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USGS2004

Stream salamanders as indicators of stream quality in Maryland, USA

Biological indicators are critical to the protection of small, headwater streams and the ecological values they provide. Maryland and other state monitoring programs have determined that fish indicators are ineffective in small streams, where stream salamanders may replace fish as top predators. Because of their life history, physiology, abundance, and ubiquity, stream salamanders are likely representative of biological integrity in these streams. The goal of this study was to determine whether stream salamanders are effective indicators of ecological conditions across biogeographic regions and gradients of human disturbance. During the summers of 2001 and 2002, we intensively surveyed for stream salamanders at 76 stream sites located west of the Maryland Coastal Plain, sites also monitored by the Maryland Biological Stream Survey (MBSS) and City of Gaithersburg. We found 1,584 stream salamanders, including all eight species known in Maryland, using two 15 ? 2 m transects and two 4 m2 quadrats that spanned both stream bank and channel. We performed removal sampling on transects to estimate salamander species detection probabilities, which ranged from 0.67-0.85. Stepwise regressions identified 15 of 52 non-salamander variables, representing water quality, physical habitat, land use, and biological conditions, which best predicted salamander metrics. Indicator development involved (1) identifying reference (non-degraded) and degraded sites (using percent forest, shading, riparian buffer width, aesthetic rating, and benthic macroinvertebrate and fish indices of biotic integrity); (2) testing 12 candidate salamander metrics (representing species richness and composition, abundance, species tolerance, and reproductive function) for their ability to distinguish reference from degraded sites; and (3) combining metrics into an index that effectively discriminated sites according to known stream conditions. Final indices for Highlands, Piedmont, and Non-Coastal Plain regions comprised four metrics: number of species, number of salamanders, number of intolerant salamanders, and number of adult salamanders, producing classification efficiencies between 87% and 90%. Partial validation of these indices was obtained when a test of the number of salamanders metric produced an 82% correct classification of 618 MBSS sites surveyed in 1995-97. This study supports the use of stream salamander monitoring and a composite stream salamander index of biotic integrity (SS-IBI) to determine stream quality in Maryland.

Applied Herpetology↗

USGS2007

Evaluation of seven aquatic sampling methods for amphibians and other aquatic fauna

To design effective and efficient research and monitoring programs researchers must have a thorough understanding of the capabilities and limitations of their sampling methods. Few direct comparative studies exist for aquatic sampling methods for amphibians. The objective of this study was to simultaneously employ seven aquatic sampling methods in 10 wetlands to compare amphibian species richness and number of individuals detected with each method. Four sampling methods allowed counts of individuals (metal dipnet, D-frame dipnet, box trap, crayfish trap), whereas the other three methods allowed detection of species (visual encounter, aural, and froglogger). Amphibian species richness was greatest with froglogger, box trap, and aural samples. For anuran species, the sampling methods by which each life stage was detected was related to relative length of larval and breeding periods and tadpole size. Detection probability of amphibians varied across sampling methods. Box trap sampling resulted in the most precise amphibian count, but the precision of all four count-based methods was low (coefficient of variation > 145 for all methods). The efficacy of the four count sampling methods at sampling fish and aquatic invertebrates was also analyzed because these predatory taxa are known to be important predictors of amphibian habitat distribution. Species richness and counts were similar for fish with the four methods, whereas invertebrate species richness and counts were greatest in box traps. An effective wetland amphibian monitoring program in the southeastern United States should include multiple sampling methods to obtain the most accurate assessment of species community composition at each site. The combined use of frogloggers, crayfish traps, and dipnets may be the most efficient and effective amphibian monitoring protocol. ?? 2007 Brill Academic Publishers.

Applied Herpetology↗

USGS2008

Brown treesnake (Boiga irregularis) trappability: Attributes of the snake, environment and trap

