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In many areas, small fossorial snakes are among the most abundant vertebrates present; yet, the ecology of these species remains poorly understood. Between 1999 and 2002 we collected 210 small fossorial snakes representing five species in a small area of northern Mecklenburg and southern Iredell Counties, North Carolina. The eastern worm snake (Carphophis amoenus; n = 116) was the most frequently captured species in this region, with fewer numbers of ringneck snakes (Diadophis punctatus; n = 44), brown snakes (Storeria dekayi; n = 24), redbellied snakes (S. occipitomaculata; n = 20), and smooth earth snakes (Virginia valeriae; n = 6). The three most abundant species exhibited significant sexual dimorphism, with females being larger and having shorter relative tail lengths than males. Carphophis amoenus were more abundant in dry upland forest than D. punctatus, which were most prevalent in moist, lowland forest. Snake activity was weakly correlated with environmental conditions. A peak in activity of male C. amoenus, D. punctatus, and S. occipitomaculata during September suggests fall breeding seasons for these species.
The relationship between predator and prey is dependent on resource availability, the predators' hunting strategy, the prey's suite of antipredatory mechanisms, and the complexity of the habitat. We conducted a laboratory experiment to evaluate background preferences by tadpoles of Bufo woodhousii Girard and the predaceous water bug Belostoma lutarium Stål (Hemiptera: Belostomatidae). Our results indicate that 1) tadpoles switched preference away from black backgrounds when a chemical signal from B. lutarium was introduced, 2) earlier stage tadpoles exhibited a stronger effect than later stage tadpoles in the presence of the predator's chemical signal, 3) hemipterans were observed randomly on both backgrounds but were mostly found associated with vegetative cover, and 4) B. lutarium killed significantly more tadpoles on dark backgrounds compared to light backgrounds.
Nolina brittoniana is endemic to the central ridges of peninsular Florida. Its scrub and sandhill habitats have suffered extensive anthropogenic modification. Analysis of isozymes from populations throughout its range revealed less genetic variation than generally reported for endemic plants. Populations were well differentiated, with significant clines in allele frequency along the north-south axis of distribution. Pair-wise F-statistics calculated at four levels of population geographic substructure revealed that current and inferred historical habitat patches had similar genetic structure. We found no evidence of recent bottlenecks or changes in genetic structure due to habitat loss and fragmentation, consistent with populations having always been small, isolated and low density. Our data support preservation of populations from throughout the species' range to meet conservation objectives.
Conservation planning is only as good as the science on which it relies. This paper evaluates the science underlying the least-cost-path model, developed by Meegan and Maehr (2002), for the Florida panther, Puma concolor coryi. It also assesses the resulting claim that private lands in central Florida are desirable for panther colonization (Maehr et al. 2002a, p. 187; Maehr 2001, pp. 3–4; Maehr and Deason 2002, p. 400). The paper argues that panther conservation planning, as proposed by Maehr, is flawed because of its (1) poor analysis of panther-habitat requirements, owing largely to use of only daytime telemetry, a black-box model, and failure to take account of spatial and temporal uncertainties; (2) use of stipulative and misleading definitions of key biological terms, such as “forest obligate” and panther “dispersal”; (3) employment of question-begging value judgments to rank habitat; (4) weak testing of the model; (5) inconsistency in evaluation of forest habitat; (6) inconsistency in evaluation of agricultural lands; and (7) inconsistency in assessing effects of highways on panther habitat.
The endangered Florida panther (Puma concolor coryi) shares its shrinking habitat with agriculture, surface mining, and rapid urban growth. Although panthers have extensive home ranges and use diverse land covers, methods that dominate panther habitat evaluation for Endangered Species Act (ESA) consultations and regional land use planning consider only forested day-use elements within the landscape mosaic. Maehr and Deason (2002) present a Panther Habitat Evaluation Model (PHEM) that, in addition to excluding nonforested habitat, reduces the assessed value of forest patches based on criteria for patch size, forest type, proximity to a “core” area, and connectivity to other patches. An examination of the foundations of PHEM is therefore warranted. Building on earlier work that included an evaluation of panther habitat selection studies (Comiskey et al. 2002), we examine PHEM in light of data quality criteria and the panther's known life history requirements. We conclude that the precepts and rules of the PHEM methodology are based on unwarranted assumptions, nonstandard methods of analysis, and exclusion of relevant data, leading to an undue emphasis on day-use land cover and forest patches larger than 500 ha. Large areas of southern Florida that have abundant prey and are intensively used by panthers would score low in PHEM habitat assessments because they lack large forest patches. We discuss the conservation implications of applying a methodology that discounts substantial portions of occupied panther habitat as unsuitable, and describe an alternative approach to habitat definition and evaluation that is both consistent with panther habitat requirements and applicable to conservation decision-making. Conserving sufficient habitat for recovery of the panther extends an umbrella of protection to the many species that dwell within its range.
