Herpetology I

Contributed Paper
ROOM: HCCC, Room 16

12:50PM Linking Perennial Surface Water and Aquatic Food Subsidies to Terrestrial Lizards in Arid Environments
Earyn N. McGee; Noel Hamideh; Rezwana Islam; Michael Bogan
Severe drought driven by climate change and water use by humans is causing perennial streams to flow intermittently, presenting an unprecedented level of disturbance. The loss of aquatic prey could negatively impact riparian and terrestrial species, including lizards. Because lizards play important roles in riparian food webs (e.g. predators, nutrient cycling), it is crucial to understand the cascading effects of stream drying on lizard communities. We hypothesized that perennial streams provide aquatic subsidies to terrestrial species. We predicted that lizard abundances would be greater, and that individuals within a species would grow larger and faster, along perennial streams compared to ephemeral streams. This study was done in the Chiricahua Mountains of southeastern Arizona. We surveyed three paired 100-meter perennial and ephemeral reaches with similar microhabitat but differing water availability. We measured individual growth rate during a 2-month mark-recapture study of Yarrow’s spiny lizard (Sceloporus jarrovii) and the striped plateau lizard (Sceloporus virgatus). We used emergence traps to quantify the availability of aquatic prey. Aquatic insects were collected in high abundances, suggesting a potential food source for lizards along perennial streams that may be unavailable along ephemeral streams. When considering mass at first capture, we found that S. jarrovii were larger at perennial versus ephemeral reaches (P = 0.0025). However, this pattern did not hold true for S. virgatus (P = 0.53). Additionally, we failed to detect differences in lizard abundances between paired perennial and ephemeral reaches (P = 0.37 for S. jarrovii; P = 0.5 for S. virgatus). Low sample sizes prevented us from performing statistical analysis on the mark-recapture data. Although more research is needed to confirm these results, they indicate that emerging aquatic insects may be an important resource to riparian lizard species in arid environments. Future research should quantify trophic links between lizards and potential aquatic subsidies.
1:10PM Evaluating Snake Density and Home Range Size Using Passive Integrated Transponder (Pit) Telemetry and Spatial Capture-Recapture Analyses
Wendy Leuenberger; Allison G. Davis; Jennifer McKenzie; Andrea Drayer; Steven J. Price
Snakes are often elusive and difficult to study in field settings. As such, little is known about their population ecology despite conservation needs for many species. Recent advances in field technologies and analytical approaches offer potential to improve investigations of snake populations. Our objective was to use passive integrated transponder (PIT) telemetry and spatial capture-recapture analyses for linear habitats to calculate snake density, home range size, and detection probability. We tracked northern watersnakes (Nerodia sipedon, n = 94) and queensnakes (Regina septemvittata, n = 119) in six low-order streams in central Kentucky from June through October 2016. We modeled population density as a function of individual streams and land cover type (forest or suburban), home range size as a function of sex, and detection probability as a function of sex and survey-level covariates. Individual streams were a better predictor of snake density than land cover type; density estimates ranged from 7 ± 3 N. sipedon/km (mean ± SE) to 132 ± 21 N. sipedon/km and 10 ± 4 R. septemvittata/km to 80 ± 13 R. septemvittata/km. Female R. septemvittata had a larger home range size (218 ± 16 m) than male R. septemvittata snakes (161 ± 14 m), with no difference for N. sipedon (females: 159 ± 14 m, males: 135 ± 13 m). Detection rates for both species decreased over the course of the season and with fewer days since last rain. R. septemvittata detection rates decreased with increased rain accumulation between surveys and higher water temperatures. Our approach of PIT telemetry and spatial capture-recapture analyses for linear habitats resulted in precise estimates of population density, home range size, and detection rates for two watersnake species. This combination of field and analytical techniques can improve estimates of population status and assess conservation needs for these and similar elusive species.
1:30PM How to Build a Better Ecopassage: Evaluating Amphibian Use and Preference of Various Ecopassage Designs.
