Geology topics

H. Brian Underwood

Publications and source records attributed to H. Brian Underwood.

14 recordsLinked to original sources

USGS2024

Abundance and distribution of white-tailed deer on First State National Historical Park and surrounding lands

We estimated both abundance and distribution of white-tailed deer ( Odocoileus virginianus ) on the Brandywine Valley unit of First State National Historical Park (FRST) and the Brandywine Creek State Park (BCSP) during 2020 and 2021 with two widely used field methods — a road-based count and a network of camera traps. We conducted 24 road-based counts, covering 260 km of roadway, and deployed up to 16 camera traps, processing over 82,000 images representing over 5,000 independent observations. In both years, we identified bucks based on their body and antler characteristics, tracking their movements between baited camera trap locations. We tested seven estimators commonly reported in the literature, comparing the relative merits for managers of small, protected natural areas like FRST. Deer densities estimated from conventional road-based distance sampling were approximately 10 deer/km 2 lower than densities estimated from camera-trapping surveys. We attribute the bias in roadbased distance sampling to the difficulty of recording the precise effort expended to obtain the counts. Modifying the distance sampling method addressed many of the issues associated with the conventional approach. Despite little substantive differences in land cover types between the two methods, a clear spatial segregation of male and female deer at camera trap locations could bias roadbased counts if the sexes are not encountered in proportion to their abundances. There was a distinct gradient in deer distribution across the study area, with higher proportions of deer recorded in camera traps at FRST than BCSP, which harvests 20–60 deer annually during a regulated, hunting season. The most reliable (i.e., low bias, acceptable precision) methods, Spatial Capture Recapture (SCR) and Density Surface Modeling (DSM), produced deer densities of approximately 50 deer/km 2 in each year — a number which is consistent with previous estimates for New Castle County, Delaware, and our experience in similar, unhunted natural areas. Across both FRST and BCSP, these densities translated into area-wide (~1000 ha) population sizes between 650–1000 deer, with about one-half to two-thirds comprising the FRST population. Density surface modeling of mapped locations of deer detected during surveys, combined with camera-trapping and a time-to-event data analysis might be the only practical means of reliably assessing white-tailed deer abundance in small (<2000 ha), protected natural areas like FRST. Most other approaches are either too time-consuming, require identification and tracking of individual deer, the use of bait, or require intervention by a subject-area expert.

Delaware, Pennsylvania↗

USGS2020

Latitudinal variation in snowshoe hare (Lepus americanus) body mass: A test of Bergmann’s Rule

The relationship between body size and latitude have been the focus of dozens of studies across many species. However, results of testing Bergmann’s Rule – that organisms in colder climates or at higher latitudes possess larger body sizes – have been inconsistent across studies. We investigated whether snowshoe hares (Lepus americanus) follow the Rule by investigating differences in body mass using data from six published studies and from data of 755 individual hares captured from ten populations across North America covering 26° of latitude. We also explored alternative hypotheses related to variation in hare body mass, including winter severity, length of growing season, elevation, and snow depth. We found body mass of hares varied throughout their range, but the drivers of body mass differed based on geographic location. Females in northern populations followed Bergmann’s rule, whereas males did not. In northern populations male mass was related to average snow depth. In contrast, in southern populations body mass of both sexes was related to length of the growing season. These differences likely represent variation in the drivers of selection. Specifically, in the north, a large body size is beneficial to conserve heat because of low winter temperatures, whereas in the south, it is likely due to increased food supply associated with longer growing seasons.

