Being En Route

Through an ethnography of unauthorized migration from El Salvador to the United States, I explore "clandestinity" as a hidden, yet known, dimension of social reality. Unauthorized migrants who are en route to the United States have to make themselves absent from the spaces they occupy. When they become clandestine, such migrants embody illegality; in some cases, they literally "go underground" should they die and be buried en route. Because their presence is prohibited, unauthorized migrants do not fully arrive even when they reach their destinations. There are parallels between the ways that migrants are present in yet absent from nations, and the ways that ethnographers are present in yet absent from the field. This ethnography of migrants en route therefore suggests how anthropological knowledge practices also produce realities that are hidden, yet known.     

FOSSIL DIAGENESIS IN THE BURGESS SHALE

Abstract:  Current models for the exceptional preservation of Burgess Shale fossils have focused on either the HF-extractable carbonaceous compressions or the mineral films identified by elemental mapping. BSEM, EDX and microprobe analysis of two-dimensionally preserved Marpolia , Wiwaxia and Burgessia identifies the presence of both carbonaceous and aluminosilicate films for most features, irrespective of original lability. In the light of the deep burial and greenschist facies metamorphism documented for the Burgess Shale, the aluminosilicate films are identified as products of late-stage volatilization and coincident mineralization of pre-existing compression fossils, whereas the three-dimensionally preserved gut-caecal system of Burgessia is interpreted as an aluminosilicate replacement of a pre-existing carbonate phase. The case for late diagenetic emplacement of aluminosilicate minerals is supported by the extensive aluminosilicification of trilobite shell and (originally) calcareous veinlets in the Burgess Shale, as well as documentation of other secondarily aluminosilicified compression fossils. By distinguishing late diagenetic alteration from the early diagenetic processes responsible for exceptional preservation, it is possible to reconcile the range of preservational modes currently expressed in the Burgess Shale.     

Microhabitat Characteristics of Preble's Meadow Jumping Mouse High-Use Areas

ABSTRACT Riparian wetlands are complex ecosystems containing species diversity that may easily be affected by anthropogenic disturbances. Preble's meadow jumping mouse (Zapus hudsonius preblei) is a federally threatened subspecies dependent upon riparian wetlands along the Front Range of Colorado and southeastern Wyoming, USA. Although habitat improvements for Preble's meadow jumping mouse are designed at multiple spatial scales, most knowledge about its habitat requirements has been described at a landscape scale. Our objective was to improve our understanding of Preble's meadow jumping mouse microhabitat characteristics within high-use areas (hotspots), which are essential for the development of effective management and conservation strategies. We evaluated Preble's meadow jumping mouse habitat by describing areas of high use and no use as determined from monitoring radiocollared individuals. A comparison of microhabitat characteristics from random samples of high-use and no-use areas indicated that mice use areas closer to the center of the creek bed and positively associated with shrub, grass, and woody debris cover. Distance to center of the creek bed, and percent of shrub and grass cover also had the greatest relative importance of habitat variables modeled when describing high-use areas. High-use areas contained 3 times more grass cover than forb cover, and overall had a greater proportion of wetland shrub and grass cover. However, proportion of cover type (shrub or grass) did not vary greatly between high-use and no-use areas. Our results suggest that management and conservation efforts should continue to focus on establishment of native wetland vegetation near streams and creeks. For example, vegetation should include shrubs such as willow (Salix spp.), narrowleaf cottonwood (Populus angustifolia), alder (Alnus incana), grasses such as fescue (Fescue spp.), sedges (Carex spp.), and rush (Juncus spp).     

Survival of Breeding Pacific Common Eiders on the Yukon-Kuskokwim Delta,Alaska

ABSTRACT Populations of Pacific common eiders (Somateria mollissima v-nigrum) breeding in Alaska, USA, have declined markedly over the past 40 years. We studied survival of adult female Pacific common eiders using capture—recapture of nesting hens at 3 sites on the Yukon-Kuskokwim Delta (YKD), Alaska from 1994 to 2004. We used data consisting of 268 recapture events from 361 uniquely marked individuals to investigate temporal, geographic, and environmental variation in adult female survival. Our results suggest apparent annual survival of adult eiders from the YKD was high (0.892, SE = 0.022) and spatially and temporally invariant (σ² = 0.005), a pattern consistent with other long-lived marine birds. Moreover, our results suggest adult survival may be functionally fixed for Pacific common eiders, and at the present, adult survival may be relatively unresponsive to environmental or management perturbations. Our data did not support hypothesized variation in survival relative to mortality factors such as predation on breeding grounds, physiologic costs of reproduction, and wintering conditions. Although changes in adult survival likely have a large potential effect on prospective population growth, our results suggest viable management actions aimed at increasing survival may be extremely limited.     

