Biology subjects

Lengagne, T.

Publications and source records attributed to Lengagne, T..

8 recordsLinked to original sources

bioRxiv2026

Ontogenic shift in the usage and function of a symbolic bird gesture

Gestures are an integral part of human communication, and the characterisation of pointing (deictic) and meaningful (symbolic) gestures in non-human primates helps retracing the origins of our own communication system. A recent discovery in Japanese tits (Parus minor) suggested that individuals use a symbolic wing-fluttering gesture to prompt the mating partner to enter the nest first. Symbolic gestures are thus likely more ancestral than previously thought, but the presence of this gesture in related species, the degree to which it is tied to feeding context and whether gestural usage changes across development remain unexplored. To fill these gaps, we studied the wing-fluttering gesture in great tits (Parus major), observing both fledglings and adults in various contexts around nests and away from nests in their natural environment. Our findings showed that wing-fluttering was primarily used by females near nests, almost exclusively in the presence of their mate, and stopped when the mate entered the nest. As in Japanese tits, our results suggest that wing fluttering serves as a symbolic gesture prompting the mate to enter the nest more quickly to feed the nestlings. In contrast, fledglings used wing-fluttering to prompt their parents to feed them and stopped gesturing after having been fed. Our study further indicates deep evolutionary roots of symbolic communication and highlights how functional shifts in gestural usage can operate across development to match age-specific needs.

animal behavior and cognition↗

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↗

bioRxiv2024

Ionizing radiation has negligible effects on the age, telomere length, and corticosterone levels of Chornobyl tree frogs

Pollutants, such as ionizing radiation, released at high levels by human activities can shape ecological and evolutionary processes. The accident occurred at Chornobyl nuclear power plant (Ukraine, April 1986) contaminated a large extension of territory after the deposition of radioactive material. Beyond the immediate negative impact caused by the accident, it is still under debate whether the chronic exposure to the radiation levels currently present in the area signifies a serious threat for organisms. One hypothesis suggests that current levels of radiation may cause unobservable damage in the short-term, but have long-term effects such as decreases in longevity. Here, we investigate through a field-based approach, whether current levels of radiation in Chornobyl negatively impact the age of a semi-aquatic vertebrate, the Eastern tree frog Hyla orientalis. We also explore whether radiation induces changes in an ageing marker, telomere length, or in the stress hormone corticosterone. We found no effect of total individual absorbed radiation (including both external and internal exposure) on frog age (n = 197 individuals sampled in three consecutive years). We also did not find any relationship between individual absorbed radiation and telomere length, but a negative relationship between individual absorbed radiation and corticosterone levels. Our results suggest that radiation levels currently experienced by tree frogs in Chornobyl may not be high enough to cause severe chronic damage to semi-aquatic vertebrates such as this species. This is the first study addressing age and stress hormones in Chornobyl wildlife, and thus future research will confirm if these results can be extended to other taxa.

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↗

bioRxiv2022

Acoustic cues and season affect mobbing responses in a bird community

Heterospecific communication is common for birds when mobbing a predator. However, joining the mob should depend on the number of callers already enrolled, as larger mobs imply lower individual risks for the newcomer. In addition, some community informant species seem more reliable regarding the information transferred in mobbing calls. Birds should therefore rely on both the number of callers and the species identity of the caller(s) when mobbing. In the present study, we tested the potential interaction between two acoustic cues. In a playback experiment, we modified the number of callers (through an increased number of calling individuals correlated to an increased duty cycle) and the emitter species (crested tits versus coal tits). Overall, we found that soundtracks with three callers triggered more mobbing than soundtracks with one caller and that soundtracks with coal tits calls triggered more mobbing than soundtracks with crested tits calls. Our results therefore support the hypothesis that birds consider both the species and the number of callers when joining a mobbing chorus in winter. Finally, we replicated the experiment in spring and did not record the same responses from the bird community. Indeed, only soundtracks with three coal tits triggered a mobbing response, suggesting therefore that the seasonal context can affect the results of studies on heterospecific communication. The potential mechanisms implicated in the varying responses to different acoustic cues and different seasons are discussed and should deserve further investigations.

ecology↗

bioRxiv2021

Large-scale deregulation of gene expression by artificial light at night in tadpoles of common toads

Artificial light at night (ALAN) affects numerous physiological and behavioural mechanisms in various species by potentially disturbing circadian timekeeping systems. Although gene-specific approaches have already shown the deleterious effect of ALAN on the circadian clock, immunity and reproduction, large-scale transcriptomic approaches with ecologically relevant light levels are still lacking to assess the global impact of ALAN on biological processes. Moreover, studies have focused mainly on variations in gene expression during the night in the presence of ALAN but never during the day. In a controlled laboratory experiment, transcriptome sequencing of Bufo bufo tadpoles revealed that ALAN affected gene expression at both night and daytime with a dose-dependent effect and globally induced a downregulation of genes. ALAN effects were detected at very low levels of illuminance (0.1 lux) and affected mainly genes related to the innate immune system and, to a lesser extend to lipid metabolism. These results indicate that a broad range of physiological pathways is impacted at the molecular level by very low levels of ALAN potentially resulting in reduced survival under environmental immune challenges.

ecology↗