Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

A population of the red-eared slider, Pseudemys scripta, in north central Texas was studied from 1975 to 1980. A life history energy budget was developed for a typical individual in the population and the population dynamics were estimated. A growth model relating growth rate to mean plastron length (PL) was developed from recapture data and used to 1) establish age classes and 2) age individuals. Growth rate was highly variable in both sexes. Females grew more rapidly than males and attained a larger maximum size (230 mm and 195 mm PL in females and males respectively). Females reached sexual maturity in their ninth year at a PL of 185-190 mm. Males matured in their sixth year at a PL of 90-100 mm. Females produced three clutches annually; clutch size ranged from 7 to 14 (X=10.3; N=20). Ova were enlarged in the early spring and ovulation began in late April and early May. Egg laying occurred from mid- May through June. Both egg size and clutch size increased with female body size. Lipid levels were variable within and among seasons. No annual lipid cycling pattern was evident in females. The proportion of assimilated energy devoted to reproduction, a measure of reproductive effort (RE), by females, was 13 per cent the first year of maturity (9 y) and increased to 20 per cent by their twentieth year. Lifetime RE was 16 per cent. Population density was estimated as 51 males and 50 females per ha in a 8.2-ha area of the lake. Young juveniles (less than 2 y) were not present although other subadult age classes were about equally represented. Fewer adults were encountered. An annual total production of 4000 eggs was estimated for the population present in 1977. A survival rate of from 2 to 18 per cent was estimated for the period between egg laying to 3 y. The large group of turtles younger than 10 y represented an expanding (Rₒ=1.8) lake population and the small group of older turtles were the remnants of a creek population present before Moss Lake was formed. The demographic environment, high juvenile mortality and low adult mortality, was suggested as a primary selective force shaping the life history characteristics of the Moss Lake scripta population.

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references. Also available on the World Wide Web.

My thesis deals with the study of the population of the Long-eared Owl (Asio otus) on a wintering place in Kladno - Kročehlavy. I mention numbers, arrivals and departures of the Long-eared Owl during the years 2013-2015 and the influence of abiotic factors on these results. I also deal with ringing and recoveries of these owls in the territory of Kladno. I verify the hypothesis of the influence of warm weather, rainfall and snow cover on the representation of small mammals and birds species in the diet of the Long-eared Owl in this thesis. In addition, my thesis is devoted to the analysis of methodology and species identification in food of the Long-eared Owl by skulls and pelvic bones. In my thesis, when determining the type of small mammals I deal with sexing of Common Vole (Microtus arvalis) and Wood Mouse (Apodemus sylvaticus) of the pelvic bones. According to bone fragments of the pelvis dominant representation of male Common Voles and Wood Mouse in a certain period of winter was investigated. On the basis of the obtained results I have compiled charts and tables and I have compared them with previous research from the years 2006 - 2012 in the same study area in Kladno - Kročehlavy. Keywords: Long-eared Owl (Asio otus), diet, weather, Common Vole (Microtus arvalis), Wood Mouse (Apodemus...

Thesis--Auburn University, 2008. / Abstract. Vita. Includes bibliographical references.

Thesis (Ph. D.)--Carleton University, 1997. / Also available in electronic format on the Internet.

Thesis (Ph. D.)--West Virginia University, 2010. / Title from document title page. Document formatted into pages; contains xiii, 181 p. : ill. (some col.), maps (some col.). Includes abstract. Includes bibliographical references.

In this study I examine the effect of seasonal resource limitation on the behaviour and population dynamics of white-eared kob, Kobus kob leucotis, in the Boma region of the southern Sudan. This population, numbering over 800,000, migrates seasonally between savannah grasslands in areas with low rainfall and ephemerally swamped grasslands in areas with high rainfall. The aims of the study were: (1) to examine whether kob migration tracks ephemeral distributions of food or water resources, (2) to test the hypothesis that the Boma kob population is limited by food availability, (3) to determine if calf production is cued to seasonal peaks in food abundance, and (4) to evaluate the effect of breeding synchrony on lekking behavior and male competition. Seasonal climatic changes produced pronounced changes in the distribution and abundance of both green forage and water supplies. Dry season migration primarily tracked limited supplies of water. Within the dry season range, kob aggregated at high densities (over 1,000 per km²) in low-lying meadows that supported grass re-growth when little green grass was available elsewhere in the ecosystem. However, southerly movements in the wet season were not explainable by the resource hypothesis, since both food and water were widely distributed during the wet season. I suggest that kob may move southward in order to avoid surface flooding during the wet season. Kob mortality during the dry seasons of 1982 and 1983 was considerably higher than estimated mortality during the wet season. Unusual rainfall during the dry season of 1982 provided a "natural experiment" to test the food limitation hypothesis. Adult mortality was significantly lower during the dry season of 1982 than during the more typical dry season of 1983. Calf mortality did not vary significantly between years. Adult mortality rates were related to dry season duration. Dry season mortality was related to sub-maintenance food intake and declining fat reserves. The age structure of the kob population in 1983 suggests that large-scale mortality (ca. 40%) occurred in the 1980 drought that immediately preceded this study. These findings support the food limitation hypothesis. Kob exhibited a 4 month period of calf production during the late wet season, when food availability was highest. As a consequence, females continued lactation through the dry season period of food scarcity. I suggest that kob reproductive phenology may result from an obligatory delay during which females restore their fat reserves prior to calving or selection pressures imposed by predation during the vulnerable post-partum period. Synchronous breeding in the Boma kob was related to increased rates of aggression between males and increased color dimorphism, in comparison to the asynchronous breeding Uganda kob, Kobus kob thomasi. Male aggression served not only to establish dominance relations between males on leks, but also disrupted the mating activities of neighboring males. Young adult males suffered higher age-specific mortality than females, possibly resulting from injuries incurred during strenuous fighting on leks. In order to analyze the age structure of the kob population, I devised a new method for estimating age-specific mortality rates that is free of the restrictive assumptions that underlie most conventional techniques. The proposed method has somewhat greater sampling variation, but is considerably more robust, than two current methods. Moreover, the proposed method permits calculation of age-specific mortality at frequent intervals during periods of population fluctuation and, under some circumstances, population numerical trends may be directly determined from age structure. / Science, Faculty of / Zoology, Department of / Graduate