Urban Maternity-Roost Selection by Big Brown Bats in Colorado

Abstract: Despite prevalent use of anthropogenic structures by bats and the associated implications for public health, management, and bat conservation, very little quantitative information exists about urban roost characteristics and their selection by bats. During the summers of 2001 to 2004 we conducted fieldwork in Fort Collins, Colorado, USA, situated on the northern end of Colorado's Front Range, to address questions of roost selection by the big brown bat (Eptesicus fuscus). The city has experienced its greatest growth in the past half century, with its population increasing by 30% in the last decade. Similar growth in new buildings has occurred, with the number of new housing permits issued annually doubling in the past decade. We located 142 roosts using radiotelemetry or by citizen calls in response to a newspaper article and flyers. To determine characteristics of roost selectivity by bats, we compared variables for known maternity roosts and randomly selected buildings at microhabitat and landscape scales using logistic regression; we used an information theoretic approach to determine which variables were most important. We considered 44 and 100 buildings in the microhabitat and landscape scale analyses, respectively. At the microhabitat scale maternity roosts had exit points with larger areas that were higher from the ground and had warmer average temperatures than randomly selected buildings. At the landscape scale distances to similarly categorized roosts were smaller, and urbanization variables such as lower building density, higher street density, and lower traffic count density were most important. Results for variables important to urban-roosting big brown bats were often analogous to studies that characterized maternity roosts found in tree snags and rock crevices. In addition, changes in the landscape, not only in the form of anthropogenic structures but also in water availability and vegetation structure such as riparian forests, may have led to population increases and range expansions of the big brown bat. Because big brown bats appear to selectively choose specific combinations of characteristics found at maternity roosts, not all available structures can be considered suitable and exclusion from established maternity roosts may negatively impact bat populations.     

Numerical and Demographic Responses of Pumas to Changes in Prey Abundance: Testing Current Predictions

ABSTRACT Information on factors affecting population size of pumas (Puma concolor) can be important because their principal prey over most of the western United States are valued big game species (e.g., mule deer [Odocoileus hemionus], elk [Cervus elaphus], and bighorn sheep [Ovis canadensis]). Based on the hypothesis that puma numbers are limited by their food supply, puma populations should track changes in prey abundance by growing exponentially with increases in prey and by declining with a lag response when prey decreases. Additional predictions proposed by researchers are that body mass of pumas, female productivity, kitten survival, and adult survival should decrease after a prey decline. We used a 15-year database from a hunted population of pumas in southern Idaho and northwestern Utah to test these predictions. During the 15-year time span of the database, a major decline in mule deer abundance occurred. Estimates of puma numbers and demographic characteristics came from intensive capture and radiocollaring efforts. We calculated kitten and adult survival with MICROMORT software. We found that adult puma numbers increased exponentially at r = 0.07 during a period of increasing mule deer numbers. Four years after the mule deer abundance declined, puma numbers decreased at a rate of r = −0.06. Body mass of female pumas was lower after the decline in puma numbers (42.6 ± SE = 1.2 kg, n = 40 vs. 40.1 ± 0.64 kg, n = 34, t = 5.06, P = 0.045). Kitten survival was less after the decline in deer abundance (0.573 ± 0.016, n = 30 vs. 0.856 ± 0.015, n = 25, Z = 2.40, P < 0.01). Survival of resident females was significantly less after the decline in puma numbers (0.783 ± 0.03 vs. 0.929 ± 0.019, U = 55.0, P = 0.009). Female productivity did not differ before or after the decline in deer abundance. Our results supported the majority of the predictions concerning the impact of changing deer abundance, which supported the hypothesis that the abundance of mule deer limited our population of pumas.     

