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Parasites can influence host population health and dynamics and are often an overlooked aspect of the ecology of ecosystems. Understanding the impacts of ecological interactions between parasites and small mammals can provide insights into ecosystem dynamics. We live trapped small mammals within the Apostle Islands archipelago (2017-2020) and assessed factors influencing the presence of mites from the Trombiculidae family. Archipelagos provide unique research opportunities because in small mammal-parasitic trombiculid systems, they are essentially closed systems. We detected trombiculids on 47% of red-backed vole (Myodes gapperi (Vigors, 1830)) individuals but rarely detected trombiculids on other species. We developed and ranked a set of a priori logistic regression models of trombiculid presence relative to habitat quality, host abundance, body condition, sex, and sexual maturity to identify factors significant in predicting trombiculid infection for M. gapperi. Parasitic trombiculids were more likely when M. gapperi abundance was high and body condition was poor; however, it is unknown whether trombiculids affect condition or if trombiculids are more likely to parasitize hosts in poor condition. The significance of host abundance may indicate density-dependent transmission. Our work suggests that host density and body condition are important factors influencing parasitism by trombiculids in M. gapperi populations. Key words: density dependence, host condition, Myodes gapperi, parasitism, red-backed vole, Trombiculidae Les parasites peuvent influencer la santé et la dynamique des populations de leurs hôtes et constituent souvent un aspect négligé de l'écologie des écosystèmes. La compréhension des impacts des interactions écologiques de parasites et de petits mammifères peut fournir de l'information sur la dynamique des écosystèmes. Nous avons piégé vivants de petits mammifères dans l'archipel des îles des Apôtres (2017-2020) et évalué les facteurs qui influencent la présence d'acariens de la famille des trombiculidés. Les archipels offrent des possibilités de recherche uniques parce que, pour des systèmes à petits mammifères-trombiculidés parasites, ils constituent essentiellement des systèmes fermés. Nous avons décelé des trombiculidés sur 47 % des campagnols à dos roux de Gapper (Myodes gapperi (Vigors, 1830)), mais rarement sur d'autres espèces. Nous avons élaboré et ordonné un ensemble de modèles de régression logistique a priori de la présence de trombiculidés en fonction de la qualité de l'habitat et de l'abondance, de l'embonpoint, du sexe et de la maturité sexuelle des hôtes afin de cerner les facteurs significatifs pour la prédiction d'infections aux trombiculidés de M. gapperi. Si la présence de trombiculidés parasites était plus probable quand l'abondance des campagnols était élevée et que leur embonpoint était faible, il n'est pas possible de dire si les trombiculidés ont une incidence sur l'embonpoint ou s'ils sont plus susceptibles de parasiter des hôtes de faible embonpoint. La significativité de l'abondance des hôtes pourrait refléter une transmission dépendante de la densité. Nos travaux donnent à penser que la densité et l'embonpoint des hôtes sont des facteurs importants qui influencent le parasitisme de trombiculidés dans les populations de M. gapperi. [Traduit par la Rédaction] Mots-clés : dépendance sur la densité, embonpoint de l'hôte, Myodes gapperi, parasitisme, campagnol à dos roux, trombiculidés, Introduction Parasites can influence the structure and function of ecosystems. Host manipulation by parasites can cause phe-notypic alterations that modify competition processes, food web structure and energy flow, as well [...]

Habitat selection is a critical aspect of a species' ecology, requiring complex decision‐making that is both hierarchical and scale‐dependent, since factors that influence selection may be nested or unequal across scales. Elk (Cervus canadensis) ranged widely across diverse ecoregions in North America prior to European settlement and subsequent eastern extirpation. Most habitat selection studies have occurred within their contemporary western range, even after eastern reintroductions began. As habitat selection can vary by geographic location, available cover, season, and diel period, it is important to understand how a non‐migratory, reintroduced population in northern Wisconsin, USA, is limited by the lack of variation in topography, elevation, and vegetation. We tested scale‐dependent habitat selection on 79 adult elk from 2017 to 2020 using resource selection functions across temporal (i.e., seasonal) and spatial scales (i.e., landscape and home range). We found that selection varied both spatially and temporally, and elk selected areas with the greatest potential to influence fitness at larger scales, meaning elk selected areas closer to escape cover and further from "risky" features (e.g., annual wolf territory centers, county roads, and highways). We found stronger avoidance of annual wolf territory centers during spring, suggesting elk were selecting safer habitats during calving season. Elk selected habitats with less canopy cover across both spatial scales and all seasons, suggesting that elk selected areas with better access to forage as early seral stage stands have greater forage biomass than closed‐canopy forests and direct solar radiation to provide warmth in the cooler seasons. This study provides insight into the complexity of hierarchical decision‐making, such as how risky habitat features and land cover type influence habitat selection differently across seasons and spatial scales, influencing the decision‐making of elk. Scale‐dependent behavior is crucial to understand within specific geographic regions, as these decisions scale up to influence population dynamics. [ABSTRACT FROM AUTHOR]

