A Model for Management Predictions of Territorial Bird Populations

Author Institution: Biomathematics Program, Department of Statistics, North Carolina State UniversityA model was developed to compare alternative management schemes that can be employed to regulate the population level of birds having a territorial or resource limited breeding organization. The alternatives of habitat modification, removal of birds, and sterilization were compared. The model is based on the dynamics of the female segment of the population, but provision is made in the case of sterilization for predicting the effects of treatment cither of females only or of both sexes

Determination of the urinary aglycone metabolites of vitamin K by HPLC with redox-mode electrochemical detection

We describe a method for the determination of the two major urinary metabolites of vitamin K as the methyl esters of their agyclone structures, 2-methyl-3-(3-3-carboxymethylpropyl)-1,4-naphthoquinone (5C-side-chain metabolite) and 2-methyl-3-(5-carboxy-3-methyl-2-pentenyl)-1,4-naphthoquinone (7C-side-chain metabolite), by HPLC with electrochemical detection (ECD) in the redox mode. Urinary salts were removed by reversed-phase (C18) solid phase extraction (SPE) and the predominately conjugated vitamin K metabolites hydrolysed with methanolic HCl. The resultant carboxylic acid aglycones were quantitatively methylated with diazomethane and fractionated by normal-phase (silica) SPE. Final analysis was by reversed-phase (C18) HPLC with a methanol-aqueous mobile phase. Metabolites were detected by amperometric, oxidative ECD of their quinol forms, which were generated by post-column coulometric reduction at an upstream electrode. The assay gave excellent linearity (r2 typically = 0.999) and high sensitivity with an on-column detection limit of <3.5 fmol (<1pg). The inter-assay precision was typically 10%. Metabolite recovery was compared to that of an internal standard (2-methyl-3-(7'-carboxy-heptyl)-1,4-naphthoquinone), added to urine samples just before analysis. Using this methodology we confirmed that the 5C- and 7C-metabolite were major catabolites of both phylloquinone (vitamin K1) and menaquinones (vitamin K2) in humans. We propose that the measurement of urinary vitamin K metabolite excretion is a candidate non-invasive marker of total vitamin K status

Characterisation of the muon beams for the Muon Ionisation Cooling Experiment

A novel single-particle technique to measure emittance has been developed and used to characterise seventeen different muon beams for the Muon Ionisation Cooling Experiment (MICE). The muon beams, whose mean momenta vary from 171 to 281 MeV/c, have emittances of approximately 1.2–2.3 π mm-rad horizontally and 0.6–1.0 π mm-rad vertically, a horizontal dispersion of 90–190 mm and momentum spreads of about 25 MeV/c. There is reasonable agreement between the measured parameters of the beams and the results of simulations. The beams are found to meet the requirements of MICE

Forcing and Dynamics of Seafloor-Water Column Exchange on a Broad Continental Shelf

Relict sediments of elevated permeability characterize the majority of continental shelves globally (Emery, 1968). In these settings, interactions between benthic boundary layer (BBL) flows and seabed topography generate pressure fluctuations that drive advective and dispersive porewater transport, dramatically increasing the magnitude and variability of porewater solute and particulate exchange across the sediment-water interface (Huettel et al., 1996; Huettel and Rusch, 2000). On broad shallow shelves with a relatively large area-to-volume ratio, the seafloor’s role is magnified. Energetic events may reorganize bedforms across a significant fraction of the shelf, leading to altered exchange dynamics that may persist long after the organizing event. Ecosystem-based management of both resources and environmental status requires improved fundamental understanding of dynamic benthic exchange processes. Scattered, short-time-scale observations are unlikely to capture the full spectrum of events that affect sediment-water exchanges; a persistent observational presence on the seafloor is required

