour beetles and common gartersnakes, respectively. In chapter two, I modify the isodar model of habitat selection to account for the effect of temperature on ectotherms, derive predictions from the modified model, and test these predictions with controlled experiments with red flour beetles selecting between habitats that differ in food quantity and temperature. Finally, in chapter four, I examine the effect of density on metrics of fitness and habitat selection with common gartersnakes. Red flour beetles exhibited strong density dependence in both habitat selection and fitness at their optimal temperature, but density dependence weakened at lower temperatures. Common gartersnakes exhibited mostly density-independent habitat selection with a strong preference for warm field habitat over cool forest habitat, but exhibited some density dependence in habitat selection within field habitat. Overall, my thesis demonstrates that ectotherms have variable density-dependent responses, and that these responses are strongly modulated by temperature.

The Rocker b Ranch on the southern Rolling Plains has one of the last sizeable populations of pronghorn (Antilocapra americana) in Texas. To investigate habitat utilization on the ranch, pronghorn were fitted with GPS/VHF collars and were released into pastures surrounded by a variety of fences to determine how fence types affected habitat selection. Habitat parameters chosen for analysis were vegetation, elevation, slope, aspect, and distances to water, roads, and oil wells. Results showed that pronghorn on the ranch crossed modified fencing significantly less than other types of fencing. Pronghorn selected for all habitat parameters to various degrees, with the most important being vegetation type. Habitat selection could be attributed to correspondence of vegetation type with other parameters or spatial arrangements of physical features of the landscape. Seasonal differences in habitat utilization were evident, and animals tended to move shorter distances at night than they did during daylight hours.

abstract: Human land use and land cover change alter key features of the landscape that may favor habitat selection by some species. Lizards are especially sensitive to these alterations because they rely on their external environment for regulating their body temperature. However, because of their diverse life-history traits and strategies, some are able to respond well to disturbance by using their habitat in various ways. To understand how they use their habitat and how human modifications may impact their ability to do this, biologists must identify where they occur and the habitat characteristics on which they depend. Therefore, I used species occupancy modeling to determine (1) whether disturbance predicts the presence of two sympatric congeneric (species of the same genus) lizard species Sceloporus grammicus and S. torquatus, and (2) which habitat characteristics are essential for predicting their occupancy and detection. I focused my study in central Mexico, a region of prevalent land use and land cover change. Here, I conducted visual encounter and habitat surveys at 100 1-hectare sites during the spring of 2019. I measured vegetation and ground cover, average tree diameter, and abundance of refuges. I recorded air temperature, relative humidity, and elevation. I summarized sites as either undisturbed or disturbed, based on the presence of human development. I also summarized sites by ecosystem type, desert or forest, based on vegetation composition (i.e., desert-adapted vs. non-desert-adapted plants), evidence of remnant forest, air temperature, and relative humidity. I found that S. torquatus was more likely to be present in disturbed habitat, whereas S. grammicus was more likely to be present in areas with leaf litter, tree cover, and woody debris. S. torquatus was twice as likely to be detected in forests than deserts, and S. grammicus was more likely to be detected at sites with high elevation and high relative humidity, low temperature, and herbaceous and grass cover. These results emphasize the utility of species occupancy modeling for estimating detection and occupancy in dynamic landscapes. / Dissertation/Thesis / Masters Thesis Biology 2020

No description available.

The conversion of natural habitat to urban areas has lasting impacts on wildlife and biodiversity. Known effects to urban wildlife include direct mortality while crossing roads, reduced species diversity, and habitat fragmentation and degradation. Among wildlife occupying urban areas, turtle populations can be particularly impacted in anthropogenic landscapes. Snapping Turtle (<i>Chelydra serpentina</i>) is one of the most common species found within urban wetlands, but populations are beginning to show declines in northern portions of their geographic range. The preservation and management of this species is aided by knowledge related to its spatial ecology. I investigated <i>C. serpentina</i> home range, movement, habitat use, and habitat selection in a midwestern USA urban wetland complex during two active seasons (May-August 2019 and 2020) using radiotelemetry. Home range sizes and movement did not differ between sex or sample year except the mean movement of males decreased from 2019 to 2020. No differences in mean monthly movement were found between sexes but mean monthly movement did differ between month and year. Habitat use was skewed during the active season and did not differ between sex or year, but there were positive habitat associations between forested wetlands and modal centers of activity (MCA). Habitat selection was tested at two spatial scales by comparing random points to home ranges and turtle locations using Euclidean Distance Analysis. Turtles appeared to select home ranges from available habitat site-wide but did not select habitat within home ranges. Home range selection included semi-permanent open water, trail, road/barrier, permanent open water, scrub-shrub, ditches, shoreline, and vegetated ponds, while upland forest, field and agriculture habitat were avoided. Home ranges appear to be constrained by available habitat and movement differences between years may be due to anthropogenic change in water levels. The use of space seems to be more affected by wetland size and connectivity than proximity to barriers, which suggests that management practices that protect turtles from accessing roads and railways will benefit populations. Additionally, habitat selection and association indicate that ditches are utilized as corridors between wetland areas. When feasible, increasing the connectivity of large wetlands containing many habitat types should have positive impacts on the persistence of populations in human dominated landscapes.

