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At least 1,531 records · Page 85Linked to original sources

USGS2017

Estimating occurrence and detection probabilities for stream-breeding salamanders in the Gulf Coastal Plain

Large gaps exist in our knowledge of the ecology of stream-breeding plethodontid salamanders in the Gulf Coastal Plain. Data describing where these salamanders are likely to occur along environmental gradients, as well as their likelihood of detection, are important for the prevention and management of amphibian declines. We used presence/absence data from leaf litter bag surveys and a hierarchical Bayesian multispecies single-season occupancy model to estimate the occurrence of five species of plethodontids across reaches in headwater streams in the Gulf Coastal Plain. Average detection probabilities were high (range = 0.432–0.942) and unaffected by sampling covariates specific to the use of litter bags (i.e., bag submergence, sampling season, in-stream cover). Estimates of occurrence probabilities differed substantially between species (range = 0.092–0.703) and were influenced by the size of the upstream drainage area and by the maximum proportion of the reach that dried. The effects of these two factors were not equivalent across species. Our results demonstrate that hierarchical multispecies models successfully estimate occurrence parameters for both rare and common stream-breeding plethodontids. The resulting models clarify how species are distributed within stream networks, and they provide baseline values that will be useful in evaluating the conservation statuses of plethodontid species within lotic systems in the Gulf Coastal Plain.

Journal of Herpetology↗

USGS2021

Stopover ecology of red knots in southwestern James Bay during southbound migration

Many shorebirds rely on small numbers of staging sites during long annual migrations. Numerous shorebird species are declining and understanding the importance of these staging sites is important for successful conservation. We surveyed endangered rufa red knots ( Calidris canutus rufa ) staging in James Bay, Ontario, Canada, during southbound migration in 2017 and 2018. We used mark‐resight data and count data in an integrated Bayesian analysis to quantify migration phenology, estimate passage population size, and model the age structure of the stopover population. Many adult red knots arrived in James Bay in a single wave in early August in 2017, whereas adult red knots arrived in multiple smaller waves in July and mid‐August in 2018. These waves may correspond with breeding phenology where more red knots bred successfully and arrived in one large event in 2017 and the higher number of earlier arrivals in July 2018 may have been failed breeders. We included a binomial generalized linear model in the integrated analysis to estimate that 20% and 10% of staging red knots were juveniles in 2017 and 2018, respectively. In future applications, this method could provide a metric to assess breeding performance and develop our understanding of its role in population declines. Overall, we estimated that up to 23% of the estimated rufa red knot population staged in southwestern James Bay for an average of 10–12 days. The region is a key staging site for endangered red knots and could be included in conservation planning.

James Bay↗

USGS2014

Spatiotemporal associations of reservoir nutrient characteristics and the invasive, harmful alga Prymnesium parvum in West Texas

Golden alga ( Prymnesium parvum ) is a harmful alga that has caused ecological and economic harm in freshwater and marine systems worldwide. In inland systems of North America, toxic blooms have nearly eliminated fish populations in some systems. Modifying nutrient profiles through alterations to land or water use may be a viable alternative for golden alga control in reservoirs. The main objective of this study was to improve our understanding of the nutrient dynamics that influence golden alga bloom formation and toxicity in west Texas reservoirs. We examined eight sites in the Upper Colorado River basin, Texas: three impacted reservoirs that have experienced repeated golden alga blooms; two reference reservoirs where golden alga is present but nontoxic; and three confluence sites downstream of the impacted and reference sites. Total, inorganic, and organic nitrogen and phosphorus and their ratios were quantified monthly along with golden alga abundance and ichthyotoxicity between December 2010 and July 2011. Blooms persisted for several months at the impacted sites, which were characterized by high organic nitrogen and low inorganic nitrogen. At impacted sites, abundance was positively associated with inorganic phosphorus and bloom termination coincided with increases in inorganic nitrogen and decreases in inorganic phosphorus in late spring. Management of both inorganic and organic forms of nutrients may create conditions in reservoirs unfavorable to golden alga.

