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USGS2000

Space use of killdeer at a Great Basin breeding area

Wetland conservation efforts require knowledge of space use by a diversity of waterbirds. However, determining space use of animals requires intensive monitoring of individual organisms. Often, activity patterns during much of the annual cycle are neglected in analyses of home range and habitat use. From 1995-97, we monitored space use in a population of individually marked killdeer ( Charadrius vociferus ) that breed, and reside for a number of additional months each year, in the western Great Basin. We used linear distance measures and home range-area estimates, derived by fixed-kernel methods, to examine patterns of space use of adults prior to, during, and following nesting. Overall, killdeer used a local area of approximately 6 ha. Birds remained closer to nests while tending eggs than either before or after nesting, although extensive movements away from the nest were observed during all time periods. Females tended to move farther from nests than did males. Birds nesting farther from water bodies were generally observed at greater distances from nests than those nesting closer to shorelines during all time periods. Twenty-seven percent of individuals were observed greater than 1 km from nest locations, particularly during postnesting periods. During nesting periods, males were less likely to be observed at longer distances from nests than were females. There were no differences in home range size based upon sex, time period, or distance from water. We suggest that home range size may not always accurately measure differences in space use and that multiple measures, including distance from nests, should be considered. Understanding the sedentary nature of killdeer during much of the annual cycle and their intense use of local areas is important for making management decisions. Coupled with data on other shorebird species, this information also has broader implications for management of wetland systems by indicating large scale spatial and habitat requirements and the connectivity of geographically distinct habitat patches.

California, Idaho, Nevada, Oregon, Washington↗

USGS2000

Factors limiting mallard brood survival in prairie pothole landscapes

In order to estimate mallard (Anas platyrhynchos) production from managed and unmanaged lands, waterfowl biologists need measurable predictors of brood survival. We evaluated effects of percent of seasonal basins holding water (WETSEAS), percent of upland landscape in perennial cover (PERNCOVER), rainfall (RAIN), daily minimum ambient temperature (TMIN), hatch date (HATCHDATE), brood age (BA; 0-7 or 8-30 days), age of brood females, and brood size on mallard brood survival in prairie pothole landscapes, and developed a predictive model using factors found to have significant effects. Sixteen of 56 radiomarked broods experienced total loss during 1,250 exposure days. Our final fitted model of brood survival contained only main effects of WETSEAS, HATCHDATE, and RAIN. Total brood loss during the first 30 days of exposure was 11.2 times more likely for broods hatched on areas with <17% WETSEAS than those on areas with >59% WETSEAS. Total brood loss was 5.2 times more likely during rainy conditions than during dry periods, and the hazard of total brood loss increased by 5% for each 1-day delay in hatching between 17 May and 12 August. High survival of mallard broods in landscapes where most seasonal basins contain water underscores the importance of maintaining seasonal wetlands as a major component of wetland complexes managed for mallard production. Because early hatched broods have higher survival, we also suggest that waterfowl managers focus their efforts on enhancing nest success of early laid clutches, especially in wet years.

Journal of Wildlife Management↗

USGS1995

Using known populations of pronghorn to evaluate sampling plans and estimators

Although sampling plans and estimators of abundance have good theoretical properties, their performance in real situations is rarely assessed because true population sizes are unknown. We evaluated widely used sampling plans and estimators of population size on 3 known clustered distributions of pronghorn ( Antilocapra americana ). Our criteria were accuracy of the estimate, coverage of 95% confidence intervals, and cost. Sampling plans were combinations of sampling intensities (16, 33, and 50%), sample selection (simple random sampling without replacement, systematic sampling, and probability proportional to size sampling with replacement), and stratification. We paired sampling plans with suitable estimators (simple, ratio, and probability proportional to size). We used area of the sampling unit as the auxiliary variable for the ratio and probability proportional to size estimators. All estimators were nearly unbiased, but precision was generally low (overall mean coefficient of variation [CV] = 29). Coverage of 95% confidence intervals was only 89% because of the highly skewed distribution of the pronghorn counts and small sample sizes, especially with stratification. Stratification combined with accurate estimates of optimal stratum sample sizes increased precision, reducing the mean CV from 33 without stratification to 25 with stratification; costs increased 23%. Precise results ( x̄ CV = 13) but poor confidence interval coverage (83%) were obtained with simple and ratio estimators when the allocation scheme included all sampling units in the stratum containing most pronghorn. Although areas of the sampling units varied, ratio estimators and probability proportional to size sampling did not increase precision, possibly because of the clumped distribution of pronghorn. Managers should be cautious in using sampling plans and estimators to estimate abundance of aggregated populations.

