Why do winners keep winning?

Summary Winners of aggressive interactions often continue to win in future encounters. I propose that this phenomenon is a by-product of two other phenomena occurring simultaneously: first, initiators of aggressive interactions typically win those interactions and, second, winners of aggressive encounters often become more likely to initiate future interactions. I propose that these phenomena can be explained, in turn, by selection favoring an individual's initiating an interaction only when it is likely to win that interaction. I found support for this two-step explanation for the winning begets winning phenomenon by observing aggressive interactions among captive dark-eyed juncos (Junco hyemalis oreganus). First, initiators of interactions almost always won. Second, based on characteristics of winners in birds' home aviaries, I could predict which birds would initiate against novel competitors — winners were long-winged males with dark hoods, and birds with these characteristics were more likely to be the first to initiate in novel triads. In addition, aggression was directed preferentially towards other dark-hooded males. The results of this study may expand our understanding of the dynamics of aggressive interactions.     

US Energy Conservation and Efficiency: Benefits and Costs

With increased energy conservation plus the adoption of diverse energy efficient technologies, the US economy could save about 32 quads or about 33% of its current energy consumption, if sound conservation energy use policies were implemented over approximately 10 years. This potential of 32 quads is slightly greater than the current US oil imports. The systems that have the greatest potential to provide major energy savings are transportation, residential energy use, and the food system. Not only saving energy has merit in itself, but it would save US citizens approximately $438 billion per year, helping support the US economy, a high standard of living, and energy security. In addition, this analysis suggests that reducing the $40 billion in taxpayer money spent on subsidies of the energy industries would further increase conservation.     

A simple technique for obtaining high quality chromosome preparations from chorionic villus samples using FdU synchronization

A fluorordeoxyuridine (FdU) synchronization technique was applied to 30 chorionic villus samples (CVS) from patients undergoing first trimester fetal diagnosis. The villi were incubated for 15 h in the presence of FdU. The block in DNA synthesis was subsequently released using thymidine and after an additional 5 h of incubation the mitotic cells were arrested in metaphases using a high concentration of colcemid. This method results in improved morphology of the chromosomes and a high mitotic index. A diagnostic chromosome analysis could be obtained in each clinical case using at least 15 well-spread metaphases. G-banded karyotypes were prepared of four metaphases in each case. The diagnostic procedure was completed within 48 h from the time of CVS. Use of this technique significantly improves the success rate of ‘direct’ chromosome analyses from CVS in a busy cytogenetic laboratory.     

Temporal shifts in the allocation of energy in the arrow squid,<Emphasis Type="Italic"> Nototodarus gouldi</Emphasis>: sex-specific responses

Squid typically display considerable intra-specific plasticity in size and age-at-maturity in response to ambient environmental conditions, yet little is known of the mechanisms driving these variations. We examined the intra-specific variability in Nototodarus gouldi reproductive traits to determine patterns of energy allocation between somatic and reproductive processes over short temporal scales. Females caught during the cool months of May and July were larger, had slower lifetime growth, lower gonad investment, and better somatic condition than females caught during the warmer months, suggesting a trade-off between gonad investment and somatic condition in females. On the other hand, males showed a tight coupling between somatic condition and gonad investment for most months, with increases in somatic and gonad tissue occurring concurrently. In male squid, an increase in lifetime growth rate was coupled with an increase in the relative weights of somatic and reproductive structures, whereas in females, percent increase in body weight per day was correlated only with gonad development. Patterns of repro-somatic investment in mature females had implications for spawning strategies, since female squid with higher levels of gonad investment apparently released batches of eggs together as a group, regardless of body size, whereas females with low gonad investment possibly spawned their eggs independently of one another. In terms of life-history theory, male squid were able to respond rapidly to environmental fluctuations without compromising either the gonad or the soma. However, although mature females did not appear to respond as quickly to ambient conditions, female squid possibly produced two different reproductive strategies, possibly to maximise offspring survival in either a stable or a variable environment. It seems from our study that monthly variations in ambient conditions may have large effects on life-history strategies.Communicated by M.S. Johnson, Crawley     

Species- and stage-specific differences in trace element tissue concentrations in amphibians: implications for the disposal of coal-combustion wastes

