Journal of Soil Science and Plant Nutrition

AbstractThe Lorestan newt (Neurergus kaiseri) is a vulnerable amphibian endemic to the Zagros Mountains in Iran. This study aimed to identify core habitats, assess potential dispersal corridors, and evaluate the effectiveness of current conservation efforts. Ensemble species distribution models predicted suitable habitat across the newt's range, with annual precipitation and temperature as the most influential factors. Connectivity simulations revealed critical core habitats, primarily concentrated in the northwestern region, that spanned 2,233.43 km², none of which fell within designated protected areas. Corridor analysis identified viable dispersal pathways between northern and southern populations, but only 2.77% of the corridor network was protected. Roads and dams frequently intersected putative corridors, posing significant fragmentation threats. These results underscore the urgent need for expanded conservation efforts, including the establishment of new protected areas and measures to mitigate habitat fragmentation, to ensure the connectivity and long‐term viability of Lorestan newt populations. Our findings provide valuable insights to guide future conservation strategies for this endangered species.

AbstractAoudad (Ammotragus lervia), native to northern Africa, were introduced as exotic game animals to the Chihuahuan Desert in West Texas, USA, and have become invasive. Aoudad and bighorn sheep (Ovis canadensis mexicana) are adapted to rugged terrain in arid climates, and both persist in desert regions with low primary productivity and limited perennial water availability, which suggests potential for competition for food and water resources. Aoudad are highly adaptable, which could make them more resilient to a changing environment with extreme conditions, providing a competitive edge over bighorn sheep. To evaluate the potential for exploitative competition between invasive aoudad and endemic desert bighorn sheep, we used genetic metabarcoding to assess diet composition using fecal samples collected from adults of each species in the Sierra Vieja Mountains in West Texas. We collected 32 composite samples from aoudad and 27 composite samples for bighorn sheep and identified 88 genera consumed. Bighorn sheep and aoudad diets (as inferred by genera) were most different during the warm‐wet season (16 June–15 October; Kulczynski similarity index = 0.81) and most similar during the warm‐dry season (16 February–15 June; Kulczynski similarity index = 1.05). During the warm‐wet season, the 2 herbivores tended to consume different genera, suggesting the possibility of resource partitioning, with less likelihood of resource partitioning during the warm‐dry season when forage was more limited and diets were similar. Diet diversity, measured by Shannon's diversity index, did not vary substantially between species, but for aoudad it was highest during the warm‐wet season (1.1 ± 0.0.1 [SE]) and lowest during the cool‐dry season (16 October–15 February, 0.9 ± 0.0.1). For bighorn sheep, diet richness was highest during the cool‐dry season (1.1 ± 0.2) and lowest during the warm‐dry season (0.8 ± 0.10). Bighorn sheep may specialize on high‐quality forage species, particularly during the warm‐wet season, while aoudad have a more generalist foraging strategy, although temporal windows for increased competition for food resources likely occur. Aoudad are well‐adapted to low‐quality forage and arid climates, which could increase their competitive ability and compromise bighorn sheep conservation efforts in areas of sympatry.

AbstractIn an effort to restore extirpated elk to their historical range, 52 elk were reintroduced to Great Smoky Mountains National Park (GRSM) in North Carolina, USA, during 2001 and 2002. Since their reintroduction, elk numbers have increased, and elk have extended their range beyond GRSM boundaries. We used spatially explicit capture‐recapture (SCR) methods based on fecal DNA to identify individual elk and estimate population abundance (N), apparent survival (φ), per capita recruitment (f), and population growth rate (λ) in western North Carolina. We walked a series of transects during 3 winter field seasons (2020–2022) and collected elk pellets encountered along those transects. We created spatially explicit capture histories and incorporated those data into both closed and open population SCR models. The top performing closed SCR models for males and females estimated density by year and as a function of the scaled distance to the nearest field, with densities decreasing as the distance increased. Combined male and female N were 179 elk (95% CI = 149–215) in 2020, 220 elk (95% CI = 188–256) in 2021, and 240 elk (95% CI = 207–279) in 2022. The top open population model estimated both φ and λ as functions of sex and year. The estimate of φ for males was 0.682 (95% CI = 0.317–0.908) during 2020–2021 and 0.339 (95% CI = 0.152–0.596) during 2021–2022 and for females was 0.953 (95% CI = 0.830–1.000) during 2020–2021 and 0.829 (95% CI = 0.601–1.000) during 2021–2022. The annual population growth rate (λ) for males was 1.127 (95% CI = 0.806–1.575) during 2020–2021 and 0.811 (95% CI = 0.566–1.163) during 2021–2022 and for females was 1.559 (95% CI = 1.162–2.091) during 2020–2021 and 1.122 (95% CI = 0.876–1.437) during 2021–2022. Our elk abundance estimates in areas >300 m from fields were negligible, and we suggest that sampling only the areas in and adjacent to fields in the future will result in reliable but more cost‐efficient population estimates. Confidence intervals for vital rate parameters were wide for our 3‐year dataset, but continued annual pellet sampling will increase sample sizes for vital rate estimation and thus improve precision. If elk herd expansion on public lands is desired, we suggest habitat modification to establish open grasslands adjacent to forests.

