National Park Service
  • Washington, D.C., United States
Recent publications
Iguanas exhibit diverse colors and behaviors reflecting evolutionarily adaptation to various habitats; in particular, the Galápagos iguanas represent unique color morphologies with distinct ecological niches. While external coloration in iguanas has ecological implications, comprehensive studies on the histological and ultrastructural aspects of their skin can provide insight into their adaptation to extreme environments, such as high UV exposure. Starting from these considerations the present study investigates the histological, ultrastructural and immunohistochemical features to comprehensively characterize the skin in adults of three species of Galápagos iguanas (A. cristatus, C. subcristatus and C. marthae). Morphological analysis revealed significant differences among the species, with the black-colored skin of A. cristatus showing a melanin-rich but vessel-poor dermis, while C. subcristatus and C. marthae displayed varying distributions of melanosomes and melanocytes. Notably, the absence of iridophores was consistent across all samples due to the absence of birefringent material under the optical microscope. Morphometric evaluations highlighted interspecific differences in the stratum corneum thickness, particularly between black- and non-black-colored (irrespectively if yellowish or pink) skin. The ultrastructural investigation confirmed the absence of iridophores in all analyzed samples. The cytokeratin expression assessed by immunohistochemistry showed stratified epithelium in the epidermis of C. marthae non-black-colored (pink) skin. The presence of a thickened stratum corneum and the stratification of the epidermis in non-pigmented skin could help the pink iguana to cope with the extreme conditions of the Wolf volcano, especially in relation to UV exposure. These skin characteristics may reduce the penetration power of UV rays into the superficial loose dermis, thereby attenuating potential UV-related damage such as DNA breaks and ROS generation. These findings offer insights into the adaptive strategies of these iguanas.
Context Forest canopies shape subcanopy environments, affecting biodiversity and ecosystem processes. Empirical forest microclimate studies are often restricted to local scales and short-term effects, but forest dynamics unfold at landscape scales and over long time periods. Objectives We developed the first explicit and dynamic implementation of microclimate temperature buffering in a forest landscape model and investigated effects on simulated forest dynamics and outcomes. Methods We adapted the individual-based forest landscape and disturbance model iLand to use microclimate temperature for three processes [decomposition, bark beetle (Ips typographus L.) development, and tree seedling establishment]. We simulated forest dynamics with or without microclimate temperature buffering in a temperate European mountain landscape under historical climate and disturbance conditions. Results Temperature buffering effects propagated from local to landscape scales. After 1,000 simulation years, average total carbon and cumulative net ecosystem productivity were 2% and 21% higher, respectively, and tree species composition differed in simulations including versus excluding microclimate buffering. When microclimate buffering was included, Norway spruce (Picea abies (L.) Karst.) increased by 9% and European beech (Fagus sylvatica L.) decreased by 12% in mean basal area share. Some effects were amplified across scales, such as a mean 16% decrease in local-scale bark beetle development rates resulting in a mean 45% decrease in landscape-scale bark beetle-caused mortality. Conclusions Microclimate effects on forests scaled nonlinearly from stand to landscape and days to millennia, underlining the utility of complex simulation models for dynamic upscaling in space and time. Microclimate temperature buffering can alter forest dynamics at landscape scales.
Light pollution disrupts the natural dark–light rhythmicity of the world and alters the spectral composition of the nocturnal sky, with far-reaching impacts on natural systems. While the costs of light pollution are now documented across scales and taxa, community-level mitigations for arthropods remain unclear. To test two light pollution mitigation strategies, we replaced all 32 streetlights in the largest visitor center in Grand Teton National Park (Wyoming, USA) to allow wireless control over each luminaries’ color and brightness. We captured fewer arthropods, across most Orders, in the blended-red light compared to white (3000 K). Interestingly, we found an effect of light brightness and color, suggesting that, overall, more arthropods were attracted by brighter, and white color hues compared to blended-red. Our findings provide valuable insights into the mitigation of artificial light at night, likely one of the primary drivers of global arthropod declines.