We examined the relationship between habitat availability and nest site selection by southern two-lined salamanders (Eurycea cirrigera) during Spring 2002. We added natural slate tiles to two second-order streams in the Georgia Piedmont and surveyed the streams during the nesting season (April). Seventeen nests were found in Boscoe Creek and 20 in Lee Creek. Nesting females ranged from 34–42 mm snout-vent-length (mass: 0.8–1.3 g), and clutch size varied from 10 to 72. Salamanders only nested under tiles in Boscoe Creek (n = 7), which suggests that nest cover-objects may have been limited. Principal component analysis demonstrated that salamander nests were over-represented in shallow areas with gravel/cobble substrata and under-represented in deep areas with silt substratum. We did not detect significant correlations between female size (either SVL or mass) and clutch size, developmental stage of eggs/larvae, nest cover-object volume or surface area, or nest cover-object depth. Future actions (e.g., development, road construction) that increase sedimentation in Piedmont streams may reduce the availability of suitable nesting habitat for these salamanders.
Allelic variation at hypervariable, nuclear-encoded loci and mitochondrial (mt)DNA was studied among three geographic samples (40 individuals) of the critically endangered Cape Fear shiner, Notropis mekistocholas. Genetic variation, as measured by allelic richness and gene (microsatellite) or nucleon (mtDNA) diversity, was similar to that in other fish species. Homogeneity tests of allele and genotype distributions and analysis of molecular variance (amova) at nuclear-encoded loci revealed significant genetic heterogeneity among localities. No differences in mtDNA allele (haplotype) frequencies were detected. The ratio of the number of microsatellite alleles to the range in allele size suggested that significant reductions in effective size have occurred at two of the three localities. Long-term (inbreeding) effective population size differed among the samples and ranged from ∼1,300 to ∼3,000. Collectively, these results indicate that (i) Cape Fear shiners at these localities are not genetically impoverished, (ii) separate populations of Cape Fear shiners may exist in the Cape Fear drainage, (iii) recent reduction in effective size may have occurred in two of the three localities, and (iv) ancestral populations of Cape Fear shiners may have been of sufficient effective size to offset extinction due to genetic factors.
We conducted surveys of concrete bridges in southern Mississippi from 2000–2002 to determine the phenological pattern of use by Rafinesque's big-eared bat, Corynorhinus rafinesquii. The earliest dates on which we located maternity colonies were 9 March 2000, 20 April 2001, and 15 May 2002. Maternity colonies increased in size and abundance as spring progressed. Pups were born in mid- to late May (first observed 12 May 2000, 15 May 2001, 27 May 2002) and nursed through midsummer (lactating females last captured 14 July 2000, 25 July 2001, 16 July 2002). Colony size and percentage of bridges occupied by bats declined in late summer. Colonies were absent during fall and winter, although we occasionally found solitary individuals during these seasons. Number of bats present under an occupied bridge ranged from 1 to 25. The mean number of individuals per occupied bridge was 4.6 (SD = 5.8) in 2000, 3.9 (SD = 5.0) in 2001, and 3.0 (SD = 4.4) in 2002. The mean number of adult females per maternity colony was 5.6 (SD = 3.1). Although we found males throughout the study period, females were largely absent from bridges outside of the maternity season, suggesting that much of the population used alternate roosts during this time.
We compared the efficacy and biases of pitfall trapping and Winkler extraction of sifted leaf litter for sampling the diversity of ground-dwelling ants in native oak-hickory hardwood forest and cultivated pine stands on the Cumberland Plateau in southern Tennessee. Samples yielded 2,635 individuals from 23 species, 17 genera, and 4 subfamilies. According to estimates of expected species richness, our sampling effort inventoried at least 82% of the ant fauna likely to be captured by these methods at a given site. Litter sifting yielded more individuals, more species and more occurrences of most species than did pitfall traps, but neither method captured all species. Most myrmicine and all ponerine species showed a significant bias toward capture by litter sifting, whereas pitfall traps tended to be more effective at capturing large-bodied Camponotus ants and species that forage outside of prime daylight hours, when litter samples were collected. Large pitfalls (75 mm diameter) caught more species and more individuals than small pitfalls (25 mm diameter). The preliminary survey indicated that a change from native hardwood to cultivated pine reduced species richness and altered the assemblage of ant species present, but did not alter community diversity or abundance of ants. Larger scale surveys involving commercial pine plantations are needed for more accurate assessments of how this type of land use change affects local ant diversity and ecosystem functioning.
