Erik E Osnas

• PhD
• Biometrician at U.S. Fish and Wildlife Service

Coastal wetland salinization related to warming climate has the potential to impact ecological systems globally. In Alaska, the Yukon‐Kuskokwim Delta (YKD) supports large concentrations of breeding water birds and is an ecologically important area for conservation of migratory bird biodiversity. On the YKD, the majority of waterfowl nest in low ele...

ABSTRACT Anas acuta (Northern pintail; hereafter pintail) was selected as a model species on which to base a decision-support framework linking regional actions to continental-scale population and harvest objectives. This framework was then used to engage stakeholders, such as Landscape Conservation Cooperatives’ (LCCs’) habitat management partners...

Assessing species status and making classification decisions under the Endangered Species Act is a critical step towards effective species conservation. However, classification decisions are liable to two errors: i) failing to classify a species as threatened or endangered that should be classified (underprotection), or ii) classifying a species as...

An array of eight Distributed Biological Observatory (DBO)sites serve as long-term monitoring areas for three geographic regions: the northern Bering, eastern Chukchi, and Beaufort seas. The locations of the DBO sites were largely determined based on abundance and diversity of benthic invertebrates. It is not clear how well these fixed sampling sit...

Surveillance is critical for early detection of emerging and re‐emerging infectious diseases. Weighted surveillance leverages heterogeneity in infection risk to increase sampling efficiency. Here, we apply a Bayesian approach to estimate weights for 16 surveillance classes of white‐tailed deer in Wisconsin, USA, relative to hunter‐harvested yearlin...

Ratcheting up wild virulence Partially protective vaccination can sometimes select for increasingly virulent pathogens. Fleming-Davies et al. asked what happens in a natural system. In the United States, the house finch population is suffering an increasingly virulent epidemic caused by Mycoplasma gallisepticum . The pathogen induces incomplete imm...

Decisions regarding endangered species recovery often face sparse data and multiple sources of uncertainty about the effects of management. Structured decision making (SDM) provides a framework for assembling knowledge and expert opinion and evaluating the tradeoffs between different objectives while formally incorporating uncertainty. The Atlantic...

Previous efforts to relate winter-ground precipitation to subsequent reproductive success as measured by the ratio of juveniles to adults in the autumn failed to account for increased vulnerability of juvenile ducks to hunting and uncertainty in the estimated age ratio. Neglecting increased juvenile vulnerability will positively bias the mean produ...

Abstract We explore pathogen virulence evolution during the spatial expansion of an infectious disease epidemic in the presence of a novel host movement trade-off, using a simple, spatially explicit mathematical model. This work is motivated by empirical observations of the Mycoplasma gallisepticum invasion into North American house finch (Haemorho...

In 2007, several important initiatives in the North American waterfowl management community called for an integrated approach to habitat and harvest management. The essence of the call for integration is that harvest and habitat management affect the same resources, yet exist as separate endeavours with very different regulatory contexts. A common...

Expected pathogen load (log10 scale), given a positive observation, in the conjunctiva of house finches inoculated with M. gallisepticum isolates. Isolates were eastern (A) (experiment 1) or western (B) (experiment 2) in origin, and means are presented for each observation day PI. (TIFF)

Detailed statistical methods and WinBUGS model code. (DOCX)

Methods and results for a related experiment that examined within-flock transmission rates of three M. gallisepticum isolates that vary in virulence. (DOCX)

Host origin (Arizona or Alabama) and experiment (1 versus 2) effects on virulence (eye score) of M. gallisepticum. Mean effects are plotted for each observation day PI. AL, Alabama; AZ, Arizona. Bars represent 95% Bayesian credible intervals, and are graphed only for VA1994.2.AL in order to improve clarity. (TIFF)

The relationship between the mean pathogen load of four index birds used to initiate an epidemic (in two flocks per isolate) and the probability that a naïve house finch became infected 26 d after introduction of one of three M. gallisepticum isolates. Bars represent standard errors around the mean for each isolate. See Methods S2 for experimental...

Probability of observing a positive pathogen load in the conjunctiva of house finches inoculated with M. gallisepticum isolates. Isolates were eastern (A) (experiment 1) or western (B) (experiment 2) in origin, and means are presented for each observation day PI. Results are plotted on a logit scale in order to improve clarity. (TIFF)

The evolution of higher virulence during disease emergence has been predicted by theoretical models, but empirical studies of short-term virulence evolution following pathogen emergence remain rare. Here we examine patterns of short-term virulence evolution using archived isolates of the bacterium Mycoplasma gallisepticum collected during sequentia...

