Amphibian use of urban stormwater wetlands: the role of natural habitat features

Urbanization is recognized as a major driver of amphibian declines globally. To maintain urban biodiversity, features that promote local amphibian populations must be identified. The construction of stormwater ponds is a useful tool for mitigating wetland loss and retaining water runoff from impermeable urban surfaces, yet their value as breeding habitat for amphibians that require both terrestrial and aquatic habitat to persist remains poorly known. Within the City of Edmonton, Canada, we surveyed 75 urban wetlands (stormwater, natural upland and river valley) using call surveys and trapping for amphibian species. We related amphibian occurrence to 14 within-wetland parameters (reflecting water chemistry and aquatic vegetation) and four landscape features. We used an information-theoretic approach to identify predictors of anuran occurrence. Three of the five amphibian species known to occur regionally (wood frog, boreal chorus frog, and western tiger salamander) were found at all wetland types. Overall, natural wetlands had higher levels of occurrence and abundance of calling wood and boreal chorus frogs than stormwater wetlands; however, constructed stormwater wetlands did frequently serve as breeding habitat for amphibians. Total nitrogen concentrations and aquatic vegetation were the best within-wetland predictors of frog occurrence whereas the nature of terrestrial habitat and amount of wetlands surrounding breeding habitats were the best landscape predictors. Within-wetland habitat could be improved if stormwater wetlands were designed to promote the growth of emergent and submerged aquatic plants. Urban amphibian populations would benefit if managers preserved or restored terrestrial habitat surrounding stormwater sites

The effects of urbanization on North American amphibian species: identifying new directions for urban conservation

Urbanization is a pervasive and growing threat to amphibian populations globally. Although the number of studies is increasing, many aspects of basic amphibian biology have not been investigated in urban settings. We reviewed 32 urban studies from North America and quantified the number of species studied and their response to urbanization. We examined existing research on breeding habitats, life-history stages, movement patterns, and habitat use relative to urbanization. We found amphibians as a whole respond negatively to urbanization (69 reported responses were negative, 6 were positive and 35 showed no effect). We caution, however, that many North American species still lack or are associated with conflicting information regarding species-specific responses (e.g., 89 potential responses were unknown). Approximately 40% of all anuran and 14% of caudate species in North America were investigated in the literature; however, the most diverse genera (e.g., Plethodon and Eurycea) were the most understudied likely due to their cryptic terrestrial lifestyles and biases in sampling protocols that assess wetland habitats via call surveys. Research on movement and small scale habitat use was deficient. Adult, juvenile, tadpole, and egg mass life-history stages commonly served as direct measures of species presence and abundance; however, such data do not accurately reflect recruitment into subsequent age classes and population persistence. The lack of data on many North American species may be contributing to poor management of urban amphibian populations and their habitats

Long-toed Salamander (Ambystoma macrodactylum) hibernacula in Waterton Lakes National Park revealed using Passive Integrated Transponder telemetry

Long-toed Salamanders (Ambystoma macrodactylum) spend most of their lives on land; however, their fossorial nature makes studying their use of habitat difficult. Using Passive Integrated Transponder (PIT) telemetry over two years, we found and characterized nine overwintering sites of Long-toed Salamanders in the vicinity of Linnet Lake and Stable Pond in Waterton Lakes National Park, excavating five of them. These sites were typically associated with stumps and decaying root systems that gave the salamanders access to deep subterranean hibernacula. Overwintering sites were located up to 168 m from the shores of breeding ponds. Given the importance of such terrestrial sites to these populations of Long-toed Salamanders, it is vital that conservation efforts include the preservation of these features and ensure that a sufficient area surrounding breeding ponds remains undisturbed