Canadian Journal of Zoology↗

USGS2019

Evaluating legacy effects of hyperabundant white-tailed deer (Odocoileus virginianus) in forested stands of Harriman and Bear Mountain State Parks, New York

Executive Summary White-tailed deer (Odocoileus virginianus) are among the most impactful herbivores in the eastern United States. Legacy forest effects, those accrued from intense herbivory over time, manifest as low seedling regeneration, high cover of plant species that are infrequently browsed by deer, presence or expansion of nonnative or invasive plant species, few herbaceous species, and diminished capacity for recovery. Interfering vegetation (that is, species that increase in cover and density due to avoidance by deer, such as American beech sprouts, Pennsylvania sedge, and hay-scented fern) increase competition for light and hinder recruitment of trees into the forest canopy. The lower Hudson Valley in New York has been heavily browsed by white-tailed deer since the early 20th century. The region has some of the lowest tree regeneration rates in New York State as a result of deer browsing and subsequent increases in interfering vegetation. The U.S. Geological Survey and the State University of New York College of Environmental Science and Forestry studied sites where deer hunting is permitted (case sites) and nearby sites where hunting is currently prohibited (control sites) to assess and identify forest structure and composition differences. Instead of using deer exclosures, which are time-consuming and expensive to install and maintain, we used a case-control study because such studies are well-suited to effects with long latency and rare outcomes. Case-control studies seek to describe the relation between an outcome of interest (in this study, forest understory recovery from chronic herbivory) and forest condition. We inferred recovery by comparing these characteristics on adjacent sites in the lower Hudson Valley with similar forest communities and land uses but different deer population management histories. Case plots were on lands where deer management has taken place annually for several decades. Control plots were on lands where deer populations have not been consistently managed to lowered abundance. We accounted for differences in forest recovery not attributable to deer by first matching case and control plots along several important environmental gradients (slope, aspect, elevation, moisture, canopy openness). By controlling for these gradients, we looked for associations between measured forest conditions and deer herbivory reduction through population management. We surveyed more than 200 plots in upland forest types across case and control sites where we assessed forest condition by estimating density (number per unit area) and composition and cover (percent) of important vegetation constituents in ground, shrub, subcanopy, and canopy layers of the forest. We recorded 37 tree species, 22 shrub species, 57 herbaceous species, and 19 species of grasses and sedges in our plot surveys, including a number of nonnative and invasive plants. We also estimated the ages of a number of common canopy trees by counting rings from cores extracted from individual stems. Effects of more than 100 years of chronic deer browsing manifested in low herbaceous ground cover and little to no tree recruitment (saplings) on lands without deer management. In contrast, sustained deer management resulted in forests with conditions that indicated substantial recovery from chronic herbivory in the ground, shrub, and subcanopy layers. Sites with ongoing deer management exhibited greater ground cover of tree seedlings and herbs and less ground cover of interfering vegetation and nonnative species. The well-developed sub-canopy layer of small trees, saplings, and tall shrubs on sites with deer management indicates a high potential for sapling recruitment to the canopy of the future forest. Of the 25 subcanopy trees sampled on control sites, most were more than 100 years old, indicating little to no regeneration in areas sampled for more than 100 years. The forest canopy, a relic of land uses of bygone days, requires a source of young trees to replace itself as older trees die. Without an abundant layer of young trees in the subcanopy, a forest cannot be sustained over time. Reduction in deer herbivory promotes forest recovery and could benefit Harriman and Bear Mountain State Parks (the control sites for the study), but removal of interfering vegetation may be necessary to mitigate legacy effects where they currently hinder ground layer recovery. To successfully promote a more desirable forest condition that includes elimination of nonnative plant species, promotion of tree recruitment into the forest canopy, and development of diverse and abundant herbaceous cover in ground layer vegetation, future management decisions could include information on herbivory reduction and management of interfering vegetation where necessary.