Many reptiles, including the red-eared slider turtle (Trachemys scripta elegans), exhibit temperature-dependent sex determination (TSD). Temperature determines sex during a temperature sensitive period (TSP), when gonadal sex is labile to both temperature and hormones -- particularly estrogen. Estrogen production is a key step in ovarian differentiation for many vertebrates, including TSD reptiles, and temperaturebased differences in aromatase expression during the TSP may be a critical step in ovarian determination. Steroidogenic factor-1 (Sf1) is a key gene in vertebrate sex determination and regulates steroidogenic enzymes, including aromatase. The biological actions of steroid hormones are mediated by their receptors, defined here as the classic transcriptional regulation of target genes. To elucidate the mechanism of estrogen action estrogen during sex determination, I examined aromatase, Sf1, ER[alpha], ER[beta], and AR expression in slider turtle gonads before, during and after the TSP, as well as following sex reversal via temperature or steroid hormone manipulation by administering exogenous estradiol (E2) or aromatase inhibitor (AI) to the eggshell. Sf1 is expressed at higher levels during testis development and following maleproducing temperature shift and AI treatment, while aromatase increases during ovary determination and feminizing temperature shift and E2 treatment. My results do not lend support to a role for Sf1 in the regulation of aromatase expression during slider turtle sex determination, but do support a critical role for estrogen in ovarian development. Estrogen receptor [alpha] and AR levels spike at the female-producing temperature just as aromatase levels are increasing during ovarian sex determination, while ER[beta] remains constant and only increases late in ovarian differentiation -- well after estrogen levels have increased, indicating that ER[alpha] and ER[beta] may have distinct roles in slider turtle ovarian development. Estrogen receptor [alpha] and ER[beta] are expressed along developing sex cords in the absence of estrogen (AI treatment). When shifted to female-producing temperatures, embryos maintain medullary ER[alpha] and AR expression while ER[beta] is reduced. By contrast, ER[alpha] and ER[beta] redirect to the cortex in E2-created ovaries. Warmer temperature and E2 result in the same endpoint (ovarian development), but may entail different steroid signaling patterns between temperature- and estrogen-induced feminization. / text

Despite the hemispheric importance of Great Salt Lake (GSL) as a staging area for migratory birds, little is known about the resources that GSL provides to these birds, or how changes to the GSL ecosystem might impact the avian community. Three species of migratory waterbirds that stage at GSL are Wilson’s phalaropes (Phalaropus tricolor), red-necked phalaropes (Phalaropus lobatus), and eared grebes (Podiceps nigricollis). My objective for this research was to study the impacts of prey availability on the staging ecology of these species. In Chapter 2, I examined the use of GSL habitats by both species of phalaropes. In the high-salinity bays of GSL, phalaropes were most strongly associated with shallow water. In the low-salinity bay, there were no strong associations between phalarope presence and particular habitat characteristics. In Chapter 3, I analyzed the behaviors of phalaropes relative to prey densities. Phalaropes commonly foraged in Carrington Bay, which had the highest densities of brine fly (Ephydridae) adults, and in Farmington Bay, which had high densities of benthic macroinvertebrates. Foraging behavior differed between Wilson’s and red-necked phalaropes, with Wilson’s phalaropes spinning more often than red-necked phalaropes. In Chapter 4, I examined interannual and nightly variations in eared grebe fall migration departures in relation to prey availability and environmental conditions. Eared grebes began migration relatively early when lake temperatures were relatively warm, densities of brine shrimp (Artemia franciscana) adults were high, and densities of brine shrimp cysts were low. The likelihood that eared grebes would depart on a given night was positively associated with the average barometric pressure 12 hours prior to sunset. The resources provided by GSL support substantial proportions of the staging populations of phalaropes and eared grebes. Management efforts should seek to maintain the habitats and resources needed by phalaropes and eared grebes at GSL. Future large-scale diversions of freshwater may threaten GSL’s suitability as a staging area for these birds.