Bruit de trafic routier : implications comportementales et écophysiologiques chez la rainette verte Hyla arborea

Road traffic noise is undoubtedly the most important source of anthropogenic noise on terrestrial habitat. This thesis, at the interface between behaviour and physiology was designed to experimentally determine the impacts of road traffic noise exposure on both animal communication systems (acoustic and visual) and physiology (stress, immunity ...) The choice of Hyla arborea, species using both acoustic and coloured signals for communication, allowed us to efficiently test our various hypotheses. While in many bird species changes in acoustic communication system have been observed (in both the transmitter and receiver) my results do not show such disturbances in H. arborea. However, for the first time, I was able to highlight the impact of road traffic noise on visual communication, chronic exposure to traffic noise resulting in colouration loss in male. In addition, physiological measures have allowed me to show that road traffic noise exposure is stressful (corticosterone level rise) and has immunosuppressive effect (due stress rise) in H.arborea. Thus, this thesis demonstrates that road traffic noise may have a larger effect than previously thought by impacting, in addition to the acoustic communication, visual communication (impact on coloured signals) and animal physiologyLe bruit engendré par le trafic routier est aujourd'hui une des nuisances sonores d'origine anthropique les plus importantes en milieu terrestre. Cette thèse, à l'interface entre comportement et écophysiologie, a eu pour but de déterminer expérimentalement les impacts d'une exposition à du bruit de trafic routier tant sur les systèmes de communication (acoustique et visuelle) que sur la physiologie (stress, immunité…) animale. Le choix de Hyla arborea, espèce utilisant à la fois des signaux acoustiques et colorés pour la communication, nous a permis de tester efficacement nos différentes hypothèses. Alors que chez de nombreuses espèces d'oiseaux des modifications du système de communication acoustique ont été observées (tant chez l'émetteur que le récepteur), mes travaux n'ont pas mis en évidence de telles perturbations chez Hyla arborea. Cependant, et pour la première fois, j'ai pu mettre en évidence un impact du bruit de trafic routier sur la communication visuelle, une exposition chronique à du bruit de trafic routier entraînant une perte de couleur chez les mâles. Enfin, des mesures physiologiques m'ont permis de montrer qu'une exposition chronique à du bruit de trafic routier est stressant (élévation du niveau de corticostérone) et a un effet immunosuppresseur (dû à l'augmentation du stress) chez H.arborea. Ainsi cette thèse démontre que le bruit de trafic routier peut avoir un impact plus large que ce qui était suggéré jusqu'à présent en impactant, en plus de la communication acoustique, la communication visuelle (signaux colorés) et la physiologie des animau

Road traffic noise : behavioral and physiological impacts on the European treefrog Hyla arborea

Le bruit engendré par le trafic routier est aujourd'hui une des nuisances sonores d'origine anthropique les plus importantes en milieu terrestre. Cette thèse, à l'interface entre comportement et écophysiologie, a eu pour but de déterminer expérimentalement les impacts d'une exposition à du bruit de trafic routier tant sur les systèmes de communication (acoustique et visuelle) que sur la physiologie (stress, immunité…) animale. Le choix de Hyla arborea, espèce utilisant à la fois des signaux acoustiques et colorés pour la communication, nous a permis de tester efficacement nos différentes hypothèses. Alors que chez de nombreuses espèces d'oiseaux des modifications du système de communication acoustique ont été observées (tant chez l'émetteur que le récepteur), mes travaux n'ont pas mis en évidence de telles perturbations chez Hyla arborea. Cependant, et pour la première fois, j'ai pu mettre en évidence un impact du bruit de trafic routier sur la communication visuelle, une exposition chronique à du bruit de trafic routier entraînant une perte de couleur chez les mâles. Enfin, des mesures physiologiques m'ont permis de montrer qu'une exposition chronique à du bruit de trafic routier est stressant (élévation du niveau de corticostérone) et a un effet immunosuppresseur (dû à l'augmentation du stress) chez H.arborea. Ainsi cette thèse démontre que le bruit de trafic routier peut avoir un impact plus large que ce qui était suggéré jusqu'à présent en impactant, en plus de la communication acoustique, la communication visuelle (signaux colorés) et la physiologie des animauxRoad traffic noise is undoubtedly the most important source of anthropogenic noise on terrestrial habitat. This thesis, at the interface between behaviour and physiology was designed to experimentally determine the impacts of road traffic noise exposure on both animal communication systems (acoustic and visual) and physiology (stress, immunity ...) The choice of Hyla arborea, species using both acoustic and coloured signals for communication, allowed us to efficiently test our various hypotheses. While in many bird species changes in acoustic communication system have been observed (in both the transmitter and receiver) my results do not show such disturbances in H. arborea. However, for the first time, I was able to highlight the impact of road traffic noise on visual communication, chronic exposure to traffic noise resulting in colouration loss in male. In addition, physiological measures have allowed me to show that road traffic noise exposure is stressful (corticosterone level rise) and has immunosuppressive effect (due stress rise) in H.arborea. Thus, this thesis demonstrates that road traffic noise may have a larger effect than previously thought by impacting, in addition to the acoustic communication, visual communication (impact on coloured signals) and animal physiolog

