<p> The main goal of this study was to determine the thermal ecology of the small tree lizard <i>Urosaurus ornatus</i> in a Chihuahuan Desert landscape. The study site was located at Indio Mountains Research Station (IMRS), Hudspeth County, Texas. We obtained body temperature (Tb) data on 385 lizards collected from April 2007 to June 2014 during the active period using a cloacal thermometer. Additionally, we recorded air temperature (Ta) and substrate temperature (Ts) of lizard microhabitats at the time of capture, and the operative temperature of lizard models left in the sun and shade from May to September 2014. My results showed that the mean Tb for all adult lizards was 33.6 &plusmn; 2.8&deg;C, with a range of 24.0 to 40.2&deg;C. This average Tb was similar but lower than those found in other populations in Southwestern United States. The results indicated that <i>U. ornatus </i> at IMRS displays mostly a thigmothermic behavior. Thermoregulatory behavior of these individuals showed that <i>U. ornatus</i> is a thermoconformer on IMRS. There was no statistical difference in mean Tb between males and females or between non-gravid females. However, there was a significant difference between lizards found in the sun and lizards found in the shade. It is expected that rising global temperatures will influence this region and therefore will have an impact on the population of <i>U. ornatus </i> too; possibly affecting aspects such as time for feeding, reproducing, and of course thermoregulating. Thus, it is important for us to understand the thermoregulatory needs of ectothermic organisms as they are dependent on the direct environmental temperatures for survival, especially since many recognize that rapid global warming has already been activated by human misuse of natural resources.</p>

<p> Seabirds are ecosystem engineers with two major impacts on island ecosystems: they bring large quantities of marine nutrients to the terrestrial environment in the form of guano, carcasses, feathers, eggs, and spilled food, and they disturb the soil surface. Burrowing seabirds can denude the soil surface of all seedlings and leaf litter, plowing them under and loosening the soil. However, seabirds are colonial, and burrows are not even spaced over the surface of an island, producing spatial variability within a single island that might reveal how seabird activities control island ecosystem function. </p><p> In this dissertation I review seabird island ecology in general, focusing on how introduced predators have reduced seabird populations, interrupting seabird activities and altering island ecology. I then describe three studies designed to quantify the effects of seabirds on soil and plant properties within individual islands and compare these patterns across islands varying in seabird density, especially where seabirds have declined because of invasive rats (<i>Rattus</i> spp.). </p><p> I used geostatistics to quantify the spatial variance in seabird burrows and various soil and plant properties (including soil and leaf N) within six islands of low, intermediate, and high burrow density. I found that burrow density was not a good predictor at within-island scales, and though the variance of some soil properties (pH, soil &delta;¹⁵N, and soil compaction) peaked on intermediate islands as expected, variables reflecting the soil N cycle (net ammonification and net nitrification potential, NH₄⁺ and NO₃^-) continued to increase in variability on very high-density seabird islands. Ecosystem properties clearly responded to seabirds at different spatial scales, possibly because seabirds deposit guano at different spatial scales than they dig. </p><p> Using data within three rat-invaded and three rat-free islands, I used structural equation models to examine seabird influences on N cycling. I found some mechanisms that were constant across islands, such seabird-related decreases in soil water and pH, but other mechanisms differed between invaded and uninvaded islands, suggesting that rats manifest an alternative state for island N cycles, which may or may not be reversible. </p><p> Finally, I investigated whether plants can use ammonia (NH₃ gas) volatilized from seabird islands, measuring NH₃ concentrations across 10 islands and within a single island where I also experimentally manipulated plant N demand. Both rat-invaded and rat-free islands produced meaningful concentrations of NH₃ gas, and multiple plant species including <i> Melicytus ramiflorus</i> and <i>Coprosma macrocarpa</i> used it for up to 20% and 30% (respectively) of their total leaf N. Plant N demand modified NH₃ uptake, suggesting that plants located not on seabird colonies, but downwind, may benefit the most from this gaseous N source. </p><p> I suggest that future studies attempt to estimate thresholds of burrow density at which seabird-controlled ecosystem properties can recover from rat invasion.</p>

