Conservation and Ecology of Reptiles and Amphibians I

Contributed Paper
ROOM: Room 110 – Galisteo
SESSION NUMBER: 60
 

10:30AM Modeling Qualitative Vulnerability of Desert Amphibians and Reptiles to Climate Change
Kerry L. Griffis-Kyle; Krista Mougey; Sharmistha Swain; Matt Van Landeghem; Joseph Drake; Samantha Kahl
Desert amphibians and reptiles are threatened by climate change and other stresses as a function of their life histories. Consequently, it is imperative that we: 1) determine species-specific stressors and the levels of exposure that make herpetofauna vulnerable to our changing environment, and 2) establish and evaluate standardized assessment methods to easily compare vulnerability among species. To address these issues, we conducted qualitative vulnerability assessments for 25 common desert herpetofauna species using NatureServe’s Climate Change Vulnerability Index (CCVI). We then examined the sensitivity of vulnerability scores to alterations in climate model inputs comparing the CCVI provided previous generation (CMIP3) SRES A1B climate data to the equivalent in the latest generation of models, (CMIP5) RCP 6.0. Finally, we evaluated changes in vulnerability based on the interactions of climate model severity and spatial scale using 3 magnitudes of RCP models and 4 spatial scales. Alarmingly, native desert amphibians were much more vulnerable than the invasive American bullfrog, and amphibians in general were more vulnerable to climate change than reptiles because of their dependence on surface water. Reptiles with higher vulnerabilities tended to have limited ranges with significant barriers to dispersal. The older SRES A1B climate data resulted in higher average vulnerability scores than the RCP 6.0, with twice as many species listed as extremely vulnerable. As expected, we found that higher-magnitude RCP climate scenarios resulted in higher average vulnerability scores. There was also an important interaction between climate data and spatial scale, where the type of spatial data was more important at much milder (and unrealistic) climate scenarios, but was lost at more realistic RCPs. Our work suggests that using broad-scale species range data and realistic climate scenarios will, in many cases, be adequate to perform qualitative vulnerability analyses.
10:50AM Timber Rattlesnake Habitat Use and Selection: A Thermal Landscape Perspective
William E. Peterman; Andrew S. Hoffman
Temperature is of paramount consideration for ectothermic animals, directly affecting biochemical processes and behavior. Numerous studies have thoroughly described multiscale habitat selection and use in rattlesnakes generally, and timber rattlesnakes (Crotalus horridus) specifically. However, there is currently limited understanding of how habitat use and selection are related to the thermal landscape. The primary objective of this study is to understand how habitat use and selection by timber rattlesnakes relates to the thermal landscape. To create a down-scaled near-surface air temperature model, we deployed remote temperature loggers across our focal landscape in Southeast Ohio. We then used fine-scale (<10-m resolution) LiDAR data to derive spatial topographic surfaces as well as surfaces describing canopy height and canopy cover. Using hourly temperature data collected from loggers, we fit linear mixed effects models to describe the spatial variation of near-surface air temperature as a function of spatial landscape covariates and local weather conditions. We then fit resource use and resource selection functions to timber rattlesnake telemetry data. Our near-surface air temperature model fit the data well with high predictive power. Resource selection and use functions indicated that near-surface temperature, canopy height, and topographic position are all important landscape variables. However, surface temperature was the overall best predictor. Use and selection of the thermal landscape depended upon reproductive condition (gravid/non-gravid female) and age, as well as whether a snake was hunting or had recently consumed a meal. Our study provides a novel perspective of habitat use and selection in timber rattlesnakes, and adds to the limited knowledge of timber rattlesnake ecology in the Midwest. A clear understanding of the landscape features affecting near-surface air temperatures and the spatial thermal ecology of timber rattlesnake and has the potential to facilitate more effective and targeted habitat management.
11:10AM The Rocky Reality of Roadways and Rattlesnakes
Garrett P. Sisson; Willem M. Roosenburg; Shawn R. Kuchta
