Abstract Accurate home range knowledge is essential for conserving species that are highly constrained by spatial features. The critically endangered European mink ( Mustela lutreola ) is a wetland specialist whose movements are constrained along rivers or in wetlands. In dendritic landscapes, conventional home range estimators such as Minimum Convex Polygons tend to include unsuitable areas in estimated home ranges. Using VHF telemetry data from 16 individual-years tracked in France between 1996–1999 and 2020–2022, we compared four methods: Kernel Density Estimator (KDE), an adaptative sphere-of-influence local convex hull (a-LoCoH), a newly developed Ecological Home Range method (EHR), and a Generalized Additive Model (GAM) approach integrating hydrographic covariates. Our objective is to determine which method best accounts for the European mink’s specialization in wetlands, considering the spatial distribution of locations. Evaluation with a wetland-specific metric showed KDE consistently overestimated range extent and included unsuitable areas, and a-LoCoH yielded mixed results, but these indicated that the method was not effective in excluding unused areas. It was EHR and GAM methods that aligned more closely with ecological constraints. We therefore recommend GAM because it matches our objective and has the capacity to integrate additional environmental variables. Using the GAM, male home ranges averaged 3,074 ha—26 times larger than female ranges (116 ha)—and were significantly larger in river than marsh landscapes. These are the largest ranges reported for the species. Large spatial requirements heighten vulnerability to road fatality and predation, both significant threats for remaining French populations. Our findings highlight the need for conservation strategies that integrate precise, spatial-constraint-based range estimates. The GAM method offers a robust, adaptable framework for managing European mink and other semi-aquatic species in complex landscapes.

Habitat loss and degradation are the primary drivers of biodiversity decline worldwide and affect particularly wetlands as more than 87% of this habitat have disappeared since the 18th century. Freshwater species are among the most threatened taxa, highlighting the need to better understand their habitat requirements to improve both species and habitat conservation strategies. We investigated habitat selection of the critically endangered European mink (Mustela lutreola), one of the most threatened European mammals. Using VHF radiotracking data collected from four habitat-contrasted French populations, we analyzed habitat selection at both landscape and home-range level. We modelled the effects of 19 environmental, hydrographic and anthropogenic variables on European mink presence at two spatial scales using Resource Selection Functions to identify the main determinants of habitat selection and assess potential differences among populations. European mink consistently selected habitats associated with wetland conditions and with dense vegetal cover, including areas with a high probability of wetland occurrence, permanent water, forests and bushes cover. In contrast, pine forests, crops, buildings and areas near roads were generally avoided. Habitat selection varied according to both the spatial scale and the level considered, showing the importance of adopting a multi-scale approach. Significant differences among populations were also detected. Indeed, several habitat variables showed contrasting effects depending on local landscape context, illustrating the species' plasticity to adjust habitat use to resource availability. Our results confirm the strong dependence of European mink on natural wetland habitats while revealing previously undocumented effects of hydrographic and anthropogenic variables. They further highlight the need for conservation and restoration strategies tailored to local environmental conditions, particularly in the context of future reinforcement and reintroduction programs.

Habitat degradation induced by human activities can exacerbate the spread of wildlife disease and could hinder the recovery of imperiled species. The endangered green turtle Chelonia mydas is impacted worldwide by fibropapillomatosis (FP), a neoplastic infectious disease likely triggered by the Scutavirus chelonidalpha5 with coastal anthropogenic stressors acting as cofactors in disease development. Here, we studied fibropapillomatosis dynamics and its demographic consequences using an 11-year capture-mark-recapture dataset in Anse du Bourg d’Arlet/Chaudière (ABAC) and Grande Anse d’Arlet (GA), two juvenile green turtle foraging grounds in Martinique, French West Indies. Afflicted turtles had similar mortality and permanent emigration rates to the non-afflicted ones. Fibropapillomatosis was commonly observed in large individuals and disease recovery may take several years. Consequently, permanent emigration before full recovery from the disease is suspected and might affect the developmental migration success. Additionally, the results revealed that the FP had higher prevalence and severity, and progressed two times faster in ABAC than in GA despite the proximity (< 2 km) and the similarity of the two foraging grounds. The reasons for these differences remain unidentified. Locally, further studies should be focused on the determination of the external and internal cofactors related to the observed FP dynamics. Finally, the investigations should be extended at a global regional scale to determine potential deleterious effect of the FP on the adult life-stage. These perspectives improves upon our overall understanding on the interplay between wildlife diseases, hosts and environmental factors.