Cheating for sex: inherent disadvantage or energetic constraint?

International audienceIn many species, some males gain access to females by cheating, i.e. by exploiting the reproductive investment made by other males. There are two main nonmutually exclusive hypotheses to explain the decision of an individual to switch from the classical reproductive tactic to the parasitic one: the inherent disadvantage and energetic constraint hypotheses. For the ␣rst time, we tested and compared these two hypotheses in an experimental design by manipulating food availability of males with different degrees of inherent disadvantage in the caller/satellite system of Hyla arborea. Small males were more likely to be satellites than large individuals as predicted by the inherent disadvantage hypothesis. However, food deprived males were not more likely to be satellites than those that were fed, suggesting that the energetic constraint is not the main process explaining the use of a parasitic reproductive tactic. Moreover, all else being equal, males were more likely to act as satellites if confronted with an attractive competitor than if confronted with an unattractive one. In addition, males had a greater probability of being satellites at the beginning and end of the night, whereas they were more likely to call during the middle of the night. These results could highlight synchronization between male tactics and expected female availability during the course of the night

Effects of traffic noise on tree frog stress levels, immunity, and color signaling

International audienceDuring the last decade, many studies have focused on the detrimental effects of noise pollution on acoustic communication. Surprisingly, although it is known that noise exposure strongly influences health in humans, studies on wildlife remain scarce. In order to gain insight into the consequences of traffic noise exposure, we experimentally manipulated traffic noise exposure as well as the endocrine status of animals to investigate physiological and phenotypic consequences of noise pollution in an anuran species. We showed that noise exposure increased stress hormone level and induced an immunosuppressive effect. In addition, both traffic noise exposure and stress hormone application negatively impacted H. arborea vocal sac coloration. Moreover, our results suggest profound changes in sexual selection processes because the best quality males with initial attractive vocal sac coloration were the most impacted by noise. Hence, our study suggests that the recent increases in anthropogenic noise worldwide might affect a broader range of animal species than previously thought, because of alteration of visual signals and immunity. Generalizing these results to other taxa is crucial for the conservation of biodiversity in an increasingly noisy world

A phytohaemagglutinin challenge test to assess immune responsiveness of European tree frog Hyla arborea

Immune responsiveness, one measure of individual quality, can be used as a sensitive, non-lethal variable that may be negatively affected in animals exposed to degraded, contaminated or otherwise disturbed areas. One frequently used technique to measure immune responsiveness is the phytohaemagglutinin (PHA) challenge test. Swelling occurring at the injection sites are measured before and 24 h after PHA injection. The immune response is considered to be the difference between the two measures. Although this method is easily performed with wild animals, it has been rarely used on small amphibians. Here, we test the possibility of using a PHA test with the European tree frog, Hyla arborea, and we identify the optimal procedure for measuring immune responsiveness in this species. The results allowed us to simplify the procedure in eliminating phosphate-buffered saline (PBS) injection and reducing the duration of the experiment. Injection of PHA into the leg of H. arborea triggered an immune response with a peak of swelling 14 h after injection. A second injection of PHA into the same animal induced more intense leg swelling. In addition, haematological responses showed that the total number of leucocytes increased after PHA injection. A link between the leg swelling and the total leucocytes count recorded in blood has been found. Consequently, this method may provide a useful tool for predicting the pro-inflammatory capacity of field populations of small amphibians.</jats:p