How unpredictable is the individual scanning process in socially foraging mammals?

In group-forming prey species, theory assumes that individuals within groups should scan independently of one another, with vigilance sequences being relatively unpredictable, making interscan durations highly variable. We attempted to detect any divergence from randomness in the scanning process in three mammalian prey species phylogenetically and geographically separated and exposed to different levels of predation: waterbuck, Kobus ellipsiprymnus defassa, under a high observed predation risk, eastern grey kangaroo, Macropus giganteus, still experiencing occasional predation and European roe deer, Capreolus capreolus, under a very low natural predation risk. Our results revealed that the focal interscan duration increased when the duration of the preceding interscan increased, whatever the studied species and the predation risk that its individuals experienced, and decreased with the preceding scan duration in two species under, respectively, occasional and low predation risks. The exponential distribution was the tested model that fitted the observed distributions of interscan durations least well. We discuss what can trigger non-randomness in scanning, through a non-homogenous Poisson process, at both intra-individual and inter-individual levels, particularly with regard to previous studies that have demonstrated synchronisation of vigilance in such mammals. Our results suggest the need to reconsider any assumption of randomness in scanning in the basic model predicting form and frequency of scanning behaviour by prey species.     

A large-scale experiment on mass transfer of trichloroethylene from the unsaturated zone of a sandy aquifer to its interfaces

A large-scale experiment was conducted to investigate the transport of trichloroethylene (TCE) vapors in the unsaturated zone and to determine the mass transfer to the groundwater and the atmosphere. The experiment involved injection of 5 1 of TCE in the unsaturated zone under controlled conditions, with multidepth sampling of gas and water through the unsaturated zone and across the capillary zone into underlying groundwater. The mass transfer of TCE vapors from the vadose zone to the atmosphere was quantified using a vertical flux chamber. A special soil water sampler was used to monitor transport across the capillary fringe. Experimental data indicated that TCE in the unsaturated zone was mainly transported to the atmosphere and this exchange reduced significantly the potential for groundwater pollution. The maximum measured TCE flux to the atmosphere was about 3 g/m(2)/day. Observed and calculated fluxes based on vertical TCE vapor concentration gradients and Fick's law were in good agreement. This confirms that TCE vapor transport under the experimental conditions was governed essentially by molecular diffusion. TCE vapors also caused a lower, but significant contamination of the underlying groundwater by dispersion across the capillary fringe with a corresponding maximum flux of about 0.1 g/m(2)/day. This mass transfer to groundwater is partly uncertain due to an inadvertent entry of some nonaqueous phase liquid (NAPL) from the source area into the saturated zone. Application of an analytical solution to estimate the TCE flux from the unsaturated zone to the groundwater indicated that this phenomenon is not only influenced by molecular diffusion but also by vertical dispersion. The mass balance indicates that, under the given experimental conditions (e.g. proximity of the source emplacement relative to the soil surface, relatively high permeable porous medium), nearly 95% of the initial TCE mass was transferred to the atmosphere.     

Impact of peri-urban landscape on the organic and mineral contamination of pond waters and related risk assessment

Environmental Science and Pollution Research - Ponds are important for their ecological value and for the ecosystem services they provide to human societies, but they are strongly affected by human...     

Normative barriers improvement through the MADS/MOSAR methodology

During the past 30 years, safety and environmental topics have moved up on the list of society’s significant concerns. Administrations and regulatory bodies have to publish rules for the protection of the public, decide whether to authorize the use of a chemical product or the construction of a new plant, limit the environmental impact, regulate waste disposal, etc. All these rules i.e. the legislative, normative and procedural corpus of a country, a state, a city or a factory can be designated to a barrier function. These barriers are indispensable and play an important role in industrial safety management. In developed countries, growth during the past few years in the number of laws directed at regulating environmental and safety aspects in industry is well known to everyone. Now the definition, classification and performance of the legislative and normative barriers definitely allow the management of technological risks. So it is possible to permit the identification of the flux of hazard and to perform risk reduction in order to enhance the acceptability in a regional context. A systemic risk analysis methodology was applied to Colombian industrial sectors. The current legislation was analyzed with three scenarios. A global panorama of the different existing instruments allowing future management opportunities was suggested. The obtained analysis results propose a point of view, which could be useful for a local government or a whole national system to evaluate or improve the risk legislative and normative barriers. This modeling can be applied to other countries and to other industrial sectors.     