Many small carnivore populations are declining and urgently require evidence-based conservation. Despite their ecological importance, the spatial dynamics of small carnivores remain understudied compared to large carnivores. The Eurasian otter (Lutra lutra) represents a rare example of a recovering small carnivore population in Europe, following nearly a century of decline. However, recovery remains slow in some regions, with populations still vulnerable across much of the species' range. In France, spatial and temporal heterogeneity in data availability has hindered the development of accurate, high-resolution distribution maps, limiting insights into the drivers of this recovery and the factors constraining populations.Here, we mapped the evolution of otter distribution in France from 2009 to 2023 using an integrated species distribution model. This approach combined opportunistic occurrence data and standardized detection/non-detection data from diverse monitoring programs while accounting for non-detection and environmental variability.Our results revealed an expanding distribution, including the reconnection of historical population cores and the emergence of active colonization fronts spanning multiple regions. While occurrence was slightly higher in salmonid-rich rivers with forested banks at broader scales, habitat preferences varied significantly at regional scales, indicating that otters are now occupying more diverse habitats.This study demonstrates the potential of integrating heterogeneous data sources to study carnivore distributions. Our findings provide valuable insights into the status and trends of Eurasian otters in France and offer a framework for guiding effective national-scale conservation efforts.

Introduction of invasive alien species (IAS) is one of the main threats to biodiversity. The Northern raccoon ( Procyon lotor ), here after named “raccoon,” recently introduced and rapidly expanding in three main populations in France, is one of the 47 IAS of concern in the European Union. At this date, there is no study on the ecology of the raccoon in France, yet the acquisition of knowledge of the species in its new environment is an essential step for a better evaluation of its impacts and improving its management. We studied space use and habitat selection by French raccoons in a rural population in the Marne department and in a suburban population in Gironde department, respectively, by tracking 14 individuals with GPS collars between May 2019 and August 2021. We estimated the home ranges’ size using minimum convex polygon (MCP), adaptative local convex hull (a-LoCoH), and dynamic Brownian bridge motion model (dBBMM). Habitat selection was studied at the second and third order using Ivlev’s electivity index and integrated step selection analysis (iSSA) models, respectively. Our results show that raccoons of the rural population have home ranges twice larger than those of the suburban population. Habitats are selected differently according to the population, highlighting the great plasticity of the raccoon. Woodlands are the most used habitats for both populations; however, anthropized areas also appear to be very attractive for the rural population. Surprisingly, this is not the case for the suburban population, which tends to avoid these habitats in favor of the wetland.

Host’s fitness can be affected by its genotype and gut microbiota, defined as the microbes living in the host’s intestinal tract. This study explored how the genetic diversity of the host influences its bacterial communities in the context of captive breeding programs, for the critically endangered European mink (Mustela lutreola). As stated by the ecosystem on a leash model, mechanisms such as inbreeding depression may lead to changes in immunomodulation and will therefore induce modifications of the gut microbiota. We investigated variation in the gut bacteria through 16S rRNA metabarcoding, related to the genetic diversity of European mink held in captivity in two breeding centers representing separate breeding stocks originating from the western and eastern populations. The genetic diversity of the host was assessed through diversity analysis of the adaptive MHC class I and II genes as well as neutral microsatellite markers. Results indicate lower diversity in neutral and MHC class I genes for the western population, and the opposite for MHC class II. A lower MHC class II gene variability led to an increase in microbial phylogenetic diversity and in abundance depending on the presence of specific MHC-II motifs. This shows the importance of integrating both neutral and adaptive markers when investigating genetic variation in the context of ex situ conservation, as well as gut microbial community assessment. We advocate for more natural mating systems in captive breeding program to foster genetic diversity as a whole to mitigate the effects of genetic drift on those small, isolated populations.