Charlene B. Hopkins; Shawn R. Kuchta; Willem M. Roosenburg
As roadways impact amphibian and reptile population sizes, disrupt connectivity, and degrade habitat, mitigation measures are increasingly being implemented. Barrier-ecopassage systems are a common strategy used to mitigate roadway impacts. Barriers limit access to roadways and may direct animals toward ecopassages, which are corridors designed to conduct animals safely over or under the roadway. We assessed use and preference of various ecopassage parameters by utilizing manipulative choice experiments and an observational choice experiment along a two-lane highway in southeastern Ohio. Using amphibians, and some reptiles, we tested preference for the aperture size of passages, levels of sky exposure in the passages, and maintenance of ability to see across the passage. Testing animals throughout 2017, We found that amphibians prefer passages that are 100cm wide, provide 90% sky exposure, and maintain full sight across the passage. The results from the manipulative and observational experiments did not vary significantly, and our observational experiment was able to reduce mortality along the roadway stretch where it was in place. These findings have potential implications for the implementation of future barrier-ecopassage mitigation projects.
1:50PM Landscape-Scale Control of Invasive Brown Treesnakes on Guam with an Automated Bait Manufacturing and Aerial Delivery System
Shane R. Siers; Robert J. Gosnell; Mary Jo Mazurek; John D. Eisemann; Larry Clark; Craig S. Clark; Michael C. Messaros; William C. Pitt
Objectives: After decades of biodiversity loss and economic burden caused by the invasive Brown Treesnake (Boiga irregularis) on the Pacific island of Guam, relief hovers on the horizon. Through a public-private partnership, USDA’s Wildlife Services and National Wildlife Research Center collaborated with Applied Design Corporation to engineer and test an automated toxic bait manufacturing and aerial delivery system for landscape-scale control of Brown Treesnakes. Methods: The core technology is a biodegradable acetaminophen bait cartridge, assembled by an automated bait manufacturing system. When aerially applied, cartridges open and tangle in the tree canopy, making the bait available to treesnakes and out of reach of terrestrial nontarget organisms. Mounted on a rotary- or fixed-wing airframe, the automatic dispensing system (ADS) can broadcast payloads of 3,600 cartridges at a rate of four per second, treating 30 hectares of forest at 120 baits/ha within 15 minutes of firing time. In July of 2016, we conducted the first experimental evaluation of the ADS, applying acetaminophen baits over 110-hectares of forest on Guam. We monitored non-toxic bait takes before and after treatment as an index of snake reduction. Results: Monitoring indicated an immediate drop of > 40% in snake feeding activity in the treatment area, with no decrease in surrounding untreated habitat. After a year without follow-up treatments, snake activity was still 15% lower than in untreated habitat. Conclusions: After further process improvements and fabrication of production-grade components, the first sustained operational treatments, in a 55-hectare forest restoration site, are planned to begin in the summer of 2018. For the first time, a tool exists for the drastic suppression of invasive Brown Treesnakes on a landscape scale. Applications include reduction of snake numbers around transportation infrastructure and within core habitats for the reintroduction of native birds that were extirpated by this troublesome invasive predator.
2:10PM Changes in Ambystoma Salamander Population Size in Response to Terrestrial and Aquatic Habitat Modification.
Michael Benard; Hilary Rollins; Kacey Dananay
Many amphibians require two environments to complete their life cycle, often an aquatic larval environment and a terrestrial post-metamorphic environment. Changes in the size or quality of either environment can affect amphibian abundance and extinction risk. To investigate the effects of manipulations of larval and aquatic environments, we conducted an 8-year study on population size and breeding pond use of a mixed population of smallmouth salamanders (Ambystoma texanum) and all-female unisexual Ambystoma salamanders. This study took place at two sites that were each surrounded by an urban matrix. A large construction project at one site and consequent wetland mitigation efforts at the other site provided the impetus for this project. At the aquatic-habitat-increase site, a new pond suitable for salamander breeding and larval development was created between two existing ponds. At the terrestrial-habitat-reduction site, varying amounts of forest around two ponds were removed. Adult salamander population size was estimated with capture-mark-recapture methods. Larval abundance and growth was quantified with trapping and dipnet sampling. At the site with the newly created pond, there was approximately a two-year lag before adult salamanders began breeding in the new pond. Creation of the new pond did not appreciably increase overall salamander abundance across the entire site. However, adult salamanders distributed themselves across all three breeding ponds such that fewer adults used the old ponds, and more adults used the newly created pond. At the site where terrestrial habitat was removed, adult population size at two breeding ponds did not decline, and actually increased in one pond. This was in contrast to information on Ambystoma terrestrial habitat use that predicted the populations should have declined precipitously. Our results emphasize the importance of experimental tests of models of amphibian population size based on aquatic and terrestrial habitat size and quality.
