Biology subjects

Benard, A.

Publications and source records attributed to Benard, A..

6 recordsLinked to original sources

bioRxiv2025

What We Miss on the Road: Visual Attention and Species Detectability in Roadkill Surveys

Wildlife-vehicle collisions pose a substantial threat to biodiversity, and yet roadkill counts--one the main ways used to quantify mortality--are often susceptible to underestimate true collision rates due to imperfect detection. This study investigates how carcass size and survey methodology affect detection rates during roadkill surveys. Using taxidermied specimens placed along roads, we compare roadkill detection in standardized surveys vs. opportunistic conditions that mimic citizen science data collection, in which observers are not asked to focus on roadkill search alongside roads prior to the survey. Results show that detection probability increases with body mass but declines sharply when observers are not explicitly focused on locating roadkill, with informed participants up to 27 times more likely to detect carcasses than uninformed ones. Even large-bodied species, such as red foxes and European badgers, were frequently missed in opportunistic contexts. By applying species-specific detection probabilities and carcass persistence estimates to a regional citizen science roadkill dataset (Faune-AuRA), we reveal that reported carcass counts represent as little as 0.8-5% of estimated collision numbers. These results demonstrate that roadkill counts, regardless of survey methodology, may substantially underestimate road mortality and distort assessments of species-specific vulnerability in transportation ecology.

ecology↗

bioRxiv2025

Experimental and Simulated Approaches to RoadkillPersistence: Implications for Road MortalityAssessment

The time during which roadkill remains available for detection following a collision is a central issue in road ecology. Not accounting for roadkill persistence leads to underestimating the actual impact of vehicular traffic on populations. Moreover, disregarding the inconsistent rates of disappearance across species, seasons and roads prevents carcass counts from being comparable both within and across studies. This can lead to a misidentification of roadkill hotspots and species for which road mortality is the highest. However, finding the appropriate experimental method to estimate roadkill persistence is difficult: both placing carcasses on roads to conduct removal trials and periodic monitoring of roadkill already present may fail to accurately describe the underlying distribution in persistence times. In this study, in order to assess the potential for systematic bias in roadkill persistence studies depending on the methodology, we simulate roadkill appearance and removal from the road by fitting a survival distribution based on experimental data. We then explore the discrepancies between methods by analysing empirical persistence data derived from both carcass trials and periodic monitoring. We find that, both in theory and in practice, monitoring tends to produce inflated estimates of roadkill persistence compared to carcass removal trials. Accurately describing the distribution of roadkill persistence times may therefore present a greater challenge than previously anticipated.

ecology↗

bioRxiv2023

Influence of traffic and weather on carcass persistence time of small wildlife on roads

The rapidly expanding road network threatens the persistence of many terrestrial species through habitat loss, fragmentation, chemical, light and noise pollution and mortality associated with wildlife-vehicle collisions. Roadkill monitoring under-estimate actual collision numbers as the time during which roadkill carcasses remain visible on the road is often shorter than the frequency of road monitoring. By placing passerines (< 20 g) and amphibian carcasses on stretches of roads we surveyed every 2 hours, we fine-tuned existing persistence estimates for these species. We found median disappearance times (time for half of the carcasses to disappear) of less than 30 minutes for birds and 1-18 hours for amphibians depending on the volume of traffic, which is much shorter than previous estimates. Rainfall did not impact carcass persistence. We show the implications of these results by (1) correcting the results of roadkill surveys performed on common toads in reproductive migration for the number of removed carcasses and (2) estimating the number of passerine-vehicle collisions in the Auvergne-Rhone-Alpes (AuRA) region of France using the citizen-science database Faune-AuRA. We estimate that a road survey conducted 3 hours after amphibian road crossing under-estimates the number of roadkill by half, and that about 6800 passerine collisions were missed in 2022 by contributors because of short carcass persistence on the road. Small-bodied carcasses are hard to detect for drivers, and for a collision-report rate of 1%, total collision numbers for passerines could be as high as 700 000 individuals from 21 reported passerine species in 2022 in AuRA.

