Production de bois et autres ressources (gibier, champignons,...), conservation de la biodiversité et gestion des paysages, la forêt a suscité de riches débats depuis quelques années, le Grenelle de l'Environnement ayant révélé des intérêts parfois contradictoires. Si le gestionnaire forestier tente de développer autant que possible une gestion multifonctionnelle de ses forêts, il reste dépendant des connaissances fragmentaires sur les interactions dans les écosystèmes forestiers. La politique actuelle, qui vise à concilier la production de bois et la préservation des espèces, repose plus sur des expériences de terrain que sur des études étayées scientifiquement. Les Chiroptères comptent des espèces candidates pour étudier l'influence de la gestion forestière sur la biodiversité : le jour, elles occupent des gîtes arboricoles et, la nuit, elles exploitent des habitats forestiers pour chasser leurs proies, qui dépendent elles-mêmes de micro-habitats forestiers. Pour aider le gestionnaire à mettre en œuvre une stratégie de gestion conservatoire, nous avons étudié l'utilisation des ressources de la forêt par trois espèces : Myotis bechsteinii, Myotis nattereri et Plecotus auritus. La radio-localisation a permis d'identifier des réseaux d'arbres-gîte dont l'occupation varie selon les espèces, leur statut reproducteur et l'implication dans le comportement de fission-fusion des colonies de parturition. Les différentes utilisations des gîtes impliquent une stratégie de gestion propre à chaque espèce, voire à chaque colonie de reproduction. Procurant a priori de potentiels gîtes et proies, le bois mort debout favorise la richesse spécifique des Chiroptères forestiers à partir de 25 m3 à l'hectare, mais une stratification de la végétation pourrait être un objectif de gestion, la réponse des espèces était essentiellement liée à la structure forestière des trouées induites par le bois mort. Ce travail a ensuite nécessité de s'intéresser aux méthodes permettant de comprendre l'utilisation de l'espace par chaque individu (domaine vital) et la façon dont chacun d'eux fréquente ses terrains de chasse (sélection de l'habitat). Compte tenu des limites technologiques, le Kernel semble actuellement la meilleure méthode de représentation et de calcul de surface du domaine vital alors que la K-select a livré des résultats significatifs pour mettre en évidence des facteurs de sélection d'habitat. Les surfaces des domaines vitaux et des centres d'activité varient selon les espèces, Myotis bechsteinii associe de petites surfaces à un comportement territorial, surtout en période d'allaitement. M. nattereri et Plecotus auritus peuvent exploiter de grands espaces sur lesquels ils se limitent à de petits centres d'activité. Les colonies de ces dernières pourront plus facilement se déplacer dans leur domaine vital au gré des itinéraires de gestion mis en œuvre. Les caractéristiques des habitats forestiers utilisés comme terrains de chasse varient selon les espèces, voire le sexe, l'âge et le statut reproducteur des individus, mais toutes trois montrent une forte sélectivité pour les peuplements forestiers présentant un fort encombrement végétal, des gros arbres et une forte structuration du peuplement. Cinq principes de gestion dans un contexte fort de production de bois sont développés en conclusion des résultats avec deux exemples de stratégies de gestion destinée au maintien des Chiroptères. / The forest is the center of many interests that fuel the debates of our society. These debates are particularly exacerbated since the french " Grenelle de l'Environnement " in 2008. Among the various expectations, forest produce wood that is the subject of attentions, both by an increased demand for certain types of trees and by the naturalist world which sees in it one of last refuges for biodiversity in our modified landscapes. Thus, if the forest manager is trying to develop a management that is as much multifunctional as possible, it remains dependent on fragmented knowledge on the link between biodiversity and the forest ecosystem. Despite the establishment of a conservation policy that seeks to balance timber production and species preservation, the way to conduct such a policy is based on concrete field experiences yet scientifically unsubstantiated. Bats are good candidate species to study the response of biodiversity to forest management: they select networks of tree-roosts in which they form breeding colonies composed of several dozen individuals and they exploit forest habitats to hunt their prey, prey which themselves depend on forest microhabitats. However, their study is recent in forest and provides very vague management guidelines. To help managers implement a conservation management strategy, we thus studied the behavior of forest usage by three species of gleaning bats, Myotis bechsteinii, Myotis nattereri and Plecotus auritus. This work required to focus on the methods available to understand the use of space by each individual (home range) and how each individual selects its hunting habitats. We showed that each species had a unique response to available habitats and that the status of individuals (sex, age and reproductive status) intervenes in explaining the selection of tree roosts and hunting grounds. Both compartments are constrained by the availability of suitable habitat, helping to explain the structuring of habitat selection factors and the shape and surface of individual home ranges. Furthermore, the way networks of tree-roost are used partly explains the types of roosts selected. These different results means that it is necessary to lay down specific management strategies for each species, even each breeding colony. Finally, we studied the role of deadwood to explain the presence of bats in forests. We have shown that species richness increased from standing deadwood of 25m3 per hectare, while the response of species to deadwood was mainly restricted to forest habitat structure produced by the gaps resulting from the deadwood patch, favoring particularly edge-foraging species. Some species do however clearly benefit from insects emerging from deadwood. Five recommendations are proposed for the conservation of these species in a context of strong wood production.