North Dakota↗

USGS1998

The seventy-fourth Christmas bird count. 315. Southern Dorchester County, Md

Because limited information is available regarding preferences for nocturnal habitat during winter, we studied use of nocturnal habitats by American woodcock (Scolopax minor) wintering in the Georgia Piedmont (1994-95). During the evening crepuscular period, woodcock on the wintering grounds move from forested to field habitats, presumably to feed, conduct courtship displays, roost, and avoid predators. We conducted crepuscular flight surveys and tracked radio-marked woodcock to compare the use of fields of different sizes (<5.5 ha, 5.540.0 ha, >40.0 ha) and types (seed tree-clearcuts, fallow-old fields, hayfields, pastures). Fields > 5.5 ha were used more frequently than fields <5.5 ha (P < 0.001). Seed tree-clearcuts and fallow-old fields were more frequently used than pastures (P = 0.003). Woodcock also most frequently used fields with greater foliage volume at 0.82.0 m in height and a high percentage of bare soil (P < 0.001). Nocturnal use of fields or forests by radio-marked woodcock did not differ among age or sex classes. However, females moved an average of 230 + 32.1 m between diurnal and nocturnal locations while males moved 525 + 53.1 m ( P = 0.085). Movements differed among moon phases (P < 0.003), ranging from 579 + 79.6 m during the new moon to 213 + 50.5 m during the full moon. To manage habitat on the wintering grounds, seed tree-clearcuts and fallow-old fields should be created or maintained near preferred diurnal habitats.

Journal of Wildlife Management↗

USGS2016

Book review: Inside the Equal Access to Justice Act: Environmental litigation and the crippling battle over America's lands, endangered species, and critical habitats

Inside the Equal Access to Justice Act is authored by Lowell E. Baier, an attorney, political scientist, and historian whose conservation portfolio includes the J. N. “Ding” Darling Conservation Award from the National Wildlife Federation (2016), Citizen Conservationist Award from the Association of Fish and Wildlife Agencies (2013), Conservationist of the Year Award from Outdoor Life magazine (2010), and Conservationist of the Year Award from the National Fish and Wildlife Foundation (2008). In the book, Baier stresses the need to reform the Equal Access to Justice Act (EAJA) because of unintended provisions that incentivize and reward environmental litigants for filing suit against federal regulatory and land management agencies, consequentially hindering pro-active, cooperative, conservation efforts. The book is the culmination of several years of legal research, case history analyses, and personal interviews with several key individuals from congress, conservation management agencies, and non-government organizations. Review info: Inside the equal access to justice act: Environmental litigation and the crippling battle over America's lands, endangered species, and critical habitats. By Lowell E. Baier, 2016. ISBN: 978-1442257443, 678 pp.

