Rural populations of the red fox Vulpes vulpes show little evidence of reproductive senescence

International audienceThe ageing theory predicts fast and early senescence for fast-living species. We investigated whether the pattern of senescence of a medium-sized, fast-living and heavily-culled mammal, the red fox (Vulpes vulpes), fits this theoretical prediction. We used cross-sectional data from a large-scale culling experiment of red fox conducted over six years in five study sites located in two regions of France to explore the age-related variation in reproductive output. We used both placental scars and embryos counts from 755 vixens’ carcasses aged by the tooth cementum method (age range : 1-10) , as proxies for litter size. Mean litter size per vixen was 4.7 ± 1.4. Results from Generalized Additive Mixed Models revealed a significant variation of litter size with age. Litter size peaked at age 4 with 5. 0 ± 0.2 placental scars and decreased there after by 0.5 cubs per year. Interestingly, we found a different age-specific variation when counting embryos which reached a plateau at age 5-6 (5.5 ± 0.2)and decreased slower than placent al scars across older ages, pointing out embryo resorption as a potential physiological mechanism of reproductive senescence in the red fox. Contrary to our expectation, reproductive senescence is weak, occurs late in life and takes place at an age reached by less than 11.7% of the population such that very few females exhibit senescence in these heavily culled populations

Human disturbance is the most limiting factor driving habitat selection of a large carnivore throughout Continental Europe

Habitat selection is a multi-scale process driven by trade-offs between benefits, such as resource abundance, and disadvantages, such as the avoidance of risk. The latter includes human disturbances, to which large carnivores, with their large spatial requirements, are especially sensitive. We investigated the ecological processes underlying multi-scale habitat selection of a large carnivore, namely Eurasian lynx, across European landscapes characterized by different levels of human modification. Using a unique dataset of 125 lynx from 9 study sites across Europe, we compared used and available locations within landscape and home-range scales using a novel Mixed Effect randomForest approach, while considering environmental predictors as proxies for human disturbances and environmental resources. At the landscape scale, lynx avoided roads and human settlements, while at the home-range scale natural landscape features associated with shelter and prey abundance were more important. The results showed sex was of relatively low variable importance for lynx's general habitat selection behaviour. We found increasingly homogeneous responses across study sites with finer selection scales, suggesting that study site differences determined coarse selection, while utilization of resources at the finer selection scale was broadly universal. Thereby describing lynx's requirement, if not preference, for heterogeneous forests and shelter from human disturbances and implying that regional differences in coarse-scale selection are driven by availability rather than preference. These results provide crucial information for conserving this species in human-dominated landscapes, as well as for the first time, to our knowledge, generalising habitat selection behaviour of a large carnivore species at a continental scale.acceptedVersio

Integrating animal tracking datasets at a continental scale for mapping Eurasian lynx habitat

Aim: The increasing availability of animal tracking datasets collected across many sites provides new opportunities to move beyond local assessments to enable de-tailed and consistent habitat mapping at biogeographical scales. However, integrating wildlife datasets across large areas and study sites is challenging, as species' varying responses to different environmental contexts must be reconciled. Here, we compare approaches for large-area habitat mapping and assess available habitat for a recolo-nizing large carnivore, the Eurasian lynx (Lynx lynx).Location: Europe.Methods: We use a continental-scale animal tracking database (450 individuals from 14 study sites) to systematically assess modelling approaches, comparing (1) global strategies that pool all data for training versus building local, site-specific models and combining them, (2) different approaches for incorporating regional variation in habi-tat selection and (3) different modelling algorithms, testing nonlinear mixed effects models as well as machine-learning algorithms.Results: Testing models on training sites and simulating model transfers, global and local modelling strategies achieved overall similar predictive performance. Model performance was the highest using flexible machine-learning algorithms and when incorporating variation in habitat selection as a function of environmental variation. Our best-performing model used a weighted combination of local, site-specific habi-tat models. Our habitat maps identified large areas of suitable, but currently unoccu-pied lynx habitat, with many of the most suitable unoccupied areas located in regions that could foster connectivity between currently isolated populations.Main Conclusions: We demonstrate that global and local modelling strategies can achieve robust habitat models at the continental scale and that considering regional variation in habitat selection improves broad-scale habitat mapping. More generally, we highlight the promise of large wildlife tracking databases for large-area habitat mapping. Our maps provide the first high-resolution, yet continental assessment of lynx habitat across Europe, providing a consistent basis for conservation planning for restoring the species within its former range.publishedVersio

Influence des activités anthropogéniques sur la régime alimentaire et la réponse numérique de la hyène tachetée en savane arborée dystrophique dominée par l'éléphant