Journal of the American Water Resources Associatio↗

USGS2021

Gray wolf (Canis lupus) predation patterns following recent recolonization in a multi-predator, multi-prey system

Predator–prey interactions are among the most fundamental of ecological relationships. Recolonizing gray wolf ( Canis lupus Linnaeus, 1758) populations present new challenges for wildlife management in multi-prey, multi-carnivore systems. We documented diet composition and kill rates for wolves in a recently recolonized area over winter and summer seasons (2014–2015). Elk ( Cervus canadensis Erxleben, 1777) were the primary ungulate prey (63%) located at wolf kill sites. Deer (mule deer ( Odocoileus hemionus (Rafinesque, 1817)) and white-tailed deer ( Odocoileus virginianus (Zimmermann, 1780))) were less prevalent than elk in wolf diets, but the amount of deer in diets (40%–50%) varied by pack and season. Juvenile elk were the most prevalent class of prey in wolf diets during summer (63.3%) and winter (36.3%), with adult elk (32.5%) observed nearly as often as juveniles in winter. Kill rates varied by season, with rates 2.3 times higher in summer (mean = 3.5 ungulates/week per pack) than winter (mean = 1.5 ungulates/week per pack), consistent with increased availability and use of neonate prey. Prey biomass acquisition did not vary by pack or season (summer = 243 kg/week per pack; winter = 182 kg/week per pack). Our study quantified predation patterns for a recolonizing wolf population, and patterns that we documented were similar to other multi-prey systems in North America.

Oregon↗

USGS2012

Impact of wildfire and slope aspect on soil temperature in a mountainous environment

Soil temperature changes after landscape disturbance impact hydrology, ecology, and geomorphology. This study used field measurements to examine wildfire and aspect effects on soil temperatures. Combustion of the litter and duff layers on north-facing slopes removed pre-fire aspect-driven soil temperature controls. Wildfire is one of the most significant disturbances in mountainous landscapes and can affect soil temperature, which can in turn impact ecologic and geomorphologic processes. This study measured the temperature in near-surface soil (i.e., top 30 cm) during the first summer after a wildfire. In mountainous environments, aspect can also affect soil temperature, so north- vs. south-facing aspects were compared using a fully factorial experimental design to explore the effects of both wildfire and aspect on soil temperature. The data showed major wildfire impacts on soil temperatures on north-facing aspects (unburned ∼4–5°C cooler, on average) but little impact on south-facing aspects. Differences in soil temperatures between north-facing and south-facing unburned aspects (north ∼5°C cooler, on average) were also observed. The data led to the conclusion that, for this field site during the summer period, the forest canopy and litter and duff layers on north-facing slopes (when unburned) substantially decreased mean soil temperatures and temperature variability. The sparse trees on south-facing slopes caused little to no difference in soil temperatures following wildfire in south-facing soils for unburned compared with burned conditions. The results indicate that wildfire can reduce or even remove aspect impacts on soil temperature by combusting the forest canopy and litter and duff layers, which then homogenizes soil temperatures across the landscape.

Vadose Zone Journal↗

USGS2002

Sampling effort affects multivariate comparisons of stream assemblages

Multivariate analyses are used widely for determining patterns of assemblage structure, inferring species–environment relationships and assessing human impacts on ecosystems. The estimation of ecological patterns often depends on sampling effort, so the degree to which sampling effort affects the outcome of multivariate analyses is a concern. We examined the effect of sampling effort on site and group separation, which was measured using a mean similarity method. Two similarity measures, the Jaccard Coefficient and Bray–Curtis Index were investigated with 1 benthic macroinvertebrate and 2 fish data sets. Site separation was significantly improved with increased sampling effort because the similarity between replicate samples of a site increased more rapidly than between sites. Similarly, the faster increase in similarity between sites of the same group than between sites of different groups caused clearer separation between groups. The strength of site and group separation completely stabilized only when the mean similarity between replicates reached 1. These results are applicable to commonly used multivariate techniques such as cluster analysis and ordination because these multivariate techniques start with a similarity matrix. Completely stable outcomes of multivariate analyses are not feasible. Instead, we suggest 2 criteria for estimating the stability of multivariate analyses of assemblage data: 1) mean within-site similarity across all sites compared, indicating sample representativeness, and 2) the SD of within-site similarity across sites, measuring sample comparability.

