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Testing Of An Oral Dosing Technique For Double-Crested Cormorants, Phalacocorax Auritus, Laughing Gulls, Leucophaeus Atricilla, Homing Pigeons, Columba Livia, And Western Sandpipers, Calidris Mauri, With Artificially Weather Mc252 Oil, Karen M. Dean, Dave Cacela, Michael W. Carney, F. L. Cunningham, C. Ellis, A. R. Gerson, C. G. Guglielmo, Katie C. Hanson-Dorr, K. E. Harr, Katherine A. Healy, Katherine E. Horak, John P. Isanhart, L. V. Kennedy, J. E. Link, I. Lipton, Andrew K. Mcfadden, J. K. Moye, C. R. Perez, C. A. Pritsos, Karen L. Pritsos, Thivanka Muthumalage, S. A. Shriner, S. J. Bursian

United States Department of Agriculture Wildlife Services: Staff Publications

Scoping studies were designed to determine if double-crested cormorants (Phalacocorax auritus), laughing gulls (Leucophaues atricilla), homing pigeons (Columba livia) and western sandpipers (Calidris mauri) that were gavaged with a mixture of artificially weathered MC252 oil and food for either a single day or 4–5 consecutive days showed signs of oil toxicity. Where volume allowed, samples were collected for hematology, plasma protein electrophoresis, clinical chemistry and electrolytes, oxidative stress and organ weigh changes. Double-crested cormorants, laughing gulls and western sandpipers all excreted oil within 30 min of dose, while pigeons regurgitated within less …

Panmixia And Limited Interspecific Introgression In Coyotes (Canis Latrans) From West Virginia And Virginia, Usa, Justin H. Bohling, Lauren L. Mastro, Jennifer R. Adams, Eric M. Gese, Sheldon F. Owen, Lisette P. Waits

United States Department of Agriculture Wildlife Services: Staff Publications

The expansion of coyotes (Canis latrans) into the eastern United States has had major consequences for ecological communities and wildlife managers. Despite this, there has been little investigation of the genetics of coyotes across much of this region, especially outside of the northeast. Understanding patterns of genetic structure and interspecific introgression would provide insights into the colonization history of the species, its response to the modern environment, and interactions with other canids. We examined the genetic characteristics of 121 coyotes from the mid-Atlantic states of West Virginia and Virginia by genotyping 17 polymorphic nuclear DNA microsatellite loci. These …

Frightening Devices, Michael L. Avery, Scott J. Werner

United States Department of Agriculture Wildlife Services: Staff Publications

By their nature, avian frightening devices are intended to provide temporary (days, weeks) relief from a specific depredation or conflict situation. Ideally, the method applied will produce an immediate fright response, causing depredating birds to leave and to stay away as long as the method is in place. Longer-term (months, years) resource protection would involve methods such as crop varietal improvement, blackbird population management, or habitat manipulation. Frightening devices primarily affect the avian auditory and visual senses. With few exceptions (e.g., avian distress or alarm calls), frightening devices are not species-specific.Very few frightening devices have been subjected to adequate scientific …

Demographic And Temporal Variations In Immunity And Condition Of Polar Bears (Ursus Maritimus) From The Southern Beaufort Sea, Lorin A. Neuman-Lee, Patricia A. Terletzky, Todd C. Atwood, Eric M. Gese, Geoffrey D. Smith, Sydney Greenfield, John Pettit, Susannah S. French

United States Department of Agriculture Wildlife Services: Staff Publications

Assessing the health and condition of animals in their natural environment can be problematic. Many physiological metrics, including immunity, are highly influenced by specific context and recent events to which researchers may be unaware. Thus, using a multifaceted physiological approach and a context-specific analysis encompassing multiple time scales can be highly informative. Ecoimmunological tools in particular can provide important indications to the health of animals in the wild.We collected blood and hair samples from free-ranging polar bears (Ursus maritimus) in the southern Beaufort Sea and examined the influence of sex, age, and reproductive status on metrics of immunity, …

The Roles Of Habitat And Intraguild Predation By Coyotes On The Spatial Dynamics Of Kit Foxes, Robert C. C. Lonsinger, Eric M. Gese, Larissa L. Bailey, Lisette P. Waits

