Bobcat Hair Cortisol Correlates with Land Use and Climate

Bobcats (Lynx rufus) have been increasing in abundance in the northeast United States despite a corresponding trend of increased anthropogenic land uses. Inhabiting areas of high human land use can affect stress levels, and hence cortisol titers, for wildlife species by increasing frequency of human interaction and altering habitats. In turn, increased cortisol levels can have negative effects at the individual and population level including decreased immune function, slowed growth and tissue repair, reduced reproductive capacity, and nutritional deficiencies. We quantified cortisol in bobcats across New Hampshire and Vermont, USA, using hair samples, then explored associations between hair cortisol and various organismal, land use, land cover, and climatic variables at 2 different spatial scales. Hair cortisol differed by season and bobcat mass. On average, cortisol levels were higher in fall than in spring, and larger bobcats had lower cortisol levels. Anthropogenic land uses—especially residential and agricultural uses—were the most important predictors of hair cortisol at the town scale ( area = 93 km²). At a larger scale (Wildlife Management Units; area = 1,256 km²), temperature and precipitation were better predictors of hair cortisol, suggesting that extreme weather may have significant effects on bobcat population dynamics. Our results highlight the importance of landscape composition and local conditions in the sustainable management of furbearer populations. © 2021 The Wildlife Society.     

Evidence for Depressed Reproduction of Golden Eagles in Washington

Beginning in 1977 the Washington Department of Fish and Wildlife conducted annual surveys to determine statewide golden eagle (Aquila chrysaetos) occupancy and productivity. Current interest in the regional and national status of the species prompted our investigation to determine utility of historical data in assessing trends in reproduction, and to test efficacy of a sampling protocol that surveyed randomly selected territories and also accounted for detection probability. We found evidence indicating poor reproduction from 38 annual surveys conducted at 301 known territories statewide between 1977 and 2014. At 256 territories in eastern Washington, USA, apparent occupancy was low ( = 50.9%) and nesting success declined by 22%. All reproductive parameters were higher than at 45 territories in western Washington. We tested efficacy of a sampling protocol in 2013 and 2014 by surveying 108 randomly selected eastern territories. Probability of detecting eagles for these years from ground (= 89%) was greater than from air (= 66%). Our estimate of territory occupancy, corrected by probability of detection, was lower in 2013 (= 56.7%, 95% CI = 46.3–66.7%) than in 2014 (= 73.7%, 95% CI = 64.8–81.7%), as was the estimated number of breeding pairs (2013: = 158, 95% CI = 151–164; 2014: = 187, 95% CI = 182–192). Higher productivity (young/occupied territory) in 2013 (= 0.59, 95% CI = 0.40–0.82) than in 2014 (= 0.41, 95% CI = 0.27–0.59) and lower proportions of ≥1 immature eagle among nesting pairs in 2013 (16%) than in 2014 (31%), suggested higher immature pairing among sampled pairs contributed to inter-year differences in these reproductive parameters. Current and historical evidence for depressed golden eagle nesting in Washington is consistent with documented effects from habitat conversion, prey declines, lead contamination, and wind power development. We recommend future surveys in eastern Washington adhere to the random sampling protocol and conduct surveys at regular intervals to allow for trend analysis of reproductive parameters to better monitor golden eagle status. Surveys in western Washington, conducted exclusively from ground at all nests, will improve detection and cost efficiency. © 2020 The Wildlife Society.     

Anthropogenic Disturbance and Population Viability of Woodland Caribou in Ontario