Journal of Wildlife Management↗

USGS2018

Factors influencing elk recruitment across ecotypes in the Western United States

Ungulates are key components in ecosystems and economically important for sport and subsistence harvest. Yet the relative importance of the effects of weather conditions, forage productivity, and carnivores on ungulates are not well understood. We examined changes in elk ( Cervus canadensis ) recruitment (indexed as age ratios) across 7 states and 3 ecotypes in the northwestern United States during 1989–2010, while considering the effects of predator richness, forage productivity, and precipitation. We found a broad‐scale, long‐term decrease in elk recruitment of 0.48 juveniles/100 adult females/year. Weather conditions (indexed as summer and winter precipitation) showed small, but measurable, influences on recruitment. Forage productivity on summer and winter ranges (indexed by normalized difference vegetation index [NDVI] metrics) had the strongest effect on elk recruitment relative to other factors. Relationships between forage productivity and recruitment varied seasonally and regionally. The productivity of winter habitat was more important in southern parts of the study area, whereas annual variation in productivity of summer habitat had more influence on recruitment in northern areas. Elk recruitment varied by up to 15 juveniles/100 adult females across the range of variation in forage productivity. Areas with more species of large carnivores had relatively low elk recruitment, presumably because of increased predation. Wolves ( Canis lupus ) were associated with a decrease of 5 juveniles/100 adult females, whereas grizzly bears ( Ursus arctos ) were associated with an additional decrease of 7 juveniles/100 adult females. Carnivore species can have a critical influence on ungulate recruitment because their influence rivals large ranges of variation in environmental conditions. A more pressing concern, however, stems from persistent broad‐scale decreases in recruitment across the distribution of elk in the northwestern United States, irrespective of carnivore richness. Our results suggest that wildlife managers interested in improving recruitment of elk consider the combined effects of habitat and predators. Efforts to manage summer and winter ranges to increase forage productivity may have a positive effect on recruitment.

Journal of Wildlife Management↗

USGS2016

Population dynamics of mallards breeding in eastern Washington

Variation in regional population trends for mallards breeding in the western United States indicates that additional research into factors that influence demographics could contribute to management and understanding the population demographics of mallards across North America. We estimated breeding incidence and adult female, nest, and brood survival in eastern Washington in 2006 and 2007 by monitoring female mallards with radio telemetry and tested how those parameters were influenced by study year (2006 vs. 2007), landscape type (agricultural vs. natural), and age (second year [SY] vs. after second year [ASY]). We also investigated the effects of female body condition and capture date on breeding incidence, and nest initiation date and hatch date on nest and brood survival, respectively. We included population parameters in a stage-based demographic model and conducted a perturbation analysis to identify which vital rates were most influential on population growth rate (λ). Adult female survival was best modeled with a constant weekly survival rate (0.994, SE = 0.003). Breeding incidence differed between years and was higher for birds in better body condition. Nest survival was higher for ASY females (0.276, SE = 0.118) than SY females (0.066, SE = 0.052), and higher on publicly managed lands (0.383, SE = 0.212) than agricultural (0.114, SE = 0.058) landscapes. Brood survival was best modeled with a constant rate for the 7-week monitoring period (0.50, SE = 0.155). The single variable having the greatest influence on λ was non-breeding season survival, but the combination of parameters from the breeding grounds explained a greater percent of the variance in λ. Mallard population growth rate was most sensitive to changes in non-breeding survival, nest success, brood survival, and breeding incidence. Future management decisions should focus on activities that improve these vital rates if managers want to increase the production of mallards in eastern Washington.

Washington↗

USGS2011

Estimating occupancy dynamics in an anuran assemblage from Louisiana, USA

Effective monitoring programs are designed to track changes in the distribution, occurrence, and abundance of species. We developed an extension of Royle and Kéry's (2007) single species model to estimate simultaneously temporal changes in probabilities of detection, occupancy, colonization, extinction, and species turnover using data on calling anuran amphibians, collected from 2002 to 2006 in the Lower Mississippi Alluvial Valley of Louisiana, USA. During our 5-year study, estimates of occurrence probabilities declined for all 12 species detected. These declines occurred primarily in conjunction with variation in estimates of local extinction probabilities (cajun chorus frog [ Pseudacris fouquettei ], spring peeper [ P. crucifer ], northern cricket frog [ Acris crepitans ], Cope's gray treefrog [ Hyla chrysoscelis ], green treefrog [ H. cinerea ], squirrel treefrog [ H. squirella ], southern leopard frog [ Lithobates sphenocephalus ], bronze frog [ L. clamitans ], American bullfrog [ L. catesbeianus ], and Fowler's toad [ Anaxyrus fowleri ]). For 2 species (eastern narrowmouthed toad [ Gastrophryne carolinensis ] and Gulf Coast toad [ Incilius nebulifer ]), declines in occupancy appeared to be a consequence of both increased local extinction and decreased colonization events. The eastern narrow-mouthed toad experienced a 2.5-fold increase in estimates of occupancy in 2004, possibly because of the high amount of rainfall received during that year, along with a decrease in extinction and increase in colonization of new sites between 2003 and 2004. Our model can be incorporated into monitoring programs to estimate simultaneously the occupancy dynamics for multiple species that show similar responses to ecological conditions. It will likely be an important asset for those monitoring programs that employ the same methods to sample assemblages of ecologically similar species, including those that are rare. By combining information from multiple species to decrease the variance on estimates of individual species, our results are advantageous compared to single-species models. This feature enables managers and researchers to use an entire community, rather than just one species, as an ecological indicator in monitoring programs.