AbstractThe Aleutian tern (Onychoprion aleuticus) is a species of high conservation concern in Alaska, USA, owing to large declines at known breeding locations since the 1960s. The small population size and ephemeral behavior of this species have limited the collection of basic biological information and hindered the identification of potential drivers of this decline. Significant unknowns include the factors, and their relative importance, influencing nest survival. To investigate these questions, we estimated daily nest survival (DNS) for 148 nests from 5 breeding colonies during 2017 to 2020 in the Kodiak Archipelago, Alaska with 105 monitored using remote cameras. We used the nest survival model in program MARK to estimate DNS rates as a function of colony location, year, within‐season time trends, vegetation cover and height, and 6 daily weather covariates. Our top model suggested that DNS rates increased with vegetation height, decreased as the season progressed, and included a significant interaction between year and colony. Average nest success (i.e., percent chance that a nest survived to hatch) over the 22‐day incubation period varied by colony but was generally very low, averaging 1.2% (95% CI = 0–11%) in 2017–2018 to 14% (95% CI = 0.1–38%) in 2019–2020 across all colonies. The importance of year in the model suggests that a large‐scale annual driver, like food availability, may have played an important role in this species' breeding success. A severe marine heatwave was present in the Gulf of Alaska during 2014–2016 and our results suggest that some effects of this anomalous event, such as reduced prey availability, lingered even after temperatures returned to normal. Additionally, the variation in DNS across colony locations indicated that local factors, such as predation pressure, may also drive significant variation in Aleutian tern productivity. These findings suggest that a combination of local factors and climate change may be important drivers of the >90% decline in Alaska's breeding population of Aleutian terns.

AbstractRoads are pervasive and ubiquitous landscape features that have substantial and predominantly negative effects on wildlife. Conducting road surveys to count animals that have been struck and killed by vehicles is a common method for estimating the impact of roads on wildlife, especially for species at risk and animals with low road avoidance (i.e., herpetofauna). For road surveys to provide accurate animal mortality data, information about carcass persistence in different environmental contexts and in relation to survey frequency is necessary, but few studies have implemented these data into evaluations of road effects. Using road survey data collected in Ontario, Canada, in 2015 and survival analysis, we quantified anuran carcass (n = 91) persistence and determined the effects of carcass characteristics (size, species, condition), road characteristics (lane position, traffic volume), and environmental characteristics (precipitation, temperature) on carcass persistence on the road. Contrary to previous findings, we found that anuran carcasses persisted on roads longer than expected (5.5 ± 4.4 days, mean ± SD), with some carcasses persisting for up to 30 days. Temperature and precipitation had the greatest influence on the duration of anuran carcass persistence. Carcass condition, (i.e., intact versus partially intact carcasses), species, location on the road, and traffic volume had little to no effect on persistence. We recommend incorporating carcass persistence into road ecology studies, especially in the context of evaluating population‐level impacts of road mortality. Failure to do so could alter estimates of population viability and misinform management decisions.