Information on species- and stage-specific patterns of contaminant accumulation is generally lacking for amphibians, yet such information could provide valuable knowledge on how amphibians interact with contaminants. We assessed concentrations of As, Cd, Cu, Ni, Pb, Se, Sr, and Zn in whole bodies of larval, recently metamorphosed, and adult life stages in Bufo terrestris and Rana sphenocephala from a site that currently receives coal combustion waste (CCW) discharge, a site where CCW was formerly discharged that has undergone natural attenuation for 30 years, and a nearby reference site. For the majority of elements (As, Cd, Cu, Ni, Pb, Zn), concentrations were highest in larvae, but Se and Sr concentrations remained elevated in later life stages, likely because these elements are S and Ca analogs, respectively, and are thus retained throughout structural changes during metamorphosis. Element concentrations were generally higher in B. terrestris than in R. sphenocephala. Concentrations of As, Se, and Sr were up to 11-35 times higher in metamorphs emigrating from CCW-polluted wetlands compared to unpolluted wetlands, suggesting metamorphosed amphibians can transport trace elements from aquatic disposal basins to nearby uncontaminated terrestrial habitats. In addition, anurans utilizing naturally revegetated sites up to 30 years after CCW disposal ceases are exposed to trace elements, although to a lesser degree than sites where CCW is currently discharged.     

Nutrient losses by surface run-off following the application of organic manures to arable land. 1. Nitrogen

Research was conducted on nitrogen (N) surface run-off losses following organic manure applications to land, utilising a purpose-built facility on a sloping site in Herefordshire under arable tillage. Different rates and timing of cattle slurry, farmyard manure and inorganic N and phosphorus (P) fertiliser were compared, over a 4-year period (1993-97). P losses from the same studies are reported in a separate paper. The application of cattle slurries to the silty clay loam soil increased the loss of solids and NH4(+)-N in surface water flow compared to control plots receiving inorganic fertiliser only, or no treatment, but had little effect on NO3(-)-N losses by this route. Results were consistent with other observations that rainfall events immediately after manure applications are particularly likely to be associated with nutrient run-off losses. Losses via subsurface flow (30 cm interflow) were consistently much lower than via surface water movement and were generally unaffected by treatment. Increasing slurry application rate and, in particular, slurry solids loading, increased solids and NH4(-)-N losses via surface run-off. The threshold, above which the risk of losses via surface run-off appeared to be greatly increased, was ca. 2.5-3.0 t/ha slurry solids, which approximates to the 50 m3/ha limit suggested for slurry within UK 'good agricultural practice'. Sealing of the soil surface by slurry solids appears to be a possible mechanism by which polluting surface run-off may occur following slurry application on susceptible soils. Total losses of NH4(+)-N and NO3(-)-N during the 4-year monitoring period were insignificant in agronomic terms, but average soluble N concentrations (NH4(+)-N + NO3(-)-N) in run-off, ranging from ca. 2.0 mg/l, up to 14.0 mg/l for the higher rate slurry treatments. Peak concentrations of NH4(+)-N > 30 mg/l, are such as to be of concern in sensitive catchments, in terms of the potential for contribution to accelerated eutrophication and adverse effects on freshwater biota.     

Elevated salinity and isotopic composition of fish otolith carbonate: stock delineation of pink snapper, <Emphasis Type="Italic">Pagrus auratus</Emphasis>, in Shark Bay,Western Australia

Analysis of stable isotopes of oxygen and carbon in the otolith carbonate of pink snapper, Pagrus auratus, from several locations in Shark Bay, Western Australia, indicated that snapper are highly location specific. The hypersaline (36 to >60‰) Shark Bay, on the coast of Western Australia, generated strongly characteristic isotopic signatures in the otolith carbonate of snapper collected from the various locations indicating low levels of individual movement of the species. Oxygen isotopes showed enrichment in ¹⁸O in otolith carbonate with salinity (0.10: Δ δ¹⁸O/Δ salinity ‰) typical for the evaporation of seawater. The enrichment in ¹³C (up to 1.75‰) was attributed to the incorporation of metabolically derived CO₂ from an enrichment of ¹³C in the food web within Shark Bay. This was possibly a result of lower concentrations of dissolved CO₂ with increasing salinity causing a reduction in isotope fractionation during photosynthesis. Results complement recent genetic and tagging studies and provide further evidence of the complex nature of snapper stock structure in the Shark Bay region. Published online: 17 July 2002