United States Department of Agriculture Wildlife Services: Staff Publications

Intraguild predation (IGP) by a dominant predator can drive the spatial dynamics of a subordinate predator and may explain space-use patterns that deviate from theoretical predictions that species will use areas that maximize the availability of limited resources (resource availability hypothesis). Intraguild predation may suppress the distribution and abundance of mesopredators, but spatial resource partitioning may facilitate coexistence, with the subordinate carnivore utilizing suboptimal habitats. In arid systems, free-standing water was historically scarce, limiting the distribution of larger-bodied predators and offering large areas of refugia for smaller, arid-adapted species, such as the kit fox (Vulpes macrotis). In these …

The Future Of Blackbird Management Research, Page E. Klug

United States Department of Agriculture Wildlife Services: Staff Publications

Human society values birds for their intrinsic and aesthetic value as well as the ecosystem services they provide as pollinators, consumers of pests, and distributors of nutrients and seeds (Wenny et al. 2011). At the same time, conflict between birds and humans is an age-old phenomenon that has persisted as society has transformed and the scale of agriculture has expanded (Conover 2002). Managing conflict between birds and agriculture is challenging for many reasons. Foremost, the need to consider both human welfare and conservation of protected bird species is paramount, with nonlethal management methods preferred to lethal measures from societal, economical, …

Coyote (Canis Latrans) Diet In An Urban Environment: Variation Relative To Pet Conflicts, Housing Density, And Season, S. A. Poessel, E. C. Mock, S. W. Breck

United States Department of Agriculture Wildlife Services: Staff Publications

Coyotes (Canis latrans Say, 1823) are highly successful in urbanized environments, but as they populate cities, conflict can occur and often manifests in the form of incidents with pets. To better understand whether coyotes view pets as prey or, alternatively, as competitors or a threat, we conducted a diet analysis of coyotes in the Denver metropolitan area (DMA) by analyzing scats. We also examined differences in diet between high- and low-density housing and among seasons. We found only small percentages of trash and domestic pets in the coyote diet. The presence of pets in the diet did not coincide …

Human Development And Climate Affect Hibernation In A Large Carnivore With Implications For Human–Carnivore Conflicts, Heather E. Johnson, David L. Lewis, Tana L. Verzuh, Cody F. Wallace, Rebecca M. Much, Lyle K. Willmarth, Stewart W. Breck

United States Department of Agriculture Wildlife Services: Staff Publications

1. Expanding human development and climate change are dramatically altering habitat conditions for wildlife. While the initial response of wildlife to changing environmental conditions is typically a shift in behavior, little is known about the effects of these stressors on hibernation behavior, an important life-history trait that can subsequently affect animal physiology, demography, interspecific interactions and human-wildlife interactions. Given future trajectories of land use and climate change, it is important that wildlife professionals understand how animals that hibernate are adapting to altered landscape conditions so that management activities can be appropriately tailored.

2. We investigated the influence of human development …

Large Carnivore Science: Non-Experimental Studies Are Useful, But Experiments Are Better, Benjamin L. Allen, Lee R. Allen, Henrik Andrén, Guy Ballard, Luigi Boitani, Richard M. Engeman, Peter J. S. Fleming, Adam T. Ford, Peter M. Haswell, Rafal Kowalczyk, John D. C. Linnell, L. David Mech, Daniel M. Parker

United States Department of Agriculture Wildlife Services: Staff Publications

1. Response to Bruskotter and colleagues

We recently described the following six interrelated issues that justify questioning some of the discourse about the reliability of the literature on the ecological roles of large carnivores (Allen et al., in press):

1. The overall paucity of available data,

2. The reliability of carnivore population sampling techniques,

3. The general disregard for alternative hypotheses to top-down forcing,

4. The lack of applied science studies,

5. The frequent use of logical fallacies,

6. The generalisation of results from relatively pristine systems to those substantially altered by humans.

We thank Bruskotter et al. (2017) for …

Linking Animals Aloft With The Terrestrial Landscape, Jeffrey J. Buler, Wylie C. Barrow Jr., Matthew E. Boone, Deanna K. Dawson, Robert H. Diehl, Frank R. Moore, Lori A. Randall, Timothy D. Schreckengost, Jaclyn A. Smolinsky

