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From 1992 to 2003, we captured and permanently marked 829 Dasypus novemcinctus (nine-banded armadillo) at the Tall Timbers Research Station in northern Florida. From 2004 to 2006, an attempt was made to eliminate all armadillos from Tall Timbers as part of an experiment to remove nest predators of Colinus virginianus (Northern Bobwhite). Data from armadillos killed at Tall Timbers during this period showed a rapid decline in previously marked individuals, with only 4 collected in 2006. Even though the resident population thus seemed to have been exterminated quickly, total numbers of armadillos collected remained stable over all 3 years. This did not appear to be due to an increase in reproductive success such that more juveniles were produced to replace the animals being lost. Rather, the data were more consistent with the hypothesis of immigration by adults into the population to colonize areas vacated by culled animals. This scenario supports previous reports of large numbers of transient armadillos that move extensively, and may provide insight into how armadillos have successfully invaded most of the southern United States in just the last 200 years. Finally, these findings also suggest that, at least in this area, culling animals is not likely to be an effective means of eliminating armadillo predation on quail eggs.
Daytime refuges are important to nocturnal rodents for protection from predators and environmental extremes. Because refuges of forest-dwelling rodents are often associated with woody debris, we examined refuge use by 37 radio-collared Peromyscus gossypinus (cotton mice) in experimental plots with different levels of woody debris. Treatment plots had six times (≈ 60 m3/ha) the volume of woody debris as control plots (≈ 10 m3/ha). Of 247 refuges, 159 were in rotting stumps (64%), 32 were in root boles (13%), 19 were in brush piles (8%), and 16 were in logs (6%); 10 refuges could not be identified. Stumps were the most common refuge type in both treatments, but the distribution of refuge types was significantly different between treatment and control plots. Root boles and brush piles were used more on treatment plots than on control plots, and logs were used more on control plots than on treatment plots. Refuge type and vegetation cover were the best predictors of refuge use by cotton mice; root bole refuges and refuges with less vegetation cover received greater-than-expected use by mice. Abundant refuges, particularly root boles, may improve habitat quality for cotton mice in southeastern pine forests.
We report the first interspecific double captures (n = 14) of Peromyscus leucopus (white-footed mouse) and Ochrotomys nuttalli (golden mouse). Intraspecific double captures of white-footed mice (57.0% of all double captures) were heterosexual (likely mating pairs). Overall, 62.0% of the double captures for both species were heterosexual, suggesting that there appears to exist a strong conspecific, heterosexual odor preference. The large number of intra- and interspecific double captures (n = 103) also suggests minimal interference or exploitation competition between these two small mammal species of similar body mass and life histories.
Principal component analysis, correlation, and multiple regression were used to evaluate the relationships of 12 environmental variables to the recorded values of density and biomass of Corbicula fluminea (Asian clam) collected in a 13-km segment of the lower Roanoke River delta, NC, in 1992–1993. Sediment fractions, pH, conductivity, and oxygen saturation accounted for the most variance in density, and, with the addition of shell length, water temperature, and river kilometer, accounted for the most variance in biomass. Similar variables were important in principal component analysis and multiple regression, although regression was less useful due to lower tissue weights of clams at two stations, which resulted in low predictive power for some regressions. The results of this preliminary census indicate that there were relationships among Asian clam density and biomass and various environmental factors. Higher density and biomass were found where the substrate was > 40% fine sand, < 45% silt, and < 8% organic content. This habitat type was limited in the study area and resulted in the majority of Asian clams living in a 4-km segment. Seasonal extremes in water temperature, low pH and calcium concentration, and phytoplankton limitations may also have contributed to the low weight of Asian clams in the Roanoke River. A more extensive sampling effort is warranted to further define the role of environmental stressors in the Asian clam population.
Chelydra serpentina (Common Snapping Turtle) is a wide-ranging and often abundant turtle species in the eastern United States, but relatively little is known of its basic ecology in the Southeast. The objective of our study was to examine the ecology and population biology of and describe the morphology of Common Snapping Turtles in northwestern Florida. We intensively sampled five localities in Leon County, FL using traps and hand collection (n = 111), and we also opportunistically collected Common Snapping Turtles as we encountered them through the course of other studies (n = 11). Analysis of seven morphological characters from a subset of individuals indicated that the Common Snapping Turtle in this study is an intergrade between C. s. serpentina and C. s. osceola. Estimated early growth rates were 20 mm carapace length (CL)/year, and females matured at about 220 mm CL (156 mm PL, approximately 6–8 years). Male Common Snapping Turtles (CL mean = 299 ± 6 mm) were larger than females (CL mean = 270 ± 5 mm), and the overall adult sex ratio was 1:1. Diet consisted primarily of aquatic plants (n = 4). Nesting females were found from early April through mid-May, and clutch size ranged from 5 to 49 eggs (n = 3). Common Snapping Turtle abundance varied over the five sites, but was highest (an average density of 16 individuals/ha) in small suburban ponds with abundant aquatic vegetation, a thick layer of organic sediment, and no alligators. In northwestern Florida, predation by alligators and humans and primary productivity appear to be the factors that influence the distribution and abundance of Common Snapping Turtles.