2:30PM Refreshment Break
3:20PM Forest Communities and Amphibians: Linking Trees to Colonization
Michael P. Graziano; William Peterman; Stephen Matthews
Plants shape ecosystems, affecting both physical and chemical attributes of the landscape, and their communities are shifting worldwide as a result of multiple anthropogenic influences. Amphibians are also experiencing population shifts and declines, yet relatively few studies investigate the implications of how changing plant community can impact amphibian populations. Studies that have investigated the effect of the plant community on amphibians focus on the capacity of leaf litter to alter the larval stage, with few investigating impacts to the adult breeding community. Our study investigates the underlying drivers of colonization of novel breeding sites by amphibians with a focus on the surrounding forest community. Fourteen ponds were created of similar size and depth along a gradient of tree communities ranging from oak dominance to maple-dominance in 2014. We documented colonizing amphibians in 2015 and 2016, comprising 1114 captures of 12 species. Generalized linear model-based analyses performed at the community level consistently found that the tree community was a significant predictor of amphibian colonization of isolated woodland pools. These data demonstrate that changing plant communities as a result of altered disturbance regimes within the landscape have the potential to influence amphibian communities. Further, these changes were documented within contemporary forests and suggest that with increases pressures due to invasion by non-native species and climate change, amphibian communities may also respond. From a conservation perspective, we suggest activities that maintain or restore landscape-level heterogeneity to facilitate conservation efforts will benefit a robust assemblage of amphibians.
3:40PM Niche Partitioning Strategies of Endemic Dwarf Geckos at the Salt Flats Refuge in Cabo Rojo, Puerto Rico
Rhianna F. Smith
The conservation of endemic reptiles is essential to maintain ecological balance in fragile xeric island ecosystems. Terrestrial geckos within the genus Sphaerodactylus are some of the world’s smallest amniotes. Detailed descriptions regarding interspecific and intraspecific ecology in Puerto Rico are scarce in literature. Our research aimed to provide novel information regarding Sphaerodactylus nicholsi and Sphaerodactylus roosevelti ecology while in sympatry at The Salt Flats Refuge in Cabo Rojo, Puerto Rico. Our main research objective was to discern if resource partitioning occurs among Sphaerodactylus within The Salt Flats refuge. Using transects during one year, we captured individuals of each species and collected microhabitat data. We classified substrate as one of the following types: Leaf litter (LL), Vegetation (V), Mixed (M), Bare Ground (BG) and Other (O). Over-story cover (%) was measured using a Spherical Densiometer. Capture time was also recorded. We used an electronic digital caliper and Pesola© scale to obtain morphometrical data such as snout-vent length (mm), tail length (mm) and weight (g). We then classified each gecko within the following age categories: Hatchling, Juvenile or Adult. We also sexed adult individuals whenever possible. Our results demonstrate that significant differences exist within interspecific substrate type (p=<0.0001, α=0.05). Interspecific differences are also significant in temporal preference (p= <0.0001, a=0.05) with S.roosevelti being more nocturnal than S.nicholsi. Significant differences (p= <0.0001, α=0.05) are also present between S.nicholsi age categories for substrate type, over-story cover (%) and temporal preference. Likewise, S.roosevelti age categories significantly differed in substrate type (p= 0.0175, α=0.05) and over-story cover (%) (p= 0.0373, α=0.05), but not in temporal preference (p= 0.3296, α=0.05). Our results demonstrate interspecific and intraspecific spatial and temporal resource partitioning at The Salt Flats Refuge. Our findings are relevant to future conservation efforts concerning worldwide sphaerodactylids threatened by unprecedented climate change effects.
4:00PM Maintenance of Shade Options Is Critical for Reptile Persistence Under Climate Warming: Evidence From Field Experiments on Turtles and Lizards
Jeanine Refsnider
Climate change is predicted to have severe effects on ectotherms such as reptiles due to physiological and behavioral traits that are highly dependent on environmental temperatures, and temperature-dependent sex determination, which can lead to climate warming-induced biases in sex ratios. Reptiles’ capacity to respond to climate change has important implications for population persistence. Reptiles tend to evolve slowly and are poor dispersers; therefore, adaptive evolution and geographic range shifts may not be mechanisms by which many reptiles can keep pace with climate change. Instead, a more immediate mechanism for coping with a warming climate may be necessary. Behavioral phenotypic plasticity, particularly in shade use, may be critical in allowing reptiles to quickly match their behavior and habitat use to environmental conditions. I discuss empirical evidence from two field experiments demonstrating that shade use is phenotypically plastic and allows reptiles to immediately adjust their behavior to match novel climatic conditions. First, in a common-garden experiment, female painted turtles (Chrysemys picta) from five populations adjusted the amount of shade under which they nested to match local conditions, demonstrating that choice of shade cover over nest sites is phenotypically plastic and can prevent sex ratio skews in a species with temperature-dependent sex determination. Second, horned lizards (Phrynosoma hernandesi) reciprocally transplanted between high- and low-elevations immediately adjusted their use of light environment to match that of local lizards, demonstrating that light-environment use, one component of thermoregulatory behavior, is phenotypically plastic. Critically, although plasticity in shade use is clearly an important mechanism allowing reptiles to compensate for short-term changes in climate, there may be ecological constraints preventing such plasticity from being expressed. In particular, managers of vulnerable populations should ensure that a range of shade cover options are available so that reptiles can express phenotypic plasticity and use cooler, shadier microhabitats as the climate warms.
