Showing papers in "American Midland Naturalist in 2009"

Conformation to Bergmann's Rule in White-tailed Deer can be Explained by Food Availability

Abstract: The body size of white-tailed deer (Odocoileus virginianus) increases with latitude and thus exhibits the pattern predicted by Bergmann's rule on the basis of surface to volume ratios and heat loss. This pattern is more simply explained by the distribution of food available per individual animal, which is driven by two factors, the net primary production (NPP) of plants and deer population density. Food availability is often overlooked as a cause of an increase in body size in large terrestrial herbivores in temperate latitudes because of a fundamental misconception about the global distribution of plant productivity. Within a small latitudinal range, white-tailed deer body size as evidenced by modern deer and Holocene paleozoological remains is inversely related to population density and directly related to food availability. Food availability per animal is a product of plant productivity and population density, and is correlated with both local and regional body size variability. These local and regional food-body size patterns are consistent with recent analyses of global NPP datasets which show that ecologically relevant NPP is highest in the north temperate latitudes where white-tailed deer attain their largest body size.

Grassland Bird Use of Remnant Prairie and Conservation Reserve Program Fields in an Agricultural Landscape in Wisconsin

Abstract: Because of the declines in grassland bird populations across North America, many state and federal agencies are making efforts to manage for grassland bird populations, particularly in a landscape context. To effectively manage for grassland birds, we need to understand how grassland bird species use different habitat types within landscapes. We determined the densities of grassland birds in remnant prairie patches and Conservation Reserve Program (CRP) fields and compared those to managed agricultural habitat types (pastures, alfalfa hay and strip crop fields). We also investigated whether densities were associated with landscape features. This study took place in the Military Ridge Prairie Heritage Area (MRPHA) in southwestern Wisconsin May–Jul. 2002 and 2003. Land use in the MRPHA is primarily agricultural, with a relatively large portion of the land in pasture, hay, small grains and idle grasslands enrolled in CRP and relatively few acres of corn and soybeans compared to other areas of the st...

Prey Consumed by Eight Species of Insectivorous Bats from Southern Illinois

Abstract: We collected data on the diet of eight species of insectivorous bats (Chiroptera, Vespertilionidae): big brown bats (Eptesicus fuscus), red bats (Lasiurus borealis), evening bats (Nycticeius humeralis), northern myotis (Myotis septentrionalis), little brown myotis (M. lucifugus), Indiana myotis (M. sodalis), southeastern myotis (M. austroriparius) and eastern pipistrelles (Perimyotis subflavus). Bats were mist netted during the summers of 1999 and 2000 at 41 forest sites throughout southern Illinois. We analyzed prey remains in fecal pellets of 305 individuals to assess diet similarity among species and relationships between bat body mass and prey diversity and hardness. Larger species included big brown bats and evening bats that ate primarily hard-bodied beetles (Coleoptera). These bats had the greatest dietary similarity index value compared with the other chiropterans in the community, and the highest hardness indices of prey consumed. Red bats, second only to E. fuscus in mean body mass, ate...

Range Expansion of Barred Owls, Part I: Chronology and Distribution

Abstract: During the past century, Barred Owls (Strix varia) expanded their range from forests east of the Great Plains to forests throughout most of central and western North America. Here in Part I, I map more than 12,500 records of Barred Owls in their expanded range from the earliest records to the present, draw the species' distribution in its expanded range and infer the general timing and flow of the range expansion. Evidently, Barred Owls originally traveled across the northern Great Plains via the forested riparian corridors of the Missouri, Yellowstone and Musselshell rivers into east-central Montana by 1873. From there, they accessed western forests in southwestern Montana (1909), moved to northwestern Montana (1922) and then expanded their range in two general directions. They moved north and east to northern Alberta (1934) and Saskatchewan (1948) where they apparently encountered other Barred Owls coming westward from Manitoba. They also moved north to northern British Columbia (1943), southeastern Alaska (1967) and Northwest Territories (1977), and west and south to Washington (1965), Idaho (1968), Oregon (1972) and California (1976). In Part II (Livezey, in press), I explore what prevented Barred Owls from expanding their range westward during recent millennia and what allowed them to do so during the past century.