A Black-crowned Night-Heron (Nycticorax nycticorax) was observed bill-vibrating, a foraging behavior in which the heron submerged its bill tip in the water and rapidly opened and closed its mandibles creating a disturbance of the water surface. This fish-luring behavior has previously been reported once for a Black-crowned Night-Heron, and for several other heron species. This behavior may be used when algal growth or other water obscuring agents interferes with a heron's vision making visual foraging techniques problematic, and may have enhanced effectiveness because the algae make the predator less likely to be seen.
The defensive behavior of snakes towards humans has been well documented. Ironically, many of these early studies focused on harmless colubrid species. Knowledge of venomous snake defensive behavior is limited, and further research is necessary to understand how pitvipers react to human confrontations. I performed laboratory tests daily over a period of five days to investigate whether cottonmouths would habituate to handling. Eleven days after the last habituation test, snakes were tested again to see if cottonmouths show a recovery response. Cottonmouths exhibited a significant change in defensive behavior between Day 1 and Day 5 of the experiment. However, they did not significantly revert to their original behavior 11 days later.
Sediment quality was assessed at multiple sites in the lower Oconee River, GA to identify contaminants potentially affecting the survival of an endemic “At-Risk” species of fish, the robust redhorse (Moxostoma robustum). Five major tributaries that drain urban and agricultural watersheds enter this stretch of river and several carry permitted municipal and industrial effluents containing Cd, Cu, and Zn. Sediments for chemical analyses and toxicity tests with Hyalella azteca (Amphipoda) were collected at 12 locations that included sites above and below the major tributaries. Compared to national data bases and to the nearby Apalachicola-Chattahoochee-Flint watershed, sediments from the Oconee River had elevated concentrations of Cr, Cu, Hg and Zn. Zinc concentrations showed a marked increase in sediment downstream of the confluence of Buffalo Creek demonstrating contributions from permitted municipal and industrial effluents discharged to that tributary. When exposed to these sediments, growth of H. azteca was significantly reduced. Amphipod growth was also reduced when exposed to sediments collected from another site due to toxicity from Cr. Sediments in the lower Oconee River appear to be impaired due to metal contamination and could pose a threat to organisms, such as the robust redhorse, that are closely associated with this matrix during their life cycle.
Along the southeastern coast of the United States, hardground systems support a high diversity of sub-tropical and tropical fishes. Many of these hardgrounds occur in deep (ca. ≥ 50 m) waters and their fauna is still poorly described; however, with concentrated sampling in these deeper areas, new records of fishes continue to emerge. In the northeastern Gulf of Mexico and off North Carolina, we used the Johnson-Sea-Link submersible, remotely operated vehicles, trawling gear, and angling gear to sample deep reef systems (38–248 m). We document five records of fishes new to continental United States waters, including Liopropoma aberrans, Parasphyraenops incisus, Lipogramma regia, Apogon gouldi, and Prognathodes guyanensis. We also report range extensions for eleven species: Gymnothorax hubbsi, Gymnothorax vicinus, Lepophidium staurophor, Cypselurus comatus, Liopropoma mowbrayi, Serranus annularis, Rypticus saponaceus, Caranx lugubris, Prognathodes aculeatus, Centropyge argi, and Canthigaster jamestyleri.
Marsh managers along the Gulf Coast Chenier Plain frequently use winter burns to alter marsh vegetation and improve habitat quality for wintering waterfowl. However, effects of these burns on marsh avifauna are not well documented. We recorded abundances of breeding bird species and vegetation structure in burned and unburned control marshes during one breeding season before (1996) and two breeding seasons after (1997, 1998) experimental winter burns. We used non-metric multidimensional scaling analysis to assess the extent and direction of changes in bird community compositions of burned and unburned control marshes and to investigate the influence of vegetation structure on bird community composition. Overall, we found that Seaside Sparrows (Emberizidae: Ammodramus maritimus [Wilson]) and Red-winged Blackbirds and Boat-tailed Grackles (Icteridae: Agelaius phoeniceus [L.] and Quiscalus major Vieillot, respectively) comprised > 85% of observed birds. In burned marshes during the first breeding season following experimental burns (1997), icterid abundance increased while Seaside Sparrow abundance decreased relative to pre-burn (1996) conditions. This pattern was reversed during the second breeding season post-burn. No obvious patterns of change in avian abundance were detected in unburned control marshes over the 3-year period. Qualitative changes in breeding bird community composition were related to effects of winter burning on percent cover of dead vegetation and Spartina patens (Aiton) Muhl.