United States Geological Survey: Staff Publications

Despite using the aerosphere for many facets of their life, most flying animals (i.e., birds, bats, some insects) are still bound to terrestrial habitats for resting, feeding, and reproduction. Comprehensive broad-scale observations by weather surveillance radars of animals as they leave terrestrial habitats for migration or feeding flights can be used to map their terrestrial distributions either as point locations (e.g., communal roosts) or as continuous surface layers (e.g., animal densities in habitats across a landscape). We discuss some of the technical challenges to reducing measurement biases related to how radars sample the aerosphere and the flight behavior of animals. …

Extending The Habitat Concept To The Airspace, Robert H. Diehl, Anna C. Peterson, Rachel T. Bolus, Douglas Johnson

United States Geological Survey: Staff Publications

Habitat is one of the most familiar and fundamental concepts in the fields of ecology, animal behavior, and wildlife conservation and management. Humans interact with habitats through their senses and experiences and education to such a degree that their perceptions of habitat have become second nature. For this reason, it may be difficult at first to accept the airspace as habitat, an area that is invisible, untouchable, highly dynamic, and its occupants difficult to see. Nonetheless, the habitat concept, by definition and in practice, applies readily to the airspace. Some ecological and behavioral processes including habitat selection, foraging, and reproduction …

Coyote Removal: Can The Short-Term Application Of A Controversial Management Tool Improve Female Greater Sage-Grouse Survival Or Nest Success?, Elizabeth K. Orning, Julie K. Young

United States Department of Agriculture Wildlife Services: Staff Publications

Greater sage-grouse Centrocercus urophasianus have declined across western North America, intensifying the need for ecological research that enhances management and conservation goals. Predator–prey interactions can have widespread ecological effects but there is a paucity of information about predator effects on sage-grouse ecology. During a two-year study from 2011–2012, we modified the existing framework designed for predator management to test the effects of coyote Canis latrans removal on female sage-grouse survival and nest success in the Bighorn Basin of Wyoming, USA, where coyotes were found to be the dominant predator. We used VHF radio-telemetry to monitor female survival and locate nests …

Linking Animals Aloft With The Terrestrial Landscape, Jeffrey J. Buler, Wylie C. Barrow Jr., Matthew E. Boone, Deanna K. Dawson, Robert H. Diehl, Frank R. Moore, Lori A. Randall, Timothy D. Schreckengost, Jaclyn A. Smolinsky

United States Geological Survey: Staff Publications

Despite using the aerosphere for many facets of their life, most flying animals (i.e., birds, bats, some insects) are still bound to terrestrial habitats for resting, feeding, and reproduction. Comprehensive broad-scale observations by weather surveillance radars of animals as they leave terrestrial habitats for migration or feeding flights can be used to map their terrestrial distributions either as point locations (e.g., communal roosts) or as continuous surface layers (e.g., animal densities in habitats across a landscape). We discuss some of the technical challenges to reducing measurement biases related to how radars sample the aerosphere and the flight behavior of animals. …

Potential Effects Of Incorporating Fertility Control Into Typical Culling Regimes In Wild Pig Populations, Kim M. Pepin, Amy J. Davis, Fred L. Cunningham, Kurt C. Vercauteren, Douglas C. Eckery

United States Department of Agriculture Wildlife Services: Staff Publications

Effective management of widespread invasive species such as wild pigs (Sus scrofa) is limited by resources available to devote to the effort. Better insight of the effectiveness of different management strategies on population dynamics is important for guiding decisions of resource allocation over space and time. Using a dynamic population model, we quantified effects of culling intensities and time between culling events on population dynamics of wild pigs in the USA using empirical culling patterns and data-based demographic parameters. In simulated populations closed to immigration, substantial population declines (50±100%) occurred within 4 years when 20±60% of the population …

Effects Of Scale Of Movement, Detection Probability, And True Population Density On Common Methods Of Estimating Population Density, David A. Keiter, Amy J. Davis, Olin E. Rhodes Jr., Fred L. Cunningham, John C. Kilgo, Kim M. Pepin, James C. Beasley

United States Department of Agriculture Wildlife Services: Staff Publications

Knowledge of population density is necessary for effective management and conservation of wildlife, yet rarely are estimators compared in their robustness to effects of ecological and observational processes, which can greatly influence accuracy and precision of density estimates. In this study, we simulate biological and observational processes using empirical data to assess effects of animal scale of movement, true population density, and probability of detection on common density estimators. We also apply common data collection and analytical techniques in the field and evaluate their ability to estimate density of a globally widespread species. We find that animal scale of movement …