New York↗

USGS2019

A rapid assessment method for ground layer coastal vegetation

We aim to test a rapid ecological assessment method to monitor regenerating coastal vegetation without sacrificing accuracy. We estimated species frequency in vegetation plots using traditional point intercept methods. We also tested a rapid, digital method to take high-resolution digital photographs of plots. We navigated among plot locations using a sub-meter Differential Global Positioning System instead of using permanent plot markers, and analyzed plot photographs in a point intercept manner (i.e., grid) in Geographic Information Systems software. We assessed species frequency in 52 permanent plots using traditional and digital methods. Traditional methods required 39.2 min per plot and digital methods required 4.6 min per plot. Estimates of frequency from traditional methods were substantially higher than those from digital methods for permanent plots, so we used an independent assessment of vegetation coverage to calibrate the utility of digital methods. A logistic regression equation can be used to compare historical traditional estimates to those collected digitally. Digital point intercept methods were successfully used for rapid ecological assessment. The primary advantages of digital methods include overwhelming efficiency compared to traditional methods, a resultant increase in sample size, and the ability to recover more accurate estimates of species frequency. Disadvantages of digital methods include a restriction of use for ground layer vegetation and positional inaccuracies introduced through sub-meter navigation. While traditional methods are less accurate in estimating species frequency, they are ideal for capturing accurate temporal trends in vegetation growth since they rely upon the use of permanent plot markers.

Journal of Coastal Conservation↗

USGS2019

Deer do not affect short-term rates of vegetation recovery in overwash fans on Fire Island after Hurricane Sandy

1. Coastal resilience is threatened as storm-induced disturbances become more frequent and intense with anticipated changes in weather patterns. After severe storms, rapid recovery of vegetation, especially that of dune-stabilizing plants, is a fundamental property of coastal resilience. Herbivores may affect resilience by selectively foraging palatable plant species in disturbed areas. Knowledge of herbivore impacts to dune recovery after storm events is crucial to management of coastal properties. 2. We combined imagery classification, wildlife monitoring, and trend analysis to investigate effects of white-tailed deer on recovery rates of vegetation over four years post-storm in nine areas overwashed. We estimated local deer density with trail cameras, coupled deer density with primary productivity, and assessed the relationship between deer density and rates of vegetation recovery in overwash fans. 3. Pre-storm vegetation cover consisted of shrubs and sporadic patches of beachgrass. Post-storm cover was dominated by beachgrass. At current recovery rates, vegetation coverage will return to pre-storm conditions within the decade, though community transition from grasses to shrubs will take longer and will vary by site with the rate of dune formation. 4. The effect of deer on rates of vegetation recovery was negative, but not statistically significant nor biologically compelling. Although effects of trampling are evident in classified imagery, deer foraging on beachgrass had little effect on rates of spread throughout overwash fans. 5. Our research provides perhaps the first assessment of the effects of deer on post-storm vegetation recovery. While the rate of spread of the primary dune-building plant species was not deleteriously affected by deer, locally high deer densities will likely affect the establishment and development of more palatable herbs and shrubs.

New York↗

USGS2019

Effects of white-tailed deer (Odocoileus virginianus) exclusion on plant recovery in overwash fans after a severe coastal storm

We documented the impacts of a hyper-abundant deer population on dune vegetation recovering from severe storm surge on a barrier island through use of permanent plots and a repeated measures analysis. Three years after landfall of the storm, vegetation cover was dominated by American beachgrass, Ammophila breviligulata, though we observed twelve plant species among plots surveyed. We documented significantly greater vegetation cover in fenced than unfenced plots in overwash fans in two consecutive years. The difference in species richness between fenced and unfenced plots was significant, though richness was consistently low (≤4 species per plot) and we did not detect a statistically significant difference between years. Both deer trampling and foraging effects were captured in this study, though separation between these effects was not possible. Because trampling effects are often exacerbated on sandy soils, trampling and foraging effects should be isolated and investigated in future assessments of deer impacts on coastal vegetation. Managing deer to lower abundance may enhance coastal resilience if vegetation is allowed to recover unimpeded by foraging and trampling, though a better understanding of the precise nature of deer impacts on dune vegetation is necessary.