Range Expansion of Barred Owls, Part II: Facilitating Ecological Changes

Abstract: In Part I (Livezey, 2009), I presented the chronology and distribution of the range expansion of Barred Owls (Strix varia) from the late 1800s to the present. Here I explore what had prevented Barred Owls from expanding their range westward during recent millennia and what allowed them to do so during the past century. Using strength-of-evidence analysis, I evaluate the plausibility of the five ecological or behavioral changes proposed in the literature to have facilitated the range expansion. From this evaluation, three of these changes appear to be implausible, one appears to be plausible after modifying its location, and one appears to be very plausible. For the very plausible one, I score seven ecological changes that may have affected it using five strength-of-evidence criteria. Overall, it appears the historical lack of trees in the Great Plains acted as a barrier to the range expansion and recent increases in forests broke down this barrier. Increases in forest distribution along the Misso...

Central Place Foraging by Beavers (Castor canadensis) in a Complex Lake Habitat

Abstract: Beavers (Castor canadensis) are important as ecosystem engineers and are useful model organisms for testing central-place foraging theory. Much previous work has done this in controlled situations, whereas here we tested predictions in a complex natural habitat by collecting data on beaver-cut and uncut trees in sites at various distances from an isolated beaver lodge on a large reservoir. The most basic theoretical predictions are that selectivity of predators should increase with distance from the central place and that preferred prey size should increase with distance. Consistent with the first prediction, beavers were more selective for preferred tree species when foraging far from shore or at sites some distance from their lodge than when near the shore or at sites near their lodge. Consistent with both predictions, beavers were more selective for particular sizes of trees and selected larger sizes of trees as distance from the shore increased. Overall, beavers showed a preference for intermediate tree sizes, avoiding both very large and very small trees, but as distance from shore increased, beavers cut fewer trees from the smaller end of this size range and more from the upper end in such a manner as to increase both selectivity and mean size. Similarly and within this same size range, as distance from the lodge through the water increased, beavers cut larger trees at greater distances due to reduced cutting of small trees and increased cutting of larger ones. In this case, however, overall selectivity did not increase, just an increase in the size selected. Overall, then, our study shows that central-place foraging theory can predict the behavior of beavers foraging in a complex natural landscape, and the patterns observed have implications for how beavers might influence tree species composition in forests.

Forest Dynamics Across Three Century-Length Disturbance Regimes in the Illinois Ozark Hills

Abstract: Forest community dynamics in the Illinois Ozark Hills was studied over a 300 y period that included three sequential disturbance regimes. Presettlement forest community patterns were reconstructed using witness tree data taken from the 1806–7 General Land Office survey records. Species, stem diameter and distance from the corner were obtained for a total sample of 958 witness trees on 479 section and quarter-section corners. Data were separated by site type based on 13 aspect and slope positions, but later were combined into six Ecological Land Type Phases (ELTPs) using cluster analysis and percent similarity. At the end of the presettlement and Disturbance Phase 1 (ca. 1810), Quercus and Carya species dominated forest communities (combined Importance Value, IV100 = 68–76) on the Southwest Slope, South Slope, Ridgetop and North Slope ELTPs. The combined IVs for all early successional species ranged from 74–81 while IVs of late successional fire-intolerant mesophytic species ranged from 19–26. U...