No description available.

Emerging infectious diseases of wildlife are among the greatest threats to biodiversity. Indeed, when pathogens are introduced into naïve host populations, they can impose novel selective pressures that may cause severe host declines or even extinction. However, disease impacts may vary both within and among host species. Thus, one of the key goals for management is to identify factors that drive variation in host susceptibility to infection, as they may improve our understanding of hosts' potential to develop disease resistance and/or tolerance and inform conservation strategies aimed at facilitating host persistence. For instance, Pseudogymnoascus destructans (Pd) - an invasive pathogenic fungus that causes white-nose syndrome (WNS) in hibernating bats - is highly virulent, has killed millions of bats in North America, and continues to spread at an alarming rate. Yet, the continued persistence of bat colonies in contaminated areas despite initial mass mortality events suggests variation in survival among infected individuals. I thus aimed to better understand intraspecific drivers of variation in bat susceptibility to WNS and their implications for population persistence and management in affected areas. Specifically, my objectives were to: 1) evaluate the extent to which variation in hibernaculum microclimate temperature and humidity affects Pd infection severity and disease progression in affected bats during hibernation, 2) compare how bats from colonies that vary in duration of exposure to Pd and from different age classes behaviorally respond to the infection, and examine how these behavioral changes affect host fitness and 3) model the population dynamics of remnant bat populations to assess the likeliness of persistence and the potential effectiveness of management interventions in affected colonies. I addressed these objectives through field research, experimental infection studies, and demographic modeling of the little brown myotis (Myotis lucifugus). In my dissertation, I first provide causal evidence of environmentally-driven variation in pathogen growth and infection severity on bats in the field. Both warmer and more humid microclimates contribute to the severity of the infection by promoting the production of conidia, the erosion of wing tissues, and, therefore, the transmission potential and virulence of Pd. I then document potential mechanistic links between Pd-induced behavioral change and host fitness. Higher infection levels, independent of bats' past exposure to Pd or age class, may cause individuals to groom longer, prolong euthermic arousals, accelerate the depletion of fat reserves, and ultimately increase mortality risk. Finally, I predict that populations will face a high risk of extirpation in the next decade or two if no management action is taken, but that interventions such as environmental control of Pd and hibernaculum microclimate manipulation can prevent short-term population collapse in remnant bat populations. Together, these studies provide key, mechanistic insight into the pathology of WNS and the probability of persistence of affected bat colonies, while highlighting the importance of prioritizing winter habitat preservation and enhancement for the conservation of hibernating bats. / Biology

Rafinesque’s big-eared bats (Corynorhinus rafinesquii; RBEB) and southeastern myotis (Myotis austroriparius; SEM) are listed on IUCN Red List of Threatened Species. Limited information on roost sites exists. I conducted roost surveys for RBEB and SEM on public forest lands in central Mississippi during winter and spring 2010. During winter, RBEB and SEM roosted in cavity trees with greater trunk diameters. In spring, roost trees used by SEM were located in forested areas of lower elevation, less slope, and greater distances from roads. Because imperfect detection can affect occupancy estimates, I estimated detection probabilities under different survey methods. Detection probability ranged from 95 – 100% and 92 – 99% when one to 2 observers used repeated surveys and removal method, respectfully. When estimating for abundance, presence of ≤20 bats led to count errors of <4%. When >20 bats were present, count errors were 38.1%. Observers correctly identified species 91% of the time.

