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An inherent challenge in managing rare or cryptic species is data deficiency. For this reason, ancillary data is a potentially valuable resource for generating key population estimates for priority species. We compiled ancillary commensal data collected between 1982 and 2020 during surveys of gopher tortoise (Gopherus polyphemus) burrows to estimate the terrestrial distribution of gopher frogs (Rana capito) from potential breeding wetlands. Gopher frogs were detected in gopher tortoise burrows 30‒3,879 m from identified wetlands. A global model of all records from all sites indicated that the probability of a gopher frog residing in a gopher tortoise burrow declined with increasing distance from a wetland. This pattern also held for 4 of 5 sites with a sufficient number of gopher frog detections to model independently. Based on the full data set, we estimated that 50%, 90%, and 99% of gopher frog observations occurred within 392 m, 1,019 m, and 2,752 m of the nearest wetland, respectively. Our results indicate a higher proportion of gopher frogs emigrate longer distances from wetlands than was previously reported using other methods, such as radio‐telemetry. This information can directly assist with management decisions, notably the spatial extent for application of habitat management surrounding breeding wetlands. More generally, this study illustrates the capacity of ancillary data to fill data deficiencies for a rare and cryptic species and highlights the importance of these data. Ancillary data is a potentially valuable resource for generating key population estimates for priority species. We used ancillary commensal data collected during gopher tortoise (Gopherus polyphemus) burrow surveys to estimate the terrestrial distributions of gopher frogs (Rana capito) from potential breeding wetlands. Our work highlights the utility of ancillary data and demonstrates its ability to generate useful data for estimating important population parameters, such as how gopher frogs are distributed spatially from wetlands.

Line‐transect distance sampling (LTDS) surveys are commonly used to estimate abundance of animals or objects. In terrestrial LTDS surveys of gopher tortoise (Gopherus polyphemus) burrows, the presence of ground‐level vegetation substantially decreases detection of burrows of all sizes, but no field or analytical methods exist to control for spatially heterogeneous vegetation obstruction as a source of variation in detection. We propose the addition of a simple measurement of ground‐level vegetation that serves as a covariate for the detection function. We present a Bayesian hierarchical model in which covariates burrow width and nearby vegetation height help to account for detection bias and improve precision of estimated density. We investigate the performance of this covariate by simulation and by using real LTDS data collected before and after application of prescribed fire. We collected data in 2018 at the Jones Center at Ichauway in Newton, Georgia, USA. Across all simulations, our model including both covariates produced the most accurate density point estimates of any of the models tested. For our case study, our Bayesian model with vegetation covariates tended to produce similar estimates of density before and after burns. Our study indicates that any level of spatial variation in vegetation obstruction decreases detection of burrows and may lead to underestimation in population size (≤68%) and proportion of individuals with small burrow sizes (≤32%) when not considered during analysis. Our work is extensible to other terrestrial sampling efforts where systematic measurement of a spatially distributed obstructing feature is feasible during the LTDS survey. In terrestrial line‐transect distance sampling surveys of gopher tortoise burrows, the presence of ground‐level vegetation substantially decreases detection of burrows of all sizes. We present a Bayesian hierarchical model in which covariates burrow width and nearby vegetation height help to account for detection bias and improve precision of estimated density. Our study indicates that any level of spatial variation in vegetation obstruction decreases detection of burrows and may lead to underestimation in population size (≤68%) and proportion of individuals with small burrow sizes (≤32%) when not considered during analysis.