Faecal cortisol/corticosterone metabolites (FCMs) have become increasingly popular as an easy‐to‐sample, non‐invasive and feedback‐free alternative to assess glucocorticoid (GC) levels, key components of the neuroendocrine stress response and other physiological processes. While FCMs can be a powerful aid, for instance, for gaining insights into ecological and evolutionary processes, as well as to assess animal welfare or impacts of anthropogenic stressors on wildlife populations, this method comes with specific challenges. Because GCs are heavily metabolised before excretion, it is critical to validate the enzyme immunoassays (EIAs) used to measure FCMs. Additionally, because species may differ in metabolite profiles, assay validation must be performed separately for each focal species. Despite this, the use of unvalidated assays remains widespread. We performed a biological validation experiment to test a set of EIAs to measure FCMs and adrenocortical activity in free‐living Alpine marmots Marmot marmota. We capitalised on capture and handling as part of a relocation project of marmots under the assumption that capture, and handling represent a stressful event and tracked changes in FCM levels over the following 48 h. Faeces samples collected at capture were assumed to return baseline FCM levels. Of the three EIAs tested, only the 11‐oxoetiocholanolone ‘72T’ EIA detected an increase in FCM levels about 18 h after capture. This result paves the way for future studies using FCMs to investigate the adrenocortical activity in this species.
The spotted hyaena Crocuta crocuta is relatively understudied across its range despite evidence of widespread declines. It is therefore essential that robust baseline population density assessments are conducted to inform current management and future conservation policy. In Mozambique this is urgent as decades of armed conflict followed by unchecked poaching have resulted in large-scale wildlife declines and extirpations. We conducted the first robust population density estimate for a spotted hyaena population in Mozambique using spatially explicit capture recapture methodologies. We recorded a relatively low population density of 0.8-2.1 hyaenas/100 km2 in the wildlife management area Coutada 11 in the Zambezi Delta of central Mozambique in 2021. These densities are well below the estimated carrying capacity for the landscape and are comparable to published densities in high human-impact, miombo woodland-dominated and arid environments. The combination of historical armed conflict, marginal trophy hunting and bushmeat poaching using wire snares and gin traps (with physical injuries evident in 9% of identified individuals) presents persistent anthropogenic pressure, limiting the postwar recovery of this resident hyaena population. We provide insights into the dynamics of hyaena population status and recovery in such postwar landscapes, adding to mounting evidence that the species is less resilient to severe anthropogenic disturbances than previously believed. We recommend long-term monitoring of this and other carnivore populations in postwar landscapes to ascertain demographic trends and implement effective conservation interventions for population recovery.
Obruchevodid petalodonts are rare small chondrichthyans known from nearly complete to partial skeletons from the Upper Mississippian (Serpukhovian) Bear Gulch Limestone of central Montana and isolated teeth from the Upper Mississippian Bangor Limestone of northern Alabama. New records of obruchevodid petalodonts are presented here from the Middle Mississippian (Viséan) Joppa Member of the Ste. Genevieve Formation at Mammoth Cave National Park, Kentucky. Obruchevodids are here represented by multiple teeth of a new taxon, Clavusodens mcginnisi n. gen. n. sp., and a single tooth referred to ? Netsepoye sp. Clavusodens mcginnisi n. gen. n. sp. is characterized by teeth with pointed mesiodistal and lingual margins and more robust chisel-like cusps on the anterolateral and distolateral teeth. The suggestion that obruchevodid petalodonts evolved to inhabit complex reef-like environments and other nearshore habitats with a feeding ecology analogous to extant triggerfish is explored and discussed. UUID: http://zoobank.org/0955c37a-c458-4a4d-89c4-01d6915adeca
Host species heterogeneity can drive parasite dynamics through variation in host competency as well as host abundance. We explored how elk (Cervus canadensis) with apparent subclinical infestations of winter tick (Dermacentor albipictus) may be a cryptic reservoir and drive winter tick dynamics, impacting moose (Alces alces) populations. We found that winter tick infestation loads did not vary remarkably between both host species and winter ticks sourced from elk and moose produced similar numbers of larvae which activated within 5 days of each other. We also found similar larval densities in habitats predominately used by elk, moose, and both host species. Our analysis of 2793 informative single‐nucleotide polymorphisms showed genetic differentiation among tick populations that were only ~75 km apart, but fewer differences among ticks from elk or moose in the same locality, suggesting sharing of winter ticks across host species. Despite the clinical signs of high winter tick infestations being most apparent on moose, elk may be critical drivers of winter tick population dynamics and indirectly compete with moose in areas where they outnumber moose populations, a common characteristic of ungulate communities in western North America. Management interventions aimed at addressing winter tick issues on moose may wish to consider the movement patterns and abundance of cryptic reservoirs like elk.