We examined three classes of factors that may influence brown treesnake (Boiga irregularis) trappability on Guam: (1) attributes of the snake, (2) attributes of the environment and (3) attributes of the trap. The attributes of the snake we considered included body condition, length and sex. Heavier snakes for a given size (better body condition) moved less and were less easily trapped. Longer snakes were easier to trap. Males were also slightly more easily trapped than females. We compared brown treesnake trappability between two study sites that differed greatly in the abundance of diurnal skinks, an important prey item for smaller snakes. We predicted that snakes, especially small individuals (<800 mm snout-vent length), would be more easily trapped in the low prey environment, a result that received only weak support from our data. However, small snakes were rarely trapped under any circumstance. We also predicted that diurnal foraging would be observed in the site with a higher density of diurnal prey, but daytime snake captures were negligible at both sites. Two attributes of traps that we varied were attractant (mouse vs. skink) and entrance flaps (present vs. absent). Traps with mice as attractant registered 6-16 fold more snake captures. We found little influence of entrances on captures. These modulators of brown treesnake trappability may have analogues in a variety of species, especially species that undergo an ontogenetic shift in diet. ?? 2008 Brill Academic Publishers.

Applied Herpetology↗

USGS2016

Using spatial capture–recapture to elucidate population processes and space-use in herpetological studies

The cryptic behavior and ecology of herpetofauna make estimating the impacts of environmental change on demography difficult; yet, the ability to measure demographic relationships is essential for elucidating mechanisms leading to the population declines reported for herpetofauna worldwide. Recently developed spatial capture–recapture (SCR) methods are well suited to standard herpetofauna monitoring approaches. Individually identifying animals and their locations allows accurate estimates of population densities and survival. Spatial capture–recapture methods also allow estimation of parameters describing space-use and movement, which generally are expensive or difficult to obtain using other methods. In this paper, we discuss the basic components of SCR models, the available software for conducting analyses, and the experimental designs based on common herpetological survey methods. We then apply SCR models to Red-backed Salamander ( Plethodon cinereus ), to determine differences in density, survival, dispersal, and space-use between adult male and female salamanders. By highlighting the capabilities of SCR, and its advantages compared to traditional methods, we hope to give herpetologists the resource they need to apply SCR in their own systems.

Journal of Herpetology↗

USGS2001

Applying linear programming to estimate fluxes in ecosystems or food webs: An example from the herpetological assemblage of the freshwater Everglades

We present the application of Linear Programming for estimating biomass fluxes in ecosystem and food web models. We use the herpetological assemblage of the Everglades as an example. We developed food web structures for three common Everglades freshwater habitat types: marsh, prairie, and upland. We obtained a first estimate of the fluxes using field data, literature estimates, and professional judgment. Linear programming was used to obtain a consistent and better estimate of the set of fluxes, while maintaining mass balance and minimizing deviations from point estimates. The results support the view that the Everglades is a spatially heterogeneous system, with changing patterns of energy flux, species composition, and biomasses across the habitat types. We show that a food web/ecosystem perspective, combined with Linear Programming, is a robust method for describing food webs and ecosystems that requires minimal data, produces useful post-solution analyses, and generates hypotheses regarding the structure of energy flow in the system.

Ecological Modelling↗

USGS2015

Invasive Species Science Branch: research and management tools for controlling invasive species

Invasive, nonnative species of plants, animals, and disease organisms adversely affect the ecosystems they enter. Like “biological wildfires,” they can quickly spread and affect nearly all terrestrial and aquatic ecosystems. Invasive species have become one of the greatest environmental challenges of the 21st century in economic, environmental, and human health costs, with an estimated effect in the United States of more than $120 billion per year. Managers of the Department of the Interior and other public and private lands often rank invasive species as their top resource management problem. The Invasive Species Science Branch of the Fort Collins Science Center provides research and technical assistance relating to management concerns for invasive species, including understanding how these species are introduced, identifying areas vulnerable to invasion, forecasting invasions, and developing control methods. To disseminate this information, branch scientists are developing platforms to share invasive species information with DOI cooperators, other agency partners, and the public. From these and other data, branch scientists are constructing models to understand and predict invasive species distributions for more effective management. The branch also has extensive herpetological and population biology expertise that is applied to harmful reptile invaders such as the Brown Treesnake on Guam and Burmese Python in Florida.

