The dynamics of group formation in large mammalian herbivores: an analysis in the European roe deer

International audienceIn large mammalian herbivores, herd size usually increases with openness of the environment, but the proximate mechanisms that underlie this phenomenon remain poorly known. We investigated the dynamics of group formation in a population of roe deer, Capreolus capreolus, living in open cultivated plain. Our results show the high spontaneous instability of groups. The probability of fission per unit time increased approximately as the square of group size, and the sizes of the groups resulting from a splitting-up followed a uniform distribution. Attraction between groups was the main cause of fusion and was at work over distances of more than 200&nbsp;m, far exceeding the perception radius of roe deer in forest. In addition, when not yet separated by than more than 200&nbsp;m, two groups resulting from a single splitting-up had a high probability of remerging and restoring the parent group. Our results are thus consistent with the assumption that in large herbivores group size increases with habitat openness, not because of a change in individual's behaviour, but because groups are unstable and any increase of the distance at which animals perceive one another enhances the rate at which groups merge.</p

Coordination, independence or synchronisation of individual vigilance in the eastern grey kangaroo?

International audienceVigilance activity is usually considered an adaptive advantage of group living conferring protection against predators. An individual of a prey species is assumed to benefit from an increase in the number of group members by reducing its own investment in vigilance. However, the proximate mechanism generating the decrease in vigilance with increasing group size is unclear. Most models of this relation assume that either individuals coordinate their scans in nonoverlapping bouts of vigilance or animals scan independently of one another.We studied the relation between vigilance and group size in the eastern grey kangaroo, Macropus giganteus, analysing vigilance at two structural levels, individual vigilance and collective vigilance of the group. We tested both assumptions, coordination and independence of scanning. The time that an individual spent vigilant decreased with group size. However, the time during which at least one individual in the group scanned the environment (collective vigilance) increased up to a group size of seven individuals but decreased thereafter. Analyses revealed that individuals neither coordinated their scanning in an asynchronous way nor scanned independently of one another. On the contrary, both the onset and the end of individuals’ scanning bouts were synchronized between group members, producing waves of collective vigilance. Bouts of vigilance and nonvigilance activity tended to be synchronized. Our results appear to support a hypothesis of allelomimetic vigilanc

Développement d'une méthodologie analytique pour le dosage de composés soufrés malodorants dans différentes matrices environnementales.

Ces travaux de thèse se sont attachés à développer des méthodologies analytiques qui permettraient l'analyse des composés soufrés malodorants par des techniques simples à mettre en œuvre, fiables et peu coûteuses pour des fortes concentrations (g m-3) jusqu'aux limites de perception olfactives (~æg m-3). L'analyse de fortes concentrations des gaz soufrés était effectuée en injectant directement l'échantillon gazeux dans l'appareillage chromatographique GC/PFPD (chromatographe en phase gazeuse/ photomètre de flamme pulsée). Pour des concentrations de l'ordre du æg m-3, l'utilisation d'une méthode de préconcentration d'échantillons, la microextraction sur phase solide (SPME), a été évaluée en mode d'échantillonnage ponctuel et passif pour les milieux gazeux ainsi que sur certains effluents liquides. Les limites d'utilisation de cette technique pour ces applications ont ainsi été définies et approfondies.This thesis consisted to develop analytical methodologies for the analysis of malodorous sulphur compounds using simple, reliable and low cost techniques for concentrations ranging from high (g m-3) to the human olfactory threshold (~æg m-3). The analysis of high concentrations was carried out by injecting directly the gaseous sample into the GC/PFPFD chromatographic system (gas chromatograph/ pulsed flame photometer detector). For æg m-3 concentrations level, the utilisation of a preconcentration method, SPME (Solid Phase Microextraction), was evaluated in grab and passive sampling modes on gaseous samples and also on some liquid effluents. The limits of utilisation of this technique for these various applications were then carefully defined.PAU-BU Sciences (644452103) / SudocSudocFranceF

Prey synchronize their vigilant behaviour with other group members

It is generally assumed that an individual of a prey species can benefit from an increase in the number of its group's members by reducing its own investment in vigilance. But what behaviour should group members adopt in relation to both the risk of being preyed upon and the individual investment in vigilance? Most models assume that individuals scan independently of one another. It is generally argued that it is more profitable for each group member owing to the cost that coordination of individual scans in non-overlapping bouts of vigilance would require. We studied the relationships between both individual and collective vigilance and group size in Defassa waterbuck, Kobus ellipsiprymnus defassa, in a population living under a predation risk. Our results confirmed that the proportion of time an individual spent in vigilance decreased with group size. However, the time during which at least one individual in the group scanned the environment (collective vigilance) increased. Analyses showed that individuals neither coordinated their scanning in an asynchronous way nor scanned independently of one another. On the contrary, scanning and non-scanning bouts were synchronized between group members, producing waves of collective vigilance. We claim that these waves are triggered by allelomimetic effects i.e. they are a phenomenon produced by an individual copying its neighbour's behaviour