Conservation translocations are an established method for reducing the extinction risk of plant species through intentional movement within or outside the indigenous range. Unsuitable environmental conditions at translocation recipient sites and a lack of understanding of species–environment relationships are often identified as critical barriers to translocation success. However, previous syntheses have drawn these inferences from analyses of qualitative feedback rather than quantitative environmental data. In this study, we use a data set of 235 translocations conducted in the US to understand the influences of geographic and environmental factors on three metrics of translocation success: population persistence, next‐generation recruitment and next‐generation maturity. We use random forest models to quantify the relative importance of geographic and environmental factors that characterize dissimilarity between source and recipient locations, the position of recipient sites relative to species' ranges and niche metrics derived from these ranges. We also compare the importance of these variables with more conventional predictors (e.g. founder population size). Our results indicate that geographic and environmental variables can be as insightful as conventional variables for predicting plant translocation outcomes. The climate suitability of recipient sites, estimated using species distribution models, was the strongest relative predictor of whether a population persisted, with populations situated in more suitable climates displaying greater persistence. Next‐generation recruitment and maturity were best predicted by niche metrics; species in more biotically limiting environments, including tropical regions and soils with high relative nutrient retention, as well as species with the broadest precipitation niches, were the least likely to attain these next‐generation benchmarks. Synthesis and applications. Our study is one of the first to quantify the important role of spatial and climatic factors in rare plant translocation outcomes. We provide a novel geographic and environmental perspective on outcomes in plant translocations and demonstrate opportunities to improve translocation success not only by adhering to established best practice guidelines but also by integrating spatial modelling approaches into planning and management processes.
Understanding animal behavior at the population level can be challenging, especially in the presence of intraspecific variation in behavioral tactics. Individuals within a population often vary with respect to resource exploitation and use, which may be associated with individual states (e.g., male or female) or extrinsic variation (e.g., temporal variation in food). Explicitly accounting for interindividual variation can aid ecological insights, especially for species that exhibit high behavioral flexibility. Here, we evaluated how seasonal fluctuations in resources influenced individual‐level habitat use and selection of Rocky Mountain red fox (Vulpes vulpes macroura) within Grand Teton National Park, Wyoming. Rocky Mountain red fox is a high‐elevation subspecies of the common red fox (Vulpes vulpes), and native to North America. From 2016 to 2021, we captured and GPS‐collared 18 individuals (11 males, 7 females) and evaluated spatiotemporal shifts in home range characteristics and habitat selection. We observed high individual variation in home range size, with generally larger home ranges in the winter months (x¯x \overline{x} = 72.92 km² [minimum convex polygon—MCP], 83.65 km² [Kernel], 27.20 km² [Local Convex Hull]) than in the summer (x¯x \overline{x} = 22.23 km² [MCP], 23.01 km² [Kernel], 11.11 km² [Local Convex Hull]). Similarly, we observed substantial individual variation in habitat selection across environmental gradients. Some foxes altered their selection for habitat types between summer and winter indicating behavioral plasticity with respect to seasonal resources. Distance to human features was the primary driver for habitat selection for both seasons across foxes, and on average, foxes had stronger selection for human features in the summer. These findings might indicate some foxes are concentrating on the temporal and spatial resource pulse of anthropogenic food, while others exhibited more natural tactics. Our work advanced the spatial ecology of Rocky Mountain red fox, identified variation in space use tactics associated with humans and natural resources among red foxes in a heavily recreated area, and demonstrated how human activity can influence the spatial behavior of a carnivore within a national park.