A genomic database of all Earth's eukaryotic species could contribute to many scientific discoveries; however, only a tiny fraction of species have genomic information available. In 2018, scientists across the world united under the Earth BioGenome Project (EBP), aiming to produce a database of high-quality reference genomes containing all ~1.5 million recognized eukaryotic species. As the European node of the EBP, the European Reference Genome Atlas (ERGA) sought to implement a new decentralised, equitable and inclusive model for producing reference genomes. For this, ERGA launched a Pilot Project establishing the first distributed reference genome production infrastructure and testing it on 98 eukaryotic species from 33 European countries. Here we outline the infrastructure and explore its effectiveness for scaling high-quality reference genome production, whilst considering equity and inclusion. The outcomes and lessons learned provide a solid foundation for ERGA while offering key learnings to other transnational, national genomic resource projects and the EBP.

Human infection by Baylisascaris procyonis can result in larva migrans syndromes, which can cause severe neurological sequelae and fatal cases. The raccoon serves as the definitive host of the nematode, harboring adult worms in its intestine and excreting millions of eggs into the environment via its feces. Transmission to paratenic hosts (such as rodents, birds and rabbits) or to humans occurs by accidental ingestion of eggs. The occurrence of B. procyonis in wild raccoons has been reported in several Western European countries. In France, raccoons have currently established three separate and expanding populations as a result of at least three independent introductions. Until now the presence of B. procyonis in these French raccoon populations has not been investigated. Between 2011 and 2021, 300 raccoons were collected from both the south-western and north-eastern populations. The core parts of the south-western and north-eastern French raccoon populations were free of B. procyonis. However, three worms (molecularly confirmed) were detected in a young raccoon found at the edge of the north-eastern French raccoon population, close to the Belgian and Luxemburg borders. Population genetic structure analysis, genetic exclusion tests and factorial correspondence analysis all confirmed that the infected raccoon originated from the local genetic population, while the same three approaches showed that the worms were genetically distinct from the two nearest known populations in Germany and the Netherlands. The detection of an infected raccoon sampled east of the northeastern population raises strong questions about the routes of introduction of the roundworms. Further studies are required to test wild raccoons for the presence of B. procyonis in the area of the index case and further east towards the border with Germany.

Estimating demographic parameters is key for unraveling the mechanisms governing the population dynamics of species of conservation concern. Endangered green sea turtles navigate vast geographical ranges during their life cycle and face various pressures in coastal areas, especially during their juvenile life-stage. Here, we investigated survival, abundance, recruitment and emigration of juvenile green turtles on two developmental grounds in Martinique, French West Indies, using a capture-mark-recapture dataset of 658 captures over 10 years. We detected increasing abundances of green turtles, likely attributed to the continuous recruitment of new individuals, low mortality and low rate of emigration from these two developmental sites. Local recruitment slightly decreased with small turtle densities while emigration strongly increased with large turtle densities. These results associated with known food availability and size-dependent diet preference of local green turtles suggest that the expansion of invasive seagrass H. stipulacea may facilitate the settlement of small juveniles, however it also limits the capacity of seagrass beds to sustain large juveniles. Boat anchorage, pollution and H. stipulacea invasion reduced the availability of native seagrass species. This could intensify competition between large turtles, trigger earlier emigration, therefore modifying the structure of the green turtle population in Martinique. Measures to protect native seagrass beds are essential to maintain their capacity to sustain the entire green turtle developmental life-stage. This study will help to connect sea turtle life-stages and to inspire efficient regional conservation measures. Finally, our results will help to understand the demography of endangered megaherbivores in context of grazing areas degradation.

Incidental capture of non-target species poses a pervasive threat to many marine species, with sometimes devastating consequences for both fisheries and conservation efforts. Because of the well-known importance of vocalizations in cetaceans, acoustic deterrents have been extensively used for these species. In contrast, acoustic communication for sea turtles has been considered negligible, and this question has been largely unexplored. Addressing this challenge therefore requires a comprehensive understanding of sea turtles' responses to sensory signals. In this study, we scrutinized the avenue of auditory cues, specifically the natural sounds produced by green turtles (Chelonia mydas) in Martinique, as a potential tool to reduce bycatch. We recorded 10 sounds produced by green turtles and identified those that appear to correspond to alerts, flight or social contact between individuals. Subsequently, these turtle sounds-as well synthetic and natural (earthquake) sounds-were presented to turtles in known foraging areas to assess the behavioral response of green turtles to these sounds. Our data highlighted that the playback of sounds produced by sea turtles was associated with alert or increased the vigilance of individuals. This therefore suggests novel opportunities for using sea turtle sounds to deter them from fishing gear or other potentially harmful areas, and highlights the potential of our research to improve sea turtles populations' conservation.