Gopher tortoise (Gopherus polyphemus) populations are declining range‐wide primarily because of habitat loss, fragmentation, and degradation, but low recruitment due to nest predation also may be contributing to this decline. The relationship of nest location and nest survival is unknown. Therefore, our objective was to determine whether nest location influenced depredation risk and potential recruitment success. Between 30 May 2013 and 3 September 2014, we constructed and monitored 105 artificial gopher tortoise nests (45 in 2013 and 60 in 2014) with 35 nests at each of 3 classifications of nest sites: within active burrow aprons (i.e., the mound of sand at the burrow entrance), inactive burrow aprons, and open sandy sites. Using the artificial nests, we investigated the influence of nest site classification, distance to road, and prescribed fire frequency (<1 year and 1 year since burn) on gopher tortoise nest survival. Additionally, we monitored 21 natural nests at burrow aprons to assess predation patterns as compared to artificial nests. Seventy‐two (57%) of 126 nests were fully depredated during the study, and predation rates at artificial and natural nests were similar. We identified predators at 48 nests using trail cameras; the nine‐banded armadillo (Dasypus novemcinctus) was the primary nest predator (69%). Nests in open sandy areas away from burrows exhibited greater daily survival rates (DSR; 0.991 ± 0.005 SE) compared to nests in burrow aprons (active burrow aprons: 0.967 ± 0.018; inactive burrow aprons: 0.949 ± 0.027). Additionally, nests at locations burned the year of the study had a lower chance of survival (DSR: 0.959 ± 0.022) than nests at locations burned the previous year (DSR: 0.991 ± 0.005). Management practices that maintain open sandy areas (e.g., prescribed fire) away from burrows may increase tortoise nest survival. Fire return intervals of >1 year that are implemented frequently enough to maintain open sandy areas would be beneficial to nesting tortoises. © 2016 The Wildlife Society.

Red imported fire ants (Solenopsis invicta; fire ants) are predators of turtle (Testudine) eggs and hatchlings, but little information is available indicating how and when fire ants detect turtle nests during incubation. Therefore, during 2014, we compared fire ant presence at gopher tortoise (Gopherus polyphemus) nests in burrow aprons in early and late incubation with paired burrow aprons that did not contain eggs. To determine whether fire ants were attracted to soil disturbance associated with nesting, we compared fire ant presence at physically disturbed burrow aprons without eggs (i.e., simulated empty nests) with paired burrow aprons with no disturbance or eggs at Ichauway, Georgia, USA. We found fire ants more frequently at nests than at paired aprons early in incubation, but not late in incubation. Additionally, we found no difference in fire ant presence between simulated empty nests and paired sites. Our results indicate that fire ants are attracted to gopher tortoise nests because of a factor other than the initial soil disturbance that accompanies nest deposition, possibly the mucous and moisture released by the female as eggs are laid. © 2016 The Wildlife Society.

Lethal control of coyotes (Canis latrans) is a mechanism for increasing white-tailed deer (Odocoileus virginianus) recruitment but can be difficult to implement and may be ineffective on small parcels of land because of coyote immigration. In 2003, we constructed 4 40-ha mesopredator exclosures with the objective of quantifying the influence of mesopredators, including coyotes, on select wildlife populations and communities. Camera trapping indicated neonate/adult female white-tailed deer ratios were approximately 2 times greater inside predator exclosures than in control plots. Hunter success data provided further evidence of increased recruitment associated with exclosures relative to the remainder of the study site. Because exclosures were located on the boundary of our study area and off-site white-tailed deer harvest records were not available, we used estimates of deer density, sex ratios, reproductive rates, relative use of exclosures, and neonate survival inside and outside of exclosures to parameterize a Monte Carlo simulation model to estimate the impact of our 4 exclosures on neonate recruitment into the start of the firearms hunting season on a 1,600-ha area. After 1,000 iterations, we estimated that predator exclusion provided an additional 18?±?0.13 (x¯?±?SE; median?=?15, interquartile range [IQR]?=?9–24) recruits/year above that expected without exclusion. Simulated neonate/adult female ratio was 0.74?±?0.03 (median?=?0.72, IQR?=?0.52–0.93) with exclosures and 0.41?±?0.008 (median?=?0.39, IQR?=?0.21–0.58) without. Simulated exclosure impact on recruitment was most sensitive to white-tailed deer relative use of exclosures and was least sensitive to neonate survival inside exclosures. We suggest that predator exclusion may be an effective mechanism for reducing neonate mortality and increasing white-tailed deer recruitment in areas where neonate survival is affected by predation. Exclosures may be particularly valuable on small parcels of land where predator removal would be offset by immigration. Finally, exclosures provide refuge from predators throughout the year, and we hypothesize exclosures may also contribute to adult survival and reduce impacts of predation risk that may also affect white-tailed deer population dynamics. Additional research incorporating variation in exclosure size and white-tailed deer density is needed to better evaluate predator exclosures for creating neonate refugia and mitigating sub-lethal impacts of predation. © 2015 The Wildlife Society.