<p>White croaker (<i>Genyonemus lineatus</i> family: Sciaenidae) are a benthic foraging fish associated with soft sediment and wastewater outfalls in Southern California. While they are used as a sentinel species due to their high organochlorine contaminant loads, little is known of their movements in relation to contaminated habitats. Acoustic telemetry was used to characterize the site fidelity, area use, and dispersal of 97 white croaker on the Palos Verdes Shelf, California. White croaker demonstrated generally low, but highly variable residency and recurrence to the Palos Verdes Shelf and exhibit nomadic movement patterns. Although the entire monitored shelf was visited by white croaker, habitats in proximity to wastewater outfalls and between 25&ndash;35 m depth were preferentially used. Approximately half of white croaker migrated into Los Angeles Harbor. These data are vital for understanding organochlorine contaminant exposure for planning future remediation and monitoring. </p>

<p> Between August 2010 and September 2012, acoustic telemetry was used to monitor movements of 31 Yellow Snapper and 25 Leopard Grouper at Los Islotes reserve, a small rocky reef and reported spawning site for both species in the southwest Gulf of California. Overall, both species exhibited site fidelity to Los Islotes (grouper: present 64 f 30% of days; snapper: 49 &plusmn; 30%). Both species frequented rock and wall habitats; though snapper showed greater site attachment to specific portions of the reserve, grouper exhibited greater site fidelity to the entire reserve. Approximately 30% of snapper showed indications of spawning-related migrations elsewhere in the Gulf, though no clear seasonal pattern of migration was found for grouper. The limited degree of spawning-related emigration and moderate-high levels of site fidelity indicate that if properly placed, small reserves such as Los Islotes may yet adequately protect small, resident populations of snapper and grouper.</p>

<p> The widespread introduction of round goby (<i>Neogobius melanostomus </i>) throughout the Great Lakes basin has raised concerns regarding increased risk of egg predation on nesting fish species. Five-minute observation trials were conducted to determine the identity and number of nest predators on rock bass (<i>Ambloplites rupestris</i>), pumpkinseed (<i>Lepomis gibbosus</i>), and smallmouth bass (<i>Micropterus dolomieu</i>) nests following removal of the guarding male. Rock bass had a greater proportion of nests invaded (85.4 %) and average number of predators per nest (9.32, SE 1.7) than pumpkinseed (45.0%, 1.83, SE 0.64) in 2011. Similarly, rock bass had a greater proportion of nests invaded (52.5%) and average number of predators per nest (5.3, SE 1.7) than pumpkinseed (35.0%, 2.3, SE 1.1) and smallmouth bass (37.5%, 2.7, SE 0.94) in 2012. Principal components analysis and canonical correspondence analysis of habitat variables indicates some species are more vulnerable to nest predation due to preferred spawning habitat. </p>

<p> Amphidromous species migrate between fresh water and the sea for larval development. Many caridean shrimps, especially <i>Macrobrachium </i> spp., are amphidromous, and some populations are found far-upstream within continental river systems. This project tested the hypothesis that populations of <i>Macrobrachium ohione</i> from the Atchafalaya and Mississippi Rivers are amphidromous. </p><p> In the laboratory, I tested the hypothesis that upstream populations of <i>M. ohione</i> have freshwater larval development. My results indicated that saline habitats are essential for <i>M. ohione</i> development, and larval mortality increased after 3-4 days of freshwater drifting. This provides indirect evidence that upstream populations have extended marine larval development. </p><p> Due to their limited freshwater survival, <i>M. ohione</i> must deliver larvae to the sea. Spatial-temporal analysis in the Atchafalaya and Mississippi Rivers reported an influx of reproductive-sized shrimps and females with near-hatching broods into coastal sites. This suggests that females are migrating downstream to hatch larvae in downstream habitats. </p><p> Stable isotope analysis indicated that the upstream juvenile migration originates from saline habitats. Video surveillance revealed that juveniles migrate throughout the night at an average speed of &sim; 0.56 km hr^-1, and swimming speeds were related to the water velocity they swam against. From these results, I estimated that juveniles are capable of migrating to far-upstream habitats within their life span (1-2 years). </p><p> Lastly, I investigated how dams affect the juvenile migration, and tested juvenile migrant climbing abilities. This study reported greater densities of juveniles downstream of dams than upstream of dams, indicating the dams impede the juvenile migration downstream of Old River Control. Shrimp climbing studies revealed that at various inclinations and water velocities, ~ 52% of the shrimps were climbing the shrimp ramp and ~ 12% completed the climb. These results demonstrated juveniles can climb bypass structures with detectable water flows. </p><p> My findings suggest that <i>M. ohione</i> populations within the Mississippi River System are amphidromous, because they require marine larval development and long-distance migrations are conducted to and from the sea. This study may serve as a general model for migrations of amphidromous shrimps in comparable large rivers, and potentially contribute to freshwater shrimp conservation.</p>

<p> The Nushagak River, Bristol Bay, Alaska, supports one of the largest wild sockeye salmon (<i>Oncorhynchus nerka</i>) runs in the state and also supports overlapping runs of chum (<i>O. keta</i>) and Chinook (<i>O. tshawytscha</i>) salmon. Each summer, the Alaska Department of Fish and Game deploys dual-frequency identification sonar (DIDSON) on the river to enumerate salmon to monitor escapement goals; however, salmon behavior and spawning run characteristics at the site are not incorporated into management. We investigated the feasibility of using Nushagak River DIDSON data from 2008-2011 to identify trends in run timing and compare passage rates to local environmental conditions, including tide, light intensity, and water temperature. We also used spatial analysis to examine aggregation behavior of salmon at the DIDSON site at multiple distance scales. Between all four years, run timing only varied within a few days (&lt; 1 week), regardless of water temperature. In 2009 and 2011, more salmon passed upriver during slack and ebb tides than during flood tide. Salmon were never completely spatially random, and distance scales of aggregation behavior were influenced by run period and photo period. When examining all factors together, the interaction between salmon density and run period affected distance at maximum aggregation. This research used hydroacoustics for a multi-level approach to investigating spatiotemporal patterns of Pacific salmon relative to environmental factors during their spawning migration and may help refine in-season monitoring and management of the fishery.</p>

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 68-11, Section: A, page: 4757. Adviser: Paul A. Garber. Includes bibliographical references (leaves 317-355) Available on microfilm from Pro Quest Information and Learning.

<p> While range-wide population declines have prompted extensive research on greater sage-grouse (<i>Centrocercus urophasianus</i>), basic information about southern periphery populations, such as the Bald Hills population in southern Utah, has not been documented. The objective of this research was to determine habitat preferences and space use patterns of the Bald Hills sage-grouse population which occurs in an area of high potential for renewable energy development. I tracked 66 birds via VHF telemetry in 2011 and 2012 and surveyed vegetation plots throughout the study area. I found that the population was primarily one-stage migratory with seasonal distributions that did not correspond well with previously developed suitable habitat maps (based on local biologist knowledge and lek data) for all seasons; I also found that mean home range sizes ranged from 82 km² to 157 km².</p><p> Nesting hens did not select for any measured vegetation characteristics within the study area, while brood-rearing hens selected for high forb cover. Birds at summer sites (non-reproductive bird locations during the summer season) selected for greater grass and forb cover and lower shrub cover compared with random sites. Overall, Bald Hills sage-grouse used areas with greater shrub canopy cover and lower grass and forb cover than recommended in habitat guidelines. </p><p> Ten predictor variables were used to model suitable seasonal habitat using Maximum Entropy (maxent). All models were created for the Bald Hills population and projected to the Bureau of Land Management Cedar City Field Office management area and produced excellent model fit (AUC > 0.900). The Bald Hills population had similar nesting and winter habitat preferences as other populations but different brood-rearing and summer habitat preferences. I found local management techniques to be an important driver of seasonal habitat selection; birds selected for areas that had undergone habitat treatments (such as broadcast burn and crushing) within the previous 10 years. My results indicated the Bald Hills periphery population occupies marginal habitat and has adapted unique seasonal habitat preferences. Managers of isolated, fringe, and low-density populations should develop locally specific management guidelines to address the unique adaptations and ensure the persistence of these populations. </p>

<p> Snowshoe hare (<i>Lepus americanus</i>) survival depends on the interaction of habitat characteristics with numerous biological and environmental variables. In boreal regions where considerable habitat heterogeneity exists, hares balance food availability with predation risk by moving among habitats seasonally, but it is largely unknown how often they move at shorter time scales. I investigated the seasonal effects of habitat, weather, and individual hare characteristics on survival and movement in two common but fundamentally different boreal habitats. Survival was highest in summer, for hares with higher body condition, and in black spruce rather than early successional forest. Hares moved among core use areas in different habitats twice per day on average, using more open areas at night when they were presumably feeding on preferred browse. Movement rates were lowest in mid-afternoon when hares appeared to be resting under dense cover. Behavior of individuals varied greatly with some hares repeatedly moving up to 1 km between defined patches in less than 5 hours and others remaining roughly within a 1 ha area. These findings illustrate the complexity of snowshoe hare ecology in an area where habitat variation promotes daily movement of hares among radically different habitats over a few hundred meters.</p>