Maize bushy stunt in native corn: implications for Mexican “subsistence farmers”

Native corn in Mexico can be affected by maize bushy stunt disease (MBS), which can negatively impact maize-farming operations. Maize bushy stunt symptoms in native corn were linked to the presence of phytoplasmas through molecular analysis of symptomatic native corn plants in Mexico. These findings motivated a socioeconomic characterization and identification of the management strategies developed by the “subsistence farmers” of those communities to answer the questions: What elements of farming affect the presence of MBS disease in “subsistence farmers” fields? What do “subsistence farmers” know about MBS disease and the pathogen associated with MBS disease? How best can MBS disease be managed in small farming communities in Mexico? Through face-to-face interviews with growers and the corresponding analyses of their responses, we identified a widespread lack of knowledge about MBS disease, its causal agent and its vector(s). This study highlighted factors useful to guide future management decisions and education programs, as well as further research to transmit information about MBS disease among “subsistence farmers” in rural communities in Mexico.     

Internal distribution of uranium and associated genotoxic damages in the chronically exposed bivalve Corbicula fluminea

Uranium (U) internal distribution and involved effects in the bivalve Corbicula fluminea have been studied after direct chronic exposure (90 d, 10 μg.L-1). U distribution was assessed at the subcellular level (Metal Rich Granules -MRG-, pellets and cytosol fractions) in two main organs of the bivalve (gills and visceral mass). Micro-localisation was investigated by TEM-EDX analysis in the gills epithelium. DNA damage in gill and hemolymph samples was measured by the Comet assay. The 90-d exposure period led to a significant increase of U concentration in gills over time (×5) and a large U quantity in subcellular granules in gills. Finally, a significant increase (×2) in DNA damage was noted in exposed gills and haemocytes. This study shows that the accumulation levels and consequently the potential toxicity cannot be successfully predicted only on the basis of concentration in water or in tissues and subcellular fractions after chronic exposure.     

Individual variation in the relationship between vigilance and group size in eastern grey kangaroos

The mean vigilance of animals in a group often decreases as their group size increases, yet nothing is known about whether there is individual variability in this relationship in species that change group sizes frequently, such as those that exhibit fission–fusion social systems. We investigated variability in the relationship between group size and vigilance in the eastern grey kangaroo (Macropus giganteus) by testing whether all individuals showed decreased vigilance with increased group size, as has been commonly assumed. We carried out both behavioural observations of entire groups of kangaroos and focal observations of individually recognised wild female kangaroos. As in other studies, we found a collective group-size effect on vigilance; however, individuals varied in their vigilance patterns. The majority (57%) of the identified individual kangaroos did not show significant group-size effects for any of the recorded measures of vigilance. The females that did not show a negative group-size effect were, on average, more vigilant than those females that did show a group-size effect, but this difference was not significant. We propose that some females exhibit higher levels of social vigilance than others, and that this social vigilance increases with group size, cancelling out any group-size effect on anti-predator vigilance for those females. Our results therefore suggest that only some prey individuals may gain anti-predator benefits by reducing their time spent scanning when in larger groups. The large amount of variation that we found in the vigilance behaviour of individual kangaroos highlights the importance of collecting and analysing vigilance data at the individual level, which requires individual recognition.     

Study of the Degradation of Poly(ethyl glyoxylate): Biodegradation, Toxicity and Ecotoxicity Assays

Biodegradation of poly (ethyl glyoxylate) (PEtG), a functionalized polyacetal, was investigated over 6?month according to ASTM 5988-96 modified method and compared to micronized cellulose. More than 95?% of the polymer was converted into CO₂ over that period attesting the biodegradability of PEtG. The degradation by-products toxicity and ecotoxicity were evaluated. Toxicity was checked using an innovant non-mammalian toxicological model using the nematode Caenorhabditis elegans. Ecotoxicity was performed using a plant growth test with cress (Lepidium Sativum), and barley (Hordeum vulgare). In all cases, results concluded on the harmlessness of PEtG and relative by-products.