Critical to our understanding of wildlife diseases is the recovery phase, a period during which individuals clear infections and return to normal patterns of behavior and physiology. Most research on effects of white nose syndrome (WNS), an emerging fungal disease in bats, has focused on the pathophysiology of winter mortality and the effects of WNS on hibernating populations. The period immediately following emergence from hibernation has received little attention, but is a critically important time for survivors of the disease. During this time, survivors face significant physical and physiological challenges as they migrate to summer habitats, potentially begin gestation in the case of reproductive females, and begin to recover from wing damage caused by the fungus, which can be extensive and may greatly increase the energetic cost of flight. In this study, I (1) test the hypothesis that free-ranging bats heal from WNS-induced wing damage, (2) determine how WNS-induced wing damage changes skin surface lipid profiles on free-ranging bats, and (3) describe the temporal process of disease recovery in a colony of captive bats, including analyses of body mass, wing damage, pathogen load, skin surface lipid profiles, and histopathological metrics of WNS. I find that bats can quickly heal from wing damage in the wild and appear healthy as early as mid-July in New England. Analysis of skin surface lipids does not reveal any striking differences between bats with wing damage and those without, although there are trends towards lower total surface lipids and increased levels of cutaneous cholesterol in bats with severe wing damage. Finally, I show that within 40 days of emerging from hibernation, bats quickly clear the fungal infection and gain body mass, undergoing rapid healing of wing damage and changes in skin surface lipid composition. Bats depend on their wings for a variety of vital processes including physiological regulation, locomotion and feeding. To fully understand the consequences of WNS and develop actionable management strategies, it is important to consider the long-term effects of this disease. My study helps fill critical knowledge gaps and will aid in the future conservation and management of affected bat species.

<p dir="ltr">Bat population numbers are declining in the Midwestern United States. Reasons for decline are multifaceted (habitat degradation, fatalities at wind turbines, White Nose Syndrome, and declining insect populations), and many species are listed as endangered (Myotis sodalis, Myotis septentrionalis, Perimyotis subflavus). Other species in the Midwestern United States have no conservation status (Eptesicus fuscus), or are only listed as a species of concern (Lasiurus cinereus, Lasiurus borealis, Lasionycteris noctivagans). Bats play a crucial role in our ecosystems, providing both ecological and economic benefit as pollinators and insect population regulators. Thus, conserving these species is vital. To gain better insight into the ecology of Midwestern bat species I studied five species in two respects. First, I investigated the availability of roosts for a colony of endangered Myotis sodalis near Indianapolis. This colony has withstood high levels of urbanization and habitat degradation. Therefore, understanding what aspects of the roosting area has allowed for continued use by the colony is crucial for future conservation efforts. I used an Akaike’s Information Criteria approach to rank models that best differentiate between the current roosting area and surrounding landscape. I identified that the roosting area contained a greater number of large standing dead trees (Snags >42.6 cm) that are able to serve as primary roosts for the colony. These results demonstrate that a colony of Indiana bats may be able to withstand urbanization if they have enough large DBH snags available in the area. Future conservation efforts in a heavily urbanized environment should focus on the maintaining large snags as primary roosts. Second, I studied the morphological variation of four species (Lasiurus cinereus, Lasiurus borealis, Lasionycteris noctivagans, and Eptesicus fuscus) to parse out differences that may lead to niche specialization. These four species share habitat and foraging range and therefore may directly compete for resources. However, despite declining insect populations these four species have moderately stable populations. I collected approximately 30 craniums and mandibles for each species and compared the linear size differences between landmarks and the overall shape variation from these landmarks. Due to different phylogenies and body sizes, the four species were different from one another in all 24 linear measurements. In regards to shape variation, the Eptesicini bat craniums had characteristics of more gracile species. In addition, the mandibles of Eptesicini were highly distinct. Lasionycteris noctivagans was the least durable and Eptesicus fuscus had 10 specialization for hard bodied prey consumption. These results suggest potential niche specialization due variation in morphology.</p>

No description available.

