1,962 research outputs found

    Ecological engineering across a spatial gradient: Sociable weaver colonies facilitate animal associations with increasing environmental harshness

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    1. The spatial distribution of animals in a landscape depends mainly on the distribution of resources. Resource availability is often facilitated by other species and can positively influence local species diversity and affect community structure. Species that significantly change resource availability are often termed ecosystem engineers. Identifying these species is important, but predicting where they have large or small impacts is a key challenge that will enhance the usefulness of the ecosystem engineering concept. 2. In harsh and stressful environments, the stress gradient hypothesis predicts that community structure and function will be increasingly influenced by facilitative interactions. 3. To test this hypothesis, we investigate how the ecosystem engineering role and importance of sociable weavers Philetairus socius varies across a spatial gradient of harshness, for which aridity served as a proxy. These birds build large colonies that are home to hundreds of weavers and host a wide range of avian and non‐avian heterospecifics. We investigated the use of weaver colonies on multiple taxa (invertebrates, reptiles, birds and mammals) at multiple sites across a >1,000 km aridity gradient. 4. We show that sociable weaver colonies create localized biodiversity hotspots across their range. Furthermore, trees containing sociable weaver colonies maintained localized animal diversity at sites with lower rainfall, an effect not as pronounced at sites with higher rainfall. 5. Our results were consistent with predictions of the stress gradient hypothesis, and we provide one of the first tests of this hypothesis in terrestrial animal communities. Facilitation and amelioration by ecosystem engineers may mitigate some of the extreme impacts of environmental harshness

    Mature open cows are rarely persistently infected with bovine viral diarrhea virus

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    Bovine viral diarrhea virus (BVDv) is an immunosuppressive virus affecting cattle in a multitude of ways. The varied presentation makes this disease difficult to identify in cow herds and the signs of a BVD infection may be very subtle. The syndrome causes economic problems by reducing herd fertility and increasing disease rates. The persistently infected (PI) animal is a unique reservoir for BVDv. These cattle are the result of in utero exposure to the noncytopathic biotype of BVDv prior to the development of a competent fetal immune system at about 125 days of gestation. Persistently infected animals are the primary method for the disease to propagate over time. PI cattle consistently shed BVD virus in relatively high levels and this exposure to the breeding herd can result in new PI calves. PI animals propagate BVDv in the herd and decrease pregnancy percentages compared to herds without PI animals. Farms must assess risk and manage for biosecurity when purchasing adult animals with an unknown history of disease exposure. Breeding herds that introduce new animals to the herd face the risk of importing a BVD PI animal. To mitigate this risk, PI animals must be accurately identified prior to herd introduction, but visual appraisal is not an accurate method of discovering these animals. Multiple diagnostic tests are available to determine the BVD status of incoming animals and all have an associated cost. Economic feasibility of determining the BVD PI status of animals depends to a large degree on the frequency with which PI animals occur in a population. Previous research has illustrated that PI calves entering the feedyard phase of production are fairly rare (about three per 1,000 calves); however, very little work has been done in mature animals. This project provides an estimate of BVD PI frequency for a specific population. This assessment should allow the formulation of a BVD-specific risk management plan which addresses the economic efficiency of testing mature females upon arrival. The primary objective of this research is to determine the prevalence of BVD PI animals in a population of young (3- to 6-year-old) cows purchased as non-pregnant mature animals. The results can guide biosecurity decisions for producers when purchasing and introducing this class of animal to the herd

    Letter to the Editor

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    A within-country study of biased comparative judgements about the severity of environmental problems

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    The spatial and temporal reach of contemporary environmental problems are unparalleled. Collective efforts to address global environmental problems are required but actions to tackle these problems demand initial recognition of their seriousness. Cross-cultural research has shown a reliable bias in comparative judgements about the severity of environmental problems for geographically distant places, with environmental issues perceived to be more severe “there” than “here.” The robustness of this effect may have unwarranted consequences since perceiving environmental problems as being worse elsewhere might lead individuals to not take actions in their locality. We conducted a within-country study to test whether this spatial bias would emerge for samples from all Brazilian states (k = 27, N = 4,265; 85% female; Age M = 24; Age SD = 9.67). Providing further support for a biased comparative judgement, we observed that the severity of environmental problems was judged as worse at the country level than at the state level (mean spatial bias score among Brazilian states = 0.54). Only 2% of the variation in spatial bias was attributable to across-state differences. By replicating cross-cultural findings within a single nation, our findings provide further support for the prevalence and generalizability of biased comparative judgements about the severity of environmental problems. We discuss critical future directions for spatial bias research

    Alice in recidivism land: The Queens logic and child protection workers\u27 assessment of sexual dangerousness

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    This article is based on a case that highlights the dearth of cogent and pertinent risk assessment information in the reports and testimonies of many involved in assessing risks to children in real life problematic circumstances. In the case, the decision to exclude an intrafamilial sexual offender from the family home was made in large measure on the basis that the offender\u27s wife accepted the offender\u27s "denial of guilt" to accusations previously made against him. Keeping families apart should not be entertained without reliable and valid evidence pointing to that decision. However, as will be seen, the evidence often relied upon by child protection workers, albeit in good faith, is neither. The assessment processes described in the case point directly to what appears to be a wider lack of knowledge specific to assessment of recidivism, to misrepresentation of risk assessment information, and to overarching epistemological issues that appear to be widely ignored and/or misunderstood within the overall field of risk assessment and threat management. The purpose of this article is to describe how the information used to decide upon exclusion in the case cannot be considered probative and to iterate the methodological processes that must be considered in such cases if miscarriages of justice are to be avoided