One of the most challenging tasks in wildlife conservation and management is to clarify how spatial variation in land cover due to anthropogenic disturbance influences wildlife demography and long-term viability. To evaluate this, we compared rates of survival and population growth by woodland caribou (Rangifer tarandus caribou) from 2 study sites in northern Ontario, Canada that differed in the degree of anthropogenic disturbance because of commercial logging and road development, resulting in differences in predation risk due to gray wolves (Canis lupus). We used an individual-based model for population viability analysis (PVA) that incorporated adaptive patterns of caribou movement in relation to predation risk and food availability to predict stochastic variation in rates of caribou survival. Field estimates of annual survival rates for adult female caribou in the unlogged ( 0.90) and logged ( 0.76) study sites recorded during 2010–2014 did not differ significantly (P > 0.05) from values predicted by the individual-based PVA model (unlogged: = 0.87; logged: 0.79). Outcomes from the individual-based PVA model and a simpler stage-structured matrix model suggest that substantial differences in adult survival largely due to wolf predation are likely to lead to long-term decline of woodland caribou in the commercially logged landscape, whereas the unlogged landscape should be considerably more capable of sustaining caribou. Estimates of population growth rates (λ) for the 2010–2014 period differed little between the matrix model and the individual-based PVA model for the unlogged (matrix model = 1.01; individual-based model = 0.98) and logged landscape (matrix model = 0.88; individual-based model = 0.89). We applied the spatially explicit PVA model to assess the viability of woodland caribou across 14 woodland caribou ranges in Ontario. Outcomes of these simulations suggest that woodland caribou ranges that have experienced significant levels of commercial forestry activities in the past had annual growth rates <0.89, whereas caribou ranges that had not experienced commercial forestry operations had population growth rates >0.96. These differences were strongly related to regional variation in wolf densities. Our results suggest that increased wolf predation risk due to anthropogenic disturbance is of sufficient magnitude to cause appreciable risk of population decline in woodland caribou in Ontario. © 2020 The Authors. The Journal of Wildlife Management published by Wiley Periodicals, Inc. on behalf of The Wildlife Society.     

Optimal Strategies for Managing Wildlife Harvest Under System Change

Wildlife populations are experiencing shifting dynamics due to climate and landscape change. Management policies that fail to account for non-stationary dynamics may fail to achieve management objectives. We establish a framework for understanding optimal strategies for managing a theoretical harvested population under non-stationarity. Building from harvest theory, we develop scenarios representing changes in population growth rate () or carrying capacity () and derive time-dependent optimal harvest policies using stochastic dynamic programming. We then evaluate the cost of falsely assuming stationarity by comparing the outcomes of forward projections in which either the optimal policy or a stationary policy is applied. When declines over time, the stationary policy leads to an underharvest of the population, resulting in less harvest over the short term but leaving the population in a higher-value state. When declines over time, the stationary policy leads to overharvest, resulting in greater harvest returns in the short term but leaving the population in a lower and potentially more vulnerable state. This work demonstrates the basic properties of time-dependent harvest management and provides a framework for evaluating the many outstanding questions about optimal management strategies under climate change. Published 2021. This article is a U.S. Government work and is in the public domain in the USA.     

Long-Term Spatiotemporal Dynamics and Factors Associated with Trends in Bare-Nosed Wombats

Geographically widespread species present challenges for conservation assessment. We used long-term spotlight surveys to assess spatiotemporal dynamics of bare-nosed wombats (Vombatus ursinus), encompassing 34 years of surveys for the Tasmanian mainland sub-species (V. u. tasmaniensis, 1985–2018) and 25 years for the Flinders Island sub-species (V. u. ursinus, 1994–2018). Wombat populations increased on the Tasmanian mainland by 2.59 times and on Flinders Island by 3.51 times ( = 1.05 and 1.1 times increase/yr, respectively). At smaller spatial scales on mainland Tasmania, increases in wombat counts generally occurred within meteorological regions and regional zones, except for the Central North (West Tamar) region where a decrease in wombats is linked to a sarcoptic mange disease epizootic. We used generalized additive models to assess relationships between variables and wombat counts. The most supported variables at the mainland Tasmania scale were (in order of importance) year, positive associations with time-lagged minimum temperature, Tasmanian devil (Sarcophilus harrisii) counts, and moonlight, and a negative association with time-lagged rainfall. Among meteorological regions, variables associated with wombat counts exhibited some heterogeneity, with temperature and rainfall the most frequently associated variables. Our long-term, large-scale, and ecologically diverse analysis of bare-nosed wombats supports spotlight monitoring as a valuable, relatively simple, and affordable survey method in Tasmania and beyond. © 2021 The Wildlife Society.     