Louisiana↗

USGS2004

Survival, cause-specific mortality, and harvesting of male black-tailed deer in washington

We determined survival rates, causes of mortality, and documented impacts of harvest on ???1.5-year-old male (hereafter, male) Columbian black-tailed deer (Odocoileus hemionus columbianus) in 2 Washington, USA, game management units (GMUs; Skookumchuck and Snoqualmie) characterized by different hunting-season structures. We monitored 66 males (n = 28 and 38 annually) in Skookumchuck and 58 males (n = 26 and 32 annually) in Snoqualmie, September 1999-September 2001. Annual survival rates were 0.498 (SE = 0.066) in Skookumchuck and 0.519 (SE = 0.067) in Snoqualmie. Survival rates derived from population age structure did not differ from rates derived from radiotelemetry. Harvest was the primary mortality factor for each population, accounting for 67% (SE = 7; Skookumchuck) to 44% (SE = 9; Snoqualmie) of total annual mortality. Annual harvest-specific mortality rates were 0.317 (SE = 0.032) in Skookumchuck and 0.211 (SE = 0.021) in Snoqualmie, likely due to longer hunting seasons and greater hunter effort in Skookumchuck. Following the elimination of a late buck season centered on the rut in Snoqualmie, male harvest declined 56% and annual survival increased 60%, indicating that male harvest was largely additive to other mortality. Our results indicated that harvest was the primary influence on male black-tailed deer populations in Washington, was additive, and that the effect of harvest varied with hunting-season structure and hunter effort. Managers should not assume that harvesting removes a constant proportion of the male population annually, and management models that assume compensatory mortality in adult harvest may result in over-harvest of male populations.

Journal of Wildlife Management↗

USGS1973

Land use and prairie grouse population relationships in North Dakota

The relationship between prairie grouse and land use was studied during the period 1964-71. Prairie chickens ( Tympanuchus cupido ) declined from 48 males in 1964 to none in 1971. Sharp-tailed grouse ( Pedioecetes phasianellus ) declined from 166 males in 1964 to 57 in 1971. These declines were related to the decline in vigor and eventual loss of Soil Bank habitat on the study area. Two new courtship grounds, established near fields recently retired under the Cropland Adjustment Program, were used by 44 percent of the male sharp-tailed grouse population in 1971. Hay lands on the study area did not support prairie grouse. Pasture lands were of no apparent value to prairie chickens and of limited value to sharp-tailed grouse. Management for prairie grouse should be directed toward developing and maintaining vigorous grass-forb communities on retired croplands and native prairie.