Fact Sheet↗

USGS2012

A history of herpetologists and herpetology in the U.S. Department of the Interior

The U.S. Department of the Interior (DOI) has a long and distinguished history of employing herpetologists to conduct basic and applied research to better manage amphibian and reptile populations on public lands and even outside the boundaries of the United States. This history extends back over 125 years with roots in the U.S. Biological Survey, the Fish and Wildlife Service, the Bureau of Land Management, the National Park Service and later, the National Biological Service. In more recent times, the DOI employed more professional herpetologists than any single organization in the world, especially in the U.S. Geological Survey. In 1938, Henry Fitch was the first Interior scientist hired who conducted substantial herpetological research. William and Lucille Stickel of the Fish and Wildlife Service conducted herpetological research throughout the period from the 1940s-1980s but most DOI herpetologists were hired from 1975-80 with another hiring spike from 2000-2005. The former spike was congruent with early versions of the Endangered Species Act while the latter reflected growing recognition of global amphibian decline and the creation of the Amphibian Research and Monitoring Initiative in DOI. Collectively, these herpetologists produced hundreds of books, scientific publications and other scholarly publications, many of which are classics in the literature. In addition, many have served as officers and on the boards of numerous scientific societies particularly those specializing in amphibian and reptile research. The DOI shows a continuing commitment to funding herpetological research by hiring young scientists to replace the aging ranks of herpetologists who started their careers in the 1970s. This commitment is critical given the global decline of both amphibians and reptiles, including those found on public lands in the United States.

Herpetological Conservation and Biology↗

USGS2008

Modeling the effect of toe clipping on treefrog survival: Beyond the return rate

Some studies have described a negative effect of toe clipping on return rates of marked anurans, but the return rate is limited in that it does not account for heterogeneity of capture probabilities. We used open population mark-recapture models to estimate both apparent survival ( ϕ ) and the recapture probability ( p ) of two treefrog species individually marked by clipping 2–4 toes. We used information-theoretic model selection to examine the effect of toe clipping on survival while accounting for variation in capture probability. The model selection results indicate strong support for an effect of toe clipping on survival of Green Treefrogs ( Hyla cinerea ) and only limited support for an effect of toe clipping on capture probability. We estimate there was a mean absolute decrease in survival of 5.02% and 11.16% for Green Treefrogs with three and four toes removed, respectively, compared to individuals with just two toes removed. Results for Squirrel Treefrogs ( Hyla squirella ) indicate little support for an effect of toe clipping on survival but may indicate some support for a negative effect on capture probability. We believe that the return rate alone should not be used to examine survival of marked animals because constant capture probability must be assumed, and our examples demonstrate how capture probability may vary over time and among groups. Mark-recapture models provide a method for estimating the effect of toe clipping on anuran survival in situations where unique marks are applied.

Journal of Herpetology↗

USGS2017

Amphibians, pesticides, and the amphibian chytrid fungus in restored wetlands in agricultural landscapes

Information on interactions between pesticide exposure and disease prevalence in amphibian populations is limited, especially from field data. Exposure to certain herbicides and insecticides has the potential to decrease the immune response in frogs, which can potentially lead to increased abundance of Batrachochytrium dendrobatidis (Bd) zoospores on individuals and in the wetlands. In contrast, exposure to certain fungicides can decrease Bd abundance on frog skin. We examined the relationships between the abundance of Bd on the skin of individual Boreal Chorus Frogs (Pseudacris maculata) and the concentrations of pesticides in the water and in frog tissue at six agriculturally dominated wetlands in Iowa, USA. We collected frogs from each wetland, swabbed them for Bd, and analyzed their tissues for a suite of fungicides, herbicides, and insecticides. We collected surface water from the wetlands and we analyzed it for the same suite of pesticides. We observed no relationship between Bd zoospores on the skin of individual frogs and the concentrations of total pesticides, total herbicides/insecticides and total fungicides in frog tissue. Similarly, we observed no relationship between Bd zoospore abundance in water and the concentration of total pesticides or total herbicides in water. However, we observed a negative relationship between Bd zoospore abundance in water and neonicotinoid concentrations in surface water. Negative results are seldom reported but can be important contributors to a more complete understanding of the complex and potentially synergistic relationships between disease and pesticides. Data from field studies on these relationships are particularly scarce. As our laboratory understanding of these relationships expands, the need for field based, or applied, studies grow.