Influence of Landscape Characteristics on Hunter Space Use and Success

Sport hunting of ungulates is a predominant recreational pursuit and the primary tool for managing their populations in North America and beyond, given its influence on ungulate distributions, social organization, and population performance. Similarly, land management, such as motorized vehicle access, influences ungulate distributions during and outside hunting seasons. Although research on ungulate responses to hunting and land use is widespread, knowledge gaps persist about space use of hunters and what landscape features discriminate among hunt types and between successful and unsuccessful hunters. We used telemetry location data from hunters (n = 341) to estimate space use from 2008–2013 during 3 types of controlled, 5-day hunts for antlered mule deer (Odocoileus hemionus) and elk (Cervus canadensis) in northeastern Oregon, USA: archery elk, rifle deer, and rifle elk. To evaluate space use, we developed utilization distributions for each hunter, created core areas (50% contours) for groups of hunters, and derived several metrics of space-use overlap between successful and unsuccessful hunters. We also modeled predictors of space use using resource utilization functions with beta regression and stepwise model building. Hunter space use was compressed, with even the largest core area (unsuccessful rifle elk hunters) encompassing <16% (1,178 ha) of the area. We found strong similarities in space use of rifle hunters compared to archers, and core areas of successful hunters were markedly smaller than those of unsuccessful hunters (e.g., = 104 ha vs. 681 ha, respectively, for archers). Percentage cover and distance from open roads were the most consistent covariates in the 6 final models (successful vs. unsuccessful for each of 3 hunts) but with different signs. For example, predicted use of archery and rifle elk hunters increased with cover but decreased for rifle deer hunters. Although the same covariates were in the final models for unsuccessful and successful rifle elk hunters, their negligible spatial overlap suggested they sought those features in different locales, a pattern also documented for rifle deer hunters. Our models performed well (Spearman's rank correlation coefficients = 0.99 for 5 of 6 models), reflecting their utility for managing hunters and landscapes. Our results suggest that strategic management of open roads and forest cover can benefit managers seeking to balance hunter opportunity and satisfaction with harvest objectives, especially for species of special concern such as mule deer, and that differences in space use among hunter groups should be accounted for in hunting season designs. © 2021 The Wildlife Society. This article has been contributed to by US Government employees and their work is in the public domain in the USA.     

Effects of Midazolam on Corticosterone and Blood Gases in Spectacled Eiders Prior to Transmitter Implantation

Stress and physical exertion may affect the physiology and behavior of wildlife during and after capture, and consequently, survival following release. Such effects may reduce the quality and quantity of the data obtained from captured wildlife. We captured spectacled eiders (Somateria fischeri), a species listed as threatened under the United States Endangered Species Act, in western Alaska, USA, during spring 2018 for surgical implantation of satellite transmitters. We evaluated the efficacy of midazolam, a benzodiazepine sedative given at capture, to reduce stress and physical exertion. We dosed spectacled eiders with either midazolam (5 mg/ml, = 2.2 mg/kg intramuscular; n = 20) or saline (0.7 ml intramuscular; n = 20) at the point of capture. We assessed sedation level and collected blood samples upon arrival to the field surgery site and at anesthetic induction. We found that midazolam reduced mean corticosterone concentration by 29% and median lactate concentration by 30.3% at the mean arrival time (42 min post-dosing) relative to the control group. These effects had abated by the mean induction time (99 min post-dosing). Unexpectedly, blood pH was reduced in the midazolam treatment relative to controls at both arrival and induction, which likely resulted from sedative-induced respiratory depression that was easily treated with intubation and mechanical ventilation, and administration of the reversal drug, flumazenil. Low blood pH was not associated with negative post-surgical outcomes, as had been found in spectacled eiders with acidosis caused by anaerobic metabolism typical of physical exertion. Intramuscular injection of midazolam in the field effectively reduced stress and physical exertion in spectacled eiders prior to surgical implantation of transmitters. © 2021 The Wildlife Society.     

Comparison of Woodland Caribou Calving Areas Determined by Movement Patterns Across Northern Ontario

Adult female survival and calf recruitment influence population dynamics, but there is limited information on calving and neonatal mortality of boreal woodland caribou (Rangifer tarandus caribou; caribou) in Ontario, Canada. We identified calf parturition sites and 5-week neonatal mortality using a movement-based approach across 3 northern Ontario study regions (Pickle Lake, Nakina, and Cochrane) that vary in their capacity to support caribou populations. In comparing 22 caribou-years of video-collar footage during 2010–2013 to predictions of the movement-based approach, we found live parturition events were 100% correctly classified, date of parturition was within 1.08 ± 0.28 ( ± SE) days, and mortality events up to 5 weeks postpartum were 88% correctly classified. Across study regions, 87% of 186 caribou were pregnant and 76% of 107 caribou-years indicated birth events with median parturition dates a week later in Cochrane (23 May) than in Pickle Lake (17 May) and Nakina (16 May). Based on selection ratios of caribou-years with calves-at-heel (n = 80), caribou consistently selected for lowlands and closed-canopied forests and mostly against early-seral stands (<20 yrs old) and areas near linear features during the neonatal and the post-neonatal period (up to 35 days postpartum). Based on the video footage and movement models, 30% of 81 caribou-years that indicated live births also showed females lost their calf within the first 5 weeks postpartum, with higher risk of neonatal mortality associated with increased use of lowlands and greater postpartum movement rates. This study provides informative metrics of caribou reproduction across northern Ontario that will contribute to future population modeling and identifies important landscape features to be considered in future industrial development and land use planning for caribou conservation. © 2020 The Wildlife Society.     