Journal of the North American Benthological Societ↗

USGS2009

Evaluating the validity of using unverified indices of body condition

Condition indices are commonly used in an attempt to link body condition of birds to ecological variables of interest, including demographic attributes such as survival and reproduction. Most indices are based on body mass adjusted for structural body size, calculated as simple ratios or residuals from regressions. However, condition indices are often applied without confirming their predictive value (i.e., without being validated against measured values of fat and protein), which we term ‘unverified’ use. We evaluated the ability of a number of unverified indices frequently found in the literature to predict absolute and proportional levels of fat and protein across five species of waterfowl. Among indices we considered, those accounting for body size never predicted absolute protein more precisely than body mass, however, some indices improved predictability of fat, although the form of the best index varied by species. Further, the gain in precision by using a condition index to predict either absolute or percent fat was minimal (rise in r 2 ≤0.13), and in many cases model fit was actually reduced. Our data agrees with previous assertions that the assumption that indices provide more precise indicators of body condition than body mass alone is often invalid. We strongly discourage the use of unverified indices, because subjectively selecting indices likely does little to improve precision and might in fact decrease predictability relative to using body mass alone.

Journal of Avian Biology↗

USGS2004

Habitat use and spatial structure of a barking frog (Eleutherodactylus augusti) population in southeastern Arizona

Barking Frogs ( Eleutherodactylus augusti ) are the northernmost ranging member of the large tropical family Leptodactylidae. We investigated the ecology of this saxicolous species at the northern edge of its range in a canyon in southern Arizona. We captured 54 frogs on discontinuous rock outcrops; eight of nine females and 39 of 45 males were on limestone outcrops. The remaining frogs were closer to limestone outcrops by more than 200 m than would be expected if they were distributed randomly with respect to limestone formations. Seven of 10 frogs radio-tracked had core home ranges (50% fixed kernel) from 94 to 100% on limestone; the other three frogs did not have any part of their home range on limestone outcrops. During five years of mark-recapture efforts, no frogs were found on a different outcrop from the one where they were originally captured; no radio-tracked frogs moved between outcrops during the breeding season. We estimated that four to 20 Barking Frogs occupied each outcrop; these groups probably are connected primarily by juvenile dispersal. As an organism living at the edge of its range, Barking Frogs in Arizona may rely heavily on extensive underground areas such as those found in limestone to protect them from a physiologically challenging environment. To manage for the persistence of Barking Frogs in southern Arizona, we must identify and protect habitat patches and movement pathways among them.

Arizona↗

USGS2013

Cost-effectiveness analysis of sandhill crane habitat management

Invasive species often threaten native wildlife populations and strain the budgets of agencies charged with wildlife management. We demonstrate the potential of cost-effectiveness analysis to improve the efficiency and value of efforts to enhance sandhill crane ( Grus canadensis ) roosting habitat. We focus on the central Platte River in Nebraska (USA), a region of international ecological importance for migrating avian species including sandhill cranes. Cost-effectiveness analysis is a valuation process designed to compare alternative actions based on the cost of achieving a pre-determined objective. We estimated costs for removal of invasive vegetation using geographic information system simulations and calculated benefits as the increase in area of sandhill crane roosting habitat. We generated cost effectiveness values for removing invasive vegetation on 7 land parcels and for the entire central Platte River to compare the cost-effectiveness of management at specific sites and for the central Platte River landscape. Median cost effectiveness values for the 7 land parcels evaluated suggest that costs for creating 1 additional hectare of sandhill crane roosting habitat totaled US $1,595. By contrast, we found that creating an additional hectare of sandhill crane roosting habitat could cost as much as US $12,010 for some areas in the central Platte River, indicating substantial cost savings can be achieved by using a cost effectiveness analysis to target specific land parcels for management. Cost-effectiveness analysis, used in conjunction with geographic information systems, can provide decision-makers with a new tool for identifying the most economically efficient allocation of resources to achieve habitat management goals.