AbstractMinimizing human‐related manatee mortality is a priority management action for Florida manatee (Trichechus manatus latirostris) conservation and recovery. Manatees encounter navigational locks and water control structures along travel corridors, and fatal encounters can occur from crushing, impingement, or entrapment that subsequently result in drowning. Extensive mitigation efforts have been made to protect manatees. This study evaluates the effectiveness of manatee protection systems at navigational locks and water control structures using negative binomial regression models and Friedman's tests with pairwise comparisons from 1974–2020 mortality data. Mitigation effort was stratified into 4 groups ranging from no mitigation to fully mitigated. Regression models for 223 structure‐related manatee deaths showed the expected number of annual mortalities was ≤0.26 for all mitigation groups at each structure type. Friedman's tests indicated a difference in mortalities among mitigation efforts for navigational locks (χ22 = 10.75, P = 0.004) and water control structures (χ22 = 16.63, P ≤ 0.001). Mortalities at fully mitigated water control structures were lower than at partially mitigated structures in pairwise testing for both analyses; navigational lock mitigation efforts only differed in Wilcoxon rank sums tests. Combined results show that when current manatee protection systems are functional and protocols are followed, mortality is reduced. While these systems are a conservation achievement, continued re‐evaluation of mitigation efforts and investigation into new technologies are needed to ensure the continued reduction or elimination of structure‐related manatee mortalities.

AbstractUnderstanding habitat selection is critical in habitat prioritization for species of conservation and management concern. Information on habitat selection is particularly important for grassland bird species whose populations have suffered steep declines over the last few decades. We assessed ring‐necked pheasants' (Phasianus colchicus) habitat selection in a dynamic agricultural landscape. The population dynamics of pheasants are partially related to nest survival, which may be influenced by the quality of nesting habitat. Consequently, knowledge of vegetation composition and structural characteristics associated with the selection and survival of nests would help inform management decisions to improve nest success. We monitored nests from 103 radio‐collared pheasants inhabiting an agricultural landscape in South Dakota, USA, from 2017–2019 to determine the effect of landscape composition and configuration on nest‐site selection and nest survival. We explored nesting behavior at 2 orders of selection: resource selection within the home range (third order) and selection of specific resource items from a resource patch (fourth order). Proportion of row crop and connectivity of row crop was negatively associated with nest‐site selection at the third order. At the fourth order, pheasants tended to select for taller vegetation and greater percent grass cover than at paired random sites. Pheasants also selected areas with more grasslands. A 1% increase in grass cover and proportion of grassland increased the odds of nest‐site selection by 1% and 2%, respectively. Connectivity of row crop patches was negatively associated with daily nest survival. We also evaluated factors affecting pheasant brood‐site selection. A 1‐unit increase in grass cover and Hemiptera biomass increased the odds of brood‐site selection by 4%. The probability of brood‐site selection also increased with fewer row crop patches. Weather played a crucial role in driving nest survival. The consideration of local weather trends and regional variation in habitat can inform habitat management for pheasants. Pheasant populations may benefit from research that identifies thermal landscapes and land management techniques that promote cooler microclimates for nesting and brood‐rearing activities.

AbstractEliminating supplemental feeding is a common regulatory action within chronic wasting disease (CWD) management zones. These regulations target the potential for increased animal‐animal contact and environmental contamination with CWD prions. Prions, the causative agent of CWD, have been detected on feeder surfaces in CWD‐positive, captive deer facilities but not among free‐ranging populations, and information on the relative risk of transmission at anthropogenic and natural food sources is limited. In this study, we established and maintained 13 gravity feeders from September 2022 to March 2023 in a CWD zone in northern Mississippi, USA (apparent prevalence ~30%). We set up feeders up in 3 ways: no exclusion (deer feeders, n = 7), exclusion of deer using fencing with holes cut at the ground‐level to permit smaller wildlife to enter (raccoon feeders, n = 3), and environmental control feeders, which were fully fenced and not filled with feed (control feeders, n = 3). We swabbed feeder spouts at setup and at 4 intervals approximately 6 weeks apart to test for prion contamination via real‐time quaking‐induced conversion (RT‐QuIC). We detected prions 12 weeks after setup on all deer and raccoon feeders. We compared relative transmission risk using camera traps at these feeders, 6 agronomic plantings for wildlife forage (i.e., food plots), and 7 oak mast trees. Weekly visitation rate by white‐tailed deer (Odocoileus virginianus; hereafter: deer) differed (P = 0.02) among deer feeders (median = 24.5 deer/week, range = 15.6–65.7), food plots (median = 12.7, range = 3.8–24.7), and mast trees (median = 2.0, range = 0.4–5.1). Contact rates between individual deer also differed between site types (P < 0.01): deer feeders (median = 2.1 deer‐to‐deer contacts/week, range = 0–10.1), food plots (median = 0.1, range = 0–4.0), and mast trees (median = 0, range = 0–0.3). Raccoons also visited feeders at greater rates than food plots and mast trees (P < 0.04). Finally, we swabbed 19 feeders in 2 areas where CWD was newly detected, finding prion contamination on swabs from 4 feeders. We show that deer feeders in free‐ranging populations with high CWD prevalence become contaminated with CWD prions quickly, becoming a potential site of exposure of deer to CWD prions. Our results also demonstrate the ability to find evidence of prion contamination on deer feeders, even in areas where CWD is newly detected.