Landscape Genetics of American Beaver in Coastal Oregon

American beaver (Castor canadensis) have been translocated for population restoration, reduction of human-wildlife conflict, and enhancement of ecosystem function. Yet few studies have assessed dispersal of beaver, making it difficult to determine at what scale translocations are appropriate. Genetic studies can provide inferences about gene flow, and thus dispersal. We used a landscape genetic approach to evaluate whether landscape features influenced gene flow among beaver in the Coast Range of western Oregon, USA, using samples collected April–September 2014. We collected genetic samples from live-captured (n = 232), road-killed (n = 2) and trapper-provided (n = 58) tissue samples and genotyped them at 10 microsatellite loci. We mapped records of beaver translocations into or within the study area during the twentieth century to consider the effect of those movements on genetic structure. We used population assignment tests to delimit genetic clusters, evaluated correspondence of those clusters with watershed boundaries and translocation history, and then estimated differentiation between clusters and between watersheds using model-based and model-free approaches. We evaluated how individual genetic differences varied with geographic distance, and investigated related pairs within clusters. We developed landscape resistance models incorporating slope, distance to water, and watershed boundaries at 2 scales, and estimated effective distances between sample locations with least cost path and circuit theoretic analyses. We evaluated the correlation of individual genetic distances with effective distances using a pseudo-bootstrapping approach. Landscape genetic models did not explain spatial variation in genetic structure better than geographic distance, but hierarchical genetic structure corresponded with watershed boundaries and suggested influences from historical translocations. Pairwise individual genetic distances were positively correlated with geographic distances to 61 km; highly-related pairs mostly were detected <1 km apart (median = 1.0 km, = 14.6 ± 2.3 [SE] km, n = 77). We concluded that slope and distance to water did not strongly limit dispersal and gene flow by beaver in this system, but concordance of genetic structure with watershed boundaries suggests that dispersal is more common within than between watersheds. Genetic differentiation of beaver within this topographically complex system was much greater than reported in a study at similar spatial scales in relatively flat topography. We recommend that translocation efforts of American beaver in topographically complex landscapes occur within watersheds when possible but conclude that dispersal can occur across watersheds. © 2021 The Wildlife Society. This article is a U.S. Government work and is in the public domain in the USA.     

Disturbance-Mediated Apparent Competition Decouples in a Northern Boreal Caribou Range

The most widely reported threat to boreal and mountain populations of woodland caribou (Rangifer tarandus caribou; caribou) involves habitat- or disturbance-mediated apparent competition (DMAC). With DMAC, natural and anthropogenic disturbances that increase the abundance of deciduous-browsing cervids (e.g., moose [Alces alces], deer [Odocoileus spp.]) are thought to promote predator (especially wolf [Canis lupus]) numbers, which heightens predation risk to caribou. We know most about the effects of DMAC on caribou where the species is under threat by anthropogenic activities in relatively productive southern boreal and mountain systems. Yet, >60% of extant boreal caribou range in North America consists of northern shield and taiga ecoregions of low productivity where caribou may compete with only 1 ungulate species (moose) in the context of DMAC. In this environment, we know very little of how DMAC acts as a limiting factor to caribou. In Saskatchewan, Canada, from 2014–2018, using a combination of vegetation sampling, aerial surveys, and telemetry data (n = 38 wolves), we searched for evidence of DMAC (trends in data consistent with the hypothesis) in an 87,193-km² section of the Western Boreal Shield, a poorly productive but pristine region (0.18% of land cover classed as an anthropogenic feature) with a historically high fire-return interval (47% of stands aged <40 years). Despite the high levels of disturbance, moose density was relatively low (47 moose/1,000 km²), likely because of the scarcity of deciduous or mixed-wood stands and low abundance of deciduous browse in the young conifer stands that dominated the landscape. In contrast, boreal caribou density was relatively high for the species (37 caribou/1,000 km²). Wolf density (3.1 wolves/1,000 km²) and pack sizes ( = 4.0 wolves/pack) were low and resident (established) territories were large ( = 4,360 km²; 100% minimum convex polygon). The low density of wolves mirrored the low (standardized) ungulate biomass index (UBI; moose + boreal caribou) of the study area (0.36 UBI/km²). We conclude that wolf and hence caribou populations were not responding in accordance with the outcomes generally predicted by DMAC in our study area because the requisite strong, positive response to fire of deciduous-browse and alternate-prey abundance was lacking. As a limiting factor to caribou, DMAC is likely modulated at a macroecological scale by factors such as net primary productivity, a corollary to the general hypothesis that we advance here (i.e., primary productivity hypothesis of DMAC). We caution against managing for caribou based on the presumption of DMAC where the mechanism does not apply, which may include much of boreal caribou range in the north. © 2020 The Wildlife Society.     