Nebraska↗

USGS2025

Reconciling scale using the Resist-Accept-Direct (RAD) Framework to improve management of woody encroachment in grasslands

Implementing strategies to navigate large-scale ecological transitions in grasslands is one of this century's greatest conservation challenges. In the US Great Plains, managing areas impacted by woody transitions have been reactive, short-lived, costly, and ineffective. Along with current technological innovation in rangeland monitoring, the promise of early warning science is to provide managers with sufficient time to be better prepared for novel signals of ecological change. Combining the science of early warning signals and frameworks such as the Resist – Accept – Direct (RAD) can provide land managers with guidelines to identify proactive strategies when facing ecological change. Using this approach, we found that opportunities to resist woody transitions decreased from 84 % to 60 % between 1990 and 2020 over the entire biome but remained highest in the northern and western Great Plains, which contributes to large scale conservation targets. These are key areas to prioritize resist opportunities. In contrast, 11 % of the biome exhibited early warning transition signals across all hierarchical scales by 2020, a fourfold increase since 1990. Lastly by 2020, 30 % of the biome exhibited early warning signals across multiple but not all scales. Here, efforts may be more effective when management is directed to conserve fragmented grassland legacies within a woody-dominated matrix and avoid large-scale monocultures of problematic encroaching woody species. Our multi-scale study indicates that 1) anchoring to the last remaining grassland core areas with no early warning of transitions and 2) strategically investing in these intact grasslands may provide the best results for grassland conservation.

Great Plains↗

USGS2014

Associations between water physicochemistry and Prymnesium parvum presence, abundance, and toxicity in west Texas reservoirs

Toxic blooms of golden alga ( Prymnesium parvum ) have caused substantial ecological and economic harm in freshwater and marine systems throughout the world. In North America, toxic blooms have impacted freshwater systems including large reservoirs. Management of water chemistry is one proposed option for golden alga control in these systems. The main objective of this study was to assess physicochemical characteristics of water that influence golden alga presence, abundance, and toxicity in the Upper Colorado River basin (UCR) in Texas. The UCR contains reservoirs that have experienced repeated blooms and other reservoirs where golden alga is present but has not been toxic. We quantified golden alga abundance (hemocytometer counts), ichthyotoxicity (bioassay), and water chemistry (surface grab samples) at three impacted reservoirs on the Colorado River; two reference reservoirs on the Concho River; and three sites at the confluence of these rivers. Sampling occurred monthly from January 2010 to July 2011. Impacted sites were characterized by higher specific conductance, calcium and magnesium hardness, and fluoride than reference and confluence sites. At impacted sites, golden alga abundance and toxicity were positively associated with salinity-related variables and blooms peaked at ~10°C and generally did not occur above 20°C. Overall, these findings suggest management of land and water use to reduce hardness or salinity could produce unfavorable conditions for golden alga.

Journal of the American Water Resources Associatio↗

USGS2002

Population dynamics of tule elk at point Reyes National Seashore, California

The presence of locally abundant wildlife raises questions about natural regulation and ecological consequences of overpopulation. We sought to establish precise information about population size, structure, and productivity to examine the role of natural regulation in a closed tule elk ( Cervus elaphus nannodes ) population at Point Reyes National Seashore, California, USA. We estimated an instantaneous exponential growth rate of 0.19 with an adjusted R 2 = 0.98 during 1998, 20 years after the elk were introduced. We estimated annual survival for adult cows of nearly 0.95. Calf survival from birth through the rut ending during October-November was 0.85. Male calves exhibited higher mortality than female calves. Cow mortality was associated with the calving season. We measured a 42% increase in cow:calf density from 0.733 ha -1 to 1.043 ha -1 during 1996-1998. We observed a density-correlated reduction in the rate of increase and in the cow:call ratios prior to high precipitation El Niño Southern Oscillation years, 1993, 1996, and 1997, precipitation >1.23 m year -1 . Given the high population growth rate and model evaluation of management scenarios, park managers will need to use a suite of approaches, such as contraception and removal, to maintain the elk population at levels at or near the closed-range carrying capacity for years between El Niño events.