For birds breeding in the Arctic, nest success is affected by the timing of nest initiation, which is partially determined by local conditions such as snow cover. However, conditions during the non‐breeding season can carry over to affect the timing of breeding. We used tracking and breeding data from 248 individuals of 8 species and subspecies of Arctic‐breeding shorebirds to estimate how the timing of nest initiation is related to local conditions like snowmelt phenology versus prior conditions, measured by the timing and speed of migration. Using path analysis, our global model showed that local and prior conditions have similar effect sizes (Standardised Path Coefficients ± SE of 0.44 ± 0.07 and 0.43 ± 0.07 for snowmelt and arrival timing, respectively), suggesting that both influence the timing of breeding and therefore potentially reproductive output. However, the importance of each variable varied across species. Individuals that arrived later to the breeding grounds did not leave the wintering grounds later, but instead took longer to migrate, potentially reflecting differences in flight speed or time spent at stopover sites. We hypothesise that this may be due to reduced habitat quality at some stopover sites or an inability to adjust their departure timing or migration speed to match the advancing spring phenology in the North. Individuals that migrated longer distances also arrived and nested later. Our results highlight the benefits and potential conservation implications of using a full annual cycle approach to assess the factors influencing reproductive timing of birds.
We document the importance of low‐light conditions in 136 animal species and then translate the new world atlas of skyglow, which reports artificial night sky brightness, into estimates of anthropogenic illuminance (that is, artificial light reaching Earth's surface). Quantifying habitat illuminance from skyglow facilitates understanding of the disruption of natural light cycles, such as new moon conditions, which are critical to animal ecology. We corroborated this transformation of sky brightness by comparing concurrent field measurements of skyglow and illuminance. We then quantified global artificial illuminance caused by skyglow, finding that skyglow artificially doubled illuminance of new moon conditions—a critical phase for biological processes, such as foraging, courtship, and mating—for 22.9% of the Earth's terrestrial surface, 51.0% of Key Biodiversity Areas, 77.1% of Global Protected Areas, and ~20% of highly diverse areas for mammals, birds, and amphibians. We provide summaries of artificial illuminance at 750‐m pixel resolution for each protected area to aid land managers and guide policy in reducing skyglow in areas that may yield the greatest benefits for conserving animal biodiversity.
Browsing by ungulates is commonly assumed to target the upper parts of sapling crowns, leading to reduced vertical growth or even growth cessation. However, the extent to which browsing induces shifts in resource allocation toward lateral growth remains unclear. This study explores the impact of browsing intensity (BI) and light availability on the architectural traits of six temperate tree species, focusing on height‐diameter ratio (H/D), crown slenderness (CL/CW), and crown irregularity (CI) across sapling height classes. Browsing pressure and architectural responses varied across height groups, reflecting diverse adaptive strategies. BI was weakly but negatively correlated with sapling height, indicating that even tall saplings (> 2 m) experience browsing, particularly in the lower crown. H/D consistently increased with BI across all height classes, with stronger effects in medium and tall saplings. Light influenced H/D differently between browsed and unbrowsed saplings: unbrowsed saplings showed reduced H/D only under high light conditions, while browsed saplings exhibited consistent reductions regardless of light levels. CL/CW was negatively but insignificantly affected by BI. Light increased CL/CW in unbrowsed saplings across all height classes but decreased it in browsed short and medium saplings, suggesting a ‘pruning’ effect of browsing that altered competition dynamics. Species‐specific analysis of Fagus sylvatica revealed an increase in CL/CW with BI, reflecting unique adaptive responses. CI increased significantly with BI across all height classes, with the strongest effects in medium and tall saplings. Light reduced CI in browsed short saplings but had inconsistent effects on unbrowsed individuals. Variation partitioning showed that light explained most variation in H/D and CL/CW for shorter saplings, while BI predominantly influenced CI in taller ones. By integrating the effects of browsing and light, this study provides insights into juvenile tree adaptations and resilience under ecological stressors, advancing our understanding of tree growth strategies in challenging environments.