Why are manual workers at high risk of upper limb disorders? The role of physical work factors in a random sample of workers in France (the Pays de la Loire study)

International audienceOBJECTIVE: To investigate the reasons for the excess risk of upper limb musculoskeletal disorders among manual workers compared with other workers in a random sample of 2656 French men and women (20-59 years old) participating in a study on the prevalence of work related upper limb disorders conducted by France's National Institute of Health Surveillance. METHODS: Prevalence ratios (PR) of physician-diagnosed musculoskeletal disorders of the shoulder, elbow, wrist, and hand (any of six leading disorders, rotator cuff syndrome, carpal tunnel syndrome) in manual versus non-manual workers were calculated using Cox regression models with a constant time of follow up and robust variance. RESULTS: 11.3% of men and 15.1% of women were diagnosed with an upper limb disorder. The risk was especially high in manual workers (PRs: 1.40 to 2.10). Physical work factors accounted for over 50% of occupational disparities overall, 62% (men) to 67% (women) for rotator cuff syndrome, and 96% (women) for carpal tunnel syndrome. The authors calculated that under lower levels of physical work exposures, up to 31% of cases among manual workers could have been prevented. CONCLUSIONS: In working men and women, upper limb musculoskeletal disorders are frequent. Physical work exposures, such as repetitive and forceful movements, are an important source of risk and in particular account for a large proportion of excess morbidity among manual workers

Action-orientated research and framework: insights from the French long-term social-ecological research network

International audienceMany social-ecological system(SES)-based approaches have been proposed to address environmental problems. Most social-ecological frameworks developed to date, however, lack clear operational linkages between humans and nature to efficiently guide SESs toward resilience. A conceptual framework designed to be operational is therefore necessary, as well as a network of research platforms with which to apply it. We defined explicit coupling processes that can be used as leverages to pilot an SES toward sustainability. We proposed to formalize an SES as a dynamic entity composed of two coupling interfaces, i.e., adaptive management and ecosystem services, both set within a landscape context to provide an actionable framework. These interfaces describe the way various actors, including scholars, benefit from and manage complex and changing interactions between the biophysical and social templates. Understanding the key processes underlying the interaction dynamics, especially those leveraging adaptive management processes, would help identify adaptive pathways for practices and collective actions, provide a crucial knowledge base for policy makers, and foster operationality as a requisite of an SES research agenda. Using several examples, we explained why long-term social-ecological research platforms provide an ideal operational network of research infrastructures to conduct place-based action-orientated research targeting the sustainability of SESs

Biological and Neuroimaging Markers as Predictors of 5-Year Incident Frailty in Older Adults: A Secondary Analysis of the MAPT Study

International audienceBackground This study aims to investigate the predictive value of biological and neuroimaging markers to determine incident frailty among older people for a period of 5 years. Methods We included 1394 adults aged 70 years and older from the Multidomain Alzheimer Preventive Trial, who were not frail at baseline (according to Fried’s criteria) and who had at least 1 post-baseline measurement of frailty. Participants who progressed to frailty during the 5-year follow-up were categorized as “incident frailty” and those who remained non-frail were categorized as “without frailty.” The differences of baseline biochemical factors (25-hydroxyvitamin D, homocysteine, omega-3 index, C-reactive protein), other biological markers (Apolipoprotein E genotypes, amyloid-β deposits), and neuroimaging data (gray matter volume, hippocampal volume, white matter hyperintensities) were compared between groups. Cox proportional hazard model was used to evaluate the associations between biomarkers and incident frailty. Results A total of 195 participants (14.0%) became frail over 5 years. Although 25-hydroxyvitamin D deficiency, homocysteine levels, low-grade inflammation (persistently increased C-reactive protein 3–10 mg/L), gray matter, and hippocampal volume were significantly associated with incident frailty in unadjusted models, these associations disappeared after adjustment for age, sex, and other confounders. Omega-3 index was the sole marker that presented a trend of association with incident frailty (hazard ratio: 0.92; 95% confidence interval: 0.83–1.01; p = .082). Conclusions This study failed to identify biomarkers able to predict frailty incidence in community-dwelling older adults for a period of 5 years. Further longitudinal research with multiple measurements of biomarkers and frailty is needed to evaluate the long-term relationships between changes in biomarkers levels and frailty evolution

Effect of long-term omega 3 polyunsaturated fatty acid supplementation with or without multidomain intervention on cognitive function in elderly adults with memory complaints (MAPT): a randomised, placebo-controlled trial