Southern Africa contains 58% of the world’s savannah elephant population, yet 72% of their range occurs outside of protected areas. It is, therefore, important to develop management guidelines that satisfy the needs of both elephants and people while maintaining environmental heterogeneity and ecosystem processes. Managing elephants as a metapopulation may provide the solution. The goal of this thesis was then to use a habitat-based approach to identify landscape characteristics which could contribute to the functionality of a metapopulation for elephants. Using resource selection function models, I identified habitat suitability for elephants across southern Africa and used these models to evaluate whether current habitat configurations allow for the assumptions of connectivity and asynchronous population dynamics required by a metapopulation. I found that water, tree cover, slope, and human presence were important predictors of elephant habitat selection. Furthermore, functional responses in habitat selection were present across space and time for water and tree cover, showing the adaptability of this generalist species to resource heterogeneity. Using habitat selection along with circuit theory current flow maps, I then found a high likelihood of connectivity in the central portion of our study area (i.e. between the Chobe, Kafue, Luangwa, and Zambezi cluster). Main factors limiting connectivity were the high human density in the east and a lack of surface water in the west. These factors effectively isolate elephants in the Etosha cluster in Namibia and Niassa clusters in Mozambique from the central region. Models further identified two clusters where elephants might benefit from being managed as part of a conservation network, 1) northern Zambia and Malawi and 2) northern Mozambique. Incorporating information on elephant mortalities in northern Botswana into habitat selection estimations, I found that source habitats for elephants occurred within the central Okavango Delta region and sink habitats were associated with periphery of the study area where human use was highest. Eighty percent of elephant mortalities occurred within 25 km of people. The protected designation of an area had less influence on elephant mortality than did the locations of the area in relation to human development. To exacerbate human-elephant conflicts, people tended to settle in areas of high-quality elephant habitats, creating resource competition between elephants and people. Consequently, elephant mortality near humans increased as a function of habitat suitability, and elephants responded by using less suitable habitats. While humans occupied only 0.7% of the study area, mortality and behavioural effects impacted 43%. Based on the habitat factors examined here, elephants in southern Africa could be managed as a metapopulation if (1) connectivity is maintained and encouraged and (2) spatial heterogeneity in resources and risks serves to stabilize elephant demography. This habitat-based system of management could serve to alleviate unstable elephant populations in southern Africa and create more natural, self-sustaining regulatory mechanisms. / Thesis (PhD)--University of Pretoria, 2013. / Zoology and Entomology / unrestricted

Please read the abstract in the section 00front of this document. Copyright 2003, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Bell, K 2003, Habitat selection and population dynamics of selected herbivores on Sondela Nature Reserve, Limpopo, MSc dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-07112007-094017 / > / Dissertation (MSc (Wildlife Management))--University of Pretoria, 2003. / Animal and Wildlife Sciences / unrestricted

Wetland species are declining and efforts are being made to protect wetlands and their biodiversity. In Europe, these efforts could be hampered by the recent rise in the Western European Common crane (Grus grus) population. Increasing anecdotal evidence has raised concerns that this population increase has led to an increase in crane predation on other bird species’ eggs and chicks. This study aims to investigate, weather cranes are a potential threat to other bird species by predating on eggs and chicks, and ultimately biodiversity. Proxies, like habitat selection and time devoted to foraging in wetlands, were used to investigate risk of crane predation. Habitat selection and time devotion were studied using location data derived from 13 GPS-tagged Common cranes during May and June in 2017 to 2019. Observational foraging data was collected in the protected wetland Kvismaren, Sweden in June 2019, including adult non-breeding cranes only. During daytime, the three habitats with highest mean relative probability of presence within a 95% confidence interval for cranes are open wetland (0.87, CI: 0.86-0.89), followed by inland water (0.60, CI: 0.56-0.63) and arable land (0.55, CI: 0.52-0.59). The proportion of time cranes spend in wetlands is 0.39 in May and 0.28 in June. Cranes spend a proportional majority of their time (0.69) on foraging behavior compared to other activities they perform in wetlands. Since every encounter with a chick or egg can end in predation and cranes spend most of their time foraging in wetlands a population increase in cranes could have severe impact on bird species. Future research should take into account crane diet, which categories of cranes (e.g., non-breeding versus breeding) are most likely to predate on eggs and chicks and the negative impact on bird populations in relation to crane numbers to fill in the major research gap in this field. Lastly, future studies should evaluate how an increasing crane population also could impact the abundances of other wetland species such as, rodents, amphibians, fish and invertebrates.

Seagrass beds serve critical functions in coastal Florida ecosystems. The beds serve as nursery habitat for many juvenile reef fish species and provide protection for many types of benthic organisms found in Biscayne Bay. They help stabilize sediment that would otherwise increase turbidity around coral reefs, filter the water of contaminants, and help support an entire food web. Three species of seagrass were found at the study sites in northern Biscayne Bay: Thalassia testudinum, Halodule wrightii, and Syringodium filiforme. This study focused on understanding the organism habitat interaction by determining the species diversity, seasonal densities, and the correlation between population size and individual size for Penaeid shrimp, juvenile fish, and small adult fish at each site over a one year period. Habitat selectivity of various species was determined based on the habitat complexity derived from the various different seagrasses found in each of the beds. Animals predominantly favored H. wrightii habitat (Kruskal-Wallis H test: p< 0.0001) and this was likely the result of a decrease in predation risk due to the increased habitat complexity of the seagrass beds. Species diversity did not vary significantly over the course of a year (p= 0.7790), likely due to the lack of large abiotic disturbances (e.g. boating, hurricanes, and extreme salinity changes) to the seagrass beds. Densities of inhabitants changed significantly on a monthly basis, with the overall epifauna densities greatest at the end of the wet season (p< 0.01). The lack of correlation between individual size and overall population size likely indicated the majority of the species caught did not exhibit ontogenetic migration or live in the seagrass beds for the entirety of their life cycle.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20962号 / 理博第4414号 / 新制||理||1634(附属図書館) / 京都大学大学院理学研究科生物科学専攻 / (主査)教授 湯本 貴和, 教授 古市 剛史, 教授 友永 雅己 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM