Humans have tried to separate themselves from nature and to gain an understanding of what it means to be human, through studies of nature. Ideas of human nature have political and ideological implications, and are thus important in providing information about what it means to be human and what the relation to animals and the environment "ought" to be like. The ideology of human nature makes the world hence meaningful and points out what kind of actions regarding environmental issues are appropriate. The understanding of human nature and the human relationship with nature is culturally and historically produced. Humans' cultural conception thus also influences what kind of relationships are seen as desirable with particular animals. Different animals are seen as having different relations to humans, relations in which all animals are not seen as being equal. Some animals are defined edible, others are defined as companions.

<p>One goal of community ecology is to examine proximate and ultimate factors driving interactions between species. Part of this work addresses breeding bird aggregations, termed nesting associations. I evaluated costs and benefits of nesting along an association gradient in smaller black-billed magpies (Pica hudsonia) and larger American crows (Corvus brachyrhynchos) over two nesting seasons in Jackson, Wyoming. Specifically, I explored mechanisms of proximate protective benefits gained by magpies nesting nearer crows, along with foraging costs of associating with crow competitors. I also evaluated ultimate influences of association on nesting success for crows and magpies. Protection can operate under two non-exclusive proximate mechanisms, termed predator exclusion and information transfer. I found both mechanisms influenced nest protection for magpies. Crows performed more defensive behaviors at magpie nests nearer their own nests, and magpies responded to crow defensive signals. However, I did not find fitness benefits for magpies related to nesting nearer or farther from crows. I also explored the competitive foraging costs of heterospecific nesting associations by quantifying resource discovery behaviors and providing novel resource extraction problems to crows and magpies. Crows and magpies behaviors differed related to resource extraction problems such that magpies were less neophobic than crows. However, magpies paid a cost, measured as higher food losses to kleptoparasitism, for nesting nearer to crows. Further, crows came to dominate shared resources initially discovered by magpies. These results highlight potential foraging benefits to crows for associating with magpies. Despite these proximate benefits, crows also did not have greater nesting success when nesting nearer to magpies. Crows also experienced proximate costs to associating, measured as increased defensive behaviors and longer latencies to complete more complex resource extraction problems when nearer to magpies. I found that crow nesting success was related to success of associated conspecifics, but was not related to the number of defenders participating in nest defense. In my study system of crows and magpies, both species experienced benefits and costs to nesting nearer a heterospecific associate. However, costs and benefits may balance each other out such that there is no observable difference in fitness for either species based on association.

<p> The purpose of the current study was to analyze the reproductive ecology and sexual system in <i>Ambidexter symmetricus,</i> a nxocturnal seagrass shrimp and its parasite <i>Urobopyrus processae.</i> (Abstract shortened by UMI.)</p>

The foraging behavior of six species of insectivorous foliage-gleaning birds was studied in three different communities in Arizona to examine the role of resource partitioning in coexistence. I recorded data during winter and spring, the harshest seasons. Two to four species coexisted in each community. I recorded plant species, plant life-form, foraging height, plant portion, perch size, capture size, capture technique, and foraging rate. Foraging behavior was compared to the plant distribution profile, interspecifically among sympatric guild members within a season, intraspecifically between seasons, and intraspecifically between communities within a season. Species differed most in plant species selected, foraging height, and capture technique, and varied the least in plant portion, perch site, and capture site. All species overlapped in most behaviors, but differed from other guild members in at least two foraging variables. Permanent residents showed the greatest differences. These findings are consistent with niche complementarity and the idea that competition has led to partitioning of the resources. However, other hypotheses cannot be ruled out.

I used age structure to examine the role of fire disturbance and climate on the population dynamics of the subalpine forest in the southern Sierra Nevada. I cored trees on ten 0.1 ha plots (3300-3400 m elevation) that varied in species composition, from single-species foxtail pine (Pinus balfouriana) or lodgepole pine (Pinus contorta, var. murrayana), to mixed-species stands of both pines. Crossdating was used to produce accurate dates of tree recruitment and fire events. Age structure varied by plot species composition: lodgepole pine recruitment pattern is pulsed, sometimes forming single-cohort patches in response to fire; foxtail pine plots have a more steady pattern of recruitment; mixed-species plots show an intermediate recruitment pattern. Fire may maintain a species composition mosaic in the subalpine forest. Foxtail pine regeneration may increase in areas opened by fire, although not immediately following fire. Low-intensity fire may spread over areas larger than previously reported under certain conditions in the subalpine zone. In addition, unusually frequent, extreme, and/or extended periods of drought may severely limit subalpine tree regeneration. Growing season frost events and grazing before 1900 may also have affected trees establishing in the subalpine zone.

