Browsing by Author "Ken Pollock, Committee Member"

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Factors affecting nesting success of American Oystercatchers (Haematopus pallitus) in North Carolina.
(2004-04-08) McGowan, Conor Patrick; Jaime Collazo, Committee Member; Ken Pollock, Committee Member; Theodore R. Simons, Committee Chair
American Oystercatchers are listed as a 'Species of High Concern' by the U. S. Shorebird Conservation Plan, in part because of threats during the breeding season. Oystercatchers nest on the sandy beaches of the East Coast of the United States and their nesting habitat is under increasing threat from human development and human disturbance. In this study, I analyzed 8 seasons of reproductive success data for American Oystercatchers in North Carolina. I identified the primary causes of nest failure and I examined spatial and temporal patterns of hatching success. Hatching and fledging success were very low, but highly variable among years and locations. Mammalian predation accounted for 29% of nest failures, and mammalian predator control would likely increase reproductive success of American Oystercatchers. I looked closely at the relationship between human disturbance and hatching success. Previous studies at Cape Lookout National Seashore showed that there were negative temporal and spatial associations between human disturbance and oystercatcher nesting success. I measured human disturbance three different ways; daily nest checks, beach surveys of human presence, and video monitoring at oystercatcher nests. I used logistic regression and 2x2 contingency table analyses to test for associations between higher levels of human disturbance and lower hatching success. Contingency table analyses of the daily nest check method showed that higher levels of human disturbance were associated with lower hatching success. There were no associations between human disturbance and nesting success for the other two measures of disturbance, but the analyses were constrained by small sample sizes and lack of information on the distances to sources of disturbance. I also tested the hypothesis that parental incubation behavior was a mechanism through which human disturbance lowered hatching success. I used video monitoring to record the behavior of American Oystercatchers during incubation. I calculated the rate of trips to and from the nest, and rate of movements while incubating, and the percent of time spent incubating. I assigned a cause for each trip away from a nest. Twenty-four percent of trips were associated with ATVs, 17% with trucks, 3% with pedestrians, 8% with territorial fighting, and 18% with exchanging incubation duties. I used linear regression to test for correlations between human disturbance and incubation behaviors. I also used logistic regression and 2x2 contingency table analyses to test for associations between varying levels of human disturbance and hatching success. Human disturbance, especially ATV traffic, was associated with more trips to and from nests and less time spent incubating. More frequent trips to and from the nests were associated with lower hatching success. It is probable that human disturbance reduces oystercatcher hatching success by increasing the activity of incubating adults.
Impact of Bridges and Culverts on Stream Fish Movement and Community Structure
(2006-04-27) Vander Pluym, Jennifer L.; Jim Gilliam, Committee Member; David Eggleston, Committee Chair; Jay Levine, Committee Member; Ken Pollock, Committee Member; David Genereux, Committee Member
This study was part of a larger, more comprehensive project assessing the effects of culvert designs on freshwater mussel habitat. Because many freshwater mussels depend on an obligate relationship with certain fish hosts to complete their life cycle as well as sole mechanism for dispersal, it is critical to identify obstacles to fish movement that, in turn, could negatively impact dispersal success of mussels. The primary goal of our study was to quantify the impact of four commonly used road crossings (bridge, arch culvert, box culvert, and pipe culvert) on stream fish abundance and diversity, as well as movement. We conducted a mark-recapture study in 16 streams located in the Piedmont region of the Cape Fear River Basin of North Carolina during the summer of 2004. Following electrofishing surveys, all fish were identified to species and measured to the nearest millimeter. Fish ≤ 30 mm total length (TL) were individually marked elastomer paint. These procedures were repeated four, eight, and 12 weeks after the initial sampling period. With the exception of species richness, all response variables: estimates of population size, species diversity, fish index of biotic integrity (FIBI), and Conditional Percent Movement (CPM) did not vary significantly with crossing type, position (upstream and downstream), or month. Downstream reaches of box culverts contained significantly higher species richness of stream fish than other crossing types. High diversity of stream fish downstream of box culverts may have been due to a scouring effect common below box and pipe culverts which results in pool formation and a possible change from benthic to pool fish species on a local level. The general lack of stream fish abundance and diversity responses to road crossings may be due to: the insensitivity of stream fish community variables (FIBI and diversity index) to anthropogenic effects, the overall resilience of fish communities, or the shifting baseline theory--fish communities having shifted to an impacted community prior to sampling. There were extremely low numbers of individuals that moved between stream reaches in the first study, therefore we conducted a second mark-recapture study using Passive Integrated Transponder (PIT) tags with remote antenna arrays on six streams, three streams with bridges and three streams with box culverts, during the summer of 2005. We surveyed each stream using electrofishing and marked all fish measuring ≥ 60 mm TL with an ISO PIT tag. Custom built antenna arrays, with weir nets to direct fish passage through the antenna loop, were installed in each stream either upstream or downstream of a given crossing and detected tagged fish continuously for 30 days. Estimates of mean percent movement of fish through box culverts (28.27% ± 12.24% SE) was almost half that of bridges (44.35% ± 8.77% SE); however, the percent tagged fish detected by the antenna for bridges and culverts showed no significant difference between the two crossing types. These results suggest that a larger study might detect a significant difference in fish movement through culverts as opposed to bridges. This application of PIT tags and remote antenna arrays proved a more effective and efficient use of research funding to assess stream fish movement through culverts and we recommend the antenna systems for further non-game fish research.