In response to a NWS requirement for a gridded analysis of ice accumulation, the Freezing Rain Accumulation National Analysis (FRANA) is created for nowcasting and post-event verification of freezing rain/drizzle (FZRA/FZDZ) ice accumulations. This product generates CONUS-wide hourly flat and radial ice accumulations for 1, 3, 6, 12, and 24 hour windows. The core science algorithm within FRANA that converts liquid to an ice accumulation is the Freezing Rain Accumulation Model (FRAM). The inputs to FRANA come from the High-Resolution Rapid Refresh analyses of 2-m wetbulb temperature and 10-m wind speed and the Multi-Radar/Multi-Sensor (MRMS) hourly multi-sensor Quantitative Precipitation Estimate. An additional trace ice footprint was added to FRANA to help forecasters identify areas of light FZRA/FZDZ. A three-year retrospective analysis reveals that FRANA can overestimate or underestimate the icing footprint due to NWP temperature uncertainty, precipitation-type error, radar overshooting, precipitation evaporating below the lowest radar tilt, or due to MRMS quality control. For accumulating ice, FRANA has a modest RMSE of 1.27 mm (0.05 in) and event-maximum errors typically less than 2.54 mm (0.1 in). In fact, 88% of the events in the study had less than 2.54 mm (0.1 in) absolute error which is within the tolerance range for many operational applications. Additionally, lower storm-total accumulations are found to be associated with lower absolute error. Example events show how FRANA can provide guidance to forecasters on the spatial extent of icing as well as “hot spots” where higher accumulations may cause significant socioeconomic disruptions.
Interspecific interactions are important drivers of population dynamics and species distribution. These relationships can increase niche partitioning between sympatric species, which can differentiate space and time use or modify their feeding strategies. Roe deer Capreolus capreolus and red deer Cervus elaphus are two of the most widespread ungulate species in Europe and show spatial and dietary overlap. However, limited information is available on their interspecific relationships, especially in mountainous areas. In this study we used 5 years of camera trapping data collected in the Stelvio National Park (Central Italian Alps) to investigate spatial and temporal interactions between roe deer and red deer. Analyses were based on 2060 and 9030 roe deer and red deer detections, respectively, collected from July to September, from 2019 to 2023, using 50 camera traps randomly distributed over a 10,000‐ha study area. Spatial interactions were assessed by fitting a single‐season, single‐species occupancy model to calculate the probability of roe deer detection and occupancy as a function of relative red deer abundance and site‐specific environmental covariates. Temporal interactions were obtained by comparing the diel activity patterns of the two species. Results showed no significant effect of red deer relative abundance on the probability of presence of roe deer. Spatial analysis suggested a higher probability of roe deer presence in forested habitats, at lower elevations, and in areas with gentler slopes. Diel activity patterns of roe deer were consistent across sites with higher and lower red deer relative abundance, with moderate to high interspecific overlap, suggesting moderate temporal partitioning and no major support for temporal avoidance of the latter by the former. The high degree of overlap between the two species may be the result of area‐specific ecological conditions, such as the widespread distribution of red deer during the summer period, as well as of the adoption of strategies that favor coexistence.