Iowa↗

USGS2024

Amphibian and reptile conservation in the United States of America

Wildlife stewardship is of utmost importance in the United States, where management for sustainable natural resources is extended to native species including amphibians and reptiles. The U.S. wildlife conservation framework is a nested system of authorities regulating species and habitats, science-based management and policy decisions, and adaptive management as new knowledge is applied to improve outcomes of population- and habitat-management actions. Yet the approach has evolved through time, from single-species management of game species to the conservation of entire ecosystems and the biodiversity they support. Today, the mismatch of conservation ideals with conservation capacity puts nongame species like amphibians and reptiles in the crosshairs for losses due to insufficient resources to address growing numbers of threats. Despite these challenges, optimism prevails, as the management and conservation of U.S. herpetofauna is an increasing priority of the public, with considerable investment into habitat restoration, species-specific threat mitigation, research, public outreach, and education. Herein, we outline key elements of U.S. herpetological conservation efficacy: (1) a web of legal authorities governing the management of U.S. herpetofauna and their habitats; (2) a network of people and organizations that work toward filling priority knowledge gaps by conducting scientific research and that are actively engaged in the science-management interface for species-to-ecosystem level conservation decision-making, and (3) a learning framework of adaptive management within the legal landscape (“lawscape”) and for improving effectiveness of conservation actions. Lastly, the human dimension of species conservation in the U.S. is emerging, where bottom-up local efforts are having success in addition to state- and regional-scale approaches. We propose U.S. herpetological conservation priorities under three themes: threats, research, and human dimensions (people). Together these multifaceted efforts are contributing to advances in the maintenance of U.S. amphibian and reptile diversity. The success of these efforts is notable and could be viewed as a model system, where lessons learned may apply elsewhere.

Book chapter↗

USGS2016

Spatial capture-recapture: a promising method for analyzing data collected using artificial cover objects

Spatial capture–recapture (SCR) is a relatively recent development in ecological statistics that provides a spatial context for estimating abundance and space use patterns, and improves inference about absolute population density. SCR has been applied to individual encounter data collected noninvasively using methods such as camera traps, hair snares, and scat surveys. Despite the widespread use of capture-based surveys to monitor amphibians and reptiles, there are few applications of SCR in the herpetological literature. We demonstrate the utility of the application of SCR for studies of reptiles and amphibians by analyzing capture–recapture data from Red-Backed Salamanders, Plethodon cinereus , collected using artificial cover boards. Using SCR to analyze spatial encounter histories of marked individuals, we found evidence that density differed little among four sites within the same forest (on average, 1.59 salamanders/m 2 ) and that salamander detection probability peaked in early October (Julian day 278) reflecting expected surface activity patterns of the species. The spatial scale of detectability, a measure of space use, indicates that the home range size for this population of Red-Backed Salamanders in autumn was 16.89 m 2 . Surveying reptiles and amphibians using artificial cover boards regularly generates spatial encounter history data of known individuals, which can readily be analyzed using SCR methods, providing estimates of absolute density and inference about the spatial scale of habitat use.

New York↗

USGS2022

Density estimation in terrestrial chelonian populations using spatial capture–recapture and search–encounter surveys

Having an accurate estimate of population size and density is imperative to the conservation of chelonian species and a central objective of many monitoring programs. Capture–recapture and related methods are widely used to obtain information about population size of chelonians. However, classical capture–recapture methods have strict spatial sampling requirements and do not account for lack of geographic closure caused by movement of individuals in and out of the surveyed landscape. Newly developed spatial capture–recapture (SCR) models address these limitations by specification of explicit models for spatial sampling as well as the spatial distribution of individuals in the population. Spatial capture–recapture models have not yet been applied to the study of chelonian populations. Here we demonstrate their application to a population of box turtles in Maryland that has been studied for 75 yr. Results support dramatic declines in population size of box turtles since the 1940s.

Maryland↗

USGS2003

A radio transmitter belt for small ranid frogs

Radio telemetry is a useful technique for gathering information about amphibians when associated caveats are applied (Bartelt and Peterson 2000). A number of designs for transmitter attachment are available for larger anurans including a harness-type attachment (van Nuland and Claus 1981) and various belt designs (Bartelt and Peterson 2000; Rathbun and Murphey 1996; Waye 2001). Attaching radios to small anurans is particularly problematic because of their mass, shape, and delicate skin. Small radios, 0.61 grams or less, are available, although battery life is usually only 2-3 wks (e.g., Holohil Systems Ltd; Carp, Ontario, Canada 1 ). The issues remaining are the weight and longevity of the attachment system, ease of application to the animal, and effect on the behavior and health of the animal. Here I describe an attachment assembly tested in the laboratory on juvenile leopard frogs ( Rana pipiens ) and used on wood frogs ( Rana sylvatica ) in the field.

