Jayme L. Waldron

USING BEHAVIORALLY-BASED SEASONS TO INVESTIGATE CANEBRAKE RATTLESNAKE (CROTALUS HORRIDUS) MOVEMENT PATTERNS AND HABITAT SELECTION

Both abiotic factors and behavioral patterns may influence snake activity. However, other than reproductive activities, behavioral patterns have rarely been incorporated into studies of snake habitat selection. We investigated seasonal differences in canebrake rattlesnake (Crotalus horridus) movement patterns and habitat selection. We modeled habitat selection in two ways, with and without regard to behaviorally-based seasons, and compared the two models to determine which yielded the most informative results. Behaviorally-based seasons (foraging, breeding, and hibernation) were determined from field observations of study animals. Habitat selection was modeled as habitat use versus availability using a case control sampling design for males and nongravid females using logistic regression. Males had significantly larger home ranges, moved more often, and traveled greater distances between successive locations during the breeding season as compared to nongravid females. The male no-season habitat model lacked significance, and the nongravid female no-season model revealed a positive association with pine savannas. When behaviorally-based seasons were included in the models, both sexes showed distinct seasonal variation in habitat selection, with males and nongravid females using similar habitat for breeding and hibernation, but partitioning habitat during the foraging season. Our results indicate that behaviorally-based seasons provide important details about intraspecific canebrake rattlesnake habitat selection and movement patterns, and that future research should benefit from the inclusion of snake behavior in habitat studies.

The reproductive response of an endemic bunchgrass indicates historical timing of a keystone process

Restoration of the Pinus palustris (longleaf pine)-wiregrass ecosystem of the southeastern United States requires information on reference conditions such as the historical fire regime. Aristida beyrichiana (wiregrass), a keystone perennial bunchgrass, was historically widespread throughout the southeast, but its dependence upon growing season fires for sexual reproduction hastened its decline in the face of decades of human fire suppression. The reproductive response of wiregrass is described by patterns of meristem allocation between competing life history strategies (i.e., vegetative growth vs. sexual reproduction). The temporal link between fire and flowering indicates this allocation was optimized to the historical fire regime through selection. In this study, we used the observed allocation of wiregrass reproductive effort to sexual reproduction as the response variable to examine reproductive response to fire season, using plant size as a covariate. Sexual reproduction was positively associated with plant size. Plants burned during early summer (May–June) produced a greater proportion of inflorescences than did those burned in early spring (March–April) or in late summer (August). Using state records of natural (lightning-ignited) and anthropogenic (human-ignited) fires from historical (1933–1946) and contemporary (1998–2010) periods we found that the distribution of maximum wiregrass reproductive output most closely reflected the distribution of historical fires with natural ignition sources. Moreover, while the monthly distributions of historical and contemporary fires were different for anthropogenic ignitions, they did not differ for fires with natural ignitions. Our predictions of peak allocation based upon the biology of wiregrass provide strong support for the use of wiregrass as an indicator of the historical fire season (early summer). Efforts to restore the longleaf pine ecosystem should therefore consider the biological response of wiregrass in planning prescribed fires.

Seasonal Variation and Ecological Effects of Camp Shelby Burrowing Crayfish (Fallicambarus Gordoni) Burrows

ABSTRACT Foam casts and burrow excavations were used to examine Fallicambarus gordoni burrow occupancy rates, seasonal variation in burrow morphology, correlation between crayfish abundance and burrow abundance and potential ecological effects of burrowing through soil disturbance and the creation of fossorial habitat. Burrow occupancy rates were high (75%) and consistent between active and inactive seasons, although several burrow metrics differed significantly between seasons. Crayfish abundance was strongly correlated with burrow abundance. Estimates of annual soil disturbance (82 metric tons/ha/y) and fossorial habitat created (29–49 km/ha) suggest F. gordoni serves important ecological functions within the greater habitat.

Green Salamander (Aneides aeneus) Growth and Age at Reproductive Maturity

Abstract Growth and age at reproductive maturity are two life-history parameters that add an important temporal component to species conservation, yet such information is seldom available for plethodontid salamanders. We modeled growth and age at maturity for a northern West Virginia population of Green Salamanders, Aneides aeneus, using snout–vent length (SVL) growth intervals from a five-year mark-recapture study. Growth data were fit to the von Bertalanffy and logistic growth interval models and compared using the residual error mean square. The logistic model provided the best fit to the recapture data, indicating that Green Salamanders grow slowly for plethodontids and that it takes 7–8 yr to reach reproductive maturity. Our results revealed that Green Salamanders mature at a later age than most plethodontid species, indicating that the species might have greater generation time and longevity than previously suspected. Our data may offer insight into why the species is sensitive to population declines. Thus, we suggest that future research focus on Green Salamander longevity and generation time to provide a framework from which comparisons can be made across populations.