    Does relational mobility vary across national regions? A within-country examination

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    Relational mobility is a socio-ecological construct quantifying how much freedom and opportunity a society affords individuals to choose and dispose of interpersonal relationships. Past research has confirmed that relational mobility varies across nations, but no large-scale study has examined the degree to which relational mobility may vary within a single nation. We report two studies (Study 1, N = 647; Study 2, N = 7343) exploring within-country similarity or variability in relational mobility across all 27 states and five geo-socio-political regions in the continent-size country of Brazil. Results confirmed the measurement equivalence of the Relational Mobility Scale across respondents from all Brazilian states. Notably, relational mobility scores were uniform across Brazilian regions and states, indicating a common national culture regarding the amount of opportunities Brazilians have in selecting new relationship partners within their social context. Replicating existing findings, relational mobility was positively associated with pro-active tendencies that help people retain relationships—levels of intimacy and self-disclosure toward a close friend—indicating that friends tend to feel closer intimacy to their close friends, and reveal serious personal information to a larger degree in social contexts where opportunities to find and retain relationships with like-minded others are greater

    Biological responses to glyphosate drift from aerial application in non-glyphosate-resistant corn

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    BACKGROUND: Glyphosate drift from aerial application onto susceptible crops is inevitable, yet the biological responses to glyphosate drift in crops are not well characterized. The objectives of this research were to determine the effects of glyphosate drift from a single aerial application (18.3m swath, 866 g AE ha−1) on corn injury, chlorophyll content, shikimate level, plant height and shoot dry weight in non-glyphosate-resistant (non-GR) corn. RESULTS: One week after application (WAA), corn was killed at 3m from the edge of the spray swath, with injury decreasing to 18% at 35.4m downwind. Chlorophyll content decreased from 78% at 6m to 22% at 15.8m, and it was unaffected beyond 25.6m at 1 WAA. Shikimate accumulation in corn decreased from 349% at 0m to 93% at 15.8m, and shikimate levels were unaffected beyond 25.6m downwind. Plant height and shoot dry weight decreased gradually with increasing distance. At a distance of 35.4m, corn height was reduced by 14% and shoot dry weight by 10% at 3WAA. CONCLUSIONS: Corn injury and other biological responses point to the same conclusion, that is, injury from glyphosate aerial drift is highest at the edge of the spray swath and decreases gradually with distance. The LD50 (the lethal distance that drift must travel to cause a 50% reduction in biological response) ranged from 12 to 26m among the biological parameters when wind speed was 11.2 kmh−1 and using a complement of CP-09 spray nozzles on spray aircraft

    Perceptions of vulture supplementary feeding site managers and potential hidden risks to avian scavengers

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    Under the current African vulture crisis, supplementary feeding sites (SFS), which provide carrion resources, have become a popular conservation tool to address vulture declines. In South Africa, this practice is unregulated and the context in which SFS operate and their adherence to best management practices is currently unknown. In this study, we conducted a survey with SFS managers regarding the management of their SFS to evaluate potential conservation implications of different practices. Half of the SFS surveyed were associated with livestock farming. Overall, most managers (84%) perceived some benefit from running an SFS, largely attributed to cleaning services provided by vultures. Over half of the managers perceived no disadvantages from running SFS. We found a positive correlation between numbers of vultures seen at SFS and the amount of food provided there. Despite unintentional and intentional poisoning being identified by experts as the most critical threats to vultures in Southern Africa, only 47 and 24% of managers, respectively, listed these as potential threats to vultures, highlighting limited understanding of current vulture conservation issues. Most managers (85%) vetted carcasses for provisioning suitability based on whether they had been treated with veterinary drugs, but relatively few managers (10%) did the same for lead (Pb) contamination. Only 30% of managers considered threats to vultures when they decided on a location for their SFS. Overall, this study unveils that at many SFS, safety conditions are not met and vultures may be exposed to risks, such as the ingestion of toxic substances (e.g., Pb) or electrocution by energy infrastructure. To minimize unintended negative consequences from SFS, it will be essential to increase the interaction between SFS managers and conservation practitioners, to increase the flow of information on best management practices and enforce stringent and clear guidelines that minimize any risks to vultures.Peer reviewe

    Agronomic and environmental implications of enhanced s-triazine degradation

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    Novel catabolic pathways enabling rapid detoxification of s-triazine herbicides have been elucidated and detected at a growing number of locations. The genes responsible for s-triazine mineralization, i.e. atzABCDEF and trzNDF, occur in at least four bacterial phyla and are implicated in the development of enhanced degradation in agricultural soils from all continents except Antarctica. Enhanced degradation occurs in at least nine crops and six crop rotation systems that rely on s-triazine herbicides for weed control, and, with the exception of acidic soil conditions and s-triazine application frequency, adaptation of the microbial population is independent of soil physiochemical properties and cultural management practices. From an agronomic perspective, residual weed control could be reduced tenfold in s-triazine-adapted relative to non-adapted soils. From an environmental standpoint, the off-site loss of total s-triazine residues could be overestimated 13-fold in adapted soils if altered persistence estimates and metabolic pathways are not reflected in fate and transport models. Empirical models requiring soil pH and s-triazine use history as input parameters predict atrazine persistence more accurately than historical estimates, thereby allowing practitioners to adjust weed control strategies and model input values when warranted
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