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Pituophis ruthveni (Louisiana Pinesnake) is one of the rarest snakes in the United States. Efforts to refine existing habitat models that help locate relictual populations and identify potential reintroduction sites are needed. To validate these models, more efficient methods of detection for this rare species must also be developed. Here we expand recent habitat suitability models based on edaphic factors to include mature Pinus (pine) stands that have not been cut for at least 30 years and likely have vegetation structure with the potential to support the species. Our model identified a total of 1652 patches comprising 180,050 ha of potentially suitable habitat, but only 16 (1%) of these patches were more than 1000 ha and considered worthy of conservation attention as potential reintroduction sites. We also visited potentially suitable habitat, as determined by our model, and used camera traps to survey for relictual populations at 7 areas in Texas. We observed 518 snakes of 18 species in 8,388,078 images taken from April to October 2016, but no Louisiana Pinesnakes were detected. The patchiness of the habitat model and failure to detect Louisiana Pinesnakes corroborate independent conclusions that most populations of the species are small, isolated, probably in decline, and possibly extirpated. In the context of this extreme rarity, we believe this study will help manage limited conservation resources by narrowing the search areas for relictual populations, providing a more cost-effective method of surveying those areas, and identifying the best sites for future reintroduction efforts.
Limnothlypis swainsonii (Swainson's Warbler) readily colonizes novel habitat formations that meet basic requirements for understory stem density and visual screening. Little is known about the warbler's behavioral response to naturalized populations of introduced plants. I surveyed the incidence of introduced invasive Ligustrum spp. (privet) and native Arundinaria spp. (cane) on breeding territories (n = 590) of Swainson's Warbler in the southeastern United States. Privet occurred frequently on territories in Mississippi (65.0%), Alabama (55.7%), Louisiana (52.8%), and Texas (39.5%). Territories with privet (49.6% of total) were observed in 90 counties and parishes. The survey revealed numerous instances of warbler territories located in near-monocultures of Ligustrum sinense (Chinese Privet). Territories with cane (33.1% of total) were observed in 72 counties and parishes. In a broader context, the survey data suggest that Swainson's Warbler populations have rapidly adapted to invasive privets, which are physiognomically similar to several native thicket-forming shrubs.
Faxonius neglectus neglectus (Ringed Crayfish) have been characterized as an “extraregional” invader whose range expansion has threatened native crayfish. We determined length–weight and body part–length relationships for Ringed Crayfish using reference specimens collected from their native range in the Ozark Highlands. Analysis of covariance and estimated marginal means demonstrated males are heavier and possess larger chelae than females of equal size. In addition, males' maximum values of total length, dry weight, and chela length/width were all larger than those of females. Sexual dimorphism in this species necessitated sex-specific length–weight regressions in addition to a combined model. Length–weight relationships were all significant (P < 0.001) with coefficients of determination (R2) ≥ 0.971. Both male and female Ringed Crayfish exhibited positive allometric growth (b > 3). Regression equations predicting Ringed Crayfish total length based on carapace length, abdomen length, chela length, and palm width were significant (P < 0.001) with R2 ≥ 0.925. Length–weight and body part–length equations will facilitate ecological studies of Ringed Crayfish and provide comparative data for studies investigating mechanisms of competitive interactions among sympatric crayfish species. These results contribute to the growing number of species-specific studies evaluating patterns of growth and sexual dimorphism in crayfish.
Documenting emergence of invasive species in new areas is vital to understanding spatiotemporal patterns of invasions, propagule pressure, and the risk of establishment. Salvator merianae (Argentine Black and White Tegu) has established multiple unconnected populations in southern and central Florida, and additional sightings have been reported elsewhere in the state. In 2018, land managers in Georgia received >20 reports of this species in the wild. To evaluate the probability of establishment, we assembled verified records of the non-native Argentine Black and White Tegu in Georgia over the past 9 years. We report on 47 tegu observations throughout Georgia, with a concentration of sightings (n = 38) in Toombs and Tattnall counties. In 2019, we used modified Havahart® traps and captured adult male and female tegus at 1 of our 3 locations during 3085 corrected trap nights. While we did not find evidence of a well-established population (i.e., varied size structure of tegus captured) with our limited trapping effort, we suspect Argentine Black and White Tegus are breeding in Toombs and Tattnall counties due to the concentration of captures and reports of adult males and females, the consistent reports of adults across years, the confirmed presence of the species in 2018, 2019, and 2020, and the reproductive capacity (i.e., turgid testes and secondary follicles) of individuals captured. Ongoing introductions of tegus from captivity are likely to maintain high propagule pressure in the southeastern United States. Effective early detection, funded rapid response networks, and public outreach to solicit reports of sightings of Argentine Black and White Tegus are critical to prevent establishment and associated ecological impacts of this invasive species elsewhere in the southeastern US.