Bats are crucial to ecological function and provide key ecosystem services to people but face a variety of significant threats. One current threat to North American bats is white-nose syndrome (WNS), a disease caused by the invasive fungal pathogen Pseudogymnoascus destructans (Pd) that has killed millions of hibernating bats across the continent. Remnant populations of affected bat species persist but are so depleted that they may now be highly vulnerable to new threats, or to the synergistic effects of multiple existing threats. The emergence of novel or opportunistic pathogens in bat hosts is a particular concern for the survival of these small, isolated colonies. Apart from studies of WNS and zoonotic pathogens of humans, however, bat diseases remain poorly understood. In this paper, I describe the pathology of a new, highly aggressive bat disease affecting hibernating little brown myotis (Myotis lucifugus) and identify candidate microbes as possible causative agents. The pathological signs that were observed diverged from those of WNS, and included blue fluorescence in the wings when trans-illuminated with ultraviolet light, and the rapid development of wing necroses and mortality within weeks of the onset of hibernation. Pathology, wing swab cultures, post-mortem analyses, and hemolysis testing identified an array of candidate species, but suggest that a possible cause is a polymicrobial infection involving two etiological agents – Trichosporon yeast and Serratia bacteria. Both species have been documented as part of the mycobiota and microbiota of healthy bats, and cave environments. They are also opportunistic pathogens, known to cause infection in other wild animals and immunocompromised humans. Opportunistic pathogens have been increasingly implicated as a cause of mass mortality events in wildlife. The disease identified here has, to my knowledge, not previously been described, and could represent a new threat to North American bats, compounding concerns for populations facing an already precarious situation. / Biology

京都大学 / 新制・課程博士 / 博士(情報学) / 甲第24037号 / 情博第793号 / 新制||情||134(附属図書館) / 京都大学大学院情報学研究科社会情報学専攻 / (主査)教授 大手 信人, 准教授 小山 里奈, 教授 北島 薫 / 学位規則第4条第1項該当 / Doctor of Informatics / Kyoto University / DFAM

Emerging infectious diseases (EID) pose significant threats to biodiversity. Human influence over the environment has increased opportunities for the introduction of novel pathogens to naïve hosts, potentially leading to host extinction. Understanding mechanisms of host persistence is critical for effectively conserving species affected by EIDs. Our study investigated the disease dynamics of white-nose syndrome (WNS), caused by the fungal pathogen Pseudogymnoascus destructans (Pd), in little brown bats (Myotis lucifugus) across a spatiotemporal gradient. We explored the relationship between bat roosting temperatures and Pd growth rates across three phases of pathogen invasion comprising years since WNS has been present at sites: invasion (0-3), established (4-8), and endemic (9+ years). Data used by this study comes from a combination of field-based data collection in New York where WNS has been present the longest and data from a long-running project which includes from other locations in the Northeast and Midwest regions of the United States. Our results reveal a weakening interaction between temperature and fungal growth rates time with WNS progresses. We additionally observed a decrease in early hibernation fungal loads and variation in infection prevalence over time, suggesting the onset of a coevolutionary relationship between bats and Pd. This study highlights the importance of investigating changing disease dynamics when understanding the reasonings for host persistence. / Master of Science / Emerging infectious diseases threaten species with the risk of extinction. Human activities have altered habitats which has increased the spread of new pathogens to vulnerable host populations. This research focuses on white-nose syndrome (WNS), an emerging disease caused by the fungal pathogen Pseudogymnoascus destructans (Pd). The arrival of Pd to North America resulted in widespread declines in little brown bat (Myotis lucifugus) populations, however, some populations persist at stable or growing rates. This study aims to investigate how the relationship between the growth rate of Pd and bat hibernation temperature may have changed over time. We used a combination of contemporary data collected in New York and a long-running dataset that documents the invasion and establishment of Pd across the Northeast and Midwestern regions of the United States to investigate fungal growth rates during different phases of Pd invasion: invasion, established, and endemic phases. Our results indicate the relationship between temperature and pathogen growth rate has weakened over time, suggesting potential changes in the host-pathogen relationship. Additionally, we found changes in fungal loads and infection prevalence throughout hibernation, suggesting the foundation of a coevolutionary relationship between bats and Pd. This research highlights the importance of understanding changes in disease dynamics to help understand how other species at risk of emerging infectious diseases may be able to persist.