Meta-analysis of Summer Roosting Characteristics of Two Species of Myotis Bats

Abstract: We compared roost site characteristics of the Indiana bat (Myotis sodalis) and northern bat (M. septentrionalis), which form maternity colonies in cavities and beneath bark of dead (snags) and living trees in eastern North American forests. We used published data (n = 28 sources; n = 1145 roost trees) from studies completed where the distributions of the two species overlap and evaluated a suite of habitat features that might affect roost selection and interspecific competition between these two congeners. We found no differences between these species in average height of roost aboveground, density of snags in the vicinity of roosts, selection of live trees versus snags or relative elevation. Populations of northern bats were more likely to choose roosts in crevices or cavities (88.9%) than Indiana bats (30.0%; P < 0.1), and roosted in trees that averaged smaller in diameter (30.0 ± 5.4 cm) than trees selected by Indiana bats (41.4 ± 2.4 cm; P < 0.1). Northern bats demonstrated greater variability than Indiana bats in height of roosts aboveground and in stem diameter of roost trees. Existing data indicate northern bats exhibit greater plasticity in choice of summer roosts than Indiana bats, explaining, in part, why northern bats are more widely distributed and more common in forests of eastern North America than are Indiana bats.

Effects of an Invasive Plant Species, Celastrus orbiculatus, on Soil Composition and Processes

Abstract: Celastrus orbiculatus is a non-native, invasive liana that was introduced to the United States in the 1860s and has spread rapidly throughout the Northeast. Several attributes contribute to the invasiveness of C. orbiculatus, including tolerance to a wide range of light levels and habitat types. We compared soil characteristics in seven sets of adjacent, paired plots, spanning a range of habitats and soil types, with and without C. orbiculatus. The paired plots were similar other than the presence or absence of Celastrus. Plots with C. orbiculatus had significantly higher soil pH, potassium, calcium and magnesium levels. Furthermore, nitrogen mineralization and litter decomposition rates were higher in plots with C. orbiculatus. Phosphorus levels were not significantly different between the paired plots. The results of this study contribute to the growing body of research of the effects of invasive species on ecosystem processes.

Home Range, Habitat Use and Survival of Coyotes in Western South Carolina

Abstract: Home range size, habitat use and survival of coyotes are variable throughout their range. Because coyotes have recently become established in South Carolina, we investigated their spatial distribution, habitat use and mortality on the Savannah River Site (SRS) in western South Carolina, USA. Annual survival for adult coyotes on the SRS was 0.658. Off-site trapping and shooting accounted for 60% of mortality. Home ranges averaged 30.5 km2 and 31.85 km2 by the 95% minimum convex polygon and 95% fixed kernel methods, respectively. We detected no difference in home ranges size between males and females. Intraspecific home range overlap averaged 22.4%, excluding mated pair interactions, with 87.5% of coyotes sharing their home range with one or more individuals. Coyotes selected home ranges containing higher proportions of early successional habitat than was available on the landscape. Core areas likewise contained a greater proportion of early successional habitat than available in the animal's home ...

Herbaceous-layer impoverishment in a post-agricultural southern Appalachian landscape

Abstract: Large ungulates are an important driver of plant community composition and structure. In eastern North America, white-tailed deer (Odocoileus virginianus) thrive in agricultural mosaics and fragmented forested landscapes, at times reaching unprecedented densities. Nevertheless, few long-term data sets are available that allow an assessment of the long-term consequences of chronic herbivory. We quantified herbaceous-layer change over a 26 y period in Cades Cove, Great Smoky Mountains National Park, USA. Cades Cove has a long and well-documented history of deer overabundance, with densities reaching 43 deer km−2 during the late 1970s. Over the 26 y sampling interval, mean coverage of herbaceous species declined significantly (P < 0.001) in the forests bordering Cades Cove. Although most plots only lost 1–2 species during the interval, 46 herbaceous species recorded on plots during the 1970s were wholly absent in 2004 (63% of which were forest species). Additionally, the herbaceous layer has become ...