Baroclinic Effects and Tides on the Cape Hatteras Continental Shelf

Seasonal variability has been identified on the shelf near Cape Hatteras in the semidiurnal and diurnal frequency bands. Large summertime semidiurnal currents appear to be an M2 internal tide whose propagation shoreward is supported by strong Middle Atlantic Bight (MAB) seasonal stratification. At the southern limit of the MAB, strong MAB stratification gives way to weaker seasonal stratification in the South Atlantic Bight (SAB), and the M2 internal tide propagates shoreward less effectively. Strong diurnal variability appears in K1 and O1 components in summer, achieving magnitudes as large as the M2. The diurnal components are typically much smaller than M2 in winter. However, this summer signal is unlikely to be a diurnal internal tide since at these latitudes (34.5-36.5N) the diurnal frequency is subinertial. Coastally trapped waves (CTWs) are presented as a mechanism to explain the increased variability in the diurnal band under summertime stratification. Alongshore southward propagation of the diurnal variability is evident from moorings on the middle and outer shelf ( phase speed of 2.1-2.6 m/s along the 60-m isobath) as far south as Cape Hatteras, but little energy in this band propagates past Cape Hatteras. While diurnal band CTW propagation will not occur at this latitude under well-mixed conditions, stratification could cause those frequencies to become available for a given wave number, as described in the work of Brink ( 1990). Estimates of the Huthnance ( 1978) stratification and slope parameter A, and the Burger number S, suggest the summertime diurnal signal is consistent with baroclinic CTWs. If so, these are the first observations of diurnal CTWs at Cape Hatteras. Copyright 2007 by the American Geophysical Union

Import, export, and recycling of dissolved nutrients in the Ogeechee River estuary (Georgia, USA)

We constructed an empirical mass balance model of nutrient fluxes in the Ogeechee River estuary (Georgia, USA) from eight surveys of seasonal estuarine nutrient concentrations during 2015 and 2016. The model results indicated a net removal of dissolved phosphorus and a net production of dissolved nitrogen (N) within the estuary over an annual cycle. During summer and autumn low flow periods, much of the dissolved N discharged to the ocean seems to be recycled into the estuary in the form of phytoplankton biomass. As a result, the outwelled N is not new nitrogen fueling coastal production but is nitrogen trapped within a recycling loop across the ocean–estuarine boundary. Higher flows in the fall and winter lead to direct discharge of nutrients with minimal recycling. A balanced N budget for the Ogeechee River estuary requires that estuarine N-fixation must exceed burial and denitrification losses within the estuary

Ontogenetic and ecological variation in invasion risk of Brown Treesnakes (\u3ci\u3eBoiga irregularis\u3c/i\u3e) on Guam

Size structure within populations of invasive species may have consequences for relative risk at all stages of the invasion process, with implications for management interventions such as interdiction, suppression, and eradication. To assess relative distributions of invasive Brown Treesnakes (Boiga irregularis) among demographic categories of management interest, we undertook the most comprehensive and controlled sampling in \u3e 25 years of research into this ecologically and economically destructive introduced predator. We collected a seasonally-balanced sample of 100 snakes from each of 18 sites, stratified by six habitat types, encompassing the species’ entire extralimital range. Samples indicated significant differences in distributions of female and male snakes among management classes (juvenile, transitional, and mature) by site and habitat. We found substantial heterogeneity in localized population characteristics over relatively small geographic distances, only modest influence of habitat type, higher prevalence of reproductively mature snakes in savanna and urban habitats, and an alarmingly high proportion of snakes that are too small to be effectively targeted by current rodent-baited control tools (mean = 38.2%, range = 19 to 72%). Failure to account for such variability in high risk demographic fractions may hinder successful interventions

Anatomy of a Langmuir supercell event

Langmuir supercells (LS), which are Langmuir circulations (LC) extending over full water column depth during storms and revealed by high water column backscatter from surface-origin microbubbles and bottom-origin sediment, were discovered in 2003 during several months of measurements in 15 m of water near the coast of New Jersey. Both the structures themselves and the specific forcing conditions under which they occur have been documented elsewhere. This paper provides an account of the broader oceanographic setting of supercell events, focusing on conditions at the start and end. The start of events is associated with the presence of surface waves of intermediate type that “feel bottom” with amplitudes sufficiently large to resuspend sediment and achievement of three conditions for full-depth LC: an unstratified water column, La \u3c ∼0.3 and |Ra| \u3c 105, where Ra and La are dimensionless parameters derived from scaling of the wave-averaged momentum equation. Event cessation is associated with failure of one of the latter two conditions or the reappearance of stratification. There is no fixed order in which conditions necessary for full-depth LC are met or fail. Comparison with data from a deeper site off Georgia suggests that coherent full-depth Langmuir circulations will not generally be observed in unstratified water columns much deeper than 25–30 m, a depth determined primarily by the wavelength of surface waves generated by typical storms. We also document two features of LC acting in the surface layer of the stratified water column that existed prior to onset of the prototype LS event. First, LC confined to the surface layer generated first mode internal waves with frequency that of the stratified interior. Secondly, active surface layer LC did not act efficiently as direct agents of mixed layer deepening, which occurred primarily in two separate episodes of Richardson number lowered by increased shear. Instead, as a result of quasi-organized structure and enhanced vertical penetration relative to stress-driven turbulence, the primary role of LC may be to increase efficiency of momentum transfer to the surface layer, enhancing surface layer acceleration and contributing to onset of the shear instability that does deepen the surface layer