Two species of purseweb spiders, Sphodros abboti (Blue Purseweb Spider) and S. rufipes (Red-legged Purseweb Spider), are known to occur in northern Florida and southern Georgia, and a third, S. atlanticus (Atlantic Purseweb Spider), has been recorded from northeastern Georgia. Their distributions have not been well defined, and records are sparse for S. rufipes and S. atlanticus. We conducted visual surveys for the distinctive tubular webs of these spiders in a variety of forest types. We report 141 new locality records for S. abboti, including 19 new county records in Florida and 5 in Georgia; 80 new locality records for S. rufipes, including 13 new county records in Florida, 34 in Georgia, and 1 in Alabama; and 3 new locality records for S. atlanticus, including 2 new county records for Georgia. We provide additional information on reproductive biology and habitat use.
Given the importance of crayfish in stream ecosystems, gaining insight into the role of stream permanence in maintaining predator–prey interactions is critical. Our objectives were to determine the influence of stream permanence and season on crayfish predation and assess the role of stream permanence and crayfish density on the presence of predators, while accounting for imperfect detection. We conducted surveys of crayfish density, mammalian scat, and environmental variables within 10 intermittent and 10 permanent streams in the Ozark Highlands. We used occupancy modeling to assess the relationship between predator presence, crayfish density, and environmental variables. Stream permanence did not play a role in determining relative frequency of occurrence or percent volume of crayfish prey in mammalian diets. However, percent volume and relative frequency of crayfish prey found in scats differed by season, with both highest in spring and summer. The relative frequency and percent volume of fish prey showed a significant interaction of season by stream permanence, which may be the first instance of this observation. Procyon lotor (Raccoon) had the highest detection probability (p = 0.39), whereas Neovison vison (American Mink; p = 0.15) and Lontra canadensis (River Otter; p = 0.03) had low detection probabilities. Further study into predator–prey interactions in the context of hydrology, particularly when related to imperiled groups like freshwater crayfishes, is needed since climate change is expected to alter hydrologic patterns.
Non-native Cyprinella venusta (Blacktail Shiner) are known to occur in Truman Reservoir in Missouri. In 2017, we documented hybridization between C. venusta and native C. lutrensis (Red Shiner) within the reservoir. The goal of this study was to quantify hybrid morphology relative to the 2 parent species. We examined meristic relationships among individuals based on 4 different counts including: lateral line scale number, anal fin ray number, below lateral line scale rows, and circumferential scale rows. We also gathered geometric morphometric data, based on 14 homologous landmarks, from both hybrid and parent individuals. We then used principal component analysis to describe and visualize body shape variability among individuals, and ran ANOVA using principal component scores to test for body shape differences among hybrid and parent species. Meristic data displayed greater similarity between hybrid and C. venusta individuals compared to that of hybrid and C. lutrensis individuals. Geometric morphometric analyses determined that hybrid individuals were between C. lutrensis and C. venusta in morphospace. Hybrid individual shape was significantly different from both parent species, and this distinction was mainly driven by an intermediate body depth in hybrids. These results compliment findings of previous genetic research that was conducted on C. lutrensis x C. venusta hybrids but lacked full morphological comparisons.
Deer–vehicle collisions (DVCs) are a critical cause of mortality for the endangered Odocoileus virginianus clavium (Florida Key Deer; hereafter Key Deer). Extensive research has focused on large-scale Key Deer movements throughout their range and the corresponding relationship to DVCs (e.g., dispersal of juvenile males south across US Highway 1 [US 1]). Far less data are available about the relationships among short-term movement patterns (hourly and daily) of Key Deer, US 1 traffic patterns, and DVCs. We used global positioning system collars to track female Key Deer movements on short time scales on Big Pine Key in the Lower Florida Keys. We then cross-referenced this with US 1 traffic data and DVCs. We found a significant relationship between hourly female Key Deer movement and hourly DVCs throughout the 24-hour daily period (r = 0.505, P = 0.012). Hourly US 1 traffic patterns were significantly related to hourly DVCs only during night periods (r = 0.787, P = 0.012). This information will inform Key Deer management options such as variable timing of vehicle speed enforcement and warning lights along roadways.
Environmental-flow standards are needed to maintain hydrologic regimes that can provide optimal physical habitat to support the outstanding freshwater biodiversity of rivers in the southeastern US. Here, we used the physical habitat simulation (PHABSIM) model to estimate habitat-based environmental flows for 5 river reaches across 4 physiographic provinces of Alabama, using data from published habitat suitability curves (HSCs). We found that physical habitat-flow relationships, although varying by target species and local reach characteristics, are related broadly to river size and channel geometry. For the study rivers, optimal habitat was maximized at low levels of flow on smaller rivers in the Appalachian Plateau and Piedmont regions, while suitable habitat continued increasing with increased discharge for larger rivers on the Coastal Plain.
