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Significance Invasive species can cause extinctions of native species and widespread biodiversity loss. Invader removal is a common management response, but the use of long-term field experiments to characterize effectiveness of removals in benefitting impacted native species is rare. We used a large-scale removal experiment to investigate the demographic response of a threatened native species, the northern spotted owl, to removal of an invasive competitor species, the barred owl. Removal of barred owls had a strong, positive effect on survival of spotted owls, which arrested long-term population declines of spotted owls. The results demonstrate that the long-term persistence of spotted owls will depend heavily on reducing the negative impacts of barred owls while simultaneously addressing other threats, such as habitat loss., Changes in the distribution and abundance of invasive species can have far-reaching ecological consequences. Programs to control invaders are common but gauging the effectiveness of such programs using carefully controlled, large-scale field experiments is rare, especially at higher trophic levels. Experimental manipulations coupled with long-term demographic monitoring can reveal the mechanistic underpinnings of interspecific competition among apex predators and suggest mitigation options for invasive species. We used a large-scale before–after control–impact removal experiment to investigate the effects of an invasive competitor, the barred owl (Strix varia), on the population dynamics of an iconic old-forest native species, the northern spotted owl (Strix occidentalis caurina). Removal of barred owls had a strong, positive effect on survival of sympatric spotted owls and a weaker but positive effect on spotted owl dispersal and recruitment. After removals, the estimated mean annual rate of population change for spotted owls stabilized in areas with removals (0.2% decline per year), but continued to decline sharply in areas without removals (12.1% decline per year). The results demonstrated that the most substantial changes in population dynamics of northern spotted owls over the past two decades were associated with the invasion, population expansion, and subsequent removal of barred owls. Our study provides experimental evidence of the demographic consequences of competitive release, where a threatened avian predator was freed from restrictions imposed on its population dynamics with the removal of a competitively dominant invasive species.

Over the past decade, there has been much methodological development for the estimation of abundance and related demographic parameters using mark‐resight data. Often viewed as a less‐invasive and less‐expensive alternative to conventional mark recapture, mark‐resight methods jointly model marked individual encounters and counts of unmarked individuals, and recent extensions accommodate common challenges associated with imperfect detection. When these challenges include both individual detection heterogeneity and an unknown marked sample size, we demonstrate several deficiencies associated with the most widely used mark‐resight models currently implemented in the popular capture‐recapture freeware Program MARK. We propose a composite likelihood solution based on a zero‐inflated Poisson log‐normal model and find the performance of this new estimator to be superior in terms of bias and confidence interval coverage. Under Pollock's robust design, we also extend the models to accommodate individual‐level random effects across sampling occasions as a potentially more realistic alternative to models that assume independence. As a motivating example, we revisit a previous analysis of mark‐resight data for the New Zealand Robin (Petroica australis) and compare inferences from the proposed estimators. For the all‐too‐common situation where encounter rates are low, individual detection heterogeneity is non‐negligible, and the number of marked individuals is unknown, we recommend practitioners use the zero‐inflated Poisson log‐normal mark‐resight estimator as now implemented in Program MARK.

Western North American forest ecosystems are experiencing rapid changes in disturbance regimes because of climate change and land use legacies (Littell et al. 2018). In many of these forests, the accumulation of surface and ladder fuels from a century of fire suppression, coupled with a warming and drying climate, has led to increases in the number of large fires (Westerling 2016) and the proportion of areas burning at higher severity (Safford and Stevens 2017, Singleton et al. 2018). While the annual area burned by fire is still below historical levels (Taylor et al. 2016), some forest types in the west are burning at higher severities when compared to pre-European settlement periods (Mallek et al. 2013, Safford and Stevens 2017). As such, they face an increased risk of conversion to non-forest ecosystems (e.g., shrublands, non-native grasslands) following large, severe fires because of compromised seed sources, post-fire soil erosion and loss, high-severity re-burn, and climatic thresholds (Coppoletta et al. 2016, Stevens et al. 2017, Rissman et al. 2018, Shive et al. 2018, Wood and Jones 2019). Restoration methods such as mechanical thinning and prescribed and managed wildland fire that reduce accumulated surface and ladder fuels (e.g., removal of smalland medium-sized trees, especially non-fire adapted species) may reduce the spatial extent of severe fires and increase forest resilience to fire in a changing climate (Agee and Skinner 2005, Stephens et al. 2013, Hessburg et al. 2016, Tubbesing et al. 2019) and, in doing so, promote key ecosystem services (Hurteau et al. 2014, Kelsey et al. 2017, Wood and Jones 2019).

