Mark-resight estimates of seasonal variation in harbor seal abundance and site fidelity

Monitoring trends in abundance of pinnipeds typically involves counting seals at terrestrial haul-out sites during the breeding season. Counts of seals made at other times of the year are typically lower; however, it is often unknown whether this is because fewer animals are present or whether lower counts simply reflect a reduction in haul-out probability. Here we illustrate how photo-identification data from an individual-based study of harbor seals (Phoca vitulina) can be used to estimate seasonal variation in abundance and site fidelity. Monthly data collected over a two-year period were analyzed using a mark-recapture mark-resight model accounting for individuals transitioning between observable and unobservable states. Levels of site fidelity were high throughout the year and abundance estimates showed no seasonal pattern. This suggests that individual seals used haul-out sites to the same extent throughout the year, and that peaks in counts during the breeding season are a result of seasonal changes in haul-out probability. The results of this study have implications for understanding population sub-structuring, gene flow and disease spread.     

Properties of behavior under different random ratio and random interval schedules: A parametric study

Four pigeons were trained to peck a key under different values of a temporally defined independent variable (T) and different probabilities of reinforcement (p). Parameter T is a fixed repeating time cycle and p the probability of reinforcement for the first response of each cycle T. Two dependent variables were used: mean response rate and mean postreinforcement pause. For all values of p a critical value for the independent variable T was found (T=1 sec) in which marked changes took place in response rate and postreinforcement pauses. Behavior typical of random ratio schedules was obtained at T

1 sec and behavior typical of random interval schedules at T

1 sec.     

Convergence results for contact branching processes

The link between the multi-type contact birth process and the spatial deterministic S-->I epidemic is exploited to give convergence results for a multi-type Markovian contact branching process. Let U(t) be the position of furthest spread by time t in a specific direction. The asymptotic speed of translation of the distribution function of U(t) is derived and U(t)/t is shown to converge in probability to this speed.     

Median Ranked Set Sampling with Size Biased Probability of Selection

Median ranked set sampling may be combined with size biased probability of selection. A two-phase sample is assumed. In the first phase, units are selected with probability proportional to their size. In the second phase, units are selected using median ranked set sampling to increase the efficiency of the estimators relative to simple random sampling. There is also an increase in the efficiency relative to ranked set sampling (for some probability distribution functions). There will be a loss in efficiency depending on the amount of errors in ranking the units, the median ranked set sampling can be used to reduce the errors in ranking the units selected from the population. Estimators of the population mean and the population size are considered. The median ranked set sampling with probability proportion to size and with errors in ranking is considered and compared with ranked set sampling with errors in ranking. Computer simulation results for some probability distributions are also given.     

Comparative detection,density, and reproductive performance of Kirtland's warbler in jack and red pine

The formerly endangered Kirtland's warbler (Setophaga kirtlandii) is among a growing number of conservation-reliant species that depend on active management to avoid reverting to endangered status. Because the Kirtland's warbler is a habitat specialist of young, even-aged jack pine (Pinus banksiana), managers of the recovery effort stressed creating new jack pine stands and monitoring numbers of singing males through an annual census using single visits to individual stands. Kirtland's warbler will occupy and breed in red pine (P. resinosa), but red pine has not been surveyed for Kirtland's warblers in the annual population census. Furthermore, the current monitoring approach cannot determine their species detection probability or individual detection probability, which is essential to evaluate both red pine use and the accuracy of the census. From 2016–2018 we estimated density and detection probabilities in jack pine and red pine stands through repeated visits to a limited number of stands rather than single visits to many stands. Estimates of species detection probability indicated that ≥1 male Kirtland's warbler would be detected on most sites when any were present, but individual detection probabilities were less and varied by stand type, indicating that single visits to sites would underestimate numbers and that accurate estimation of detection probability was important for estimation of density in different stand types. We offer quantitative estimates of detection probabilities for determination of Kirtland's warbler population size in jack pine versus red pine stands in the same areas and breeding seasons. Managers of Kirtland's warblers should incorporate detection probabilities into population surveys to achieve more accurate estimates of population size.     

Nonparametric estimation of distributions and diagnostic accuracy based on group-tested results with differential misclassification

This article concerns the problem of estimating a continuous distribution in a diseased or nondiseased population when only group-based test results on the disease status are available. The problem is challenging in that individual disease statuses are not observed and testing results are often subject to misclassification, with further complication that the misclassification may be differential as the group size and the number of the diseased individuals in the group vary. We propose a method to construct nonparametric estimation of the distribution and obtain its asymptotic properties. The performance of the distribution estimator is evaluated under various design considerations concerning group sizes and classification errors. The method is exemplified with data from the National Health and Nutrition Examination Survey study to estimate the distribution and diagnostic accuracy of C-reactive protein in blood samples in predicting chlamydia incidence.     