Land-Use Impacts on Watershed Health and Integrity in Indiana Warmwater Streams

Abstract: Many warmwater streams in the midwestern United States have been negatively influenced by human land-use practices. From Jun. through Aug. 2002 and 2003, tributaries (n = 50) of the upper Wabash River basin, Indiana, were sampled to investigate ecosystem health and integrity. Stream fish and macroinvertebrates were sampled along with in-stream habitat according to National Water-Quality Assessment Program protocols to examine relationships among fish community structure, benthic macroinvertebrate assemblages, physical-habitat complexity and water chemistry under varying land-use practices. Stream fish abundance was best explained by in-stream habitat quality (QHEI), watershed area and the amount of forested land use upstream of each sampling site. Overall index of biotic integrity (IBI) scores were low (mean = 35.58; range, 20 to 52), and varied predictably by riparian land-use type. The abundance of benthic macroinvertebrate taxa was best explained by the substrate QHEI metric (λ = 0.24; P...

Ecological Characteristics of Small Mammal Communities at a Superfund Site

Abstract: Wildlife species can serve as biomonitors of environmental health and are prognostic of ecotoxicological consequences when contaminants are introduced into the environment. Small mammals, particularly rodents, comprise the majority of indicator species used in terrestrial biomonitoring studies; however, many biomonitoring studies address acute effects over relatively short periods. We still know little regarding effects of chronic exposure to contaminants on small mammals. The overall goal of this study was to determine ecological characteristics of small mammal communities inhabiting a heavy metal contaminated site, Tar Creek Superfund Site, compared to reference sites located in northeastern Oklahoma over a 2 y timeframe. Primary hazardous materials present at Tar Creek Superfund Site include lead, zinc and cadmium. Mark-recapture techniques were employed to test the hypothesis that structure and composition of small mammal communities inhabiting this contaminated site would be significantly altered compared to uncontaminated reference sites. Contaminated and reference sites were similar in vegetation compositional characteristics. Small mammal communities inhabiting Tar Creek Superfund Site had reduced species diversity, including richness and evenness, compared to reference sites. Furthermore, communities within Tar Creek Superfund Site were dominated by a single species, Peromyscus leucopus (white-footed mouse). Species composition was different between contaminated sites and reference sites as evidenced by detrended correspondence analysis, with contaminated sites being more similar to each other than to either reference site. No direct link between site contamination and disparities among most ecological characteristics could be established.

Seasonal Field Metabolic Rates of American Martens in Wisconsin

Abstract: We report on FMR of free-living American martens (Martes americana) in autumn and winter in northern Wisconsin. Mean body mass was significantly higher in males (1099 ± 43 [S.E.] g) than females (737 ± 28 g), with no significant difference by season. Daily mass change rates of martens did not differ from zero, and mass change rate and percent of body fat did not differ by gender or season. These data are consistent with our expectation that non-reproductive martens balance their energy budget on a near daily basis, even in winter, and rely little on body energy reserves. Energy expenditure, and hence food requirements, declined 24% from fall (1006 ± 96 kJ/d) to winter (725 ± 96 kJ/d), despite colder temperatures and deep snow. Both males and females were active nearly 50% less in winter (4.8 ± 1.0 h/d) than in autumn (9.1 ± 0.7). It appears that, in addition to lowering core body temperature and seeking thermal cover, martens decreased activity levels from fall to winter to reduce energy expenditures and food requirements.

Food Habits of Recolonizing Cougars in the Dakotas: Prey Obtained from Prairie and Agricultural Habitats

Abstract: Food habits of cougars (Puma concolor) in North America have been documented for western populations in the United States, Canada and Mexico. Most studies assessed diets of cougars occupying typical habitats, and within established populations. We evaluated food habits of cougars in prairie and agricultural landscapes in the Dakotas (regions that had been devoid of the species for roughly a century) located well outside of known resident populations. We obtained stomach and gastrointestinal (GI) tracts from 14 cougars (10 male; 4 female) from 2003–2007, and evaluated contents via frequency of occurrence (%) of various prey items. Deer (Odocoileus spp.) had the highest frequency of occurrence (50.0%). Other native mammalian prey included jackrabbit (Lepus townsendii, L. californicus), porcupine (Erethizon dorsatum), beaver (Castor canadensis), badger (Taxidea taxus), mink (Mustela vison) and rodent species (e.g., vole). No domestic livestock species were documented as part of the cougar diet in th...