Prey Specialization by Cougars on Feral Horses in a Desert Environment

Natural controls on the distribution, abundance, or growth rates of exotic species are a desirable mode of intervention because of lower costs compared to anthropogenic controls and greater social acceptance. In the Great Basin, cougars (Puma concolor) are the most widely distributed carnivore capable of killing large ungulate prey. Populations of feral horses (Equus ferus) are widely distributed throughout the Great Basin and can grow at rates up to 20%/year. Although cougars exhibit distributional overlap with horses, it has been assumed that predation is minimal because of differences in habitat use and body-size limitations. To evaluate this hypothesis, we monitored the diets of 21 global positioning system (GPS)-collared cougars in the western Great Basin (5 males, 8 females) and eastern Sierra Nevada (2 males, 6 females) from 2009–2012. We investigated 1,310 potential kill sites and located prey remains of 820 predation events. We compared prey composition and kill rates of cougars inhabiting the Sierra Nevada and Great Basin, and among male and female cougars across seasons. We used generalized linear mixed models (GLMMs) to examine the effects of prey availability and habitat characteristics on the probability of predation on horses by cougars. Mule deer (Odocoileus hemionus) comprised 91% of prey items killed on the Sierra Nevada reference site but only comprised 29% of prey items in the Great Basin study area. Average annual kill rates for deer differed between the Sierra Nevada ( = 0.85 deer/week, range = 0.44–1.3) and Great Basin ( = 0.21 deer/week, range = 0.00–0.43). Diets of cougars in the Great Basin were composed predominantly of horses (59.6%, n = 460 prey items; 13 individuals). Ten cougars regularly consumed horses, and horses were the most abundant prey in the diet of 8 additional individuals in the Great Basin. Cougars on average killed 0.38 horses/week in the Great Basin (range=0.00–0.94 horses/week). Differences in predation on horses between the sexes of cougars were striking; Great Basin females incorporated more horses across all age classes year-round, whereas male cougars tended to exploit neonatal young during spring and summer before switching to deer during winter. Within GLMM models, the probability of predation on horses compared to other prey species increased with elevation, horse density, and decreasing density of mule deer on the landscape, and was more likely to occur in sagebrush (Artemesia spp.) than in pinyon (Pinus monophylla)–juniper (Juniperus osteosperma) forests. Behavior of individual cougars accounted for more than a third of the variation explained by our top models predicting predation on horses in the Great Basin. At landscape scales, cougar predation is unlikely to limit the growth of feral horse populations. In the Great Basin ecosystem, however, cougars of both sexes successfully preyed on horses of all age classes. Moreover, some reproductive, female cougars were almost entirely dependent on feral horses year-round. Taken together, our data suggest that cougars may be an effective predator of feral horses, and that some of our previous assumptions about this relationship should be reevaluated and integrated into management and planning. © 2021 The Wildlife Society.     