An increasing number of exotic terrestrial planarian species have established populations worldwide. In North America, the most prominent invasive flatworms are three members of the broadhead planarian genus Bipalium. Herein we report observations on the morphology, predatory behavior, and reproduction of Bipalium cf. vagum, new to this continent and report its occurrence in Florida and Texas. Individuals of this species have a distinctive combination of head shape and pattern of dark dorsal pigmentation (large head spots, complete collar, and prominent median stripe) that distinguishes them from other members of the genus. Although the other North American species of Bipalium feed on earthworms, B. cf. vagum feeds exclusively on terrestrial mollusks. Their predatory behavior includes following mucus trails and subduing the prey by capping the prey's head with the flatworm's anterior end and wrapping the prey's foot in the body of the planarian. Members of this species reproduce via egg capsules that contain small numbers of offspring. Because this is the first land planarian reported in North America that is a predator of mollusks, native land snails and slugs are unlikely to have effective defenses against it. Therefore, we should continue to monitor its geographic spread and potential ecological impact.
We describe age structure, growth, and fecundity of Hiodon tergisus (Mooneye) from the lower Tallapoosa River, AL. Mooneye (N = 49, 214–316 mm total length, 79–284 g) were aged using otoliths, and a von Bertalanffy growth model was derived for the species (L∞ = 316, K = 0.285, to = −0.7). Growth rates of Mooneye differed between the Tallapoosa River population and a previously studied population from the northern extent of the species' range (Assiniboine River, MB, Canada). In addition, fecundity of Mooneye from the Tallapoosa River was similar to the northern population, ranging from 5321 to 7432 eggs per female. Because the species is declining throughout its range in Alabama, we recommend that managers use our findings in conservation efforts. Future studies should investigate how hydrology influences the spawning success and early growth and development of Mooneye in regulated systems. More information about this species is needed regarding their early life history, including early growth, survival, and habitat use.
Shallow-water, lithophilic spawning fishes are among the most vulnerable to anthropogenic fluctuations in water levels. We monitored water levels and environmental conditions at the nest sites of Moxostoma robustum (Robust Red-horse) on a main-channel gravel bar in the Savannah River, GA–SC. During the course of the 2005 spawning season, over 50% of the observed nest sites were either completely dewatered or left in near zero-flow conditions for several days. This occurred on two separate occasions, once early during the spawning season and then again near its conclusion. We hypothesize the habitat preferences of spawning Robust Redhorse leave them vulnerable to water-level fluctuations, and this phenomenon may be widespread in regulated river systems.
Life-history aspects of Hypentelium etowanum (Alabama Hog Sucker) were investigated from 12 monthly collections in Shoal and Moore creeks (Etowah River Drainage) in Cherokee County, GA. Specimens were collected primarily from riffles, runs, and flowing pools, and examined for age, growth, food habits, and reproductive cycle. Chironomidae composed the bulk of the diet, with consumption lowest in winter and peaking in spring. Spawning appeared to occur in spring with 493–2717 ripe eggs ranging from 1.5 to 2.8 mm in diameter present in specimens collected in March, April, and May. Sexual maturity appeared to occur by 3 years of age, with a maximum lifespan of greater than 4 years. The largest specimen collected was a female 190 mm standard length and 132 g total weight.
Field collections, and laboratory observations and experiments, were conducted in Tift County, GA, to determine possible interactions among the three most abundant species of nocturnal scarab dung beetles. Light-trap data indicated that Copris minutus occurred primarily in the winter and spring, Ateuchus histeroides in the spring and summer, and Onthophagus gazella in the summer and fall. One of the species, O. gazella, is a foreign introduction, and comparative laboratory food procurement experiments revealed the superior ability of this species to obtain and remove dung from the soil surface. A confrontation experiment also demonstrated the behavioral dominance of O. gazella. A food-choice experiment indicated a more restricted diet for O. gazella than for the other two species. Implications for the future prospects of the two native species are discussed.
