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.     

Observations on the Endogenous Stages of Eimeria confusa Joseph, 1969 from the Grey Squirrel Sciurus carolinensis*

SYNOPSIS. Stages in the endogenous cycle of Eimeria confusa from the grey squirrel, Sciurus carolinensis, are described from mixed infections with another species, Eimeria lancasterensis. All corresponding stages were markedly different in the 2 species. In E. confusa infections, the parasites were located below the host cell nuclei of the epithelial cells of the villi of the jejunum and ileum. Mature schizonts were ellipsoidal, averaged 20.9 × 18.6 μm and had 18–30 merozoites. The mature microgamonts measured 34.3 × 24.7 μm and had hundreds of microgametes. Mature macrogametes were ovoid, averaged 31.3 × 25.6 μm, and contained 2 kinds of plastic granules.     

THE BACTERIOLOGY OF FARM WATER SUPPLIES: A STUDY OF THE COLONY COUNT IN 72 HOURS AT 22°

SUMMARY: The colony count at 22° of farm water supplies from springs and wells was mainly composed of biochemically inactive, non-pigmented, Gram-negative rods. Water from a stream polluted with farmyard sewage showed a similar dominance of Gram-negative rods, but orange or yellow pigmented colonies were more abundant. There were few 37° positive coli-aerogenes bacteria in either the farm water supplies or the sewage polluted stream, and Bact. coli type I was rare.
A high proportion of the bacteria from farm water supplies fermented milk in 3 days at 22°; a third developed acid, 15% proteolysis and 6.4% ropiness.
Contamination of pure spring water with surface soil from a heavily grazed pasture resulted in a hundredfold increase in colony count with aerobic sporing rods replacing Gram-negative rods as the dominant organisms, but coli-aerogenes bacteria were absent.     

Flow- and substratum-mediated movement by a stream insect

1. In streams subject to frequent hydrologic disturbance, the ability of benthic invertebrates to disperse within the channel is key to understanding the mechanisms of flow refugium use and population persistence. This study focuses on crawling invertebrates, the effects on movement of abiotic factors (specifically, flow near the stream bed and bed micro‐topography) and the consequences for dispersal. 2. In a large flume, we observed individual cased caddisflies, Potamophylax latipennis, moving in fully turbulent flows over a precise replica of a water‐worked surface. From maps of movement paths, we quantified crawling behaviour and entrainment, and the influence of bed micro‐topography. We manipulated discharge and tested its effect on movement, linear displacement and areal dispersal. The highest discharge treatment was a disturbance to the caddis; the lowest discharge was not. Crawling behaviours were used to parameterise random walk models and estimate population dispersal, and to test the effects of abiotic factors on movement. 3. Bed micro‐topography influenced crawling in several ways. Caddis spent most of their time at the junctions between proud particles and the adjacent plane bed. The frequency distribution of turn angles was bimodal, with modal values approximating the angle required to travel around median‐sized particles. Larvae generally crawled downstream, but crawling direction relative to the flow was skewed by bed micro‐topography and was not directly downstream, unlike drift. 4. Caddis crawled for most of the time and discharge affected almost every aspect of their movement. As discharge increased, caddis crawled less often, more slowly and over shorter distances; they also became entrained more frequently and over greater distances. With increased discharge, caddis spent proportionately less time at the junctions between proud particles and the adjacent plane bed, and more time on the tops and sides of proud clasts. This is curious as most entrainment occurred from the tops and sides of clasts and entrainment is generally considered to be disadvantageous during disturbances. 5. Linear displacement (drift and entrainment combined) was downstream, but the relation between total displacement and discharge was complex. Total displacement decreased at intermediate discharge as crawling decreased, but increased at high discharge as entrainment and drift played a greater role in movement. 6. Within‐stream dispersal via crawling contained elements of both a correlated random walk (we observed directional persistence in turn angles) and a biased random walk (we observed downstream bias in move direction angles) and was best described as a biased correlated random walk. Dispersal was inversely related to discharge, suggesting that the ability of P. latipennis to crawl into flow refugia on the streambed is reduced at high flow.     

Cyclic temperatures influence growth efficiency and biochemical body composition of vertically migrating fish

1. Diel vertical migrations (DVM) are frequently observed in pelagic fish and zooplankton populations. In addition to predator avoidance and foraging opportunity, bioenergetics optimisation has been hypothesised to cause the selective advantage of migrating fish. However, experimental confirmation of growth advantages of fish held at naturally observed cyclic temperatures, and food densities are surprisingly rare. 2. We compared growth rates, growth efficiencies and energy budgets of vendace (Coregonus albula, Salmoniformes) fed daily rations of 10% body mass and held at low (4.5 °C), high (8 °C) and cyclic (switch between 4.5 and 8 °C) temperatures over a period of 6 weeks. Biochemical body composition was evaluated by bioimpedance analyses and direct determination of water, lipid and protein content in a subset of fish. 3. Growth rate and food conversion efficiency were similar in fish held at high and cyclic temperatures, but higher than those found at low temperatures. Body condition of fish at cyclic temperatures was maximised, but these fish also had the highest water content. The proportion of lipids and proteins was slightly depleted in fish held at cyclic and low temperatures relative to the high temperature treatment. Accordingly, growth and biochemical composition of fish responded specifically to cyclic temperatures and were not simply intermediate between those found at low and high temperatures. 4. We could not confirm a bioenergetics advantage of fish switching between high and low temperatures. However, there were no substantial extra metabolic costs through exposure to cyclic temperatures, and hence, fish performing DVM may benefit from predation avoidance without compromising their metabolic balance and hence growth rates. These results suggest that the evolution of DVM is a multi‐faceted process with no single ultimate explanation.     

Patterns of intra- and interspecific association in leaf-mining insects on three oak host species

Abstract. 1. We determined mortality and distributional patterns of leaf miners on three oak host species (Quercus falcata, Q.nigra and Q.hemisphaerica) in northern Florida, U.S.A.
2. Patterns of intra- and interspecific occurrence within leaves, and mortality of five most abundant leaf miner species were analysed as a test of competition.
3. Miners co-occurred on leaves more often that expected by chance (P<0.05) in six of ten possible species combinations and log-linear model analysis showed no negative higher-order interactions.
4. All five miner species had highly clumped distributions between leaves (P<0.01).
5. Leaf miner survival was less than expected for four of five species when co-occurring on leaves with conspecifics than when mining with heterospecifics or alone (P<0.05).
6. We conclude that interspecific competition is unapparent within this leaf miner guild and that intraspecific competition occurs in four of the five major leaf miner species. We discuss leaf miner selection of common leaves, perhaps based on chemical/physical leaf characters, as a cause of intra- and interspecific aggregation.