The northern spotted owl (Strix occidentalis caurina) inhabits older coniferous forests in the Pacific Northwest and has been at the center of forest management issues in this region. The immediate threats to this federally listed species include habitat loss and competition with barred owls (Strix varia), which invaded from eastern North America. We conducted a prospective meta-analysis to assess population trends and factors affecting those trends in northern spotted owls using 26 years of survey and capture-recapture data from 11 study areas across the owls' geographic range to analyze demographic traits, rates of population change, and occupancy parameters for spotted owl territories. We found that northern spotted owl populations experienced significant declines of 6–9% annually on 6 study areas and 2–5% annually on 5 other study areas. Annual declines translated to ≤35% of the populations remaining on 7 study areas since 1995. Barred owl presence on spotted owl territories was the primary factor negatively affecting apparent survival, recruitment, and ultimately, rates of population change. Analysis of spotted and barred owl detections in an occupancy framework corroborated the capture-recapture analyses with barred owl presence increasing territorial extinction and decreasing territorial colonization of spotted owls. While landscape habitat components reduced the effect of barred owls on these rates of decline, they did not reverse the negative trend. Our analyses indicated that northern spotted owl populations potentially face extirpation if the negative effects of barred owls are not ameliorated while maintaining northern spotted owl habitat across their range.

The introduction of a non-native freshwater fish, blue catfish Ictalurus furcatus, in tributaries of Chesapeake Bay resulted in the establishment of fisheries and in the expansion of the population into brackish habitats. Blue catfish are an invasive species in the Chesapeake Bay region, and efforts are underway to limit their impacts on native communities. Key characteristics of the population (population size, survival rates) are unknown, but such knowledge is useful in understanding the impact of blue catfish in estuarine systems. We estimated population size and survival rates of blue catfish in tidal habitats of the James River subestuary. We tagged 34,252 blue catfish during July–August 2012 and 2013; information from live recaptures (n = 1177) and dead recoveries (n = 279) were used to estimate annual survival rates and population size using Barker’s Model in a Robust Design and allowing for heterogeneity in detection probabilities. The blue catfish population in the 12-km study area was estimated to be 1.6 million fish in 2013 (95% confidence interval [CI] adjusted for overdispersion: 926,307–2,914,208 fish). Annual apparent survival rate estimates were low: 0.16 (95% CI 0.10–0.24) in 2012–2013 and 0.44 (95% CI 0.31–0.58) in 2013–2014 and represent losses from the population through mortality, permanent emigration, or both. The tagged fish included individuals that were large enough to exhibit piscivory and represented size classes that are likely to colonize estuarine habitats. The large population size that we estimated was unexpected for a freshwater fish in tidal habitats and highlights the need to effectively manage such species.

Colorado pikeminnow Ptychocheilus lucius, a large, endangered, piscivorous cyprinid once abundant throughout warm-water reaches of North Americaís Colorado River system, has been reduced to 2 wild populations inhabiting the Colorado and Green rivers. Status and trends of these remaining populations were unknown when a recovery program was initiated in 1987. During 1991 to 2013, we used mark-recapture to monitor the smaller Colorado River population. Adult abundance was estimated and patterns of recruitment and dispersal assessed to determine if recovery actions produced a population response. In 1992, adults were rare (Ñ = 345; 95% CI = 216 to 583) in the 288 km study area, but recruitment of a strong 1986 year class began a positive trend, and adult estimates reached 674 (95% CI = 517 to 897) by 2008. A significant decline then ensued, and by 2013, an estimated 282 adults remained (95% CI = 204 to 407). Annual adult survival was relatively high and stable. Juvenile survival was variable, making catch rates of young-of-the-year unreliable predictors of later recruitment strength. An estimated average of 6.5 fish immigrated annually to the Colorado River from the larger Green River population, and movements appeared balanced in direction. Though self-sustaining over the 23 yr study, low abundance and a recent rapid decline suggest long-term population persistence is tenuous. Population increase is impeded by a high frequency of weak recruiting cohorts. Results suggest 25 yr of recovery efforts have not sufficiently addressed ongoing threats affecting recruitment, including river regulation, non-native fish invasions, and other potential threats yet to be evaluated.