Extending The Habitat Concept To The Airspace, Robert H. Diehl, Anna C. Peterson, Rachel T. Bolus, Douglas Johnson

United States Geological Survey: Staff Publications

Habitat is one of the most familiar and fundamental concepts in the fields of ecology, animal behavior, and wildlife conservation and management. Humans interact with habitats through their senses and experiences and education to such a degree that their perceptions of habitat have become second nature. For this reason, it may be difficult at first to accept the airspace as habitat, an area that is invisible, untouchable, highly dynamic, and its occupants difficult to see. Nonetheless, the habitat concept, by definition and in practice, applies readily to the airspace. Some ecological and behavioral processes including habitat selection, foraging, and reproduction …

Restricted Cross-Scale Habitat Selection By American Beavers, Robert A. Francis, Jimmy D. Taylor, Eric Dibble, Bronson Strickland, Vanessa M. Petro, Christine Easterwood, Guiming Wang

United States Department of Agriculture Wildlife Services: Staff Publications

Animal habitat selection, among other ecological phenomena, is spatially scale dependent. Habitat selection by American beavers Castor canadensis (hereafter, beaver) has been studied at singular spatial scales, but to date no research addresses multi-scale selection. Our objectives were to determine if beaver habitat selection was specialized to semiaquatic habitats and if variables explaining habitat selection are consistent between landscape and fine spatial scales. We built maximum entropy (MaxEnt) models to relate landscape-scale presence-only data to landscape variables, and used generalized linearmixed models to evaluate fine spatial scale habitat selection using global positioning system (GPS) relocation data. Explanatory variables between the …

Effective Dose And Persistence Of Rhodamine-B In Wild Pig Vibrissae, Sarah C. Webster, Fred L. Cunningham, John C. Kilgo, Mark A. Vukovich, Olin E. Rhodes Jr., James C. Beasley

United States Department of Agriculture Wildlife Services: Staff Publications

As a result of substantial ecological and economic damage attributed to wild pigs (Sus scrofa), there is international interest in using pharmaceutical baits to control populations. To assess the efficacy and specificity of baiting programs, chemical biomarkers can be used to evaluate uptake of pharmaceutical baits. Rhodamine B (RB) is known to be an effective biomarker in wild pigs. However, significant data gaps exist regarding the minimum effective dosage and persistence of RB in wild pigs. We used a controlled doubleblind study experiment conducted in spring of 2014 on the Savannah River Site, Aiken, South Carolina, USA, wherein …

Characterizing The Diversity Of Sweetpotato Through Growth Parameters And Leaf Traits: Precocity And Light Use Efficiency As Important Ordination Factors, D. A. Ramírez, C. Gavilán, C. Barreda, B. Condori, G. Rossel, R. O. M. Mwanga, M. Andrade, P. Monneveux, N. L. Anglin, D. Ellis, R. Quiroz

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Due to its low-input requirements, high yield capacity in marginal soils, and high carbohydrate and vitamin A content, sweetpotato is an important food security crop. For effective breeding strategies, knowing and understanding the traits that drive diversity among varieties is required. In this study, a set representing the diversity of sweetpotato varieties was characterized through multivariate ordination based on growth parameters and physiological leaf traits. The dynamic of light interception, light use efficiency (LUE) parameters, and partition of assimilates to the storage roots of eight representative varieties were simulated through a crop growth model. Leaf mass per area (LMA), N …

The Persistence Of Multiple Strains Of Avian Influenza In Live Bird Markets, Amy Pinsent, Kim M. Pepin, Huachen Zhu, Yi Guan, Michael T. White, Steven Riley

United States Department of Agriculture Wildlife Services: Staff Publications

Multiple subtypes of avian influenza (AI) and novel reassortants are frequently isolated from live bird markets (LBMs). However, our understanding of the drivers of persistence of multiple AI subtypes is limited. We propose a stochastic model of AI transmission within an LBM that incorporates market size, turnover rate and the balance of direct versus environmental transmissibility. We investigate the relationship between these factors and the critical community size (CCS) for the persistence of single and multiple AI strains within an LBM. We fit different models of seeding from farms to two-strain surveillance data collected from Shantou, China. For a single …