Eagle visitation rates to carrion in a winter scavenging guild

Understanding the behavioral ecology of species of conservation concern can help to inform better management. During winters 2011 through 2017, we placed camera traps at stations baited with carrion to investigate characteristics of winter scavenging by golden eagles (Aquila chrysaetos) and bald eagles (Haliaeetus leucocephalus) in eastern Washington and Oregon, USA. Our objectives were to better understand exposure risk of individual eagles to lead contaminants and evaluate factors that affect eagle visitation to carrion to inform measures that reduce lead exposure. We studied photo sequences from 108 traps ( = 2,725 ± 306 [SE] images/trap) and used plumage and physical characteristics to track visitation of 183 individual golden eagles and 90 bald eagles at deer (Odocoileus spp.) carrion until it was totally consumed. At least 1 eagle visited 76% of traps ( = 2.5 ± 0.3 unique eagles/trap). On average, an eagle visited a trap 3.4 ± 0.2 times (range = 1–19 visits) over 1.9 ± 0.1 days (range = 1–9 days). We used general linear mixed models to identify influences on number of eagle visits and pooled visit duration. Individual golden eagles visited carrion about 25% more often and 50% longer than bald eagles, and individual juvenile eagles visited carrion more often and longer than immature and adult eagles. On average, an eagle made an additional visit to carrion for every golden eagle that came to the same trap. Eagles spent less time at offal ( = 26.2 ± 6.4 min) than at a whole carcass ( = 92.9 ± 7.5 min), and understory vegetation immediately surrounding carrion was associated with a 30% reduction in visitation time. In the Pacific Northwest during winter, adult and juvenile golden eagles, by virtue of their abundance and visitation to carrion compared to the immature age class and bald eagles of all ages, have the highest potential for exposure to anthropogenic effects from carrion visitation. Concealment of offal piles in vegetation may reduce, but not eliminate, eagle use because of competing scavengers that expose carrion locations. We found no evidence that carrion proximity to nearest known nests, topography, or snow cover affect visitation by eagles. Thus, short of using alternative ammunition to lead, we recommend burial or removal of offal from hunter-killed ungulates. © 2019 The Wildlife Society.     

Influence of Juniper on Montezuma Quail Habitat Use in Texas

Montezuma quail (Cyrtonyx montezumae) inhabit oak (Quercus spp.)-juniper (Juniperus spp.) woodlands throughout Mexico and the southwestern United States. In Texas, USA, Montezuma quail occur in the Edwards Plateau and Trans-Pecos Mountains and Basins (Trans-Pecos), 2 ecoregions with contrasting juniper patterns. Ashe juniper (Juniperus ashei) dominates in the Edwards Plateau and has been increasing over decades, whereas alligator juniper (Juniperus deppeana) is a co-dominant in the Trans-Pecos and appears to have stable Montezuma quail populations. Our objectives were to compare between ecoregions the relative abundance and habitat use of Montezuma quail in relation to juniper and quantify the influence of juniper on key features of Montezuma quail habitat (grass height, grass cover, forb cover, and forb species richness). We conducted a study from March–August 2018‒2020 in the Edwards Plateau (Kinney and Edwards counties) and Trans-Pecos ecoregions (Jeff Davis County) to evaluate these objectives. We conducted call-back surveys to estimate relative abundance (number of detections/hr) of Montezuma quail and identify used locations. We collected vegetation data at a micro-scale (16-m) at used (n = 32–30 points) and random locations (n = 70–60 points) in each ecoregion. Relative abundance of Montezuma quail was considerably lower in the Edwards Plateau (0.06 ± 0.01 detections/survey hr; ± SE) than in the Trans-Pecos (1.10 ± 0.30 detections/survey hr). In addition, Montezuma quail selected areas of low Ashe juniper cover (<23% cover), density (<7 trees/80 m²), and height (<2 m) in the Edwards Plateau but selected areas of high alligator juniper cover (>18% cover), density (>4 trees/80 m²), and height (2–8 m) in the Trans-Pecos. Moreover, Ashe juniper cover had a significant, negative influence on herbaceous features, whereas alligator juniper exerted little to no influence. Our results suggest that these 2 juniper species have contrasting effects on Montezuma quail space use and their habitat, possibly as a result of the contrasting influence of these junipers on herbaceous understory. Creating habitat for Montezuma quail in the Edwards Plateau generally will involve the reduction of Ashe juniper and creating patches that possess juniper trees of small stature (<2 m) with low amounts of cover (<23%) and density (<7 trees/80 m²), whereas management in the Trans-Pecos will require site-specific assessments based on current alligator juniper influence. © 2021 The Wildlife Society.     

An estimator of the Opportunity for Selection that is independent of mean fitness

Variation among individuals in number of offspring (fitness, k) sets an upper limit to the evolutionary response to selection. This constraint is quantified by Crow's Opportunity for Selection (I), which is the variance in relative fitness (I = σ²_k/(u_k)²). Crow's I has been widely used but remains controversial because it depends on mean offspring number in a sample (). Here, I used a generalized Wright-Fisher model that allows for unequal probabilities of producing offspring to evaluate behavior of Crow's I and related indices under a wide range of sampling scenarios. Analytical and numerical results are congruent and show that rescaling the sample variance (s²_k) to its expected value at a fixed removes dependence of I on mean offspring number, but the result still depends on choice of . A new index is introduced, Δ_I = Π– E(Î_drift) = Π– 1/, which makes Î independent of sample without the need for variance rescaling. Δ_I has a straightforward interpretation as the component of variance in relative fitness that exceeds that expected under a null model of random reproductive success. Δ_I can be used to directly compare estimates of the Opportunity for Selection for samples from different studies, different sexes, and different life stages.     