Annual banding programs have allowed the estimation of key demographic parameters for many populations of harvested wildlife, yet they often provide little insight into vital rate variation among seasonally occupied habitats or among regions with differing hunting regulations. For lesser snow geese (Chen caerulescens caerulescens) in the midcontinent of North America, rapid growth in abundance and the consequent implementation of special conservation measures present a scenario where seasonal mortality estimates would be highly valuable. We evaluated variation in hunting mortality of adult and young geese among 3 seasons (autumn, winter, and spring) based on annual banding data from breeding colonies north and south of 60°N latitude, and seasonal hunting recoveries from the United States and Canada. Using band-recovery models and data covering 1999 through 2015, we first estimated annual survival for geese of both age classes and breeding locations, and then subsequently used seasonal hunting recoveries to derive estimates of seasonal hunting mortality and annual non-hunting mortality. Simulation models validated the accuracy of this approach. Hunting mortality in winter generally exceeded that during spring and autumn, but our estimates suggested that hunting mortality represented a small fraction of annual mortality for adult and young birds. Consistent with recent studies, our estimates pointed to a greater harvest effect for the smaller subarctic population breeding near southern Hudson Bay, Canada, than for the large arctic population breeding farther north. Although mean kill rates were higher for young than adult geese, natural mortality for young was high and temporally variable, implying that some hunting mortality experienced by young geese during their first year could be compensated by natural causes of death. Natural (non-hunting) mortality and annual survival showed greater temporal variation than seasonal kill rates in adults and young geese, highlighting the importance of non-harvest factors (e.g., climate, habitat, population density) to the dynamics of these populations. These novel estimates of seasonal kill rates and non-hunting mortality contribute further support to the notion that internal dynamics of the lesser snow goose midcontinent population, including natural mortality and recruitment, currently influence population trajectory more than ongoing interventions through harvest management. © 2017 The Wildlife Society.