Cryptobranchus alleganiensis alleganiensis (Eastern Hellbender) is a fully aquatic salamander of conservation concern across the southeastern US. Characterization of shelter guarding by males and interspecific behavior during the breeding season in wild populations within the Blue Ridge ecoregion of North Carolina is lacking. To this end, we characterized diurnal video sequences of natural shelter-rock and nest-guarding behavior by male Eastern Hellbenders. We documented several intraspecific behaviors between resident males and nonresident conspecifics (males and females) during the breeding season (late summer to early fall) of 2018–2019 using modified action cameras with 4–6 hour battery life deployed in the French Broad River Basin of western North Carolina. Breeding behavior was documented (gravid females entering shelter) in 5 shelters, with 4 nests later confirmed by researchers. Across 21 unique shelters, we documented several examples of aggressive behaviors by resident Eastern Hellbender males toward conspecifics, including defensive posturing, territorial behavior, fights, biting, and bite-holds. All males occupying shelters (residents) spent the majority of time actively guarding the shelter entrance (81.7% of video) followed by maintenance behavior (e.g., modifying the shelter entrance; 5.3% of video), and short bouts (mean = 3.2 minutes) away from the shelter rock (2.5% of video). This study provides the first quantitative report of male breeding-season behavior across multiple natural shelters using non-invasive, affordable, waterproof cameras in North Carolina. We report on the utility of this method for observing behavior in stream systems and its potential application for monitoring of nests and behavior in other diurnal aquatic species.
Sylvilagus palustris hefneri (Lower Keys Marsh Rabbit [LKMR]) is an endangered subspecies of marsh rabbit found only in the Lower Florida Keys. In September 2017, Hurricane Irma was measured as a Category 4 storm when it passed through the center of the LKMR range causing significant damage to human infrastructure and natural habitats. To assess the impact of Hurricane Irma to LKMR and its habitat, we compared pre- and post-hurricane monitoring data. Overall, 82% of LKMR habitat patches were abandoned, the average number of pellets per sampling plot decreased 94%, and average patch pellet density decreased by 84% following Hurricane Irma. Generally, pellets were found in plots with greater open cover, an intermediate amount of herbaceous and woody cover, and areas with more standing water post-Hurricane Irma. We also observed a slight decrease in signs of Procyon lotor (Raccoon) and Didelphis virginiana (Virginia Opossum). The decrease in rabbit pellets detected after Hurricane Irma is likely attributed to both direct mortality from the storm and flooding, as well as indirect mortality from the loss of critical, salt-sensitive herbaceous cover. Because climate-change models suggest increases in future flooding and hurricane frequency, we recommend that wildlife managers continue to closely monitor the recovery of LKMR populations and their habitat to determine if more active management actions (e.g., habitat remediation, translocations, or captive breeding) are necessary.
As scatterhoarders, Sciurus carolinensis (Eastern Gray Squirrel) usually rely on food they buried during fall to survive cold winter months. However, the range of this species includes areas of the southeastern United States where winter flooding commonly restricts access to buried food during the recovery season. In this study, we investigated the effects of winter flooding on the diet of Eastern Gray Squirrels in bottomland hardwood forests of west-central Alabama. We examined the diet of 42 Eastern Gray Squirrels through DNA analysis of stomach contents collected during fall (September–November) 2016 and winter (December–February) 2015–2016, 2016–2017, and 2018–2019. Eastern Gray Squirrels ate 21 different types of plants, with 6 principal foods (>1% of any squirrel's stomach contents) during fall and 12 principal foods during winter. Throughout both seasons, Juglandaceae (walnut) and Quercus spp. (oak) were the most important foods and together made up 94.1% of the fall diet and an average of 78.6% of the winter diet. In contrast to other studies, we found more varied diets during winter (12 primary foods eaten) than fall (6). Additionally, a majority of the plant types consumed during winter at our study area were not hard-mast plants, and many had not been previously recorded as part of the diet of the Eastern Gray Squirrel. Our results suggest Eastern Gray Squirrels cope with reduced availability of scatterhoarded food due to winter flooding by increasing the diversity of foods they eat to include more herbaceous plants.
Leucism (white skin, dark eyes) is a rare color disorder occurring in a range of invertebrates and vertebrates, and as a result, relatively few reports exist of leucistic individuals in the wild. In March 2014, we found 6 leucistic Alligator mississippiensis (American Alligator) hatchlings in coastal South Carolina. All individuals were basking under cool, cloudy conditions within ∼15 m of the den, appeared moderately emaciated, and were somewhat lethargic upon capture. The animals were removed from the field and treated for malnutrition under veterinary supervision. Three Alligators died within 6 days of collection, and the remaining 3 individuals were transferred to different institutions for long-term care and display. These animals also eventually died after surviving in captivity for ∼4.5–45 months. Leucistic Alligators are known to suffer from a variety of health problems, and the mortalities and associated causes of death in the animals we describe here were consistent with previous reports of other leucistic Alligators. The incidence of leucism among wild crocodilians is very low, and disease, increased susceptibility to predation, and collection by humans further exacerbate its rarity.
Due to its rarity, restricted range, and nocturnal habits, direct observations of the endangered Glaucomys sabrinus coloratus (Carolina Northern Flying Squirrel) are uncommon. Although a variety of predators have been documented for Glaucomys sabrinus (Northern Flying Squirrel) in the Pacific Northwest, published reports of predation events on the G.s. coloratus subspecies are lacking. Here we report on a predation incident of a Mustela frenata (Long-tailed Weasel) taking a Carolina Northern Flying Squirrel from an owl nest box.