Mycoplasma gallisepticum (MG) has become a common cause of conjunctivitis in free-living house finches (Carpodacus mexicanus) since its emergence in the early 1990s. To date, temporal and spatial genotypic variation in MG has been documented, but phenotypic variation in pathogenicity and immunogenicity has not been examined. House finches were inoc...

Many pathogens and parasites are transmitted through hosts that differ in species, sex, genotype, or immune status. In addition, virulence (here defined as disease-induced mortality) and transmission can vary during the infectious period within hosts of different state. Most models of virulence evolution assume that transmission and virulence are c...

We used a non-destructive method to identify important definitive host species in the complex life cycles for two groups of digenetic trematodes (Microphallus sp. and Notocotylus spp.). Specifically, we exposed experimental populations of the intermediate snail host Potamopyrgus antipodarum to faeces collected from New Zealand waterfowl. We found t...

We sometimes find it a little distressing how little attention is paid to the interpretation of parameters, and in particular their units, in many life science analyses. It is not uncommon to read analyses where the basic parameter units, such as log odds ratios, are never explicitly stated. This is undesirable. The starting point of every analysis...

Host genetic diversity can mediate pathogen resistance within and among populations. Here we test whether the lower prevalence of Mycoplasmal conjunctivitis in native North American house finch populations results from greater resistance to the causative agent, Mycoplasma gallisepticum (MG), than introduced, recently-bottlenecked populations that l...

Underlying dynamic event processes unfolding in continuous time give rise to spatiotemporal patterns that are sometimes observable at only a few discrete times. Such event processes may he modulated simultaneously over several spatial (e.g., latitude and longitude) and temporal (e.g., age, calendar time, and cohort) dimensions. The ecological chall...

Most models of virulence evolution assume that transmission and virulence are constant during an infection. In many viral (HIV and influenza), bacterial (TB) and prion (BSE and CWD) systems, disease-induced mortality occurs long after the host becomes infectious. Therefore, we constructed a model with two infected classes that differ in transmissio...

Emerging infectious diseases threaten wildlife populations and human health. Understanding the spatial distributions of these new diseases is important for disease management and policy makers; however, the data are complicated by heterogeneities across host classes, sampling variance, sampling biases, and the space-time epidemic process. Ignoring...

Emerging wildlife diseases pose a significant threat to natural and human systems. Because of real or perceived risks of delayed actions, disease management strategies such as culling are often implemented before thorough scientific knowledge of disease dynamics is available. Adaptive management is a valuable approach in addressing the uncertainty...

Wetland use was studied in the Pied-billed Grebe (Podilymbus podiceps) and Horned Grebe (Podiceps auritus) in southwestern Manitoba during April to August of 1997. Of the 180 wetlands surveyed, 74 had no grebe use, six were sporadically used by either grebe species, 19 were consistently used by Horned Grebe, nine switched from Horned Grebe to Pied-...

We studied the role of host ploidy and parasite exposure on immune defence allocation in a snail-trematode system (Potamopyrgus antipodarum-Microphallus sp.). In the field, haemocyte (the defence cell) concentration was lowest in deep-water habitats where infection is relatively low and highest in shallow-water habitats where infection is common. B...

How do systems respond to disturbances? The capacity of a system to respond to disturbances varies for different types of disturbance regimes. We distinguish two types of responses: one that enables the system to absorb disturbances from an existing disturbance regime, and one that enables a system to reconstruct itself after a fundamental change i...

The outcome of parasite exposure depends on the (1) genetic specificity of the interaction, (2) induction of host defenses, and (3) parasite counter defenses. We studied both the genetic specificity for infection and the specificity for the host-defense response in a snail-trematode interaction (Potamopyrgus antipodarum-Microphallus sp.) by conduct...

One of the leading theories for the evolutionary stability of sex in eukaryotes relies on parasite-mediated selection against locally common host genotypes (the Red Queen hypothesis). As such, parasites would be expected to be better at infecting sympatric host populations than allopatric host populations. Here we examined all published and unpubli...

Parasites have been found to be more infective to sympatric hosts (local adaptation) in some systems but not in others. The variable nature of results might arise due to differences in host and/or parasite migration rates, parasite virulence, specificity of infection, and to differences in the dose–response functions. We tested this latter possibil...

We developed null models that incorporate abundance of individuals at local sites to analyse community patterns of two North American duck guilds, dabbling and diving ducks. We compared patterns of species co-existence and morphological dispersion over two temporal scales, the entire breeding season and at weekly intervals. We found that patterns o...

Thesis (Ph. D.)--Indiana University, 2004.

Thesis (M. Sc.)--University of Western Ontario, 1998. Includes bibliographical references.