Receptiveness of Foraging Wild Bees to Exotic Landscape Elements

Abstract: Wild pollinators provide important services in both wild and human-dominated ecosystems, yet this group may be threatened by widespread anthropogenic landscape change. We explored the responses of wild bees to exotic floral species and novel habitat in a fragmented, suburban landscape using pollen grain identification. Pollen loads from bee specimens collected in 13 suburban grassland fragments in Denver, Colorado were sampled and compared with a pollen reference collection. Averaged across two seasonal sampling rounds, 45% of the bee-borne pollen grains were identified to the species level. Wild bees in this system were very receptive to using alien plants for pollen foraging; at least 45% of pollen sampled from bee specimens consisted of non-native pollen grains. During peak flowering in early summer, bees obtained at least 32% of their pollen resources from within-fragment sources and at least 7.5% from surrounding suburban residential yards. In midsummer, within-fragment sources represented 58% of pollen sampled while yards dropped to 1.5%. These bees appear to be more accepting of exotic floral species than of exotic habitat types (yards). The advantages and disadvantages of pollen load analysis for movement studies are discussed.

Survival and Cause-Specific Mortality of Wild Turkeys in Northern Indiana

Abstract: Information regarding survival and cause-specific mortality of eastern wild turkeys (Meleagris gallopavo silvestris) is vital to their management, especially in small or isolated populations. Between January 2003 and August 2005, we used radio telemetry to investigate survival and cause-specific mortality of 87 [44 male (24 adult and 20 juvenile) and 43 female (34 adult and 9 juvenile)] wild turkeys in northern Indiana. We estimated annual and seasonal survival using the Kaplan-Meier product-limit method. Mean male and female annual survival estimates were 0.257 and 0.777, respectively. Annual survival estimates were different between sexes within years, but were homogenous within sexes between years. Survival estimates did not differ among seasons for either sex. However, differences in survival estimates between sexes were detected in the spring, fall and winter seasons. Hunter harvest (46.2% male mortality) and predation (33.3% female mortality) were the leading known causes of mortality for m...

Selection of Seeds of Common Native and Non-native Plants by Granivorous Rodents in the Northeastern United States

Abstract: Post-dispersal seed predation by rodents represents a potentially important element of biotic resistance to plant invasion. Selection for five different types of seeds by granivorous rodents was studied in maple-beech forests, old fields and conifer plantations in Madison County, New York. Rodents visited dishes containing equal masses of seeds of the native Cornus amomum and Rubus idaeus, and the non-native Lonicera morrowii, Rhamnus cathartica and Rosa multiflora. Greater masses of C. amomum and R. idaeus seeds were consumed during a night of mammal visitation than of the three non-native species, and pattern of selection did not differ among habitats. Rodents encountered seed dishes sooner in forested habitats than old fields. The primary seed predators in our region, Peromyscus spp., were more common at forests and plantations than old fields. Patterns of habitat use by Peromyscus spp. may aid in resisting invasion of intact forests by invasive plants; however, selection of native over non-na...

Biogeographical Distribution of Chloroplast Diversity in Northern Red Oak (Quercus rubra L.)