4:20PM Habitat Succession and Landscape Connectivity Govern Meta-Demographic Rates of a Threatened Anuran
Adam Duarte; James T. Peterson; Christopher A. Pearl; Brome McCreary; Stephanie K. Galvan; Jennifer C. Rowe; Michael J. Adams
Pond-breeding amphibians play an important role in aquatic and terrestrial food web linkages. Their unique life history makes them sensitive to both aquatic and terrestrial habitat modifications, where these habitat modifications can act synergistically in reducing reproduction and survival of amphibians. Additionally, increased stream flow regulation and flood control measures have dramatically altered natural flow regimes, leading some amphibian populations to be functionally disconnected from each other. This scenario is typified by the threatened and highly aquatic Oregon spotted frog (Rana pretiosa) in central Oregon. A better understanding of the relationships between Oregon spotted frog population dynamics, habitat conditions, and landscape connectivity is needed to properly inform management decision making. We developed a spatial multi-state occupancy model to estimate meta-demographic rates (i.e., local persistence, colonization, and reproduction), while explicitly modeling landscape connectivity and accounting for imperfect detection. We fit this model to detection/non-detection data collected for Oregon spotted frog at 93 sites in the Deschutes and Klamath River Basins from 2010 to 2016. Preliminary results indicate probabilities of local persistence and reproduction, conditional on occupancy, were generally high across our study period, but strongly related to local habitat conditions. Furthermore, our results concerning the distance over which neighboring occupied sites colonize a focal unoccupied site varied markedly based on what sites we allowed to contribute to dispersal when fitting the model. This study represents the largest monitoring effort for this threatened species, sheds new light into what factors govern Oregon spotted frog meta-demographic rates, and provides the first information concerning the distance at which populations are connected via dispersal at the landscape scale. Collectively, this information will help provide a scientific basis for evaluating tradeoffs in potential management actions to maximize Oregon spotted frog viability in a heavily human-modified landscape.
4:40PM Terrestrial Salamanders in Managed Forests: Impacts of Harvest Practices on Oregon Slender Salamander and Ensatina Occupancy and Abundance.
Tiffany S. Garcia; Andrew Kroll; Jessica Homyack; Josh Johnson; David Shaw; Claudine Reynolds
Understanding how sensitive taxa respond to timber harvest practices is a critical component of sustainable forest management. We used multi-scale models to estimate occupancy and abundance of two terrestrial, forest-associated salamanders, the Oregon Slender salamander (Batrachoseps wrighti) and the Ensatina (Ensatina eschscholtzii) salamander, to harvest practices in the western Oregon Cascades, USA. The Oregon Slender salamander is strongly associated with decaying downed wood. In contrast, Ensatina are relatively common and show less dependency on downed wood. Our Before/After, Control/Impact experiment used a staggered design in which a subset of 88 stands were harvested in each year of the 6 year study. Occupancy and abundance increased with downed wood counts at the plot level for both Oregon Slender and Ensatina salamanders. We did not find evidence for treatment differences in occupancy or abundance for either species at the sub-plot or plot level, with similar estimates in harvested stands and control stands across the 2013-2018 period. Detection probability for both species varied with air temperature across treatments: As temperatures increased, we estimated lower probability of detection in harvested units relative to control units. This information will assist in the status assessment of Oregon Slender salamanders, as the species was petitioned for listing under the Endangered Species Act.


Contributed Paper
Location: Huntington Convention Center of Cleveland Date: October 8, 2018 Time: 12:50 pm - 5:00 pm