Incidental capture of non-target species poses a pervasive threat to many marine species, with sometimes devastating consequences for both fisheries and conservation efforts. Because of the well-known importance of vocalizations in cetaceans, acoustic deterrents have been extensively used for these species. In contrast, acoustic communication for sea turtles has been considered negligible, and this question has been largely unexplored. Addressing this challenge therefore requires a comprehensive understanding of sea turtles’ responses to sensory signals. In this study, we scrutinized the avenue of auditory cues, specifically the natural sounds produced by green turtles ( Chelonia mydas) in Martinique, as a potential tool to reduce bycatch. We recorded 10 sounds produced by green turtles and identified those that appear to correspond to alerts, flight or social contact between individuals. Subsequently, these turtle sounds—as well synthetic and natural (earthquake) sounds—were presented to turtles in known foraging areas to assess the behavioral response of green turtles to these sounds. Our data highlighted that the playback of sounds produced by sea turtles was associated with alert or increased the vigilance of individuals. This therefore suggests novel opportunities for using sea turtle sounds to deter them from fishing gear or other potentially harmful areas, and highlights the potential of our research to improve sea turtles populations’ conservation.

The American mink (Mustela vison) is known as a successful non-native species in Europe, impacting native species’ population sizes and habitats. This study investigates the genetic structure and diversity of American mink populations in France over two decades (1997–2016). The analysis involves feral and farmed mink sampled from various regions, using ten autosomal microsatellite loci for genotyping. The objective is to identify the putative existence of genetic lineages, especially between feral and farmed individuals, and to assess changes in genetic structure over time. Results reveal high genetic diversity and inbreeding within populations, with evidence of genetic structure influenced by both farm releases and feral colonization. The study highlights the reflection of the genetic structure in farm populations in the feral populations within the first period (1997–2007), and a decline of a lineage over time in the second period (2007–2016) with the emergence of a new genetic cluster, potentially influenced by factors such as selection, phenotypic changes, and interactions with pathogens. Overall, this research contributes to the understanding of the dynamics of American mink populations in France and their genetic variability, emphasizing the importance of ongoing monitoring and management efforts to mitigate the impact of this invasive species, especially on endangered or/and endemic species such as European mink (Mustela lutreola) and Iberian desman (Galemys pyrenaicus).

Leptospirosis is a widespread zoonosis caused by bacteria of the genus Leptospira. Although crucial to mitigate the disease risk, basic epidemiological information is lacking, such as the identities of Leptospira maintenance hosts. The raccoon (Procyon lotor), an alien invasive species in France, could pose a public health risk if it carries pathogenic Leptospira. We investigated the rate and type (selective vs. unselective) of Leptospira carriage in the two main raccoon populations in France. Out of the 141 raccoons collected, seven (5%) tested quantitative PCR positive, targeting lfb1 gene, based on kidney, lung, and urine samples. Phylogenetic analysis revealed the presence of three different L. interrogans clusters. The results suggest that raccoons were more likely accidental hosts and made only a limited contribution to Leptospira maintenance.

One of the threats that the critically endangered European mink (Mustela lutreola) faces throughout its relict range, including the occidental population, is the impact of the American mink (Mustela vison) invasion in its natural habitat. We aimed to explore the differences in microbiota and genetic diversity between European and American mink to test phylosymbiosis theory. We investigated the gut microbiota composition of European and American mink in controlled environments (captive breeding compounds and fur farms respectively) to account for the impact of the environment on gut bacterial composition. We compared them to the gut microbiota of both mink species in the natural environment across habitats. Our exploratory results showed differences between free-ranging and captive individuals, with more extreme changes in American mink compared to European mink. However, feral American mink from a long-established population exhibited gut bacterial composition closer to the free-ranging native species compared to more recently established feral populations. This result could be explained by dietary shifts in the area sampled based on prey availability through different landscape, but also to a lesser extent due to greater genetic differentiation. This exploratory work contributes to the scarce literature currently available on the dynamics between gut microbiota and mammal invasion.