California↗

USGS2016

Release of suppressed red spruce using canopy gap creation—Ecological restoration in the Central Appalachians

Red spruce ( Picea rubens ) and red spruce-northern hardwood mixed stands once covered as much as 300,000 ha in the Central Appalachians, but now comprise no more than 21,000 ha. Recently, interest in restoration of this forest type has increased because red spruce forests provide habitat for a number of rare animal species. Our study reports the results of an understory red spruce release experiment in hardwood-dominated stands that have a small component of understory red spruce. In 2005, 188 target spruce were identified in sample plots at six locations in central West Virginia. We projected a vertical cylinder above the crown of all target spruces, and in 2007, we performed a release treatment whereby overtopping hardwoods were treated with herbicide using a stem injection technique. Release treatments removed 0–10% (Control), 11–50% (Low), 51–89% (Medium), and ≤90% (High) of the basal area of overtopping trees. We also took canopy photographs at the time of each remeasurement in 2007, 2010, and 2013, and compared basal removal treatments and resulting 2010 canopy openness and understory light values. The high treatment level provided significantly greater six-year dbh and height growth than the other treatment levels. Based on these results, we propose that a tree-centered release approach utilizing small canopy gaps that emulate the historical, gap-phase disturbance regime provides a good strategy for red spruce restoration in hardwood forests where overstory spruce are virtually absent, and where red spruce is largely relegated to the understory.

Natural Areas Journal↗

USGS2004

Simulating the dynamics of linear forests in Great Plains agroecosystems under changing climates

Most forest growth models are not suitable for the highly fragmented, linear (or linearly shaped) forests in the Great Plains agroecosystems (e.g., windbreaks, riparian forest buffers) where such forests are a minor but ecologically important component of the land mosaics. This study used SEEDSCAPE, a recently modified gap model designed for cultivated land mosaics in the Great Plains, to simulate the effects of climate change on the dynamics of such linear forests. We simulated the dynamics of windbreaks with different initial planting species richness and widths (light changes as the selected resulting factor) using current climate data and nested regional circulation models (RegCMs). Results indicated that (1) it took 70-80 simulation years for the linear forests to reach a steady state under both normal (present-day) and warming climates; (2) warming climates would reduce total aboveground tree biomass and the spatial variation in biomass but increase dominance in the linear forests, especially in the upland forests; (3) linear forests with higher planting species richness and smaller width produced higher aboveground tree biomass per unit area; and (4) same species performed very differently with different climate scenarios, initial planting diversity, and forest widths. Although the model still needs further improvements (e.g., the effects of understory species should be included), the model can serve as a useful tool in modeling the succession of linear forests in human-dominated land mosaics under changing climates and may also have significant practical implications in other systems.

Canadian Journal of Forest Research↗

USGS2011

Pathology and failure in the design and implementation of adaptive management

The conceptual underpinnings for adaptive management are simple; there will always be inherent uncertainty and unpredictability in the dynamics and behavior of complex ecological systems as a result non-linear interactions among components and emergence, yet management decisions must still be made. The strength of adaptive management is in the recognition and confrontation of such uncertainty. Rather than ignore uncertainty, or use it to preclude management actions, adaptive management can foster resilience and flexibility to cope with an uncertain future, and develop safe to fail management approaches that acknowledge inevitable changes and surprises. Since its initial introduction, adaptive management has been hailed as a solution to endless trial and error approaches to complex natural resource management challenges. However, its implementation has failed more often than not. It does not produce easy answers, and it is appropriate in only a subset of natural resource management problems. Clearly adaptive management has great potential when applied appropriately. Just as clearly adaptive management has seemingly failed to live up to its high expectations. Why? We outline nine pathologies and challenges that can lead to failure in adaptive management programs. We focus on general sources of failures in adaptive management, so that others can avoid these pitfalls in the future. Adaptive management can be a powerful and beneficial tool when applied correctly to appropriate management problems; the challenge is to keep the concept of adaptive management from being hijacked for inappropriate use.

Journal of Environmental Management↗

USGS2017

Age and growth comparisons of Hovsgol grayling ( Thymallus nigrescens Dorogostaisky, 1923), Baikal grayling ( T. baicalensis Dybowski, 1874), and lenok ( Brachymystax lenok Pallas, 1773) in lentic and lotic habitats of Northern Mongolia