Gopher tortoise (Gopherus polyphemus) populations are declining throughout the Southeast, and high levels of predation on nests and juveniles have been suggested as a potential contributor to this decline. Therefore, we documented gopher tortoise nest success and hatchling survival relative to mammalian predator control. We used 4, large (approx. 40-ha) fenced, predator exclosures to exclude mid-sized mammalian predators: bobcat (Lynx rufus), raccoon (Procyon lotor), Virginia opossum (Didelphis virginianus), fox (Urocyon cinereoargenteusand Vulpes vulpes), coyote (Canis latrans), nine-banded armadillo (Dasypus novemcinctus), and skunk (Mephitis mephitis); 4 unfenced plots served as controls. We monitored nests for survival through hatching and used radio-telemetry to examine hatchling survival. We radio-tracked 40 hatchlings for up to 329 days, but we were only able to track 8 individuals from a single nest at an unfenced plot because of high nest predation. Mean nest survival was greater at exclosures than at unfenced controls (F1, 2?=?45.80, P?=?0.0001). Hatchling survival differed (?2?=?5.839, P?=?0.016) between unfenced plots (37.5%) and exclosures (74.4%), suggesting that mammals also were significant predators of hatchlings. The number of juvenile (<13?cm in diameter) and subadult tortoise burrows (13–21.9?cm) increased over a 6-year period in exclosures, providing further support for an effect of excluding mammalian predators on nest and juvenile tortoise survival. © 2012 The Wildlife Society.

Abstract:Status and trends of gopher tortoise (Gopherus polyphemus) populations are a critical information need for natural resource managers, researchers, and policy makers. Many tortoise populations are small and isolated, which can present challenges for deriving population estimates. Our objective was to compare abundance and density estimates for a small tortoise population derived using a total burrow count versus estimates obtained with line transect distance sampling (LTDS) using repeated surveys. We also compared results of the 2 survey methods using standard burrow-to-tortoise correction factors versus assessing occupancy of all burrows with a camera scope. In addition, we compared LTDS data obtained using a compass and measuring tape to define transects to those obtained using a Global Positioning System (GPS) and Personal Data Assistant (PDA) field computer to navigate transects. Line transect distance sampling with repeated surveys (both with a measuring tape and compass and with a GPS—PDA) yielded sufficient observations of tortoises to calculate population estimates. From 18% to 31% of burrows were occupied by tortoises as determined with the burrow camera. We found 25 burrows during the LTDS survey that we did not find in the total count survey, which demonstrated that the assumption of 100% detection for the total count was not met; hence, density or abundance measurements derived with this method were underestimates. We recommend using GPS—PDA technology, scoping all burrows detected, and using LTDS with repeated surveys to estimate abundance and density for small gopher tortoise populations.

ABSTRACT Although nest predation is often the single largest source of mortality in avian populations, manipulative studies to determine predator impacts on nest survival are rare, particularly studies that examine impacts of mid-size mammalian predators (hereafter, mesopredators) on nest survival of shrub-nesting birds. We quantified nest survival and identified nest predators of shrub-nesting songbirds within 4 large (approx. 40-ha) exclosures and 4 control sites within a longleaf pine (Pinus palustris) ecosystem. During 2003–2006, we located and monitored 535 shrub nests (222 with videography) for 4,804 nest-days to quantify daily nest survival and document predation events. We found no support for a treatment effect, suggesting mesopredators had little impact on daily nest survival (0.9303 in controls and 0.9260 in exclosures) of shrub-nesting songbirds. For the 5 most commonly monitored species, daily nest survival within species was constant. Our analysis suggested that shrub nests were most vulnerable during the nestling stage and presence of cameras on nests increased survival with the increase in survival being more pronounced during the incubation stage. We filmed 107 nest predation events, identifying predators at 88 nests. Of these 88 nests, snakes caused 33%, red imported fire ants (hereafter fire ants, Solenopsis invicta) 28%, raptors 17%, corvids 8%, mesopredators 6%, and small mammals 8% of nest predations. Cause-specific nest predation in controls and exclosures did not differ from expectation, providing evidence that compensatory predation did not occur. Nest predators differed from expectation with regard to nest stage; fire ants and raptors only depredated nests during the nestling stage. Presence of cameras had no effect on nest abandonment. Fire ants were the most prevalent nest predator, and nest predation by fire ants was only observed on nestlings, potentially reducing likelihood of renesting. Magnitude and timing of fire ant predation suggests that fire ants may be the most influential nest predator of shrub-nesting birds within the longleaf pine ecosystem. Our data suggest that controlling mesopredators will have no effect on nest success of shrub-nesting birds within longleaf pine forests.