North Dakota↗

USGS1998

Response of nesting ducks to predator exclosures and water conditions during drought

We investigated whether small predator exclosures might be a useful tool for increasing duck recruitment. During a period of increasing drought from 1987 to 1991, we monitored populations of dabbling ducks on 9 51-km2 study areas, 3 of which contained a centrally located 25-ha predator exclosure and 3 of which served as control areas. We did not detect an increase in duck pairs per treated area/pairs per control area with time (P = 0.37). However, an index to the proportion of females nesting in exclosures increased with time for 4 of 5 dabbling duck species: mallards (Anas platyrhynchos; P < 0.001), gadwalls (A. strepera; P = 0.009), blue-winged teal (A. discors; P = 0.021), and northern pintails (A. acuta; P = 0.009). This index did not increase for northern shovelers (A. clypeata; P = 0.33). A regression ratio estimate of breeding population used in this study produced results similar to ratio estimates based on area of land or area of water. Duck populations declined on North Dakota study areas as drought increased, but populations remained relatively stable on a Minnesota study area. Pair numbers were positively related to area of ponds for all species (P = 0.000-0.078) and to number of ponds (P = 0.0006-0.014) for all species except gadwall (P = 0.35). Area of ponds explained more variation in pair numbers than did number of ponds for all species except shovelers. As the number of ponds decreased, the number of pairs per pond increased for mallards (P = 0.001) and gadwalls (P = 0.004) but not for teal (P = 0.67), shovelers (P = 0.76), or pintails (P = 0.93). Nest densities inside exclosures averaged 1.2 nests/ha, and nest success averaged 72% over 5 years, which was substantially higher than in similar habitat outside exclosures. Our inability to detect a change in duck pairs per treated area/pairs per control area was probably a result of small sample size, drought, and variability among study areas. However, the increase in proportion of the study area populations nesting inside exclosures, as well as high nest success and density inside exclosures, suggests that management of a small area can increase duck recruitment from a population in a larger surrounding area.

Journal of Wildlife Management↗

USGS2008

A hierarchical model for estimating change in American Woodcock populations

The Singing-Ground Survey (SGS) is a primary source of information on population change for American woodcock (Scolopax minor). We analyzed the SGS using a hierarchical log-linear model and compared the estimates of change and annual indices of abundance to a route regression analysis of SGS data. We also grouped SGS routes into Bird Conservation Regions (BCRs) and estimated population change and annual indices using BCRs within states and provinces as strata. Based on the hierarchical model?based estimates, we concluded that woodcock populations were declining in North America between 1968 and 2006 (trend = -0.9%/yr, 95% credible interval: -1.2, -0.5). Singing-Ground Survey results are generally similar between analytical approaches, but the hierarchical model has several important advantages over the route regression. Hierarchical models better accommodate changes in survey efficiency over time and space by treating strata, years, and observers as random effects in the context of a log-linear model, providing trend estimates that are derived directly from the annual indices. We also conducted a hierarchical model analysis of woodcock data from the Christmas Bird Count and the North American Breeding Bird Survey. All surveys showed general consistency in patterns of population change, but the SGS had the shortest credible intervals. We suggest that population management and conservation planning for woodcock involving interpretation of the SGS use estimates provided by the hierarchical model.

Journal of Wildlife Management↗

USGS2015

Density dependence, whitebark pine, and vital rates of grizzly bears

Understanding factors influencing changes in population trajectory is important for effective wildlife management, particularly for populations of conservation concern. Annual population growth of the grizzly bear ( Ursus arctos ) population in the Greater Yellowstone Ecosystem, USA has slowed from 4.2–7.6% during 1983–2001 to 0.3–2.2% during 2002–2011. Substantial changes in availability of a key food source and bear population density have occurred. Whitebark pine ( Pinus albicaulis ), the seeds of which are a valuable but variable fall food for grizzly bears, has experienced substantial mortality primarily due to a mountain pine beetle ( Dendroctonus ponderosae ) outbreak that started in the early 2000s. Positive growth rates of grizzly bears have resulted in populations reaching high densities in some areas and have contributed to continued range expansion. We tested research hypotheses to examine if changes in vital rates detected during the past decade were more associated with whitebark pine decline or, alternatively, increasing grizzly bear density. We focused our assessment on known-fate data to estimate survival of cubs-of-the-year (cubs), yearlings, and independent bears (≥2 yrs), and reproductive transition of females from having no offspring to having cubs. We used spatially and temporally explicit indices for grizzly bear density and whitebark pine mortality as individual covariates. Models indicated moderate support for an increase in survival of independent male bears over 1983–2012, whereas independent female survival did not change. Cub survival, yearling survival, and reproductive transition from no offspring to cubs all changed during the 30-year study period, with lower rates evident during the last 10–15 years. Cub survival and reproductive transition were negatively associated with an index of grizzly bear density, indicating greater declines where bear densities were higher. Our analyses did not support a similar relationship for the index of whitebark pine mortality. The results of our study support the interpretation that slowing of population growth during the last decade was associated more with increasing grizzly bear density than the decline in whitebark pine. Grizzly bear density and its potential effect on vital rates and population trajectory warrant consideration for management of the grizzly bear population in the Greater Yellowstone Ecosystem.