Rapid Homogenization of Multiple Sources: Genetic Structure of a Recolonizing Population of Fishers

Abstract: Fishers (Martes pennanti) were extirpated from much of southern Ontario, Canada, prior to the 1950s. We hypothesised that the recent recolonization of this area originated from an expansion of the population in Algonquin Provincial Park, which historically served as a refuge for fishers. To test this hypothesis, we created a sampling lattice to encompass Algonquin and the surrounding area, and we collected contemporaneous DNA samples. We sampled fishers from each of 35 sites and genotyped them at 16 microsatellite loci. Using a Bayesian assignment approach, with no a priori geographic information, we inferred 5 discrete genetic populations and used genetic population assignment as a means to cluster sites together. We concluded that the Algonquin Park fisher population has not been a substantial source for recolonization and expansion, which has instead occurred from a number of remnant populations within Ontario, Quebec, and most recently from the Adirondacks in New York, USA. The genetic structure among sampling sites across the entire area revealed a pattern of isolation-by-distance (IBD). However, an examination of the distribution of genetic structure (F_ST/1^- F_ST) at different distances showed higher rates of gene flow than predicted under a strict IBD model at small distances (40 km) within clusters and at larger distances up to 100 km among clusters. This pattern of genetic structure suggests increased migration and gene flow among expanding reproductive fronts.     

Traffic Volume Alters Elk Distribution and Highway Crossings in Arizona

ABSTRACT We used 38,709 fixes collected from December 2003 through June 2006 from 44 elk (Cervus elaphus) fitted with Global Positioning System collars and hourly traffic data recorded along 27 km of highway in central Arizona, USA, to determine how traffic volume affected elk distribution and highway crossings. The probability of elk occurring near the highway decreased with increasing traffic volume, indicating that elk used habitat near the highway primarily when traffic volumes were low (<100 vehicles/hr). We used multiple logistic regression followed by model selection using Akaike's Information Criterion to identify factors influencing probability of elk crossings. We found that increasing traffic rates reduced the overall probability of highway crossing, but this effect depended on both season and the proximity of riparian meadow habitat. Elk crossed highways at higher traffic volumes when accessing high quality foraging areas. Our results indicate that 1) managers assessing habitat quality for elk in areas with high traffic-volume highways should consider that habitat near highways may be utilized at low traffic volumes, 2) in areas where highways potentially act as barriers to elk movement, increasing traffic volume decreases the probability of highway crossings, but the magnitude of this effect depends on both season and proximity of important resources, and 3) because some highway crossings still occurred at the high traffic volumes we recorded, increasing traffic alone will not prevent elk-vehicle collisions. Managers concerned with elk-vehicle collisions could increase the effectiveness of wildlife crossing structures by placing them near important resources, such as riparian meadow habitat.     

The role of forest maturation in causing the decline of Black Grouse Tetrao tetrix

Black Grouse Tetrao tetrix in Britain have declined through the 20th century, and most birds are now in Scotland. Many causes for this decline have been suggested, notably agricultural intensification, increased grazing levels and moorland afforestation. We examine habitat correlates of Black Grouse distribution and population change from a 700-km² area in the core of the Scottish range, where the numbers of lekking male Black Grouse declined by an estimated 70% to 270 between 1990 and 2002. Habitat data were derived from satellite imagery, in combination with map and field-collected data. Lek occurrence, lek size and changes in lek size were all correlated with forest structure, either positively with the amount of pre-thicket forest cover, or negatively with closed canopy cover. Additional effects of the cover of grass moor and dry heath suggest that Black Grouse are most likely to occur where moorland comprises Heather Calluna vulgaris and grass mosaics. Analysis of the change in Black Grouse abundance within 1.5 km of discrete forest blocks suggests that forest maturation, which has been the dominant habitat change during the course of the study, alone accounts for 58–78% of the decline. Given the close association of Black Grouse and the occurrence of woodland (and particularly conifer plantation) throughout much of their British range, these findings can be used to inform the design of management schemes for the recovery of Black Grouse.     

Are cloud forest tree structure and environment related in the Venezuelan Andes?

Cloud forest vegetation structure and composition were studied in the Venezuelan Andes at three sites in Mérida State. Although the sites are within 10 to 30 km of each other, climatic, geologic and topographic differences are remarkable. The main purpose of the study was to determine the relationship of specific environmental variables to forest vegetation characteristics, including basal area, tree height, density and diversity, and leaf area index (LAI). At 51 plots, all trees' diameter at breast height >10 cm were recorded and identified. Although the environment at the three sites is distinctive, the tree species composition of the most abundant species was very similar. None of the measured environment variables were significantly correlated with the measured vegetation structure variables, except LAI, which was correlated with slope orientation; LAI showed higher values at south‐facing plots. Tree height was relatively uniform, while basal area was highly variable and reached very high values. Stem densities were in the range reported elsewhere in cloud forests. Multivariate analysis using structure or composition data shows segregation of the plots by site. Principal component analyses by site indicate a minor impact of environmental factors on forest variables. At each site, a particular group of species are correlated with the ordination axes. We conclude that species pools and forest dynamics add to the complexity of the structure of the studied cloud forests.