Single ion occupancy and steady-state gating of Na channels in squid giant axon

The properties of the small fraction of tetrodotoxin (TTX)-sensitive Na channels that remain open in the steady state were studied in internally dialyzed voltage clamped squid giant axons. The observed Ussing flux ratio exponent (n') of 0.97 plus minus 0.03 (calculated from simultaneous measurements of TTX-sensitive current and (22)Na efflux) and nonindependent behavior of Na current at high internal [Na] are explained by a one-site ("1s") permeation model characterized by a single effective binding site within the channel pore in equilibrium with internal Na ions (apparent equilibrium dissociation constant K(Nai)(0) = 0.61 +/- 0.08 M). Steady-state open probability of the TTX-sensitive channels can be modeled by the product p(a)p(infinity), where p(a) represents voltage-dependent activation described by a Boltzmann distribution with midpoint V(a) = -7 mV and effective valence z(a) = 3.2 (Vandenberg, C.A., and F. Bezanilla. 1991. BIOPHYS: J. 60:1499--1510) coupled to voltage-independent inactivation by an equilibrium constant (Bezanilla, F., and C.M. Armstrong. 1977. J. Gen. Physiol. 70:549--566) K(eq) = 770. The factor p(infinity) represents voltage-dependent inactivation with empirical midpoint V(infinity)= -83 plus minus 5 mV and effective valence z(infinity) = 0.55 plus minus 0.03. The composite p(a)p(infinity)1s model describes the steady-state voltage dependence of the persistent TTX-sensitive current well.     

Optimizing surveys for marsh songbirds: does timing matter?

Analysis of data from point counts, a common method for monitoring bird population trends, has evolved to produce estimates of various population parameters (e.g., density, abundance, and occupancy) while simultaneously estimating detection probability. An important consideration when designing studies using point counts is to maximize detection probability while minimizing variation in detection probability both within and between counts. Our objectives were to estimate detection probabilities for three marsh songbirds, including Marsh Wrens (Cistothorus palustris), Swamp Sparrows (Melospiza georgiana), and Yellow‐headed Blackbirds (Xanthocephalus xanthocephalus), as a function of weather covariates and to evaluate temporal variability in detection probability of these three species. We conducted paired, unlimited radius, 10‐min point counts during consecutive morning and evening survey periods for our three focal species at 56 wetlands in Iowa from 20 April to 10 July 2010. Mean detection probabilities ranged from 0.272 (SE = 0.042) for Marsh Wrens to 0.365 (SE = 0.052) for Swamp Sparrows. Time of season was positively correlated with detection probability for Swamp Sparrows, but was negatively correlated with detection probability for Yellow‐headed Blackbirds, suggesting that detection probability increased during the breeding season for Swamp Sparrows and was highest early in the breeding season for Yellow‐headed Blackbirds. Understanding how detection probabilities of marsh songbirds vary throughout the breeding season allows targeted survey efforts that maximize detection probabilities for these species. Furthermore, consistent detection probabilities of marsh songbirds during morning and evening survey periods mean that investigators have more time to conduct surveys for these birds, allowing greater flexibility to increase spatial and temporal replication of surveys that could provide more precise estimates of desired population parameters.     

Deer and elk hunter recruitment,retention, and participation trends in Montana

Big game hunting is the most popular type of hunting in the United States, and deer and elk hunting are the most popular type of hunting in Montana. Similar to other states, deer and elk hunting also generates most of the revenue spent on wildlife conservation by the state of Montana. Although nationwide trends indicate a concerning decline in hunter participation, the trends in license sales and hunter participation within most states have not received as much attention. We investigated trends in resident deer and elk license sales in Montana using existing licensing databases. We then estimated hunter recruitment, hunter participation, and license purchasing probabilities using hunter education and licensing databases. We employed a multi-state mark–recapture model and 248,819 records of deer and elk license purchasing habits for individual Montana residents during 2002–2007. We used matrix population models to examine the relative influence of these parameters on trends in license sales and hunter participation. Resident deer and elk license sales increased 4% in Montana during 2002–2007. We found that males had greater recruitment rates, retention rates, and license purchasing probabilities than females, and that young adults had lesser license purchasing probabilities than other age classes. Based on analyses of matrix population models, trends in license sales in Montana are most influenced by middle-aged and baby boomer male license purchase probabilities. Trends in hunter participation are positively influenced by recruitment and retention in all male age classes, with the smallest predicted effects arising from recruitment of young adult males. Our results suggest that a focus on older age class males with programs designed to increase hunter recruitment, retention, and license purchase probabilities may have similar or larger effects on trends in license sales and hunter participation in Montana than programs directed at youth. Our analyses also provide a framework by which trends in hunter recruitment, retention, and license purchasing habits can be objectively quantified in order to inform and evaluate hunter recruitment, retention, and license purchase habit programs. © 2011 The Wildlife Society.