Abstract:The eastern diamondback rattlesnake (Crotalus adamanteus) and timber rattlesnake (Crotalus horridus) are sympatric throughout most of southern Georgia, USA. We used rattlesnake sightings to quantify and compare habitat use by these 2 species in the Gulf Coastal Plain. At the largest scale examined, univariate statistics and logistic regression models indicated that eastern diamondback rattlesnakes were associated with roads but not with any of the specific habitat types we examined. In contrast, timber rattlesnakes were closely associated with hardwood habitat and riverine systems but not with roads and edges. To effectively conserve and manage both species in the Southeast, a habitat matrix of large intact patches of both hardwood and pine (Pinusspp.) forest may be necessary.

To determine useful metrics for assessing stream water quality in the Southeastern Coastal Plain, we examined differences among two buffered and three unbuffered streams in an agricultural landscape in southwestern Georgia. Potential indicators included amphibian diversity and abundance, aquatic macroinvertebrate populations, riparian vegetative structure, water quality, and stream physical parameters. Variability among sites and treatments (buffered vs. unbuffered) existed, with sites in the same treatment as most similar, and disturbances from a nearby eroding gully strongly affecting one unbuffered site. Of the invertebrate metrics examined, percentages of clingers, Ephemeroptera‐Plecoptera‐Trichoptera (EPT), Elmidae (Coleoptera), Crustacea (Decapoda and Amphipoda), and dipterans were found to be possible indicators of stream health for perennial streams within this region. Overall, buffered sites showed higher percentages of sensitive invertebrate groups and showed lower and more stable concentrations of nitrate N, suspended solids, and fecal coliforms (FCs). Percent canopy cover was similar among sites; however, riparian vegetative coverage and percent leaf litter were greatest at buffered sites. No differences in amphibian abundance, presence, and absence within the riparian area were apparent between sites; however, instream larval salamanders were more abundant at buffered streams. In this study, stream buffers appeared to decrease nutrient and sediment loads to adjacent streams, enhancing overall water quality. Selected benthic macroinvertebrate metrics and amphibian abundance also appeared sensitive to agricultural influences. Amphibians show potential as indicator candidates, however further information is needed on their responses and tolerances to disturbances from the microhabitat to landscape levels.

We used the imported red-fire ant (Solenopsis invicta; hereafter fire ant) and hispid cotton rat (Sigmodon hispidus) as model species to address the population-level effects of an invasive ant on a semiprecocial small mammal. We stocked cotton rats into 8 enclosures, implementing a 2-way factorial design with predator (ambient or excluded) and fire ant (ambient or reduced) treatments as factors. We trapped monthly from June 2012 to June 2013 and calculated monthly recruitment and survival. Rats in enclosures with ambient predators had a risk of mortality approximately 2 times greater than rats in enclosures with predators excluded. The risk of mortality was 3 and 4.5 times greater for female and male cotton rats, respectively, in enclosures with ambient fire ants and predators compared to enclosures with reduced fire ants and excluded predators. We found no effects on recruitment. Our results indicate that native predators had the greatest influence on cotton rat populations. Nevertheless, in the absence of other predators, the effects of fire ants on cotton rat survival are compensatory.