Despite concern over the conservation status of many Mongolian salmonids and the importance of their ecological role in Mongolia's aquatic ecosystems, little is known about their basic biology. Hovsgol grayling ( Thymallus nigrescens ) is endemic to Lake Hovsgol, Mongolia and listed as endangered on the Mongolian Red List. Baikal grayling ( T. baicalensis ) and lenok ( Brachymystax lenok ) are found in lakes and rivers throughout the Selenge drainage. A detailed study of the age and growth of these three salmonids was conducted based on 1,682 samples collected from July 2006 to July 2013 in Lake Hovsgol, its outlet the Eg River, and one of the Eg's largest tributaries, the Uur River. Our results suggest that Hovsgol grayling in particular can reach a much older maximum age (17 years in our samples) than previously believed based on aging from scales. Female Hovsgol grayling were heavier at a given length than their male counterparts. Lenok had a greater average length-at-age in Lake Hovsgol compared to the rivers and greater weight-at-length in the warmer Uur River than in the Eg; female lenok from the rivers had a greater average length-at-age than their male counterparts. This study provides critical new information for the management and conservation of these threatened salmonid species in Mongolia.

Journal of Applied Ichthyology↗

USGS2022

A serological survey of Francisella tularensis exposure in wildlife on the Arctic Coastal Plain of Alaska

Tularemia is an infectious zoonotic disease caused by one of several subspecies of Francisella tularensis bacteria. Infections by F. tularensis are common throughout the northern hemisphere and have been detected in more than 250 wildlife species. In Alaska, US, where the pathogen was first identified in 1938, studies have identified F. tularensis antibodies in a diverse suite of taxa, including insects, birds, and mammals. However, few such investigations have been conducted recently and knowledge about the current distribution and disease ecology of F. tularensis is limited, particularly in Arctic Alaska, an area undergoing rapid environmental changes from climate warming. To help address these information gaps and provide insights about patterns of exposure among wildlife, we assessed the seroprevalence of F. tularensis antibodies in mammals and tundra-nesting geese from the Arctic Coastal Plain of Alaska, 2014–17. With a commercially available slide agglutination test, we detected antibodies in 14.7% of all individuals sampled ( n =722), with titers ranging from 1:20 to 1:320. We detected significant differences in seroprevalence between family groups, with Canidae (foxes, Vulpes spp.) and Sciuridae (Arctic ground squirrel, Spermophilus parryii ) having the highest seroprevalence at 21.5% and 33.3%, respectively. Mean seroprevalence for Ursidae (polar bears, Ursus maritimus ) was 13.3%, whereas Cervidae (caribou, Rangifer tarandus ) had comparatively low seroprevalence at 6.5%. Antibodies were detected in all Anatidae species sampled, with Black Brant ( Branta bernicla nigricans ) having the highest seroprevalence at 13.6%. The detection of F. tularensis antibodies across multiple taxa from the Arctic Coastal Plain and its nearshore marine region provides evidence of exposure to this pathogen throughout the region and highlights the need for renewed surveillance in Alaska.

Alaska↗

USGS2020

Direct and indirect effects of fire on eastern box turtles

Prescribed fire is an increasingly important management tool for eastern deciduous forests, but relativity little is known about the direct effects of fire on the eastern box turtle ( Terrapene carolina carolina ). We used very high frequency (VHF) transmitters to monitor mortality, movement, and spatial ecology of 118 box turtles in response to 17 prescribed fires across 4 seasons and 3 sites in east Tennessee, USA, during 2016–2018. Annual survival of box turtles that experienced a prescribed fire event was lower (0.87 ± 0.04 [SE]) than turtles that did not (0.98 ± 0.01) and was negatively correlated with fire intensity, fire temperature the turtle experienced, and litter depth. All prescribed fire‐related mortalities occurred during the early (Apr–May, n = 5) or late growing season (Sep–Oct, n = 1). Fourteen percent of box turtles we captured exhibited damage to their carapace from previous fire events. Box turtles that survived prescribed fires were in microsites that did not burn, moved to unburned areas during the fire, or burrowed following ignition. Home range size was similar before and after burns and sinuosity of movements did not differ in burned or unburned areas. Our results indicate that though box turtles are susceptible to prescribed fire during their active season, they have behavioral and physical traits that reduce the direct effects of prescribed fire. Prescribed fire practitioners should be aware of the risks of fire, particularly during the active season. We suggest managers consider altering prescribed fire intensity, seasonality, and firing pattern to minimize risk of direct effects where box turtles are of concern.

Tennessee↗