AoB PLANTS↗

USGS2019

White-tailed deer movements and space use on Fire Island: A four-year radio-telemetry study 2015-2016 post-Hurricane Sandy assessment

Hurricane Sandy provided a unique opportunity to better understand the movements of Fire Island’s dense white-tailed deer (Odocoileus virginianus borealis) herds. White-tailed deer inhabit all areas of Fire Island National Seashore and their high densities negatively affect native vegetation in several areas of the island, especially as disturbed areas attempt to recover after a catastrophic storm like Hurricane Sandy. Understanding deer movements and space use helps land managers to prioritize white-tailed deer population size and the health and recovery potential of Fire Island’s natural lands according to their management goals. The results of this study will inform Fire Island staff as they prepare to initiate the tasks set forth by the Seashore’s approved Deer Management Plan. We used radio-collars fitted with Very High Frequency (VHF) signal and Global Positioning System (GPS) technology to monitor movements of white-tailed deer for four years after Hurricane Sandy. The greatest movements of Fire Island’s adult female white-tailed deer occurred in spring each year. Home range and core area sizes varied among study areas and years, but suggested hierarchical dominance among Fire Island’s deer populations. Potentially six distinct populations were delineated through analysis of GPS radio-collar data, though these divisions also reflect the concentrated sampling efforts of deer capture. Nearly all deer monitored shared time between natural and nearby built environments. Since Hurricane Sandy, deer movements in Fire Island’s Wilderness are divided by the storm-induced breach. GPS radio-collars provided a wealth of data for analysis of deer movements and space use, and this report is simply a snapshot of the potential information we intend to gain from this study.

New York↗

USGS2018

Hierarchical patch delineation in fragmented landscapes

Purpose We developed a tool, FragPatch (FP), to delineate habitat patches for highly fragmented landscapes from a user-defined suitability map and two landscape perception values for a species of interest. Methods We wrote a Python script in ArcGIS to delineate habitat patch networks using the user inputs and ArcGIS tools such as Euclidean distance, focal maximum, and reclassify. We validated the tool from mapped locations of urban deer and classified imagery for Syracuse, New York, USA. Results FP successfully delineated salient patch networks and functional connectivity for white-tailed deer ( Odocoileus virginianus borealis ) in our fragmented study area, and complements a similar tool, PatchMorph (PM), developed for rural landscape with more uniform land cover. Conclusions A trade-off exists when choosing to use FP or PM and the decision must rely upon a well-defined research question. FP is better suited for isolating patches of habitat when the surrounding matrix is of low quality and suitable areas are highly scattered on the landscape. PM is able to identify patches when the matrix is more uniform, and is better at identifying broader scale connectivity than FP. We expect species biologists and urban landscape planners to use FP to better define patch networks and to understand the implications of fragmentation on a range of species population concerns, including conflicts with human uses.

Landscape Ecology↗

USGS2018

Movement behavior preceding autumn mortality for white-tailed deer in central New York

A common yet largely untested assumption in the theory of animal movements is that increased rates and a wider range of movements, such as occurs during breeding, make animals more vulnerable to mortality. We examined mortality among 34 white-tailed deer (Odocoileus virginianus) wearing GPS collars during the autumn breeding season of 2006 and 2007 in a heavily hunted, forest-agricultural landscape of central New York state. We evaluated whether individuals having higher rates of movement incurred higher rates of mortality and whether mortality risk was higher when deer were in less familiar areas. We used a Cox proportional hazards model to analyze how mortality risk changes with movement rates measured over 3 time periods: < 1 day, up to 2 weeks prior to death, and 3–4 weeks prior to death. Overall, deer increased their movement rates as autumn progressed, males more so than females. However, deer that died moved at a slower rate relative to surviving deer up to 2 weeks prior to death (ß = -2.22 ± 0.81; 95% confidence interval [CI] = -3.91 to -0.51) and a slower rate on their day of death compared to deer that survived (ß = -1.77 ± 0.73; 95% CI = -3.19 to -0.33). Site familiarity was not significantly related to mortality risk. Deer were equally likely to die within their 50% core use area as elsewhere within their autumn home range. We hypothesize that increased sociality associated with breeding may make animals more vulnerable to harvest mortality. Our findings contradict general assumptions about the influences of movement behavior on mortality risk, suggesting that patterns may be sensitive to the spatiotemporal context of the movement analysis.