Burmese pythons (Python bivittatus) have demonstrated prolific spread and low detectability within their invasive range in Florida, USA. Consequently, programs exist which incentivize contractors to remove pythons. While surveying, contractors collect data on search effort and python captures. We examined data from South Florida Water Management District’s Python Elimination Program to determine the effect of operational and environmental covariates on two measures of survey outcome: success (i.e., probability of removing at least one python) and efficiency (i.e., the number of pythons removed per survey hour). Additionally, we assessed the spatial distribution of contractor search effort and removals. Warm temperatures (> 25 °C) improve survey outcomes, especially when surveys occur late at night and during the wet season (May–Oct). The most efficient interval for conducting surveys occurs from 20:00 to 02:00. The spatial distribution of python removals is concentrated in four regions and coincides with contractor search effort. Our results provide insights into optimizing removal efforts for invasive Burmese pythons in Florida, which may allow for increases in removal efficiency. Moreover, this study demonstrates that community science data can be used to synthesize recommendations for invasive species removal efforts.
Resource managers require accurate estimates of large herbivore abundance and demography to maintain ecological integrity. Common methods to count these species, including observations from low altitude helicopter flights, may conflict with other protected area management objectives and struggle to produce precise estimates for more cryptic species. To address these issues, we evaluated thermal infrared (TIR) assisted counts of Shiras moose Alces alces shirasi in a temperate montane ecosystem of Colorado, USA. We binned the 694.7 km² study area into two strata, depicting higher and lower moose habitat suitability. Sixty transects (each 536 m wide by 5 km long) were randomly selected and flown from fixed wing aircraft flying at altitudes centered around ~ 610 m (2000 ft) above ground level (AGL) in July 2019 and again in July 2020. We determined abundance and demographic information using double‐observer line distance sampling with estimates produced using n‐mixture models. Detection probability of groups on the line, and of individuals within a group, conditional on the group being observed, were high. Mean moose density estimates across the study area were consistent from year to year, with reasonable confidence. We estimated 0.215 moose km‐² (HDI 0.145, 0.286) in 2019 and 0.207 moose km‐² (HDI 0.144, 0.276) in 2020. Within‐stratum estimates varied from year to year, likely an effect of the definition of suitable habitat and transect classifcation. Estimated ratios of bulls per cow and calves per cow fell within expected ranges for Shiras moose in Colorado but did vary across years. Thermal clutter created some impacts to TIR video quality. Our study indicates that this approach can reliably estimate moose densities in forested and topographically complex environments, while maintaining greater aircraft altitude above ground level when compared with traditional aerial survey methods. This reduced disturbance to wildlife, impacts to wilderness and improved aviator and aircraft passenger safety.
Theory suggests that animals make hierarchical, multiscale resource selection decisions to address the hierarchy of factors limiting their fitness. Ecologists have developed tools to link population‐level resource selection across scales; yet, theoretical expectations about the relationship between coarse‐ and fine‐scale selection decisions at the individual level remain elusive despite their importance to fitness. With GPS‐telemetry data collected across California, USA, we evaluated resource selection of mountain lions (Puma concolor; n = 244) relative to spatial variation in human‐caused mortality risk. With hierarchical resource selection, coarse‐scale selection determines availability at finer scales. This simple relationship allowed us to demonstrate that functional responses in resource selection explicitly link individual‐level resource selection decisions across scales. We show that individuals proactively avoiding risk when selecting home ranges are freed to relax this avoidance when making decisions within home ranges. However, individuals also exhibit reactive avoidance of risk at the finest scales along movement paths.
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791 members
Carol L. McIntyre
  • Denali National Park and Preserve
James Comiskey
  • Inventory and Monitoring Division
Jenny G Powers
  • Wildlife Health Branch
Kevin P. Wilson
  • Death Valley National Park, Resource Division
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Washington, D.C., United States