Serologic Evidence Of Various Arboviruses Detected In White Tailed Deer (Odocoileus Virginianus) In The United States, Kerri Pedersen, Eryu Wang, Scott C. Weaver, Paul C. Wolf, Adam R. Randall, Kyle R. Van Why, Amelia P.A. Travassos Da Rosa, Thomas Gidlewski

United States Department of Agriculture Wildlife Services: Staff Publications

White-tailed deer (Odocoileus virginianus) are an abundant mammal with a wide geographic distribution in the United States, which make them good sentinels for monitoring arboviral activity across the country. Exposure to various arboviruses has been detected in white-tailed deer, typically in conjunction with another diagnostic finding. To better assess the exposure of white-tailed deer to seven arboviruses, wetested 1,508 sera collected from 2010 to 2016 for antibodies to eastern equine encephalitis (2.5%), Powassan (4.2%), St. Louis encephalitis, (3.7%), West Nile (6.0%), Maguari (19.4%), La Crosse (30.3%), and bluetongue (7.8%) viruses. At least one arbovirus was detected in 51.3%, …

Evaluation Of Antibody Response To An Adjuvanted Hapten-Protein Vaccine As A Potential Inhibitor Of Sexual Maturation For Farmed Atlantic Salmon, Darcy S.O. Mora, Mo D. Salman, Christopher A. Myrick, Jack C. Rhyan, Lowell A. Miller, Ellen Marie Sætre, Douglas C. Eckery

United States Department of Agriculture Wildlife Services: Staff Publications

An experimental contraceptive vaccine was evaluated in Atlantic salmon (Salmo salar). A peptide derived from the beta subunit of luteinizing hormone (LH) was conjugated to two different carrier proteins, bovine serum albumin (BSA) and keyhole limpet hemocyanin (KLH), and formulated with one of four immunostimulants in a water-in-oil emulsion. Specific antibody responses to the peptide and each carrier protein were evaluated. While the antibody response to KLH was stronger than the response to BSA, both carrier proteins stimulated comparable antibody responses to the LH peptide. The immunostimulant proved to be more important for enhancing the LH peptide antibody response …

Influence Of Precipitation And Crop Germination On Resource Selection By Mule Deer (Odocoileus Hemionus) In Southwest Colorado, Emily M. Carrollo, Heather E. Johnson, Justin W. Fischer, Matthew Hammond, Patricia D. Dorsey, Charles Anderson, Kurt C. Vercauteren, W. David Walter

United States Department of Agriculture Wildlife Services: Staff Publications

Mule deer (Odocoileus hemionus) populations in the western United States provide many benefits to local economies but can also cause considerable damage to agriculture, particularly damage to lucrative crops. Limited information exists to understand resource selection of mule deer in response to annual variation in crop rotation and climatic conditions. We tested the hypothesis that mule deer select certain crops, and in particular sunflower, based on annual climatic variability. Our objective was to use movements, estimates of home range, and resource selection analysis to identify resources selected by mule deer. We used annually-derived crop-specific datasets along with Global …

A Review Of Virulent Newcastle Disease Viruses In The United States And The Role Of Wild Birds In Viral Persistence And Spread, Vienna R. Brown, Sarah N. Bevins

United States Department of Agriculture Wildlife Services: Staff Publications

Newcastle disease is caused by virulent strains of Newcastle disease virus (NDV), which causes substantial morbidity and mortality events worldwide in poultry. The virus strains can be differentiated as lentogenic, mesogenic, or velogenic based on a mean death time in chicken embryos. Currently, velogenic strains of NDV are not endemic in United States domestic poultry; however, these strains are present in other countries and are occasionally detected in wild birds in the U.S. A viral introduction into domestic poultry could have severe economic consequences due to the loss of production from sick and dying birds, the cost of control measures …

Key Differences Between Lakes And Reservoirs Modify Climate Signals: A Case For A New Conceptual Model, Nicole M. Hayes, Bridget R. Deemer, Jessica R. Corman, N. Roxanna Razavi, Kristin E. Strock