Population growth rate in long-lived bird species is often most sensitive to changes in adult survival. Sandhill Cranes (Antigone canadensis (Linnaeus, 1758)) have long life spans, small broods, and delayed first reproduction. Only territorial adult Sandhill Cranes participate in breeding, and territory acquisition reflects the interplay between the availability of suitable territories and the variation in mortality of adult birds occupying those territories. We estimated vital rates of a population at equilibrium using long-term resightings data (2000-2014; n = 451 marked individuals) in a multistate mark--resight model and used a stage-structured projection matrix to assess how strongly territorial adult survival affects population growth rate. Elasticity analysis indicated territorial birds surviving and retaining territories had a 2.58 times greater impact on population growth compared with the next most important transition rate (survival of nonterritorial adults remaining nonterritorial). Knowing how changes in vital rates of various stage classes will differentially impact population growth rate allows for targeted management actions including encouraging growth in recovering populations, assessing opportunity for recreational harvest, or maintaining populations at a desired level. This study also highlights the value of collecting demographic data for all population segments, from which one can derive reproductive output or growth rate. Key words: elasticity, population growth rate, perturbation, asymptotic, recruitment, multistate modeling, Sandhill Crane, Antigone canadensis. La survie des adultes est souvent la variable a laquelle le taux de croissance demographique chez les especes d'oiseaux longevifs est le plus sensible. Les grues du Canada (Antigone canadensis (Linnaeus, 1758)) ont une grande longevite, de petites nichees et une premiere reproduction retardee. Seules les grues du Canada territoriales adultes participent a la reproduction, et l'acquisition d'un territoire reflete l'influence mutuelle de la disponibilite de territoires convenables et des variations de la mortalite des oiseaux adultes occupant ces territoires. Nous avons estime des indices vitaux d'une population en equilibre en utilisant des donnees de longue duree sur des signalements repetes (2000-2014; n = 451 specimens marques) dans un modele multi-etats de marquage--signalement repete et utilise une matrice de projection structuree selon l'etape du cycle de vie pour evaluer l'influence du taux de survie des adultes territoriaux sur le taux de croissance de la population. L'analyse d'elasticite indique que les oiseaux territoriaux qui survivent et conservent leurs territoires ont une incidence 2,58 fois plus grande sur la croissance de la population que le taux de la deuxieme transition en importance (la survie d'adultes non territoriaux qui demeurent non territoriaux). Une connaissance des effets des variations d'indices vitaux d'oiseaux a differentes etapes sur le taux de croissance de la population rend possibles des mesures de gestion ciblees visant, notamment, a favoriser la croissance de populations en cours de retablissement, evaluer la pertinence de la chasse sportive et maintenir des populations a des niveaux souhaites. L'etude souligne aussi la valeur de la collecte de donnees demographiques pour tous les segments d'une population, qui permet de determiner l'efficacite de la reproduction ou le taux de croissance. [Traduit par la Redaction] Mots-cles : elasticite, taux de croissance demographique, perturbation, asymptotique, recrutement, modelisation multi-etats, grue du Canada, Antigone canadensis., Introduction Population growth rate in long-lived bird species is often most sensitive to changes in adult survival (Buehler et al. 1991; Bentzen and Powell 2012; Servanty et al. 2014). Many [...]