This study compared the effects of sampling metrics (basal area, density) on community structure analyses. Additionally, an oak woodland classification system was developed from the basal area data for the southwestern United States. Minimum-variance clustering was used to define communities within the oak woodlands. The communities defined by basal area data were more evenly distributed, showed more distinct communities, and were more homogeneous than the density-based communities. Thirteen communities were identified in the classification of oak woodlands, with mean basal area varying by an order of magnitude. Elevation had a major influence on the distribution of the communities.

I predicted the likely effects of fire on the abundance of grassland birds by determining which vegetal features influenced the distribution and abundance of grassland birds at the Buenos Aires National Wildlife Refuge, Arizona. Abundance of pyrrhuloxia (Cardinalis sinuatus) (r² = 0.363), Lucy's warbler (Vermivora luciae) (r² = 0.348), and total abundance of birds (r² = 0.358) was positively correlated with increasing density of mesquite (Prosopis velutina), whereas abundance of cactus wren (Campylorhynchus brunneicappillus) (r² = 0.452) was negatively correlated with increasing mesquite density. Abundance of loggerhead shrikes (Lanius ludovicianus) (r² = 0.693) was positively correlated with increasing environmental patchiness. Fire is likely to reduce the density of mesquite, thus I predict that those species positively correlated with mesquite density will decline following fire whereas species negatively correlated with mesquite density will benefit.

<p> Since European settlement, clearing for agriculture, changes in hydrology, and urbanization have reduced the coverage of bottomland forest (BLF) in the Upper Mississippi Valley (UMV) by 46%. Recently, emphasis has been placed on restoring BLF, which provides vital ecosystem services (e.g., enhanced water quality, nutrient cycling, and wildlife habitat). Beginning in 1998, the US Army Corps of Engineers has restored BLF on many sites in the UMV, ranging in area from less than 1 ha to 120 ha. Root production method (RPM^&reg;) seedlings of three species of bottomland oaks and pecan have been planted to rapidly establish large-seeded species that are not regenerating under current conditions, with the expectation that light-seeded species (e.g., silver maple, green ash, eastern cottonwood, elm) will colonize passively. A chronosequence of nine restoration sites, ranging in age from 1 to 23 yr since planting, and two mature BLF reference sites was used to assess restoration success. Five 0.1-ha circular plots were randomly located at each site. Planted trees and natural recruits with a diameter at breast height (DBH) greater than or equal to 2.5 cm were identified, tagged, and their basal diameter, DBH, and height were measured. Density of shrubs was assessed in belt transects with a total area of 100 m² and cover of herbaceous species was estimated in twenty 0.5 m2 quadrats. Tree variables by species (mean basal diameter, mean height, density, and dominance) and community variables (richness and Simpson diversity of each stratum, total tree dominance, total shrub density, total herbaceous cover and the percent exotic herbaceous species cover) were calculated at the plot scale. Trajectories of change in tree size and community structure were examined using generalized linear modeling, relative to their values in reference sites. Tree height and diameter increased with time since restoration for all species. <i> Quercus palustris, Q. macrocarpa,</i> and <i>Q. bicolor</i> are all on track to achieve dimensions typical of mature BLF within 27 to 37 yr since planting. However, the dominance models for these trees show general declines which may indicate decreasing survivorship among planted trees and no recruitment of new seedlings. Pecan has suffered high mortality and without replanting it will be underrepresented in the restored forest. Tree dominance, richness, and diversity peaked and then decreased. Both total shrub density and total herbaceous cover showed no trend with time, although diversity of both shrubs and herbaceous vegetation slightly increased. Comparison with reference sites suggest that the shrub density, although there is no trend with time, is still in line with reference plot values. Exotic cover peaked between 10 to 15 years and began to decline to levels similar to reference plots. Overall, the results indicate some restoration success (tree growth rates, shrub diversity, herbaceous richness and diversity, and declines in exotic species cover) but suggest that replanting will be necessary in most sites to overcome mortality due to prolonged flooding and other factors (e.g. white-tailed deer browsing, inhibition of tree recruits by dense grass cover). Accurate mortality data for planted tree species is necessary to evaluate and improve the success of future USACE restorations. Ideally, a subset of trees should be tagged immediately after planting and these trees should be monitored at regular intervals. Frequently updated records will allow the USACE to make site-to-site management adjustments.</p>