I studied interactions between the herbaceous weed Solanum carolinense (horsenettle) and its herbivore community in northern Virginia from 1996–2002. Thirty-two species regularly fed on the plant, including 31 insects from 6 taxonomic orders and Microtus pennsylvanicus (meadow vole). An intensive field experiment on 960 horsenettle individuals in 2001 revealed high levels of damage to all parts of the plants. Two chrysomelid beetles—Epitrix fuscula (eggplant flea beetle) and Leptinotarsa juncta (false potato beetle)—damaged leaves on nearly every plant. Roughly half of the flowers were destroyed by herbivores, with Anthonomus nigrinus (potato bud weevil) destroying 30%. Nearly three-fourths of the fruits were damaged by three species: the tephritid fly Zonosemata electa (pepper maggot), false potato beetle, and meadow vole. The weevil Trichobaris trinotata (potato stalk borer) bored in stems of 73% of the plants, and the most damaging root feeder was the moth Synanthedon rileyana (Riley's clearwing). A literature review on the horsenettle-herbivore community is integrated with new observations as a guide for applied and basic research on this economically significant species.
We investigated biotic and abiotic mechanisms that affect Quercus falcata (southern red oak) establishment from seeds in southeastern Pinus paulustris (longleaf pine) forests along a time-since-fire chronosequence (unburned since 1950, the mid-1990s, or winter 2001) and slope gradient. To determine if seed availability limits southern red oak recruitment, we measured seed production, populations of small mammals, and seed removal across sites. To determine if seedling survival limits establishment, we outplanted greenhouse-raised southern red oak seedlings and followed their survival throughout one growing season. We also measured abiotic conditions such as canopy openness, soil moisture, and soil temperature, and censused longleaf pine recruitment. Contrary to expectations based on species' fire-tolerances, longleaf pine recruitment was consistent over the chronosequence, but there was little oak seedling establishment in the long-unburned sites. Sites last burned in the mid-1990s had the lowest oak seed rain, highest small-mammal populations, and highest seed -removal rates; yet, they had the highest oak seedling establishment. Seedling survival was highest in the pre-1950 sites, and was most influenced by intermediate light levels and high soil moisture. We conclude that biotic factors, specifically, seed removal by small mammals, are less important to seedling recruitment than abiotic factors in these forests. Further, the assumption that longleaf pine forests will eventually undergo to succession to hardwoods in the absence of fire is complicated by abiotic conditions associated with landscape position.
Invasive plant species can have substantial negative impacts on native flora and fauna. We investigated the effects of the invasive shrub Ligustrum sinense (Chinese privet) on the abundance and diversity of songbirds in a southeastern forest during summer, fall, and winter. We sampled 15-m × 15-m plots assigned to one of three privet density categories (low, n = 5; medium, n = 4; high, n = 5). In addition, we sampled all flora in each plot. Bird abundance and species richness varied only during the winter, both increasing in high privet density. In general, the behaviors and types of birds did not differ among privet-density categories. In contrast, abundance and richness of native plants were reduced in high privet-density plots. Our results suggest that removal of privet would improve native plant communities, while having no substantial impact on songbird populations.
In 2000, an adult pair of non-migratory Grus americana (Whooping Crane) left Florida and settled in Michigan for the summer. On 21 November, the pair left Michigan and was radio-tracked south to the north shore of Lake Erie. The next day, only the female was detected. She was tracked to Kissimmee Prairie, FL, her release site as a subadult. This female flew from Michigan to Florida in 11 days, only stopping for 2 of those days. Her movement and flight behavior approximated natural Whooping Crane migration behavior. That this adult female could return to her release area and physiologically prepare for a long flight suggests migration is both learned and innate. Our conclusions help refine reintroduction techniques possible for migratory cranes.
On April 28, 2001, we found an unidentified egg in an artificial nest in Highlands County, FL. The artificial nests used in this study contained one Coturnix japonica (quail) egg and one tethered clay sham egg. The unidentified egg was added to the nest between days 12 and 18 of exposure. The quail egg was unmarked, but the sham was covered in small beak markings suggesting that a bird had manipulated it. Molothrus ater (Brown-headed Cowbirds) and M. bonariensis (Shiny Cowbirds) occur in the area, but Brown-headeds are far more common; however, we never observed either species near this particular artificial nest. An mtDNA sequence (300 base pairs of cytochrome b) amplified from this egg was compared to DNA sequences from GenBank, and we found a nearly perfect sequence match with the Brown-headed Cowbird. Parasitism by these birds in unattended and artificial nests is unusual, especially when host activity is not mimicked by researchers. This is the first record of Brown-headed Cowbird parasitism in Highlands County.