The Nearctic northern goshawk (Accipiter gentilis atricapillis) is a resident of conifer, broadleaf, and mixed forests from the boreal to the southwestern montane regions of North America. We report on a 20-year mark-recapture investigation (1991–2010) of the distribution and density of breeders, temporal and spatial variability in breeding, nestling sex ratios, local versus immigrant recruitment of breeders, breeding age structure, age-specific survival rates, and rate of population change (λ) of this species on the Kaibab Plateau, a forested sky island in northern Arizona, USA. We used an information-theoretic approach to rank models representing alternative hypotheses about the influence of annual fluctuations in precipitation on the annual frequency of goshawk breeding and fledgling production. We studied 125 goshawk breeding territories, representing approximately 87% of an estimated 144 total territories based on a mean distance of 3.8 km between territory centers in a 1,728-km2 study area. The salient demographic feature of the population was extensive annual variation in breeding, which manifested as large inter-annual variation in proportions of pairs laying eggs, brood sizes, nest failure rates, and fledgling production. The percent of territories known in a prior year in which eggs were laid in a current year ranged from 8% to 86% (x¯ = 37%, SE = 4.51), annual mean nest failure rate (active nests that failed) ranged from 12% to 48% (overall x¯ = 23%, SE = 2.48), and mean annual brood size of successful nests (fledged ≥1 fledgling) ranged from 1.5 young to 2.5 young (overall x¯ = 2.0 young, SE = 0.03). Inter-annual variation in reproduction closely tracked inter-annual variation in precipitation, which we hypothesize influenced primary forest productivity and bird and mammal prey abundance. The best breeding years (1992–1993, 77–87% of pairs laid eggs) were coincident with a record-long El Nino-Southern Oscillation (ENSO) wet period and the worst breeding year (2003; 8% of pairs laid eggs) was the last of a 3-year record drought. Overall breeding success was 83% with most failures occurring during incubation; once eggs hatched, goshawks tended to fledge young. The pooled 20-year nestling sex ratio did not differ from unity (53% M; n = 410 M, 366 F) but was significantly male-biased in 2 years and female-biased in 1 year. Nonetheless, the overall greater production of male fledglings followed a strong trend of greater male production in other goshawk populations, suggesting that breeders might have been adaptively adjusting their offspring sex ratio, perhaps to produce more of the rarer (male) sex. Annual recruitment of new individuals into the breeding population averaged 43% during the study. Study area recruitment rate of hawks locally born (in situ) and banded was 0.12. Both sexes had equal tendencies to return to the Kaibab Plateau to breed (no differences in philopatry) and there were no differences in natal dispersal distances (natal to first breeding site) between the sexes. During the final years of study (1999–2010), an estimated 46% of breeding recruits were locally born and 54% were immigrants from distant forests. Minimum age at first breeding was 2 years and mean age at first breeding by known-age hawks (banded as nestlings or aged on plumage at first breeding) was 3.7 years for males and 3.5 years for females. Mean lifespan (yr from first banding as nestling to last resighting) of known-age goshawks was 6.9 years for both sexes. Mean minimum apparent lifespan of breeders aged ≥4 years based on plumage at first capture was 6.5 years for both sexes. Average age of goshawks at their first detection was 3.9 years old, at which time apparent survival was estimated at 0.77 for both sexes, which was just slightly less than the peak survival of 0.78 as a function of age. Age-specific survival estimates showed a steady decline after 9 years old and approached 0 at 20 years of age. Estimates of λ for breeding adults (M, 0.94, SE = 0.037; F, 0.98, SE = 0.038) provided only weak evidence for a population decline during the study. Although sex was not in the top survival model, models including age + sex were competitive, evidencing lower male than female survival, a finding corroborated by the occurrence of sex effects in the top λ model. Lower male survival may result from higher mortality associated with hunting agile prey in vegetation-filled environments during long breeding seasons when they are the primary forager. Lower survival may be compensated by the more frequent production (53%) of male fledglings. High-severity crown fire was an existential threat to the population. In addition to 4 large high-severity fires that burned roughly 3,770 ha (equal to 3 goshawk territories) in the 30 years preceding 1991, 6 high-severity fires burned another 30,945 ha during our study and killed most (>64%) of the forests in 8 known territories and possibly another 2 that were burned before we completed surveys. Based on a lack of any recent demographic perturbations in age structure, a relatively high and time-constant annual adult survival rate, confidence intervals around adult λ estimates overlapping 1.0, and a study area saturated with territories, we surmise that the goshawk population on the Kaibab Plateau was stable during the 20-year study. Nonetheless, uncertainty remains regarding the population's future status because of a declining trend in breeding frequency, uncertain status (dead, alive, emigrated) of non-breeding adults, extensive temporal and spatial variation in breeding, and high frequency of immigrant recruits to the breeding population on the Kaibab Plateau. If the century-long decline in precipitation persists, especially at the increased rate seen since 1980, and manifests as deeper droughts, diminished wet periods, and weaker pulses in forest productivity, then the Kaibab Plateau goshawk population would be expected to show unambiguous evidence of decline. Evidence would include reduced local and regional goshawk reproduction and survival, reduced frequency of immigration, and further habitat loss to catastrophic fire. © 2017 The Wildlife Society.