International audienceBACKGROUND:No large trials have been done to investigate the efficacy of an intervention combining a specific compound and several lifestyle interventions compared with placebo for the prevention of cognitive decline. We tested the effect of omega 3 polyunsaturated fatty acid supplementation and a multidomain intervention (physical activity, cognitive training, and nutritional advice), alone or in combination, compared with placebo, on cognitive decline.METHODS:The Multidomain Alzheimer Preventive Trial was a 3-year, multicentre, randomised, placebo-controlled superiority trial with four parallel groups at 13 memory centres in France and Monaco. Participants were non-demented, aged 70 years or older, and community-dwelling, and had either relayed a spontaneous memory complaint to their physician, limitations in one instrumental activity of daily living, or slow gait speed. They were randomly assigned (1:1:1:1) to either the multidomain intervention (43 group sessions integrating cognitive training, physical activity, and nutrition, and three preventive consultations) plus omega 3 polyunsaturated fatty acids (ie, two capsules a day providing a total daily dose of 800 mg docosahexaenoic acid and 225 mg eicosapentaenoic acid), the multidomain intervention plus placebo, omega 3 polyunsaturated fatty acids alone, or placebo alone. A computer-generated randomisation procedure was used to stratify patients by centre. All participants and study staff were blinded to polyunsaturated fatty acid or placebo assignment, but were unblinded to the multidomain intervention component. Assessment of cognitive outcomes was done by independent neuropsychologists blinded to group assignment. The primary outcome was change from baseline to 36 months on a composite Z score combining four cognitive tests (free and total recall of the Free and Cued Selective Reminding test, ten Mini-Mental State Examination orientation items, Digit Symbol Substitution Test, and Category Naming Test) in the modified intention-to-treat population. The trial was registered with ClinicalTrials.gov (NCT00672685).FINDINGS:1680 participants were enrolled and randomly allocated between May 30, 2008, and Feb 24, 2011. In the modified intention-to-treat population (n=1525), there were no significant differences in 3-year cognitive decline between any of the three intervention groups and the placebo group. Between-group differences compared with placebo were 0·093 (95% CI 0·001 to 0·184; adjusted p=0·142) for the combined intervention group, 0·079 (-0·012 to 0·170; 0·179) for the multidomain intervention plus placebo group, and 0·011 (-0·081 to 0·103; 0·812) for the omega 3 polyunsaturated fatty acids group. 146 (36%) participants in the multidomain plus polyunsaturated fatty acids group, 142 (34%) in the multidomain plus placebo group, 134 (33%) in the polyunsaturated fatty acids group, and 133 (32%) in the placebo group had at least one serious emerging adverse event. Four treatment-related deaths were recorded (two in the multidomain plus placebo group and two in the placebo group). The interventions did not raise any safety concerns and there were no differences between groups in serious or other adverse events.INTERPRETATION:The multidomain intervention and polyunsaturated fatty acids, either alone or in combination, had no significant effects on cognitive decline over 3 years in elderly people with memory complaints. An effective multidomain intervention strategy to prevent or delay cognitive impairment and the target population remain to be determined, particularly in real-world settings

Associations Between Physical Activity, Blood-Based Biomarkers of Neurodegeneration, and Cognition in Healthy Older Adults: The MAPT Study

International audiencePhysical activity (PA) demonstrated benefits on brain health, but its relationship with blood biomarkers of neurodegeneration remains poorly investigated. We explored the cross-sectional associations of PA with blood concentrations of neurofilament light chain (NFL) and beta amyloid (Aβ)42/40. We further examined whether the interaction between PA and these biomarkers was longitudinally related to cognition. Four-hundred and sixty-five nondemented older adults engaged in an interventional study and who had a concomitant assessment of PA levels and blood measurements of NFL (pg/mL) and Aβ 42/40 were analyzed. A composite Z-score combining 4 cognitive tests was used for cognitive assessment up to a 4-year follow-up. Multiple linear regressions demonstrated that people achieving 500–999 and 2000+ MET-min/week of PA had lower (ln)NFL concentrations than their inactive peers. Logistic regressions revealed that achieving at least 90 MET-min/week of PA was associated with a lower probability of having high NFL concentrations (ie, ≥91.961 pg/mL [third quartile]). PA was not associated with (Aβ)42/40. Mixed-model linear regressions demonstrated that the reverse relationship between PA and cognitive decline tended to be more pronounced as Aβ 42/40 increased, while it was dampened with increasing levels of (ln)NFL concentrations. This study demonstrates that PA is associated with blood NFL but not with Aβ 42/40. Furthermore, it suggests that PA may attenuate the negative association between amyloid load and cognition, while having high NFL levels mitigates the favorable relationship between PA and cognition. More investigations on non demented older adults are required for further validation of the present findings