Patterns in the use of gastropod shells by hermit crabs were examined for a complex of hermit crabs inhabiting the Alligator Harbor region of Florida. To assess field use patterns, two sampling techniques, a straight-line transect method and a predation site method, were used. The transect method yielded large animals in relatively undamaged shells of a few gastropod genera, and the results were influenced by habitat. The predation site method yielded a wide size range of individuals in damaged shells of many gastropod species. / Simulated gastropod predation sites attract a variety of hermit crabs. Experiments with simulated predation sites revealed that chemical cues are necessary for location of newly liberated shells. Attraction to a simulated predation site is species specific for hermit crabs and is directly related to the genus of gastropod flesh at the site. In addition, there is a significant positive correlation between amount of flesh at a site and size of crab attracted. These results are discussed in terms of spatial and temporal patterns of hermit crab shell acquisition. / Regardless of the collection method, however, shell use patterns have been evaluated by using empirically derived measures of shell adequacy. Shell adequacy or shell fit has been inferred by using two indices; the shell adequacy index and the utilization efficiency index. Both indices contain statistical biases which render the interpretation of the indices ambiguous. I conclude by describing field and laboratory experiments which demonstrate that determination of shell adequacy is a complex problem which cannot be assessed by simple methods. / Source: Dissertation Abstracts International, Volume: 43-06, Section: B, page: 1721. / Thesis (Ph.D.)--The Florida State University, 1982.

Results of a two year study of colonization of two introduced trees, Quercus acutissima and Castanea crenata, by leaf-mining insects are described in Chapter I. More species of miners completed larval development on Q. acutissima, which has more local native congeners than does C. crenata. However, all miners found on Q. acutissima (subgenus Lepidobalanus) are found on native red oaks (subgenus Erythrobalanus). Leaf-miner density and survivorship were higher on C. crenata than on Q. acutissima, although most of these differences are attributable to two species. Parasitism rates for these species and all miners analyzed together were lower on C. crenata than on Q. acutissima. For some species, reduced parasitism on C. crenata was partially offset by increased predation. Successful colonization of C. crenata by at least one dominant miner may be related to the higher nitrogen content of this host. / In Chapter II, I tested the hypothesis that a significant amount of larval leaf-miner mortality on water oak, Quercus nigra, results from nutritional inadequacy of the host tree. I altered phytochemistry of water oaks with urea- and ammonium-nitrate-fertilization and drought stress. Survivorship of all leaf miners together, and of several dominant species analyzed separately, increased on fertilized trees. Generally, miners responded more to urea-fertilization of trees than to ammonium-nitrate-fertilization. Higher survivorship on fertilized trees was associated with reduced predation. Enhanced larval leaf-miner survivorship correlated with increased densities in 1981, but not in 1980. Leaf-miner survivorship and density increased on drought-stressed trees in both years. / Larvae of two bivoltine species of leaf miners feed only on young, second-flush leaves of their host trees in north Florida. In Chapter III, I show that first-generation larval densities of these species on 30 water oaks is positively correlated with amount of secondary leaf production in 1980 and 1981. During this study, five trees abscised their leaves and reflushed new ones at atypical times of the growing season. Densities of the phenologically specialized miners increased dramatically on these trees only when refoliation coincided with emergence of ovipositing adults. / Source: Dissertation Abstracts International, Volume: 43-06, Section: B, page: 1719. / Thesis (Ph.D.)--The Florida State University, 1982.