Herpetological Review↗

USGS2017

Book review: Behavioral ecology of the eastern red-backed salamander: 50 years of research

In commemoration of the 100th anniversary of the British Ecological Society, Sutherland et al. (2013) identified 100 questions of fundamental significance in “pure” (i.e., not applied) ecology. A somewhat unexpected outcome of these authors’ exercise was the realization that, after 100 years of comprehensive, intensive scientific research, there remained “profound knowledge gaps” in ecology, such as a clear understanding of “the central mechanisms driving ecosystems…communities…, and even population dynamics.” Animal behavior (along with other attributes such as physiology and genetics) is such a mechanism that can structure ecological interactions, and the study of behavioral ecology provides important insights into many fundamental ecological phenomena. For example, the well-known historical characterization of ecology as the study of the distribution and abundance of organisms (Andrewartha and Birch 1954) invokes numerous questions, such as: what factors influence coexistence among competing species, or between predators and their prey? Ultimately, the answers to these and other questions are best addressed with fine-scale, mechanistic studies of habitat selection, foraging behavior/prey selection, and movement/dispersal behavior. Similarly, at the population level, insight into the spatial distribution of individuals could be gained with studies of territoriality, dominance hierarchies, and even mate choice.

Herpetological Review↗

USGS2017

Characterization of microsatellite loci for the Gulf Coast waterdog (Necturus beyeri) using paired-end Illumina shotgun sequencing and cross-amplification in other Necturus

Amphibians are one of the most threatened groups of vertebrates (Stuart et al. 2004; Wake and Vredenburg 2008), and the application of molecular techniques to amphibian ecology and genetics has dramatically improved our ability to conserve species and populations (see Shaffer et al. [2015] for review). Microsatellites, tandem repeats of two to six nucleotides in the nuclear genome, are highly variable molecular markers that can be used to describe gene flow and genetic diversity, each of which is positively correlated with population persistence (Allendorf and Luikart 2007; Allentoft and O’Brien 2010; Avise 2004; Selkoe and Toonen 2006). Microsatellite loci have frequently been applied to studies involving terrestrial and pond breeding amphibians (Emel and Storfer 2012), but fewer studies have focused on taxa inhabiting lotic systems (Emel and Storfer 2012). For example, studies characterizing microsatellite loci are completely lacking for a group of permanently aquatic salamanders, the waterdogs and mudpuppies (Family Proteidae, Genus Necturus ) (Rafinesque 1819). The genus Necturus consists of several species of perennibranch salamanders that can be found throughout many freshwater streams, rivers, and lakes in North America (Petranka 1998). Some authorities recognize five species (Crother 2012; Petranka 1998), including the Mudpuppy ( Necturus maculosus ) (Rafinesque 1819), Gulf Coast Waterdog ( N. beyeri ) (Viosca 1937), Black Warrior Waterdog ( N. alabamensis ) (Viosca 1937), Neuse River Waterdog ( N. lewisi ) (Brimley 1924), and Dwarf Waterdog ( N. punctatus ) (Gibbes 1850). This taxonomy also recognizes two subspecies within N. maculosus , including the Common Mudpuppy ( N. m. maculosus ) and the Red River Waterdog ( N. m. louisianensis ) (Crother 2012; Petranka 1998; Schmidt 1953). Other authorities suggest that there are six or seven species within Necturus (Collins 1990; Frost 2016; Powell et al. 2016). These more diverse schemes recognize each of the aforementioned five species while also elevating the Red River Waterdog ( N. louisianensis ) (Collins 1990; Frost 2016; Powell et al. 2016; Viosca 1938) and Löding’s Waterdog ( N. lödingi or N. cf. beyeri ) (Bart et al. 1997; Guyer 2005a; Viosca 1938). Allozyme work by Guttman et al. (1990) suggests that there is at least one cryptic species of Necturus in drainages east of the Mobile Basin and south of the Alabama River, and both Bart et al. (1997) and Guyer (2005a) advise that these populations should be referred to as N. cf. beyeri . However, until range wide studies incorporating genetic and other data are published, we will follow the five species taxonomy outlined by Crother (2012) while acknowledging that certain taxa, such as N. maculosus and N. beyeri , may require systematic revision.

Herpetological Review↗