Inventory and Assessment of the Reptile and Amphibian Community of Bull Neck Swamp, Washington County, North Carolina.
(2008-02-13) Hutchens, Stan Jonathan; Chris DePerno, Committee Chair; Richard Lancia, Committee Member; Ken Pollock, Committee Member
Recent declines in reptile and amphibian populations across the globe have encouraged an increased desire to discover, document, and monitor these taxa. Arguably, the greatest cause is land-use change. Management interests for Bull Neck Swamp (BNS) encouraged research to inventory the reptile and amphibian community and to document possible impacts of land-use practices, such as silviculture and site preparation. Four habitat preserves were delineated based on plant community, leaving 1, 554ha (3, 841ac) available for management. Comparisons between habitat assemblages were used to determine if preserves were occupied by more vulnerable species and land-use effects on these species. However, variations in behavioral or environmental variables, and detection probabilities between capture techniques could provide misleading data for assemblage comparisons of community parameters. Therefore, 11 different capture techniques were employed to obtain better samples of habitat assemblages. To determine the accuracy of sampling techniques at inventorying species, techniques were categorized into primary (i.e., drift fence arrays with pitfall and funnel traps, visual encounter surveys, and coverboard arrays), secondary (i.e., road searches, polyvinyl chloride (PVC) piping grids, auditory surveys, and line transects), and tertiary (opportunistic encounters, aquatic funnel traps, crayfish traps, and basking traps) methodologies. All techniques had variable distributions and were evenly represented in all five areas when possible. All captured individuals were marked; snakes were double-marked with visible implant fluorescent elastomer to augment a concomitant laboratory experiment. Initial capture data were used to derive estimates of species richness (S) and modified Chao — Jaccard similarity indices (JSI). During May to August, 2005 and 2006, 1, 581 total captures represented 33 species, giving an estimated species richness of 34. Primary techniques sampled an estimated species richness of 14 and two unique species, species detected by only one sampling technique. Estimated species richness for secondary and tertiary techniques was 29 and 25, with three and seven unique species, respectively. If primary techniques alone were used, 59% of the reptile and amphibian community, including 10 unique species, would have been missed. Observed and estimated species richness for habitats ranged from 7 to 32 and 13 to 44, respectively. Chao — Jaccard similarity indices ranged from 0.59 to 1.0, with nine comparisons over 0.75, which indicated high similarity between habitat assemblages. These results suggested that land-use practices should be carefully planned and implemented to reduce effects to the reptile and amphibian community of BNS. Empirical results supported the use of elastomers for snakes. It is recommended that future inventory studies for all taxa employ as many capture techniques as logistically and spatially possible to derive accurate species richness. Also, assemblage comparisons should rely on species composition when determining conservation plans.
Selected Demography and Population Estimation of Trachemys scripta (Yellow-bellied Slider) in North Carolina as it Relates to Turtle Harvesting.
(2006-05-16) Miller, Veronica A.; Harold Heatwole, Committee Chair; Ken Pollock, Committee Member; Phil Doerr, Committee Member; Jamie Collazo, Committee Member; Alvin Braswell, Committee Member
In the year 2000, a reported 460 turtles were removed from North Carolina for commercial use. In 2002, the reported take of turtles soared to a staggering 23,311 turtles. A continuation of this trend could severely deplete the turtle populations of North Carolina in a short time. Therefore a moratorium on commercial turtle harvesting was instituted by the North Carolina General Assembly on July 1, 2003, effective until the NC Wildlife Resources Commission could determine rules and regulations for harvesting. It is crucial to know the level of harvest that populations can sustain, and, if a population is harvestable, which age groups are most sensitive to harvest. Regulations on reporting and validation of numbers, identifications, sizes, and sex of turtles will be crucial. I conducted a mark-recapture survey of freshwater turtles in six eastern Piedmont ponds: three of which had been harvested and three of which had no record of harvest. I tested for differences in sex ratios, size and age distributions, and population densities between the harvested and unharvested populations of Yellow-bellied Sliders (Trachemys scripta). Although no significant differences were found between the two types of populations, the amount of variance in the results does not allow any clear conclusions to be drawn. Severe weather impacts on habitat may have influenced sampling results. More research is required to determine the true effects turtle harvesting has on populations, including extensive stage-based simulation modeling and determination of metapopulations.