Roads impact wildlife through a range of mechanisms, including alteration of the biophysical environment. Previous work has shown that many terrestrial ectotherms prefer edge habitats in thermally limited landscapes, which has rarely been examined in the edges created by road right-of-ways. Misplaced mitigation structures could reduce thermal resource availability or increase vehicular mortality when organisms attempt to access preferred habitat. Our objective was to quantify the impacts of a new highway on Ohio endangered Timber Rattlesnakes (Crotalus horridus) using radio telemetry, road mortality surveys, and operative temperature modelling. We used mixed effects models to combine operative temperatures with spatially referenced data to generate a thermal landscape model that was ecologically relevant to rattlesnakes. Resource selection functions revealed that gravid rattlesnakes were selecting microhabitats concentrated in roadside areas and at the forest edge. These habitats allowed gravid snakes to maintain preferred gestation temperatures for longer durations, and thus helped to optimize their reproductive physiology. Rattlesnakes trespassed across mitigation fencing to access these resources. Despite using roadside habitats, no rattlesnakes were killed on the roadway, and correlated random walk analysis suggested that snakes avoided crossing. Our findings challenge the paradigm that roadsides are degraded habitats, and suggest that ecological traps can be converted to ecological opportunities when mitigation structures are appropriately located. These findings also identify that Timber Rattlesnakes can rapidly respond to novel habitat heterogeneity, suggesting that similar habitat manipulation could be used to alleviate basking site deficiency.
11:30AM Snakes Move in Mysterious Ways: Daily Activity Patterns and Movements of Northern Mexican Gartersnakes
Tiffany A. Sprague; Heather L. Bateman; Erika M. Nowak
Knowledge of daily activity periods and movement patterns are important components of species conservation and study design. The northern Mexican gartersnake (Thamnophis eques megalops) was listed as threatened under the Endangered Species Act in 2014. This species can be difficult to locate and monitor due to its cryptic behavior and selection of complex habitats. Our objectives were to document daily activity and movement patterns of this species and to determine influence of monitoring frequency on daily movement estimates and habitat selection. We located transmittered snakes every three hours during 24-hour periods and recorded location, distance moved, and macrohabitat type. From June 2015 – July 2016, we monitored 20 snakes during 49 sampling sessions. Snakes were more active and moved longer distances from 9:00-15:00, although some nocturnal activity was observed. Snakes also moved longer distances during the active season (March-October), but short-distance movements were common during the inactive season (November-February). Estimates of daily distanced traveled decreased with less-frequent monitoring; a sampling interval of once every 24 hours yielded only 53-62% of known daily distances moved during the active season. These results can help inform management activities and research study design. Managers and researchers should carefully assess timing and frequency of activities in order to meet project objectives.
11:50AM Species Distribution and Occupancy Models for Informing Reptile Conservation
Daniel Martin; Larissa Bailey; Cameron Aldridge; Robert Reed; Daniel Manier
Conservation planning requires an understanding of how environmental factors influence wildlife distributions. This data-driven planning is particularly relevant for species that may not be able to respond adequately to a rapidly-changing environment. We highlight how different modeling approaches can inform conservation planning for several reptile species of conservation concern in the Great Plains. This region is characterized by gradients across natural (e.g., temperature, precipitation) and anthropogenic (e.g., habitat loss) attributes, making it ideal for investigating relationships between environmental variation and reptile distributions. We applied Species Distribution Models (SDMs) to contemporary occurrence (i.e., detections) data, but resulting estimates of occurrence do not account for imperfect detection and lack estimates of precision. We compare SDM results to those from occupancy models, which do account for imperfect detection but require more robust data collection methods. We evaluate contemporary SDMs and occupancy models for landscape-scale reptile distributions in the Great Plains. Based on this comparison, we suggest approaches for data collection and analysis that would enable validation of these models and reduce sampling bias. Results from this effort will improve insight into environmental drivers of change in reptile distributions, and better inform conservation actions.

 

Contributed Paper
Location: Albuquerque Convention Center Date: September 26, 2017 Time: 10:30 am - 12:10 pm