AbstractThe investigation and management of the impacts of winter tick (Dermacentor albipictus) infestations on moose (Alces alces) in North America necessitates coordinated surveillance and intervention efforts. However, variations in parasite surveillance methods and potential biases towards sampling specific host species for this generalist parasite can impede attempts to standardize observed disease patterns across vast regions and into the future. We collected and classified records of winter tick surveillance on ungulate hosts throughout North America to identify trends and biases in species, space, and time, with the aim of identifying gaps and suggesting improvements to existing practices. We conducted a literature review spanning a century of winter tick reports on free‐roaming or wild ungulate hosts in North America, resulting in 125 relevant records. From this sample, we compiled information on host species and surveillance method details and categorized winter tick quantification techniques based on their perceived insight for analyses and interventions, assigned as an ecological information value (Eco‐IV) ranging from 0 to 3. We examined variations in Eco‐IV among free‐roaming ungulates based on species, literature type, and data source. Among the 18 identified ungulate hosts, moose, white‐tailed deer (Odocoileus virginianus), and elk (Cervus canadensis) were most frequently reported. We observed a higher Eco‐IV for moose, indicating an abundance of species‐specific information, and a lower Eco‐IV (less information available) for methods focusing on white‐tailed deer. Limited sample sizes prevented the identification of patterns of knowledge acquisition for elk. Eco‐IVs in other ungulate species were consistently lower than moose, white‐tailed deer, and elk, regardless of literature type or data source. Exotic and invasive species systematically lacked detailed methods (Eco‐IV = 0). These findings highlight significant information gaps that impede the ability to compare winter tick infestation rates across studies, geographic regions, and host species, thus hindering coordinated management actions. We recommend standardizing winter tick quantification methods for all ungulate host species, specifically other common winter tick hosts such as white‐tailed deer and elk, and increased communication among groups working on tick–host systems to address these gaps.

AbstractHighly pathogenic avian influenza virus (HPAIV) H5Nx clade 2.3.4.4b has circulated in North America since late 2021, resulting in higher rates of morbidity and mortality in wild birds than observed in this region before. The objective of this study was to determine whether baiting, which is widely conducted in Canada and the United States as part of waterfowl management practices (e.g., duck banding), influences the occurrence of avian influenza virus (AIV) in wetlands. We used a quasi‐experimental design, collecting superficial sediment samples (n = 336) and fecal samples (n = 242) from paired baited (treatment) and non‐baited (control) sites at 2 wetlands in Saskatchewan, Canada, between August and September 2022. We visited sampling sites 3 times during the sampling period: prior to the commencement of baiting activities (t0), approximately 14 days after t0 (t1), and 24 days after t0 (t2). We screened samples for AIV using real‐time reverse‐transcriptase polymerase chain reaction (rRT‐PCR) targeting the matrix gene and subjected the PCR‐positive samples to next‐generation sequencing. We used a mixed‐effects logistic regression model to estimate the effect of baiting on the odds of AIV positivity in sediment samples, while controlling for clustering by wetland. At control sites, we did not detect evidence for a difference in the odds of AIV detection in sediment at t1 or t2 versus t0; however, at baited sites, the odds of AIV detection at t1 were 5.43 (95% CI = 1.99, 14.79) times the odds at t0 and at t2 the odds of AIV detection were 8.73 (95% CI = 3.29, 23.18) times the odds at t0. We detected HPAIV clade 2.3.4.4b H5N1 in sediment at 1 treatment site following baiting. There was also a trend towards increased fecal AIV positivity and increased fecal and sediment AIV diversity in baited versus non‐baited sites; however, there was insufficient power to determine if these findings were statistically significant. Overall, our results indicate that baiting is associated with localized increases in AIV environmental contamination, with baiting potentially creating concentrated areas of AIV accumulation. As such, wetland baiting activities may pose a risk to wildlife population health through the propagation of AIV in wetlands and the waterfowl using those environments and efforts to replace, refine, or reduce this activity may be warranted depending on local ecosystem contexts and cost‐benefit analyses.