Estimation of population abundance is a common problem in wildlife ecology and management. Capture-mark-reencounter (CMR) methods using marked animals are a standard approach, particularly in recent history with the development of innovative methods of marking using camera traps or DNA samples. However, estimates of abundance from multiple encounters of marked individuals are biased low when individual heterogeneity of encounter probabilities is not accounted for in the estimator. We evaluated the operating characteristics of the Huggins logit-normal estimator through computer simulations, using Gaussian–Hermite quadrature to model individual encounter heterogeneity. We simulated individual encounter data following a factorial design with 2 levels of sampling occasions (t = 5, 10), 3 levels of abundance (N = 100, 500, 1,000), 4 levels of median detection probabilities (p = 0.1, 0.2, 0.4, 0.6) for each sampling occasion (on the probability scale), and 4 levels of individual heterogeneity (σp = 0, 0.5, 1, 2; on the logit normal scale), resulting in a design space consisting of 96 simulation scenarios (2 × 3 × 4 × 4). For each scenario, we performed 1,000 simulations using the Huggins estimators Mt, M0, MtRE, and M0RE, where the RE subscript corresponds to the random effects model. As expected, the Mt and M0 estimators were biased when individual heterogeneity was present but unbiased for σp = 0 data. The estimators for MtRE and M0RE were biased high for N = 100 and median p ≤ 0.2 but showed little bias elsewhere. The bias is attributed to the occasional sets of data that result in a low overall detection probability and a resulting highly skewed sampling distribution of Nˆ. This result is confirmed in that the median of the sampling distributions was only slightly biased high. The random effects estimators performed poorly for σp = 0 data, mainly because a log link function forces the estimate of σp > 0. However, the Fletcher cˆ statistic provided useful evidence to evaluate σp > 0, as did likelihood ratio tests of the null hypothesis σp = 0. Generally, confidence interval coverage of N appears close to the nominal 95% expected when the estimator is not biased. © 2017 The Wildlife Society.

Evaluating anthropogenic mortality is important to develop conservation strategies for red wolf (Canis lupus) recovery. We used 26 years of population data in a generalized linear mixed model to examine trends in cause-specific mortality and a known-fate model in Program MARK to estimate survival rates for the reintroduced red wolf population in North Carolina, USA. We found the proportion of mortality attributable to anthropogenic causes, specifically mortality caused by gunshot during fall and winter hunting seasons (Oct–Dec), increased significantly since 2000 and became the leading cause of red wolf death. Mortality rates were greatest for red wolves

The Northern Pike Esox lucius is invasive in the upper Green and Yampa River basins of Colorado and Utah and impedes endangered fish recovery in the upper Colorado River basin. Mechanical removal was implemented in 2004, but Northern Pike population dynamics and removal efficacy were not well understood. We analyzed mark–recapture records from 8,929 individual Northern Pike captured during 2004–2010 from three reaches of the Yampa River: Hayden to Craig (upstream reach), South Beach–Little Yampa Canyon–Juniper (middle reach), and Maybell–Sunbeam (downstream reach), encompassing 175 river kilometers. Annual survival rates for Northern Pike of the mean TL (465 mm) were highest downstream (mean = 0.54; range = 0.36–0.71) and lowest upstream (mean = 0.25; range = 0.12–0.38). Annual abundance exhibited the opposite pattern, as it was highest upstream (annual range = 1,144–4,078 fish) and lowest downstream (range = 232–746 fish). After removal occurred each year, Northern Pike abundance increased annual...