Idaho, Montana, Wyoming↗

USGS2026

Beginning with a single step: A social theory of change for managing chronic wasting disease

Emerging wildlife diseases, like chronic wasting disease (CWD), not only lead to changing dynamics within the ecology of the susceptible species but also to changes within interrelated social and management systems. Chronic wasting disease has proven challenging to manage partially because the best management practices (BMP) available have conflicted with historical cervid management paradigms. In support of CWD management decisions, we conducted an expert elicitation investigation of potential intervention strategies that experts believed would positively affect CWD management. The most prioritized intervention was “understanding audiences, outreach, and engagement with public.” Using the most prioritized intervention theme, we continued the expert elicitation process to develop a social theory of change that describes the expected results of implementing the intervention theme. The results chain describes a process of conducting social science investigation to gather evidence and understand the situation and use the gathered evidence to support the selection of appropriate behavior change strategies and pathways prior to implementing a desired CWD management action. The produced social theory of change provides CWD managing organizations with a framework for evaluating efforts to engage with the public about the actions they are taking and working to increase support or participation.

Journal of Wildlife Management↗

USGS2020

Preparing wildlife for climate change: How far have we come?

Global biodiversity is in unprecedented decline and on-the-ground solutions are imperative for conservation. Although there is a large volume of evidence related to climate change effects on wildlife, research on climate adaptation strategies is lagging. To assess the current state of knowledge in climate adaptation, we conducted a comprehensive literature review and evaluated 1,346 peer-reviewed publications for management recommendations designed to address the consequences of climate change on wildlife populations. From 509 publications, we identified 2,306 recommendations and employed both qualitative and quantitative methods for data analysis. Although we found an increase in the volume and diversity of recommendations since 2007, a focus on protected areas (26%, 596 of 2,306 recommendations) and the non-reserve matrix (12%, 276 of 2,306 recommendations) remained prominent in the climate adaptation literature. Common concepts include protected areas, invasive species, ecosystem services, adaptive management, stepping stones, assisted migration, and conservation easements. In contrast, only 1% of recommendations focused on reproduction ( n = 26), survival ( n = 14), disease ( n = 26), or human-wildlife conflict ( n = 24). Few recommendations reflected the potential for local-scale management interventions. We demonstrate limited advancement in preparing natural resource managers in climate adaptation at local, management-relevant scales. Additional research is needed to identify and evaluate climate adaptation strategies aimed at reducing the vulnerability of wildlife to contemporary climate change. © 2020 The Wildlife Society.

Journal of Wildlife Management↗

USGS2011

Spatial ecology of white-tailed deer fawns in the northern Great Plains: implications of loss of conservation reserve program grasslands