Abstract: We mapped the biogeographical distribution of chloroplast haplotypes in northern red oak (Quercus rubra L.) to test the hypotheses that the founder effects during postglacial migration will result in a latitudinal gradient of haplotype diversity with exhaustion of haplotype richness at the extreme northern edge of the range. PCR-RFLP markers for 23 populations of Q. rubra in old growth and minimally disturbed forests across 13,000 km2 of the contemporary range revealed only four of the five haplotypes detected previously at 12 sites in Indiana. The four northernmost populations were fixed for either haplotype I or haplotype II, the two most common haplotypes. Haplotype richness declined poleward, but the biogeographical pattern of 829 haplotypes across the 35 sites did not clearly indicate postglacial migration routes along latitudinal gradients from the southern edges of the study area. Although Q. rubra and the European white oak Q. robur L. are both early successional species that recolonized ...

Spatial variation in top-down direct and indirect effects on white oak (Quercus alba L.).

Abstract: Recent attention has been paid to spatial variation in the direct and indirect effects of trophic interactions. Because abundances of predators and prey vary naturally through space, their interactions and the effects of these interactions may vary as well. We conducted a bird exclosure experiment on white oak (Quercus alba L.) using a randomized block design to assess how the direct effects of bird predation on arthropods and indirect effects of birds on plant damage and growth differ between five sites separated by 350–1000 m. Insect herbivore and arthropod predator abundances varied spatially, but were not affected by the exclosure treatment. Bird abundance also varied among sites. Herbivore community structure (herbivore feeding guilds) differed by site as well. Bird predation significantly reduced damage to oak leaves, but this effect did not vary spatially. However, the size of this effect was positively correlated with insectivorous bird abundance. Thus despite herbivore and predator commu...

The Importance of Pitcher Size in Prey Capture in the Carnivorous Plant, Sarracenia alata Wood (Sarraceniaceae)

Abstract: Prey capture in pitcher plants has been found to be significantly dependent on pitcher size, but the actual importance of size is not clearly understood. We studied insect capture by the carnivorous plant Sarracenia alata and compared the rate of insect capture per unit capture area of plants with that of nonbiological models and traps. The total mass of insects captured was significantly positively related to capture area for both biological and nonbiological systems. However, the rate of insect capture was significantly greater for plants than for models and traps, which suggests a role of attractants in insect capture in pitcher plants. Odor from decaying insects was found to have a significant effect on insect capture on experimental attraction cups. Further study should focus on the nature of other attractants including nectar, UV reflectance and volatiles to determine their role in insect capture by pitcher plants.

A Comparison of Germination and Early Growth of Four Early Successional Tree Species of the Southeastern United States in Different Soil and Water Regimes

Abstract: To learn more about the basic biology of exotic relative to native tree species we conducted a greenhouse experiment comparing the germination and early seedling growth of four early successional tree species found in the southeastern United States: two exotics (Ailanthus altissima and Paulownia tomentosa) and two natives (Liquidambar styraciflua and Platanus occidentalis). Five soil types and three water regimes were used for the experiment. Liquidambar and Platanus, the native species, germinated significantly more quickly and were more sensitive to soil type than were the exotics, Ailanthus and Paulownia. Platanus grew tallest, and along with Paulownia, accumulated the greatest total biomass. Ailanthus alone exhibited a high root/shoot ratio in all soil types. In addition, species differed in their response to soil types for multiple growth traits. The results suggest that native tree species could be used to help retard the establishment of invasive tree species on bare soil.

Postdispersal Sugar Maple (Acer saccharum) Seed Predation by Small Mammals in a Northern Hardwood Forest

Abstract: Small granivorous mammals may have marked effects on plants through their seed predation. Using live-trapping efforts and tagged sugar maple (Acer saccharum) seeds in 2006 at eight mixed forest sites in the northern Great Lakes region, we asked: (1) Were small mammals seed dispersers or predators at these sites? (2) How did seed predator (i.e., all granivorous small mammals) and sciurid (chipmunks and squirrels only) biomasses affect the proportion of seeds eaten? (3) How did habitat structure affect seed predator biomasses? We found that small mammals, particularly eastern chipmunks (Tamias striatus), were predators of sugar maple seeds as the proportion of seeds eaten and seed predator biomasses were positively related. We also found a larger seed predator biomass and the presence of eastern chipmunks in areas with higher proportions of deciduous trees. Our findings have important implications for forest regeneration, as seed predators may negatively impact restoration efforts.

