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Theory on the density?body-mass (DBM) relationship predicts that the density of animal species decreases by the power of ?0.75 per unit increase in their body mass, or by the power of ?1 when taxa across trophic levels are studied. This relationship is, however, largely debated, as the slope often deviates from the theoretical predictions. Here, we tested the ability of the DBM relationship to reflect changes in the structure of communities subjected to an anthropogenic disturbance. The slope would become less steep if smaller animals were more impacted by the disturbance than the larger ones, whereas the slope would become steeper if larger animals were more affected than the smaller ones. We tested the changes in the DBM relationship by sampling soil fauna, i.e., nematodes, Collembola, and larger arthropods, from a semiarid grassland before and after spraying diesel fuel as disturbance. We applied three different treatments: a control, a light disturbance, and an intense disturbance. We found that the slopes of the DBM relationships before the disturbance were around ?1 as predicted by theory. The slope became more positive (i.e., less steep) just after the disturbance, especially after the intense disturbance as smaller fauna suffered the most and early colonizers had larger body mass. Interestingly, we observed that the slopes converged back to ?1 by 2 months post-disturbance. Our findings show that the response of soil fauna communities to anthropogenic disturbances could explain the large variation in observed slopes of the DBM relationships. We experimentally demonstrate that an animal community, when disturbed, shows a temporal pattern of DBM relationships ranging from deviations from the predicted slope to convergence to the predicted slope with time. We recommend that deviations in the DBM relationships after disturbances can provide insights in the trajectory of community recovery, and hence could be used for biomonitoring.

Retraction notice: We have been informed that because of logistical reasons the authors of Comor et al. (2019) were unable able to provide the answers requested by Duriez et al. (2020) regarding the protocols, the quantitative data, or the small and unbalanced sample sizes. At the authors' request, the article by Comor et al. published in Human–Wildlife Interactions 13(3) has been retracted. Human activities are usually considered as disturbing factors impeding the breeding success of wild animals. Protected areas can then be set up to restrict such activities aiming to improve wildlife’s breeding success and conservation. To test for the efficiency of these measures, we compared the breeding success of bearded vultures (Gypaetus barbatus) in the western French Pyrenees from autumn 2011 to spring 2017, where eyries are located either within or outside restricted areas, where potentially disturbing activities are restricted (e.g., helicopter flights, forestry works, hunting, paragliding). We monitored reproducing bearded vultures and checked the breeding success at different stages (laying, incubation, hatching, and survival at 2 months) of formed pairs. We then compared the success of each stage between eyries located in restricted and non-restricted areas, including weather data in our model. We found that the breeding success was similar in both types of areas, but that is was negatively impacted by precipitations, which may directly affect the ability of the egg or chick to withstand cold. We also focused on the potential disturbance of hunting parties on the behavior of bearded vultures and found no evidence that hunting was perceived as a threat by bearded vultures; they may in fact benefit from gut piles. Hence, our comparison of the breeding success between eyries located in restricted versus non-restricted areas shows no detrimental impact of human activities and calls for some studies to assess the effectiveness of restrictions in improving the breeding success of bearded vultures, as this species seems to show some degree of tolerance to human activities and may significantly suffer from harsh winter weather in this area.

The productivity of ecosystems and their disturbance regime affect the structure of animal communities. However, it is not clear which trophic levels benefit the most from higher productivity or are the most impacted by disturbance. The density-body mass (DBM) relationship has been shown to reflect changes in the structure of communities subjected to environmental modifications, so far, mainly in aquatic systems. We tested how different seawater inundation frequencies and cattle grazing, which both disturbed and impacted the productivity of a terrestrial system, a salt marsh, affected the size structure of soil fauna communities, expressed by their DBM relationship. We hypothesized that either: (1) all the trophic levels of soil fauna would benefit from higher productivity (i.e., amount of litter mass), reflected by a higher Y-intercept of the DBM relationship; (2) only smaller animals would benefit, reflected by a lower slope of the relationship; (3) or only larger animals would benefit, reflected by a higher slope of the relationship. We collected a large range of soil fauna from different elevation levels in grazed and ungrazed areas, thence subjected to different levels of productivity, represented by litter mass, with the most inundated and grazed area as the least productive one. Considering that pore size must be smaller in inundated and grazed areas, productivity seemed to be a greater factor influencing species distribution than soil structure. We found slopes lower than-0.75, showing that large animals dominated the community. However, a difference between the DBM relationships of the most and least frequently inundated ungrazed sites indicated that higher productivity benefited the smaller animals. Our findings show that high productivity does not equally affect the different trophic levels of this soil fauna community, suggesting inefficient transfers of energy from one trophic level to another, as smaller species benefitted more from higher productivity. © 2014 Elsevier Ltd.

FR2116; International audience; In front of land use changes, there has been a wide decline in biodiversity. In this study, we analysed the numerical response of two diurnal raptor species, the common buzzard and the Eurasian kestrel to different agricultural landscape contexts. We carried out a 3-year survey of the abundance of these two species in three agricultural landscape contexts that are known to form a gradient of land use intensity and hedgerow network fragmentation. We also considered the variation in prey abundance related to these land use changes. The two raptor species showed negative but differentiated response patterns to land use intensification and smallmammalabundance. The abundance of thecommonbuzzard decreased significantly with the reduction of hedgerows, woodlots and grasslands areas, as well as with the decrease in prey abundance at the landscape scale. The abundance of the Eurasian kestrel showed the same trend, but fall of abundance was less marked and not significant. This resulted in a reverse ratio of species density according to agricultural intensification and landscape openness. Specific feeding habits, nesting habitats and spatial partitioning in foraging areas could explain the difference in the numerical response observed for these two raptor species. Buzzards forage mainly on highly profitable prey areas and avoid highly fragmented woodland habitats for nesting. Kestrels seem less dependent on semi-natural habitats, are able to nest in more fragmented landscapes and are better adapted to exploit less abundant but more widespread small mammal prey species within the cultivated matrix. The study may help to evaluate carrying capacities of agricultural landscapes in accordance with ecological life traits of these two raptor species.

International audience; In coastal dunes, inXuenced by anthropogenic activities such as tourism, it is important to determine the relative inXuence of environmental factors at diVerent spatial scales to evaluate the sensitivity of local communities to disturbances. We analyzed beetle communities of 14 dunes of the French Mediterranean coast: four in the relatively preserved Camargue area, and ten in the Var department, where tourism is intensive. Beetle communities were studied three times in early spring using sand sampling. Species-environment relationships were evaluated at the regional, landscape and local scale using redundancy analysis (RDA) and variability partitioning. About 28 species were identified, of which 15 were sand-specialist species, which accounted for more than 93% of total abundance. The beetle communities of Camargue were signiWcantly diVerent from those of the Var department owing to the pullulation of a Tenebrionid species (Trachyscelis aphodioides Latr.) in the Var, except for one restored dune where the community was very similar to those of Camargue. Our results showed no longitudinal gradient between the two regions. Local factors (dune height, preservation and disturbance index) signiWcantly explained most of the variation in the dominance of T. aphodioides, while some other local factors were important for other psammophilous species. This study also suggests that dune beetle communities are strongly affected on beaches intensively managed for tourism, but beetles are still abundant in much disturbed sites.