Light Bait Improves Capture Success of Aquatic Funnel-Trap Sampling for Larval Amphibians

Abstract Aquatic funnel traps are a non-destructive means of surveying amphibians in lentic habitats, particularly as compared to dip-net surveys that disturb aquatic vegetation and the substrate, and affect the water column through increased turbidity. The objective of this study was to examine the utility of glow stick-baited aquatic funnel traps for larval amphibians, with a particular emphasis on ambystomatid larvae. We sampled 12 isolated ponds in the Mid-Atlantic Coastal Plain of South Carolina between April and June 2010 and used detection/non-detection capture data to model the probability of capturing larval amphibians in baited and un-baited funnel traps. Further, we used count data (captures per trap) to examine whether glow stick-baited traps captured more amphibian larvae than un-baited traps. We captured four Ambystoma species (A. mabeei, A. opacum, A. talpoideum, and A. tigrinum) and tadpoles from the families Bufonidae, Ranidae, and Hylidae in light-baited funnel traps. Captures of both Ambystoma larvae and tadpoles were positively associated with light-baited traps, and we were 8.8 times more likely to capture Ambystoma larvae and 5.7 times more likely to capture tadpoles in glow stick-baited traps as compared to un-baited traps. Our results indicate that glow sticks can greatly improve capture success of larval amphibians in funnel traps, and we recommend their use as an active sampling method that is unbiased by surveyor experience and skill-level.

Using Occupancy Models to Examine Human–Wildlife Interactions

Occupancy models provide a structural template for modeling spatial and temporal components of human–wildlife interactions in which outcomes are contingent on both human–wildlife co-occurrence and encounter probability. Because human–rattlesnake interactions are often contingent on post-encounter, human-initiated contact, we categorized these interactions into discrete components: co-occurrence of rattlesnakes and humans, and the probability that a human detects the rattlesnake. We used occupancy models to examine correlates of human–rattlesnake co-occurrence and assumed human–rattlesnake encounter probability was synonymous with detection probability. Occupancy (i.e., proportion of sites occupied) was associated with rattlesnake habitat preference, and encounter probability was influenced by air temperature. Our results indicate that covariates associated with rattlesnake activity (e.g., air temperature) were the best predictors of encounters. This article illustrates the use of occupancy models for identifying spatial and temporal drivers of human–wildlife interactions. Our results will aid management actions and policies that maximize human safety and rattlesnake conservation.

Environmental Effects on Southern Two-Lined Salamander (Eurycea cirrigera) Nest-Site Selection

Nest-site selection is a critical process in the life history of amphibians, directly influencing offspring survival and parental fitness. When and where an amphibian chooses to nest is strongly influenced by a range of environmental cues. In this study, we evaluated nest-site selection of the Southern Two-lined salamander, Eurycea cirrigera, in relation to a range of environmental conditions. We monitored nesting E. cirrigera under coverboards at two seepage wetlands in the South Carolina inner Coastal Plain during the breeding season of E. cirrigera. We examined nest-site selection by E. cirrigera at two scales (landscape scale and microhabitat scale) using logistic regression and AIC model selection. We found that E. cirrigera select nest sites using environmental cues across multiple spatial scales where females actively discriminate among nesting locations based on measures of temperature, hydrology, and water depth. Because amphibians are so sensitive to environmental change and variation, understanding the factors that influence key life history processes, particularly breeding phenology and oviposition site choice, are critical to the conservation of amphibian populations and their habitats.

Estimating Spring Salamander Detection Probability Using Multiple Methods

Abstract Many studies suffer from imperfect detection probability, i.e., species are not detected when individuals may be present. In occupancy studies, detection probability is often treated as a nuisance variable. When used as a primary variable of interest, detection probability can be examined as a function of sampling covariates with the goal of maximizing the probability of encountering target species. Efforts to determine which methods maximize detection probability will benefit monitoring programs, particularly for species that are difficult to detect. We used three sampling methods, leaf litter bag (LLB) surveys, visual encounter surveys (VES), and flip and search (FS) methods to detect larval Spring Salamanders (Gyrinophilus porphyriticus). We estimated occasion-specific estimates of detection and used an analysis of variance to determine if detection probability varied among sampling methods. We found the FS method yielded higher detection estimates than did the LLB and VES. In addition, occupancy estimates derived from FS sampling changed drastically when compared among other single-method models, suggesting that LLB and VES gave biased estimates of occupancy related to a low probability of detecting Spring Salamanders at occupied sites. Furthermore, our results suggest the FS method provided higher detection probability estimates as compared to estimates derived from models that combined all sampling methods. In conclusion, efforts to monitor Spring Salamanders should rely on FS for sampling populations to maximize detection probability to reduce costs and increase effectiveness for large, widespread research projects.

Life-History Correlates of Plant Endemism in Longleaf Pine Ecosystems

Abstract The herbaceous ground-layer community is a key target of restoration efforts in Pinns palustris (Longleaf Pine) ecosystems (LLPE). Identification of life-history traits that correlate with endemism could shed light on advantages or limitations of restoration strategies. We investigated whether dispersal and longevity (life cycle) correlate with species endemism in the LLPE. We characterized plant species as obligate associates of the LLPE (LLO), strong associates (LLP), or neither (N). We predicted that increased dependency on the LLPE (N < LLP < LLO) would correlate with decreased dispersal and greater longevity (longer life cycle). We failed to detect a significant relationship between LLPE affinity and dispersal ability. However, there was a significant positive relationship between LLPE affinity and longevity. We suggest that if dispersal is not limiting, LLO species restoration may depend on both soil properties and the precise use of fire to enhance their establishment and persistence.