At the dawn of the 21st century, protected area needs to overcome the challenge to preserve natural resources biodiversity while integrating human activities in constant growth. This study explores the effect of the addition of anthropogenic food subsidies on a carnivore-prey system, in an African savanna ecosystem (Hwange National Park, Zimbabwe), characterized by a high diversity of preys and predators species. In addition the specificity of the study site is very original to the extent that nowadays elephants represent 80% of herbivore biomass, and were subjected to a regulation politics during 25 years, politics that was suspended since 20 years. This work focuses on the functional and numerical responses of spotted hyaena (Crocuta crocuta), that is the most abundant predator but above all is characterized by a large flexibility in foraging (hunt, scavenge, kleptoparasite). It is distinguished by an extreme adaptation in carcass use. Therefore we expect that it particularly efficiently reacts to the addition of carcasses generated by human activities (culling, legal and illegal bush meat production, accidents from infrastructures) as to extreme climatic events. At local scale, an approach by the analyse of behaviour and diet composition shows that (1) elephant contributes little in the diet, (2) hyaena use anthropogenic food resources, (3) hyaena remain primary dependant on huntable herbivores the most locally abundant, as underlined in other ecosystems. At Park scale, the spatial distribution analyse and demographic trends of hyaena and preys from a long term data set (32 years) reveals, in accordance to the feeding habits analyse: (1) an aggregative response of hyaena associated to the biomass of potential preys, (2) a classical temporal relationship predator-prey, that suggests that the carcass availability related either from elephants culling, natural mortality or human activities, did not significantly disturbed the numerical answer. The results suggest that if the hyaena population is little affected by the addition of anthropogenic food resources, then the other predators are likely less, because of a foraging behaviour less adapted to scavenging. Overall results of this study suggest that the spotted hyaena would be rather a hunter than a scavenger in this preys-poor but carcass-rich savanna system. However, we can t exclude that locally some hyaena clans benefit from the high addition of anthropogenic food resources and consequently modify their hunting behaviour. Complementary studies are required to enhance the comprehension of mechanisms that link hyaena to their prey s populations, notably to test the hypothesis of the role of spotted hyaena predation in the decline of some ungulates populations in this ecosystem, particularly steenbok, common duiker, impala, blue wildebeest and great kuduEn cette aube du 21ème siècle, l aire protégée doit relever le défi de conserver la biodiversité des ressources naturelles tout en intégrant des activités humaines en constante croissance. Cette étude explore l effet de l apport de subsides alimentaires d origine anthropogénique sur un système carnivore-proie, dans un écosystème de savane africain (Parc National de Hwange, Zimbabwe), caractérisé par une forte diversité des espèces de proies et de prédateurs. La spécificité du site d'étude est par ailleurs très originale dans la mesure où les éléphants représentent actuellement 80% de la biomasse d'herbivore, et ont été soumis à une politique de régulation durant 25 ans, politique interrompue depuis 20 ans. Ce travail se focalise sur les réponses fonctionnelle et numérique de la hyène tacheté (Crocuta crocuta), qui est le prédateur le plus abondant mais qui surtout est caractérisé par une large flexibilité de tactique d'acquisition des ressources (chasse, charognage, klepto-parasistisme). Elle se distingue par une adaptation extrême à l'utilisation des charognes. On s'attend donc qu'elle réagisse particulièrement efficacement à l'adjonction de carcasses générées par les activités humaines (abattage de régulation, production légale et illégale de viande, accidents dus aux infrastructures), comme par les événements climatiques extrêmes. A l'échelle locale, une approche par l'analyse du comportement et du régime alimentaire montre que (1) l'éléphant contribue peu au régime, (2) les hyènes utilisent les ressources d'origine anthropogénique, (3) que les hyènes restent principalement dépendantes des herbivores chassables les plus abondants localement, comme cela a été mis en évidence dans d'autres écosystèmes. A l'échelle du Parc, l'analyse de la distribution spatiale et des tendances démographiques des hyènes et des proies sur un jeu de données à long-terme (32 ans) révèle, de manière très cohérente avec l'analyse des régimes alimentaires : (1) une réponse agrégative des hyènes associée à la biomasse des proies potentielles, (2) une relation temporelle classique prédateur-proie, qui suggère que la disponibilité des carcasses liée aux abattages d'éléphants, à la mortalité naturelle ou aux activité humaines, n'a pas perturbé de manière significative la réponse numérique. Les résultats suggèrent que si la population de hyènes est peu affectée par l'apport de ces ressources alimentaires d'origine anthropogénique, les autres prédateurs le seront probablement moins, du fait d'un comportement alimentaire moins adapté au charognage. L ensemble des résultats de cette étude suggère que la hyène tachetée serait plutôt chasseur que charognard dans ce système de savane pauvre en proies mais riche en carcasses. Cependant, on ne peut exclure que localement certains clans de hyènes bénéficient du fort apport des ressources d'origine anthropogénique, et modifient par conséquent leur comportement de prédation. Des études complémentaires sont nécessaires pour affiner la compréhension des mécanismes qui relient les hyènes à leurs populations de proies, notamment pour tester l'hypothèse du rôle de la prédation de la hyène tachetée dans le déclin de certaines populations d ongulés dans cet écosystème, en particulier le steinbock, le céphalophe, l impala, le gnou bleu et le grand koudouLYON1-BU.Sciences (692662101) / SudocSudocFranceF

Estimer l’effort d’échantillonnage de réseaux participatifs : l’exemple du réseau Loup-lynx

International audienceLes réseaux participatifs présentent l’avantage d’avoir une couverture performante pour échantillonner les espèces à large échelle. En revanche, ils souffrent souvent d’un déficit de mesure de l’effort, pourtant nécessaire aux analyses de données. Ici, nous utilisons la distance entre les correspondants et les indices qu'ils ont trouvés pour estimer l'effort d'échantillonnage du réseau Loup-lynx

Tirs dérogatoires de loups en France : état des connaissances et des enjeux pour la gestion des attaques aux troupeaux.

International audienceEn France, la protection des troupeaux contre les attaques de loup prévoit l'utilisation de tirs dérogatoires dans des contextes précis, notamment lorsque la pression des attaques est forte. Néanmoins, les effets de ces tirs sur les attaques restent mal connus. Nous dressons ici un état des connaissances scientifiques sur le sujet puis présentons les enjeux et le cadre méthodologique de l'étude en cours, qui s'attache à évaluer les effets des tirs dérogatoires sur les attaques et la population de loups en France