New York↗

USGS2018

Quantifying effects of deer browsing on vegetation establishment, growth and development in large-extent overwash fans

Hurricane Sandy provided a unique opportunity to better understand the potential effects of white-tailed deer ( Odocoileus virginianus borealis ) on recovering vegetation in areas overwashed by Hurricane Sandy in the Otis Pike Fire Island High Dune Wilderness Area. White-tailed deer are the dominant herbivore on Fire Island and they are known to decrease plant diversity, limit reproduction and growth of some plant species, and facilitate growth and expansion of non-native species through selective browsing. Deer also negatively affect the federally-threatened seabeach amaranth plants along the island’s beaches. Deer impacts to forest understory and regeneration have been documented in Fire Island’s Sunken Forest for decades, though their impacts to recovering dune vegetation are less understood and could restrict the resilience and recovery of primary dunes. Through use of several vegetation assessment methods, including point intercept and paired permanent exclosures, and deer monitoring with trail cameras, we documented high variability in among-overwash species richness, vegetation cover, and local deer abundance. We observed 29 vegetation species among overwash fans between 2015 and 2016. Greater vegetation cover was observed in northern (i.e., inland) areas of all overwash fans, and greater cover and species richness were documented in fenced permanent plots than in control plots. The greatest effect of deer browsing to recovering dune vegetation was in total vegetation cover, which was significantly greater in fenced permanent plots. Any amaranth plants left open (i.e., un-exclosed) were often heavily browsed and experienced early onset mortality without reproducing. Since Hurricane Sandy, total vegetation cover in overwash fans has significantly increased each year, despite deer activity and a regional drought in 2016. While deer graze and browse vegetation in overwash fans, deer and humans trample vegetation in some overwash fans and separating effects of each is not possible from exclusion studies alone. Two overwash fans have been consistently impacted by coastal disturbances since Hurricane Sandy, further complicating their recoveries. Monitoring of dune vegetation should continue as communities transition from predominantly grasses to shrubs and forbs to assess effects of deer as palatability of vegetation improves.

New York↗

USGS2016

Modeling the effects of land cover and use on landscape capability for urban ungulate populations

Expanding ungulate populations are causing concerns for wildlife professionals and residents in many urban areas worldwide. Nowhere is the phenomenon more apparent than in the eastern US, where urban white-tailed deer (Odocoileus virginianus) populations are increasing. Most habitat suitability models for deer have been developed in rural areas and across large (>1000 km2) spatial extents. Only recently have we begun to understand the factors that contribute to space use by deer over much smaller spatial extents. In this study, we explore the concepts, terminology, methodology and state-of-the-science in wildlife abundance modeling as applied to overabundant deer populations across heterogeneous urban landscapes. We used classified, high-resolution digital orthoimagery to extract landscape characteristics in several urban areas of upstate New York. In addition, we assessed deer abundance and distribution in 1-km2 blocks across each study area from either aerial surveys or ground-based distance sampling. We recorded the number of detections in each block and used binomial mixture models to explore important relationships between abundance and key landscape features. Finally, we cross-validated statistical models of abundance and compared covariate relationships across study sites. Study areas were characterized along a gradient of urbanization based on the proportions of impervious surfaces and natural vegetation which, based on the best-supported models, also distinguished blocks potentially occupied by deer. Models performed better at identifying occurrence of deer and worse at predicting abundance in cross-validation comparisons. We attribute poor predictive performance to differences in deer population trajectories over time. The proportion of impervious surfaces often yielded better predictions of abundance and occurrence than did the proportion of natural vegetation, which we attribute to a lack of certain land cover classes during cold and snowy winters. Merits and limitations of our approach to habitat suitability modeling are discussed in detail.