Effect of Removal of Hesperis matronalis (Dame's Rocket) on Species Cover of Forest Understory Vegetation in NW Indiana

Abstract: Exotic invasive plant species differ in their effects on indigenous vegetation as evidenced by research evaluating community response to their removal. We used a removal approach to quantify the response of a mesic woodland to the removal versus retention of an invasive plant, Hesperis matronalis (dame's rocket) from paired treatment plots over 3 y. Cover of H. matronalis did not differ between control and treatment plots prior to removal, declined in the removal plots and remained significantly lower in cover compared to the control plots. Removal did not significantly affect species richness and species diversity (evenness, Shannon and Simpson) at the plot scale, but did result in increased species richness overall in the removal plots in the last sampling year when compared to control plots. Non-metric multidimensional scaling ordination analysis indicated a significant compositional change in the spring plant composition of plots over the 3 y, reflecting an increase in exotic woody species. Exotic woody plants, especially Rosa multiflora and Euonymus alatus, increased in cover in response to H. matronalis removal. In the 3 y, neither native nor exotic forbs, nor native woody plants responded to the removal of H. matronalis in a statistically significant manner. The increasing cover of woody invasive plants in response to the removal of H. matronalis has important management implications for restoration of degraded communities.

Morphological and Ecological Relationships between Burrs and Furs

Abstract: Epizoochory is the mode of seed dispersal where a diaspore (disseminating plant propagule) is disseminated on the external surface of an animal. While the structures that facilitate diaspore adherence are diverse, epizoochory is considered to be relatively rare (approximately 10% of angiosperms), but is commonly utilized by several invasive plant species. We experimentally sought species specific associations between the adherence and retention of eight common plant species' diaspores and five mammalian furs, plus human clothing. We sought relationships between both fur and diaspore characteristics in both the adherence and retention of diaspores. Diaspores of Geum aleppicum were the only ones interacting significantly better with one kind of substrate (mouse fur) than diaspores of all other plant species by being retained well in mouse fur. Alternatively, bison fur behaved as a “generalist” disperser, by consistently accommodating the adherence and retention of a wide range of diaspore morpholog...

Beaver (Castor canadensis) Impacts on Herbaceous and Woody Vegetation in Southeastern Georgia

Abstract: North American beavers alter habitat properties such as stream flow, faunal composition and plant community structure. In North America, the majority of studies on impacts by beavers have occurred in the northeast or western regions. This study examined the effect of wood-cutting and foraging by beaver on the surrounding plant community in Southeastern Georgia. To determine their impact, beaver modified habitat and nearby, but non-impacted riparian habitat, were sampled in a matched pair design. Vegetation surveys were performed, and species richness, density, relative abundance and canopy cover were calculated for every site. Richness of herbaceous vegetation was higher at distances closer to shore while richness of large woody vegetation increased with distance from shore with no difference found between beaver and control sites. The composition of herbaceous or woody vegetation did not differ significantly between beaver and control sites; species had an equal chance of occurring in either site. Canopy cover was similar at the two site types. Non-native species were rare and did not differ by site type. Beavers were in low density and had a relatively benign impact on the plant community. Density of woody plants was higher at beaver sites, suggesting that beavers may favor areas of abundant woody vegetation. Beaver impact may be less in southern regions than in northern ones. This may reflect the lower density of beavers, but impact also could be due to the year round availability of and access to vegetation.