Assessing Population Viability of Black Bears using Spatial Capture-Recapture Models

The Central Georgia Bear Population (CGP) is the least abundant and most isolated of Georgia's 3 American black bear (Ursus americanus) populations. Beginning in 2011, changes to regulations governing harvest of the CGP resulted in an increase in female bear harvest, creating concern that future harvest could be an important influence on population viability. Hence, our objective was to assess viability of the CGP under various levels of female mortality. During 2012–2016, we used barbed-wire hair snares to collect bear hair samples from within the range of the CGP in Georgia, USA. We used microsatellite genotyping to identify individual bears and created robust-design, spatial detection histories for all female bears detected. We fit open population spatial capture-recapture (SCR) models to the detection histories in a Bayesian framework. We used the Widely Applicable Information Criterion (WAIC) to rank models that varied with respect to sources of variation in detection probability, survival, and per capita recruitment, and used the model with the lowest WAIC to forecast dynamics of the CGP 50 years into the future under various levels of female mortality. We assessed the 50-year extinction probability under a continuation of mortality levels documented during 2012–2016, and under incremental increases in female mortality above this baseline. The top model included density-dependent per capita recruitment, annual variation in detection probability, and a trap-level behavioral response. Abundance increased from 106 (95% CI = 86–132) females in 2012 to 136 (95% CI = 113–161) females in 2013 and remained relatively stable thereafter. Annual female survival was 0.75 (95% CI = 0.69–0.82) and did not vary among years. The per capita recruitment rate decreased over time as density increased, and was 0.49 (95% CI = 0.33–0.66) during the first time interval and 0.29 (95% CI = 0.20–0.38) during the final time interval. Annual growth rate () was 1.28 (95% CI = 1.07–1.52) between 2012 and 2013 but decreased throughout the study, ending at 1.04 (95% CI = 0.93–1.17). Forecasts indicated continuation of the female mortality levels experienced from 2012–2016 were sustainable over 50 years, with the estimated extinction risk being <0.001%. Increasing annual harvest by 5 females introduced a negligible increase in the 50-year probability of extinction, but harvesting an additional 10 females/year caused extinction risk to rise to 1.15%. We recommend that harvest regulations are structured such that mortality rates remain at current levels or do not increase by more than an annual average of 5 females above levels observed during our study. Furthermore, we recommend that managers continue to monitor the population so that harvest regulations and population models can be refined over time. © 2020 The Wildlife Society.     

The genetic architecture of maternal effects across ontogeny in the red deer

Maternal effects, either environmental or genetic in origin, are an underappreciated source of phenotypic variance in natural populations. Maternal genetic effects have the potential to constrain or enhance the evolution of offspring traits depending on their magnitude and their genetic correlation with direct genetic effects. We estimated the maternal effect variance and its genetic component for 12 traits expressed over the life history in a pedigreed population of wild red deer (morphology, survival/longevity, breeding success). We only found support for maternal genetic effect variance in the two neonatal morphological traits: birth weight ( = 0.31) and birth leg length ( = 0.17). For these two traits, the genetic correlation between maternal and direct additive effects was not significantly different from zero, indicating no constraint to evolution from genetic architecture. In contrast, variance in maternal genetic effects enhanced the additive genetic variance available to respond to natural selection. Maternal effect variance was negligible for late-life traits. We found no evidence for sex differences in either the direct or maternal genetic architecture of offspring traits. Our results suggest that maternal genetic effect variance declines over the lifetime, but also that this additional heritable genetic variation may facilitate evolutionary responses of early-life traits.     