Declines in hunter recruitment coupled with dramatic growth in numbers of white-tailed deer (Odocoileus virginianus) have challenged our ability to manage deer populations through traditional methods. We surveyed all state wildlife agencies and estimate the abundance of white-tailed deer in North America currently exceeds 30 million. Traditional methods of population management have been ineffective in reducing numbers of deer sufficiently in some environments. The only way to manage overabundant deer directly, cost-effectively, and in a timely fashion is through lethal methods. States currently are issuing record numbers of permits to hunters to increase harvest of white-tailed deer. Unfortunately, hunter participation has been declining in North America during the past two decades. Regulated commercial harvest would help state wildlife agencies manage overabundant populations of white-tailed deer andallow hunters to sell all orparts of harvested deer. We anticipate that many will criticize regulated commercial harvest of deer and claim that it is contrary to the North American Model of Wildlife Conservation (NAMWC). We can, however,argue that regulated commercial harvest meets all seven of the pillars of the NAMWC: 1) Wildlife is a natural resource of the public trust(state wildlife agencies willmanage deeranddeerwould continue to be a public resource). 2) No commercial use of wildlife [a direct reaction to exploitive and unsustainable market hunting in the 18th and 19th Centuries; commercial markets currently exist for other natural resources (e.g., furbearers, fish, timber); contemporary conservation values would not allow overexploitation; a framework for regulations, monitoring, and enforcement already isin place in every state]. 3) Democratic rule of law to regulate use of wildlife (commercial harvest of white-tailed deer would be highly regulated by wildlife agencies through public processes). 4) Hunting opportunity for all (anyone legally able to hold a deer hunting license would be eligible to apply for a Commercial Deer Harvest License (CDHL), CDHL programs would be implemented only where recreational hunting is proven inefficient or inappropriate). 5) No frivolous use of wildlife (CDHLs will beused to generate of food and other products, management would address risk to human health and safety andlosses ofagricultural resourcesto deer). 6) Wildlife is an international resource (has little to do with our proposed idea of managing overabundant resident populations of white-tailed deer, but a CDHL program may be applicable to any overabundant species, including internationally migratory species,such assnow geese,Chen caerulescens). 7) Science-based wildlife policy (a CDHL program would rely on science and research-based data to estimate densities before, during, and after commercial harvest). A CDHL program should be managed and distributed by state wildlife agencies, issued only to qualified individuals, enable harvest of an allotment of deer in areas targeted for population reduction, and permit the sale of whole carcasses and parts of harvested deer. Administration of a CDHL program will be taxing. State agencies alreadyareunderstaffed, but administrative and enforcement frameworks already exist for commercial harvest of publicly owned natural resources (e.g., furbearers, fish, timber) and the processing and handling of meat (e.g., USDA inspections). Revenue generated by CDHL programs could be directed back toward agencies and personnel who will administer and oversee these programs. Looking forward, we anticipate several issues mustbe addressed for regulated commercial harvestof deer to be accepted by agencies, hunters, and the public. The dogma against commercial use of wildlife may be well established. It may be difficult to mediate changesin attitudes in the wildlife community, stakeholders, and other publics. It will require adoption at all levels. State laws and regulations will need to be reviewed and some will have to be changed. Some will argue that we do not have the strength, stamina, or political will necessary to implement such broad sweeping changes. On the other hand, many wildlife managers will appreciate having an alternative tool for managing overabundant populations of white-tailed deer. We identified several benefits (reduce overabundant populations of deer; source of healthy, natural, green, locally-produced protein; economic growth, entrepreneurship, and market expansion; and public engagement and appreciation) and expected concerns associated with this concept(privatization of wildlife; overexploitation; food safety; competition with existing commodities; law enforcement; challenges of changing laws, regulations, and attitudes). We encourage a professional discussionof regulated commercial harvestto address the issue of overabundant white-tailed deer.

The Forest Preserve District of DuPage County culled 2,826 white-tailed deer (Odocoileus virginianus), from 16 forest preserves in winters 1992-1998, including 1,786 from the 10 km2 Waterfall Glen Preserve. Methods of culling included sharpshooting or capture with a rocket-net followed by euthanasia via a penetrating captive bolt. Operational field costs were $119 to $310/deer. Population reconstructions indicated a decrease in deer population density at Waterfall Glen Preserve from 751 deer in 1992 to 55 deer in 1998. This reduction resulted in a significant decrease (r=0.9, P=0.001, n=7) in reported deer-vehicle collisions on adjacent roads from 30 in 1992 to 4 in 1998. Mean plant height, percent vegetative ground cover, and number of plant species increased (P< 0.0001) among years in six forest preserves experiencing deer population control. Culling was successful at reducing deer population density, decreasing deer-vehicle collisions, and assisting with the restoration of native ecosystems in DuPage County Forest Preserves.

Climate change is influencing polar bear (Ursus maritimus) habitat, diet, and behavior but the effects of these changes on their physiology is not well understood. Blood‐based biomarkers are used to assess the physiologic health of individuals but their usefulness for evaluating population health, especially as it relates to changing environmental conditions, has rarely been explored. We describe links between environmental conditions and physiologic functions of southern Beaufort Sea polar bears using data from blood samples collected from 1984 to 2018, a period marked by extensive environmental change. We evaluated associations between 13 physiologic biomarkers and circumpolar (Arctic oscillation index) and regional (wind patterns and ice‐free days) environmental metrics and seasonal and demographic co‐variates (age, sex, season, and year) known to affect polar bear ecology. We observed signs of dysregulation of water balance in polar bears following years with a lower annual Arctic oscillation index. In addition, liver enzyme values increased over time, which is suggestive of potential hepatocyte damage as the Arctic has warmed. Biomarkers of immune function increased with regional‐scale wind patterns and the number of ice‐free days over the Beaufort Sea continental shelf and were lower in years with a lower winter Arctic oscillation index, suggesting an increased allocation of energetic resources for immune processes under these conditions. We propose that the variation in polar bear immune and metabolic function is likely indicative of physiologic plasticity, a response that allows polar bears to remain in homeostasis even as they experience changes in nutrition and habitat in response to changing environments. [ABSTRACT FROM AUTHOR]