Book chapter↗

USGS2014

Fine scale habitat use by age-1 stocked muskellunge and wild northern pike in an upper St. Lawrence River bay

Radio telemetry of stocked muskellunge ( n = 6) and wild northern pike ( n = 6) was used to track late summer and fall movements from a common release point in a known shared nursery bay to test the hypothesis that age-1 northern pike and stocked muskellunge segregate and have different habitat affinities. Water depth, temperature, substrate and aquatic vegetation variables were estimated for each muskellunge ( n = 103) and northern pike ( n = 131) position and nested ANOVA comparisons by species indicated differences in habitat use. Muskellunge exhibited a greater displacement from the release point and used habitat in shallower water depths (mean = 0.85 m, SE = 0.10) than northern pike (mean = 1.45 m, SE = 0.08). Both principal components analysis (PCA) and principal components ordination (PCO) were used to interpret underlying gradients relative to fish positions in two-dimensional space. Our analysis indicated that a separation of age-1 northern pike and muskellunge occurred 7 d post-release. This first principal component explained 48% of the variation in habitat use. Northern pike locations were associated with deeper habitats that generally had softer silt substrates and dense submersed vegetation. Muskellunge locations post-acclimation showed greater association with shallower habitats containing firmer sandy and clay substrates and emergent vegetation. The observed differences in habitat use suggest that fine-scale ecological separation occurred between these stocked muskellunge and wild northern pike, but small sample sizes and potential for individual variation limit extension of these conclusions. Further research is needed to determine if these patterns exist between larger samples of fishes over a greater range of habitats.

Journal of Great Lakes Research↗

USGS2004

Woodland type and spatial distribution of nymphal Ixodes scapularis (Acari: Ixodidae)

Spatial distribution patterns of black-legged ticks, Ixodes scapularis , in deciduous and coniferous woodlands were studied by sampling ticks in different woodland types and at sites from which deer had been excluded and by quantifying movement patterns of tick host animals (mammals and birds) at the Lighthouse Tract, Fire Island, NY, from 1994 to 2000. Densities of nymphal ticks were greater in deciduous than coniferous woods in 3 of 7 yr. Only engorged ticks survived the winter, and overwintering survival of engorged larvae in experimental enclosures did not differ between deciduous and coniferous woods. Nymphs were not always most abundant in the same forest type as they had been as larvae, and the habitat shift between life stages differed in direction in different years. Therefore, forest type by itself did not account for tick distribution patterns. Nymphal densities were lower where deer had been excluded compared with areas with deer present for 3 yr after exclusion, suggesting that movement patterns of vertebrate hosts influenced tick distribution, but nymphal densities increased dramatically in one of the enclosures in the fourth year. Therefore, movements of ticks on animal hosts apparently contribute substantially to tick spatial distribution among woodland types, but the factor(s) that determine spatial distribution of nymphal I. scapularis shift from year to year.

New York↗

USGS1999

Of elephants and blind men: Deer management in the U.S. National Parks

Overabundant populations of white-tailed deer ( Odocoileus virginianus ) are becoming common in the eastern United States. Faced with burgeoning deer populations in eastern parks, the National Park Service (NPS) formulated policy based on its long experience with ungulate management in western parks. That the NPS failed to find a management solution acceptable to its many constituencies was inevitable. Like blind men touching different parts of an elephant and disagreeing about its form, those engaged in the debate about deer management in parks are viewing different parts of the ecological system. None has seen the entire system, and consequently, there is neither common agreement on the nature of the problem nor on the solutions. We explore the quandary of deer management in eastern parks by addressing three questions: (1) Can the National Park Service reconcile its management goals with those of its neighbors? (2) Can thresholds be identified for determining when to intervene in natural processes? (3) Is there a scientific foundation for proceeding with effective management of deer? We argue that reconciling the NPS management with that of state conservation agencies is not possible because management policy guides these agencies in opposite directions: the NPS is charged with limiting human impact on ecological processes, and state agencies are charged with exerting human control over population abundance. Questions about thresholds and a scientific basis for management arise from concern that irrupting deer populations are a manifestation of disrupted natural processes. Several population growth paradigms are at the heart of this ecological question. The science provides no consensus about which of these paradigms are appropriate to deer in eastern ecosystems. Thus, it is premature to expect science to identify if or when natural processes have been disrupted. While the NPS cannot effectively achieve its goals without better science, neither can it wait for science to fully understand the dynamics of plant–herbivore interactions. The best hope for resolving both the biological and political dilemmas surrounding deer management is through an adaptive management approach.

Ecological Applications↗