The effects of hurricanes on the stochastic population growth of the endemic epiphytic orchid Broughtonia cubensis living in Cuba

We carried out a posthurricane evaluation of Broughtonia cubensis (Lindl.) Cogn., an endemic Cuban epiphytic orchid, after Hurricane Ivan (2004). We studied the transient responses in the stochastic dynamics of the species at three different sites over 13 successive years (2006–2019), monitored plot inventories (464 individuals in 10 transects) and built stochastic population models. The deterministic stochastic growth rate values () did not significantly differ (F = 2.76; p > 0.076) among the three sites over the 2006–2019 period. The long-term stochastic growth rate was 0.973 [0.932, 1.034]. The matrix elements that had the largest effect on were the transition to and stasis within the largest size class. Transient responses explained an average of 86% of the variation in the observed population growth rates , compared to 4% of the variation in the vital rates . Because transient dynamics are dependent on the population size composition, we ran extinction risk analyses under two scenarios: a population composed mainly of juveniles and another composed mainly of adults. There was little risk of falling below the quasi-extinction threshold before 25 year for both juveniles and adults. However, the risk of quasi-extinction was almost certain for both size classes by 80 year. We also simulated the effect of increasing the hurricane occurrence probability over 80 year on the population. There was little risk of extinction before 20 year in the baseline model, but there was a significant risk of extinction within 5 year when 90% of the individuals were affected by a new hurricane event.     

Inverse problem approach to regularized regression models with application to predicting recovery after stroke

Regression modelling is a powerful statistical tool often used in biomedical and clinical research. It could be formulated as an inverse problem that measures the discrepancy between the target outcome and the data produced by representation of the modelled predictors. This approach could simultaneously perform variable selection and coefficient estimation. We focus particularly on a linear regression issue, , where is the parameter of interest and its components are the regression coefficients. The inverse problem finds an estimate for the parameter , which is mapped by the linear operator to the observed outcome data . This problem could be conveyed by finding a solution in the affine subspace . However, in the presence of collinearity, high-dimensional data and high conditioning number of the related covariance matrix, the solution may not be unique, so the introduction of prior information to reduce the subset and regularize the inverse problem is needed. Informed by Huber's robust statistics framework, we propose an optimal regularizer to the regression problem. We compare results of the proposed method and other penalized regression regularization methods: ridge, lasso, adaptive-lasso and elastic-net under different strong hypothesis such as high conditioning number of the covariance matrix and high error amplitude, on both simulated and real data from the South London Stroke Register. The proposed approach can be extended to mixed regression models. Our inverse problem framework coupled with robust statistics methodology offer new insights in statistical regression and learning. It could open a new research development for model fitting and learning.     

Important role of genetic drift in rapid polygenic adaptation

We analyzed a model to determine the factors that facilitate or limit rapid polygenic adaptation. This model includes population genetic terms of mutation and both directional and stabilizing selection on a highly polygenic trait in a diploid population of finite size. First, we derived the equilibrium distribution of the allele frequencies of the multilocus model by diffusion approximation. This formula describing the equilibrium allele frequencies as a mutation‐selection‐drift balance was examined by computer simulation using parameter values inferred for human height, a well‐studied polygenic trait. Second, assuming that a sudden environmental shift of the fitness optimum occurs while the population is in equilibrium, we analyzed the adaptation of the trait to the new optimum. The speed at which the trait mean approaches the new optimum increases with the equilibrium genetic variance. Thus, large population size and/or large mutation rate may facilitate rapid adaptation. Third, the contribution of an individual locus i to polygenic adaptation depends on the compound parameter , where is the effect size, the equilibrium frequency of the trait‐increasing allele of this locus, and . Thus, only loci with large values of this parameter contribute coherently to polygenic adaptation. Given that mutation rates are relatively small, this is more likely in large populations, in which the effects of drift are limited.     

Valid oxygen uptake measurements: using high r2 values with good intentions can bias upward the determination of standard metabolic rate

This analysis shows good intentions in the selection of valid and precise oxygen uptake (O₂) measurements by retaining only slopes of declining dissolved oxygen level in a respirometer that have very high values of the coefficient of determination, r², are not always successful at excluding nonlinear slopes. Much worse, by potentially removing linear slopes that have low r² only because of a low signal-to-noise ratio, this procedure can overestimate the calculation of standard metabolic rate (SMR) of the fish. To remedy this possibility, a few simple diagnostic tools are demonstrated to assess the appropriateness of a given minimum acceptable r², such as calculating the proportion of rejected O₂ determinations, producing a histogram of the r² values and a plot of r² as a function of O₂. The authors offer solutions for cases when many linear slopes have low r². The least satisfactory but easiest to implement is lowering the minimum acceptable r². More satisfactory solutions involve processing (smoothing) the raw signal of dissolved oxygen as a function of time to improve the signal-to-noise ratio and the r²s.