Les faibles connaissances sur le comportement du Desman des Pyrénées Galemys pyrenaicus (É. Geoffroy Saint Hilaire, 1811) en réponse aux variations hydrauliques nous ont amenés à mettre en œuvre trois opérations de radiopistage sur deux tronçons court-circuités de cours d’eau ariégeois. Les opérations ont eu lieu en octobre 2014 et mai 2015 sur l’Aston, puis en septembre 2018 sur le Vicdessos, dans des contextes d’hydrologie variable, avec de fortes variations de débit liées à l’exploitation des ouvrages ou à des travaux de réfection. Six Desmans ont été suivis, dont un au cours des deux opérations sur l’Aston. Les données recueillies montrent que l’espèce présente une activité nocturne et diurne, avec cependant des déplacements plus importants la nuit. Elles ont également mis en exergue le caractère social des individus. En effet, certains partagent tout ou partie de leurs domaines vitaux et certains de leurs gîtes, auxquels ils sont d’ailleurs très fidèles. Nous avons pu observer des réactions aux variations de débit chez les Desmans suivis, parmi lesquelles des changements de gîtes, des translations de domaines vitaux ou bien encore une modification des cycles d’activité. Ces observations et apports de connaissances confirment l’importance d’une bonne prise en compte du Desman dans la gestion des débits mais également d’une manière plus globale pour une meilleure préservation de l’espèce.

Host’s fitness can be affected by its genotype and gut microbiota, defined as the microbes living in the host’s intestinal tract. This study explored how the genetic diversity of the host influences its bacterial communities in the context of captive breeding programs, for the critically endangered European mink ( Mustela lutreola ). As stated by the ecosystem on a leash model, loss of host genetic diversity may lead to changes in immunomodulation and will therefore induce modifications of the gut microbiota. We investigated variation in the gut bacteria through 16S rRNA metabarcoding, related to the genetic diversity of European mink held in captivity in two breeding centers representing separate breeding stocks originating from the western and eastern populations. The genetic diversity of the host was assessed through diversity analysis of the adaptive MHC class I and II genes as well as neutral microsatellite markers. Results indicate lower diversity in neutral and MHC class I genes for the western population, and the opposite for MHC class II. A lower MHC class II gene variability led to an increase in microbial phylogenetic diversity and in abundance depending on the presence of specific MHC-II motifs. Those results seem to be linked to management practices that differs between the two programs, especially the number of generations in captivity. Long term Ex situ conservation practices can thus modulate gut microbial communities, that might potentially have consequences on the survival of reintroduced animals. We suggest strategies to foster genetic diversity in captive breeding program to mitigate the effects of genetic drift on those small, isolated populations.

The present study investigated the natural recovery of the Eurasian otter (Lutra lutra) in France. The otter was widely distributed in France at the dawn of the 20th century, but then its range considerably shrank and became highly fragmented until the early 1970s, just before it was legally protected. However, for more than 25 years, the otter has been reconquering several parts of its original range and is now considered to be in expansion in France. We investigated the genetic differentiation and diversity of several populations from western and central France and northern Spain to gain insight into the recolonisation dynamics of this elusive species. The present study, based on the use of 14 microsatellite markers, revealed that otter populations seem to be split into five distinct groups. The distribution of samples in those five clusters was closely correlated with suspected refugia where the otter probably survived during the 20th century. Admixture was observed between genetic lineages, possibly enhancing their genetic diversity and thus increasing the recolonisation dynamics of these populations. This phenomenon resembles the genetic pattern noted in many invasive exotic species derived from multiple sources and introduction events. Finally, a demographic approach revealed the probable link between historical human pressure and otter population fragmentation patterns.

The riparian European mink (Mustela lutreola), currently surviving in only three unconnected sites in Europe, is now listed as a critically endangered species in the IUCN Red List of Threatened Species. Habitat loss and degradation, anthropogenic mortality, interaction with the feral American mink (Neovison vison), and infectious diseases are among the main causes of its decline. In the Spanish Foral Community of Navarra, where the highest density of M. lutreola in its western population has been detected, different studies and conservation measures are ongoing, including health studies on European mink, and invasive American mink control. We report here a case of severe parasitism with progressive physiological exhaustion in an aged free-ranging European mink female, which was accidentally captured and subsequently died in a live-trap targeting American mink. Checking of the small intestine revealed the presence of 17 entangled Versteria mustelae worms. To our knowledge, this is the first description of hyperinfestation by tapeworms in this species.