United States Geological Survey: Staff Publications

Lakes and reservoirs are recognized as important sentinels of climate change, integrating catchment and atmospheric climate change drivers. Climate change conceptual models generally consider lakes and reservoirs together despite the possibility that these systems respond differently to climate-related drivers. Here, we synthesize differences between lake and reservoir characteristics that are likely important for predicting waterbody response to climate change. To better articulate these differences, we revised the energy mass flux framework, a conceptual model for the effects of climate change on lentic ecosystems, to explicitly consider the differential responses of lake versus reservoir ecosystems. The model predicts that catchment and …

Quantile Regression Of Microgeographic Variation In Population Characteristics Of An Invasive Vertebrate Predator, Shane R. Siers, Julie A. Savidge, Robert N. Reed

United States Department of Agriculture Wildlife Services: Staff Publications

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's geographic expanse. Our study constitutes one of the most comprehensive and controlled samplings of …

Effective Dose And Persistence Of Rhodamine-B In Wild Pig Vibrissae, Sarah C. Webster, Fred L. Cunningham, John C. Kilgo, Mark A. Vukovich, Olin E. Rhodes Jr., James C. Beasley

United States Department of Agriculture Wildlife Services: Staff Publications

As a result of substantial ecological and economic damage attributed to wild pigs (Sus scrofa), there is international interest in using pharmaceutical baits to control populations. To assess the efficacy and specificity of baiting programs, chemical biomarkers can be used to evaluate uptake of pharmaceutical baits. Rhodamine B (RB) is known to be an effective biomarker in wild pigs. However, significant data gaps exist regarding the minimum effective dosage and persistence of RB in wild pigs. We used a controlled doubleblind study experiment conducted in spring of 2014 on the Savannah River Site, Aiken, South Carolina, USA, wherein …

The 17th Rocky Mountain Virology Association Meeting, Joel Rovnak, Rushika Perera, Matthew W. Hopken, Jenna Read, Derrick M. Waller, Randall J. Cohrs

United States Department of Agriculture Wildlife Services: Staff Publications

Since 2000, scientists and students from the greater Rocky Mountain region, along with invited speakers, both national and international, have gathered at the Mountain Campus of Colorado State University to discuss their area of study, present recent findings, establish or strengthen collaborations, and mentor the next generation of virologists and prionologists through formal presentations and informal discussions concerning science, grantsmanship and network development. This year, approximately 100 people attended the 17th annual Rocky Mountain Virology Association meeting, that began with a keynote presentation, and featured 29 oral and 35 poster presentations covering RNA and DNA viruses, prions, virus-host interactions and …

Clinostomum Album N. Sp. And Clinostomum Marginatum (Rudolphi, 1819), Parasites Of The Great Egret Ardea Alba L. From Mississippi, Usa, Thomas G. Rosser, Neely R. Alberson, Ethan T. Woodyard, Fred L. Cunningham, Linda M. Pote, Matt J. Griffin

United States Department of Agriculture Wildlife Services: Staff Publications

Members of the genus Clinostomum Leidy, 1856, colloquially known as yellow grubs, are cosmopolitan parasites of piscivorous birds, freshwater snails, fish and amphibians. In the southeastern United States, piscivorous birds present a continuous challenge for producers of farm-raised catfish. Ciconiiform birds are common hosts of Clinostomum spp. in North America and are endemic on most commercial catfish operations. The great egret Ardea albaL. is an avian predator often found foraging on commercial catfish operations, but to date the trematode fauna of great egrets preying on catfish ponds remains mostly understudied. Thirteen great egrets were captured from commercial catfish ponds …

Bayesian Model-Based Age Classification Using Small Mammal Body Mass And Capture Dates, Nathaneal Lichti, Kenneth F. Kellner, Timothy J. Smyser, Scott A. Johnson

United States Department of Agriculture Wildlife Services: Staff Publications

Accurate age determination is a fundamental prerequisite for demographic studies as well as population monitoring efforts that provide information for management and conservation. Yet, common age determination methods suffer from low accuracy rates, impose additional handling and time costs on animals and biologists, or rely on invasive techniques such as tooth extraction. We introduce an alternative, mixture modeling approach for age determination that exploits mammalian growth patterns to classify newly encountered animals as juveniles or adults, and present an example analysis that classifies Allegheny woodrats based solely on their capture dates and mass at capture, in combination with data from …