ecology↗

bioRxiv2023

A biologically realistic model to predict wildlife-vehicle collision risks

Road networks have major ecological impacts on living organisms consequent to habitat loss and fragmentation, chemical and acoustic pollution, and direct mortality when wildlife-vehicle collisions are involved (WVC). The many past empirical studies revealed biological traits shared by species most vulnerable to roadkills (e.g. population density). Similarly, spatial locations of WVC hot-spots are associated to landscape features at large spatial scales, and to road characteristics at small spatial scale. We currently lack a comprehensive theoretical framework for WVC. Animal movement in relation to habitats is an essential driver of encounters with roads, but this remains largely ignored in studies, even when movement ecology provides the necessary tools to investigate the impact of animal movement on WVC. We built a general individual-based model incorporating recent knowledge in movement ecology (movement typology: roaming, migratory route crossing a road, active attraction and active repulsion of roads) to estimate WVC risks. We explored the relative effects of animal and vehicle movement parameters (speed, abundance, road sinuosity and animal movement pattern) on collision probability. We show that animal behaviour toward roads has major impacts on the number and risks of WVC, but also modulate the effects of other factors (animal traveling speed, species local abundance, road traffic volume) on WVC. Sensitivity analyses show that the movement and behaviour of the animal has more influence on WVC risks than any of the characteristics of roads and vehicles we tested. Our results suggest that (1) effective roadkill mitigation should be species-specific and could vary in efficiency depending on the targets movement pattern (mating and migratory seasons, foraging habits...) and (2) empirical studies of WVC should incorporate knowledge about the behavioural habits of the focal species in relation to roads.

ecology↗

bioRxiv2020

The disproportionate effect of drift on a hypervariable master regulator of density

Symbiosis is a continuum of long-term interactions ranging from mutualism to parasitism, according to the balance between costs and benefits for the protagonists. The density of endosymbionts is, in both cases, a key factor that determines both the transmission of symbionts and the host extended phenotype, and is thus tightly regulated within hosts. However, the evolutionary and molecular mechanisms underlying bacterial density regulation are currently poorly understood. In this context, the symbiosis between the fruit fly and its intracellular bacteria Wolbachia (wMelPop strain) is particularly interesting to study. Although vertically transmitted, the symbiont is pathogenic, and a positive correlation between virulence and wMelPop density is observed. In addition, the number of repeats of a bacterial genomic region -Octomom-is positively correlated with Wolbachia density, underlying a potential genetic mechanism that controls bacterial density. Interestingly, the number of repeats varies between host individuals, but most likely also within them. Such genetic heterogeneity within the host could promote conflicts between bacteria themselves and with the host, notably by increasing within-host competition between symbiont genotypes through a process analogous to the tragedy of the commons. To characterize the determinisms at play in the regulation of bacterial density, we first introgressed wMelPop in different genetic backgrounds of D. melanogaster, and found different density levels and Octomom copy numbers in each host lineage. To determine whether such variations reflect a host genetic determinism on density regulation through Octomom copy number selection, we replicated the introgressions and performed reciprocal crosses on the two Drosophila populations with the most extreme density levels. In both experiments, we detected an absence of directionality in the patterns of infection, associated with a strong instability of these patterns across generations. Given that bacterial density was highly correlated with Octomom copy numbers in all experiments, these results rather suggest a strong influence of drift and a random increase in the frequency of certain bacterial variants. We then discuss how drift, both on the symbiont population during transmission and on the host population, could limit the efficiency of selection in such a symbiotic system, and the consequences of drift on the regulation of density and composition of bacterial populations.

evolutionary biology↗

bioRxiv2020

Interleukin-3 is a predictive marker for severity and outcome during SARS-CoV-2 infections

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a worldwide health threat. Here, we report that low plasma interleukin-3 (IL-3) levels were associated with increased severity and mortality during SARS-CoV-2 infections. IL-3 promoted the recruitment of antiviral circulating plasmacytoid dendritic cells (pDCs) into the airways by stimulating CXCL12 secretion from pulmonary CD123+ epithelial cells. This study identifies IL-3 as a predictive disease marker and potential therapeutic target for SARS-CoV-2 infections.Competing Interest StatementThe authors have declared no competing interest.View Full Text

immunology↗