To cross or not to cross: modeling wildlife road crossings as a binary response variable with contextual predictors

Roads are significant barriers to landscape-scale movements of individuals or populations of many wildlife taxa. The decision by an animal near a road to either cross or not cross may be influenced by characteristics of the road, environmental conditions, traits of the individual animal, and other aspects of the context within which the decision is made. We considered such factors in a mixed-effects logistic regression model describing the nightly road crossing probabilities of invasive nocturnal Brown Treesnakes (Boiga irregularis) through short-term radiotracking of 691 snakes within close proximity to 50 road segments across the island of Guam. All measures of road magnitude (traffic volume, gap width, surface type, etc.) were significantly negatively correlated with crossing probabilities. Snake body size was the only intrinsic factor associated with crossing rates, with larger snakes crossing roads more frequently. Humidity was the only environmental variable affecting crossing rate. The distance of the snake from the road at the start of nightly movement trials was the most significant predictor of crossings. The presence of snake traps with live mouse lures during a portion of the trials indicated that localized prey cues reduced the probability of a snake crossing the road away from the traps, suggesting that a snake’s decision to cross roads is influenced by local foraging opportunities. Per capita road crossing rates of Brown Treesnakes were very low, and comparisons to historical records suggest that crossing rates have declined in the 60+ yr since introduction to Guam. We report a simplified model that will allow managers to predict road crossing rates based on snake, road, and contextual characteristics. Road crossing simulations based on actual snake size distributions demonstrate that populations with size distributions skewed toward larger snakes will result in a higher number of road crossings. Our method of modeling per capita road crossing probabilities as a binary response variable, influenced by contextual factors, may be useful for describing or predicting road crossings by individuals of other taxa provided that appropriate spatial and temporal resolution can be achieved and that potentially influential covariate data can be obtained

Quantile regression of microgeographic variation in population characteristics of an invasive vertebrate predator

Localized ecological conditions have the potential to induce variation in population characteristics such as size distributions and body conditions. The ability to generalize the influence of ecological characteristics on such population traits may be particularly meaningful when those traits influence prospects for successful management interventions. To characterize variability in invasive Brown Treesnake population attributes within and among habitat types, we conducted systematic and seasonally-balanced surveys, collecting 100 snakes from each of 18 sites: three replicates within each of six major habitat types comprising 95% of Guam\u27s geographic expanse. Our study constitutes one of the most comprehensive and controlled samplings of any published snake study. Quantile regression on snake size and body condition indicated significant ecological heterogeneity, with a general trend of relative consistency of size classes and body conditions within and among scrub and Leucaena forest habitat types and more heterogeneity among ravine forest, savanna, and urban residential sites. Larger and more robust snakes were found within some savanna and urban habitat replicates, likely due to relative availability of larger prey. Compared to more homogeneous samples in the wet season, variability in size distributions and body conditions was greater during the dry season. Although there is evidence of habitat influencing Brown Treesnake populations at localized scales (e.g., the higher prevalence of larger snakes- particularly males-in savanna and urban sites), the level of variability among sites within habitat types indicates little ability to make meaningful predictions about these traits at unsampled locations. Seasonal variability within sites and habitats indicates that localized population characterization should include sampling in both wet and dry seasons. Extreme values at single replicates occasionally influenced overall habitat patterns, while pooling replicates masked variability among sites. A full understanding of population characteristics should include an assessment of variability both at the site and habitat level