Activity, Movements and Activity Area Size in Stinkpot Turtles (Sternotherus odoratus) in a Southwestern Michigan Lake

Abstract: We used radio telemetry to evaluate activity area size, habitat use, diurnal activity, and the influence of weather, environmental temperatures and sex on daily movements in 18 Sternotherus odoratus in southwestern Michigan. Turtles mainly moved within the highly vegetated littoral zone but two individuals used wet meadow areas adjacent to the lake and an adjoining stream. Activity area size, as measured by the 95% fixed kernel method using 40 radio telemetry days per individual, did not vary between the sexes. Mean total daily distance moved (TDDM) over a 12 h time period averaged 27 m and was not influenced by sex or by variation in daily weather conditions. However, seasonal changes in environmental temperatures were positively correlated with mean daily shell temperature (Ts) and TDDM indicating limits on activity on relatively cool days. While turtles were found to move at any time over the course of a day, distances moved during six, 4 h intervals over a 24 h period were greatest during the...

Pollination of Sisyrinchium campestre (Iridaceae) in Prairies Invaded by the Introduced Plant Euphorbia esula (Euphorbiaceae)

Abstract: Introduced plants may compete for pollination with native species, leading to increased pollinator limitation for one or both species. In this study, I test the hypothesis that the introduced plant Euphorbia esula (Euphorbiaceae, leafy spurge) competes for pollination with the native prairie perennial Sisyrinchium campestre (Iridaceae, blue-eyed grass). A breeding system study revealed that Sisyrinchium is self- incompatible, potentially increasing its vulnerability to competition for pollination. Interspecific competition for pollinator visits occurred, as visit rates were lower for Sisyrinchium near Euphorbia than for Sisyrinchium more than 10 m from Euphorbia. However, supplemental hand pollinations of Sisyrinchium did not increase fruit or seed set either near to or far from Euphorbia, indicating that visits were not limiting. More than one- third of Sisyrinchium stigmas received Euphorbia pollen, but hand-pollination experiments detected no effect of Euphorbia pollen receipt on fruit or seed...

Reproductive Success and Brood Movements of Giant Canada Geese in Eastern South Dakota

Abstract: The population of resident giant Canada geese (Branta canadensis maxima) has increased dramatically in eastern South Dakota since reintroduction efforts were initiated in the 1960s. In order to effectively manage this population of Canada geese, it is important to determine their reproductive success. We collected information on goose nesting success and related brood movements using Very High Frequency (VHF) telemetry. We captured Canada geese in seven counties in eastern South Dakota during summers, 2000–2003. The reproductive success of 88 females was monitored during spring 2001–2004. Half of the geese had successful nests, 20.5% were unsuccessful, and 29.5% did not attempt to nest. Apparent and Mayfield nesting success estimates averaged 71% and 63%, respectively. Overall egg success was 62.6% and overall hatching success was 88.8%. Mean total clutch size averaged 5.73 ± 0.17 while the number of goslings leaving the nest averaged 5.02 ± 0.25. Forty-nine percent of marked females nested on or...

Disturbance regime mediates riparian forest dynamics and physiological performance, Arkansas River, CO.

Abstract: Tamarix ramosissima has caused dramatic morphological changes to riparian ecosystems and their bank structures over the last century throughout the southwestern United States. Growing as either small trees or dense stands of shoots, Tamarix species displace or actively outcompete native species of willow (Salix exigua) and cottonwood (Populus deltoides) on the Arkansas River in Colorado. Under normal conditions for colonization by native species, Tamarix seedlings are at a great competitive disadvantage due to slow above ground biomass accumulation. However, damming and the resulting altered disturbance regime may give Tamarix an advantage over native species. Damming on the Arkansas River, Colorado, dramatically reduces the intensity and recurrence interval of downstream flooding. Using two dams in eastern Colorado as proxies for flood control, we assessed physiological, demographic and abiotic factors in order to understand how flooding and damming might influence riparian community dynamics. Our study demonstrates that drought and salinity stress may influence native species recruitment and survival in areas with reduced flooding. Moreover, Tamarix water-use may be quite plastic in drought conditions, suggesting that it conserves water at below dam sites.