AbstractAnimal foraging strategies are formulated in a complex decision‐making matrix that is predicated on balancing energy intake and expenditure within a landscape of predation risk. Game species encounter dynamic risks during hunting season as ephemeral predators (i.e., hunters) alter the predation risk landscape daily and seasonally. Predators and prey often concentrate around food sources during hunting season, further complicating the balance of energy intake and risk minimization for prey species. For example, many wetland managers provide energy‐rich food resources, such as unharvested grain, that attract waterfowl. Hunter access to these areas varies and alters the inherent risk that wintering waterfowl face to use these resources. We hypothesized use and subsequent depletion of unharvested flooded corn fields would be influenced by proximate anthropogenic disturbance and predation risk, shifting the bioenergetic landscape for waterfowl. We first sampled 145 unharvested flooded cornfields under different hunting access regimes to estimate corn biomass in October 2019 and 2020 in western Tennessee, USA. We then returned to 30 of those fields biweekly during fall‐winter 2019–2021 to estimate depletion rates in 60 fields. We modeled depletion rate as a function of hunting risk and forage accessibility by including the variables of corn ear height above water surface, field size, field ownership type, and field distance from sanctuary in our statistical model. Biomass estimates derived from initial surveys indicated private fields that were hunted provided the greatest corn biomass (7,134 ± 448 kg/ha), followed by public fields that were hunted (5,272 ± 320 kg/ha) and finally sanctuaries closed to hunting (3,995 ± 371 kg/ha). Corn biomass was depleted 2–4 times faster on sanctuaries than on hunted fields during November and December but 2 times faster in hunted fields than in sanctuary fields in January. Depletion rates increased as surface water came closer to corn ears but were unaffected by field size or field distance from unhunted sanctuary. Sanctuary fields were devoid of corn by the end of January, whereas 55% of public and 50% of private hunted fields still had corn remaining on 15 March, by which time most ducks had likely initiated migration. Private lands sampled in 2020 contributed nearly 7 times more energy than assumed in the 2015 Lower Mississippi Alluvial Valley Joint Venture energetic allocation models. Despite being devoid of hunters at night, hunted lands are not perceived by foraging waterfowl to be nocturnally similar to sanctuary areas during hunting season. In turn, hunted fields were exploited by ducks later in the season when sanctuary resources were scarce, providing available biomass for migrating birds. It may be important for managers to retain water on hunted fields through early spring given the lack of energy‐dense foraging resources available on sanctuary areas. Conservation planners should consider resource depletion as a multiplicative function of hunting risk and abundance when allocating foraging habitat objectives for waterfowl in the non‐breeding season.

AbstractRegrowth of forests across the northeastern United States in recent decades has allowed for range expansion of many forest‐dependent mammals in the region. However, these contemporary forests have smaller patch sizes, putting humans in closer proximity to previously remote forested areas, and different species compositions and structure compared to historical forests. These conditions pose an increased risk of exposure to anthropogenic disturbances and contaminants for forest‐dwelling wildlife. We evaluated the relationship between contemporary forest conditions and anticoagulant rodenticides (ARs) on recent population trends for fishers (Pekania pennanti). We acquired a snapshot of recent population trends for fishers across New York, Vermont, and New Hampshire, USA, using standardized catch‐per‐unit‐effort (CPUE) data from the regulated fall harvest spanning 2016‐2020, when harvest regulations remained consistent across the states. We used regression models to relate the probability of CPUE increase to measures of forest habitat (age, structure, productivity), length of winter snow cover, and human disturbance (land use patterns and AR detection). The top model indicated that the probability of CPUE increase declined 43% for every 10% increase in the percent of the population exposed to at least 1 AR and by 24% for every 1‐day increase in the length of winter snow cover, while measures of forest conditions had no significant relationship. The relationship between AR detection and suppressed CPUE increase is compelling, as few mammalian studies effectively link the detection of AR residues in animal tissues to population‐level performance in the wild. Nevertheless, longer time frames are required to fully understand population trends and their drivers across heterogeneous landscapes. We recommend the fisher as a model species for longer‐term monitoring of AR detections and for comparing outcomes of measures potentially designed to reduce AR impacts on wildlife in this region.