The use of fluorescent powdered pigments as a tracking technique for snakes

We describe a new technique for tracking snakes that is an alternative to radio-transmitters and thread trails. We coated the bodies of three species of garter snakes (Thamnophis) in fluorescent powder, then followed and marked the trails with a UV light at night. The use of a UV light allowed us to see very detailed paths left by the snakes. This technique was effective for snakes > 10 g and we tracked some individuals > 200 m. Because a portion of the paths ended in burrows, this technique may prove useful for locating hibernacula sites. Fluorescent powder tracking is a useful tool in determining where and how snakes move in a localized habitat

Effects of Disturbance Associated with Natural Gas Extraction on the Occurrence of Three Grassland Songbirds

Despite declines in the grassland bird guild and increasing rates of natural gas extraction on the Canadian prairies, relatively few studies have examined the effects of well sites and related infrastructure on these species. We conducted point counts on Canadian Forces Base Suffield, Alberta to investigate the effects of two well densities (high: 16 wells/2.59km², low: 9 wells/2.59km²) on Savannah Sparrow (Passerculus sandwichensis), Chestnut-collared Longspur (Calcarius ornatus), and Sprague's Pipit (Anthus spragueii) occurrence and abundance. Additionally, model building was employed to determine if landscape features, i.e., soil type, elevation, and topography, along with well density and anthropogenic disturbance to natural vegetation, i.e., the combined areas affected by wells, pipelines, trails, and roads, could predict the occurrence of the three species. For Savannah Sparrows, occurrence and abundance were higher in areas with high well densities compared with low well densities, reflecting the species' general tolerance of human disturbances. Chestnut-collared Longspurs were ubiquitous in the study area and abundance was not related to well density. Models for this species performed poorly and failed to predict occurrence accurately. Models for Sprague's Pipit were the strongest and showed that this species' occurrence was negatively related to anthropogenic disturbance. For all three species, landscape features had low predictive power. Our results indicate that disturbance caused by well sites and related infrastructure affect occurrence of some species and should be incorporated into conservation strategies for grassland birds, especially as undisturbed grasslands become candidates for energy development

The roles of spatial configuration and scale in explaining animal distributions in disturbed landscapes: a case study using pond-breeding anurans

Scale is fundamental to ecological studies as patterns exist at multiple levels of organisation. Scale is critically important when assessing a species' distribution, and it can influence the results of complex landscape analyses. If ignored, conservation and management decisions may be inappropriate. In this study, we assessed an often overlooked element in landscape analyses, spatial configuration, to uncover patterns of species distribution. Specifically, we evaluated cover by native vegetation within an urban landscape using a non-nested approach based on discrete consecutive rings (e.g., 0-50 m, 50-100 m, etc.) and a traditional nested approach based on concentric circles (e.g., 0-50 m, 0-100 m, etc.) to determine whether these approaches differ in their effectiveness in uncovering relationships between land cover and animal occurrence in a disturbed, urban landscape. We performed spatial configuration analyses using two anuran amphibian species (wood frog, Lithobates sylvaticus; and boreal chorus frog, Pseudacris maculate) sampled via call surveys at 75 wetlands (of constructed stormwater sites [n=58] and natural wetlands [n=17]) located within the city of Edmonton, Alberta, Canada. Furthermore, we evaluated the relationship between proportion of native vegetation and species occurrence at three grain sizes (10 m, 50 m, and 100 m) based on analyses of non-nested concentric zones. The nested and non-nested approaches differed in their predictions regarding the occurrence of the frog species. The nested approach explained a higher percentage of deviance when predicting wood frog occurrence than did the non-nested analyses whereas the non-nested approach explained a higher percentage of deviance when predicting boreal chorus frog occurrence. We identified locations surrounding wetlands that predicted occurrence using the non-nested approach that were not detected by the nested approach, suggesting that non-nested analyses may represent an overlooked tool for habitat assessment. Top models for predicting occurrence varied among the three grain sizes, suggesting that our ability to detect environmental heterogeneity is scale-dependent. Incorporating spatial configuration (non-nested and nested designs) and multiple grain sizes in analyses may provide better resolution of landscape patterns and help uncover causes behind species' distributions