Few studies have evaluated how wildlife, and white-tailed deer ( Odocoileus virginianus ) in particular, respond to Conservation Reserve Program (CRP) grasslands. We conducted a 3-year study (2007–2009) to determine the influence of CRP on fawn ecology during a time of declining CRP enrollment. We captured and radiocollared 81 fawn white-tailed deer during 15 May to 15 June 2007–2009 in north-central South Dakota, collected 6,505 locations, and documented 70 summer home ranges. Mean summer home ranges increased temporally during 2007–2009 ( P < 0.001) and corresponded to a 41% loss of CRP grasslands in the area (2.3% loss in land cover and approx. 21% loss in cover habitat in the study area) over the duration of the study. Additionally, mean movement between daily locations increased ( P < 0.001) from 2007 to 2009. Analysis of covariance models indicated that change in CRP influenced home-range size, and change in CRP and wheat influenced daily movement. Smaller home ranges and reduced movements were associated with greater quantity of CRP available to fawns, and increased movements were associated with more acreage of wheat available to fawns. Fawns shifted resource selection during the summer at a mean age ranging from 48.8 days to 58.6 days, and this shift was associated with height of corn (83–87 cm). During early summer, fawns consistently selected for CRP; selection of wheat progressed temporally from avoidance in 2007 to selection in 2009. During late summer, fawns consistently selected for corn habitat and used CRP at least in proportion to its availability. Reduction in CRP-grasslands seemed to increase fawn home-range size and daily movements and, influenced change in resource selection to wheat. Current legislation mandates continued decrease in CRP enrollment and concomitant increase in the planting of corn for ethanol production. Management of habitat throughout the grasslands of the Northern Great Plains that maximizes cover habitats would provide neonates with adequate cover for protection from predators.

Great Plains↗

USGS2014

Survival of surf scoters and white-winged scoters during remigial molt

Quantifying sources and timing of variation in demographic rates is necessary to determine where and when constraints may exist within the annual cycle of organisms. Surf scoters ( Melanitta perspicillata ) and white-winged scoters ( M. fusca ) undergo simultaneous remigial molt during which they are flightless for >1 month. Molt could result in reduced survival due to increased predation risk or increased energetic demands associated with regrowing flight feathers. Waterfowl survival during remigial molt varies across species, and has rarely been assessed for sea ducks. To quantify survival during remigial molt, we deployed very high frequency (VHF) transmitters on surf scoters ( n  = 108) and white-winged scoters ( n  = 57) in southeast Alaska and the Salish Sea (British Columbia and Washington) in 2008 and 2009. After censoring mortalities potentially related to capture and handling effects, we detected no mortalities during remigial molt; thus, estimates of daily and period survival for both scoter species during molt were 1.00. We performed sensitivity analyses in which mortalities were added to the dataset to simulate potential mortality rates for the population and then estimated the probability of obtaining a dataset with 0 mortalities. We found that only at high survival rates was there a high probability of observing 0 mortalities. We conclude that remigial molt is normally a period of low mortality in the annual cycle of scoters. The molt period does not appear to be a constraint on scoter populations; therefore, other annual cycle stages should be targeted by research and management efforts to change population trajectories.

Alaska, British Columbia, Washington↗

USGS2006

Demographic patterns and harvest vulnerability of chronic wasting disease infected white-tailed deer in Wisconsin

Chronic wasting disease (CWD) is a fatal disease of white-tailed deer (Odocoileus virginianus) caused by transmissible protease-resistant prions. Since the discovery of CWD in southern Wisconsin in 2001, more than 20,000 deer have been removed from a >2,500-km2 disease eradication zone surrounding the three initial cases. Nearly all deer removed were tested for CWD infection and sex, age, and harvest location were recorded. Our analysis used data from a 310-km2 core study area where disease prevalence was higher than surrounding areas. We found no difference in harvest rates between CWD infected and noninfected deer. Our results show that the probability of infection increased with age and that adult males were more likely to be infected than adult females. Six fawns tested positive for CWD, five fawns from the core study area, including the youngest (5 months) free-ranging cervid to test positive. The increase in male prevalence with age is nearly twice the increase found in females. We concluded that CWD is not randomly distributed among deer and that differential transmission among sex and age classes is likely driving the observed patterns in disease prevalence. We discuss alternative hypotheses for CWD transmission and spread and, in addition, discuss several possible nonlinear relationships between prevalence and age. Understanding CWD transmission in free-ranging cervid populations will be essential to the development of strategies to manage this disease in areas where CWD is found, as well as for surveillance strategies in areas where CWD threatens to spread.

Journal of Wildlife Management↗