Estimates of species' vital rates and an understanding of the factors affecting those parameters over time and space can provide crucial information for management and conservation. We used mark-recapture, reproductive output, and territory occupancy data collected during 1985-2013 to evaluate population processes of Northern Spotted Owls (Strix occidentalis caurina) in 11 study areas in Washington, Oregon, and northern California, USA. We estimated apparent survival, fecundity, recruitment, rate of population change, and local extinction and colonization rates, and investigated relationships between these parameters and the amount of suitable habitat, local and regional variation in meteorological conditions, and competition with Barred Owls (Strix varia). Data were analyzed for each area separately and in a meta-analysis of all areas combined, following a strict protocol for data collection, preparation, and analysis. We used mixed effects linear models for analyses of fecundity, Cormack-Jolly-Seber open population models for analyses of apparent annual survival (phi), and a reparameterization of the Jolly-Seber capture-recapture model (i.e. reverse Jolly-Seber; RJS) to estimate annual rates of population change (lambda(RJS)) and recruitment. We also modeled territory occupancy dynamics of Northern Spotted Owls and Barred Owls in each study area using 2-species occupancy models. Estimated mean annual rates of population change (lambda) suggested that Spotted Owl populations declined from 1.2% to 8.4% per year depending on the study area. The weighted mean estimate of lambda for all study areas was 0.962 (+/- 0.019 SE; 95% CI: 0.925-0.999), indicating an estimated range-wide decline of 3.8% per year from 1985 to 2013. Variation in recruitment rates across the range of the Spotted Owl was best explained by an interaction between total winter precipitation and mean minimum winter temperature. Thus, recruitment rates were highest when both total precipitation (29 cm) and minimum winter temperature (-9.5 degrees C) were lowest. Barred Owl presence was associated with increased local extinction rates of Spotted Owl pairs for all 11 study areas. Habitat covariates were related to extinction rates for Spotted Owl pairs in 8 of 11 study areas, and a greater amount of suitable owl habitat was generally associated with decreased extinction rates. We observed negative effects of Barred Owl presence on colonization rates of Spotted Owl pairs in 5 of 11 study areas. The total amount of suitable Spotted Owl habitat was positively associated with colonization rates in 5 areas, and more habitat disturbance was associated with lower colonization rates in 2 areas. We observed strong declines in derived estimates of occupancy in all study areas. Mean fecundity of females was highest for adults (0.309 +/- 0.027 SE), intermediate for 2-yr-olds (0.179 +/- 0.040 SE), and lowest for 1-yr-olds (0.065 +/- 0.022 SE). The presence of Barred Owls and habitat covariates explained little of the temporal variation in fecundity in most study areas. Climate covariates occurred in competitive fecundity models in 8 of 11 study areas, but support for these relationships was generally weak. The fecundity meta-analysis resulted in 6 competitive models, all of which included the additive effects of geographic region and annual time variation. The 2 top-ranked models also weakly supported the additive negative effects of the amount of suitable core area habitat, Barred Owl presence, and the amount of edge habitat on fecundity. We found strong support for a negative effect of Barred Owl presence on apparent survival of Spotted Owls in 10 of 11 study areas, but found few strong effects of habitat on survival at the study area scale. Climate covariates occurred in top or competitive survival models for 10 of 11 study areas, and in most cases the relationships were as predicted; however, there was little consistency among areas regarding the relative importance of specific climate covariates. In contrast, meta-analysis results suggested that Spotted Owl survival was higher across all study areas when the Pacific Decadal Oscillation (PDO) was in a warming phase and the Southern Oscillation Index (SOI) was negative, with a strongly negative SOI indicative of El Nino events. The best model that included the Barred Owl covariate (BO) was ranked 4th and also included the PDO covariate, but the BO effect was strongly negative. Our results indicated that Northern Spotted Owl populations were declining throughout the range of the subspecies and that annual rates of decline were accelerating in many areas. We observed strong evidence that Barred Owls negatively affected Spotted Owl populations, primarily by decreasing apparent survival and increasing local territory extinction rates. However, the amount of suitable owl habitat, local weather, and regional climatic patterns also were related to survival, occupancy (via colonization rate), recruitment, and, to a lesser extent, fecundity, although there was inconsistency in regard to which covariates were important for particular demographic parameters or across study areas. In the study areas where habitat was an important source of variation for Spotted Owl demographics, vital rates were generally positively associated with a greater amount of suitable owl habitat. However, Barred Owl densities may now be high enough across the range of the Northern Spotted Owl that, despite the continued management and conservation of suitable owl habitat on federal lands, the long-term prognosis for the persistence of Northern Spotted Owls may be in question without additional management intervention. Based on our study, the removal of Barred Owls from the Green Diamond Resources (GDR) study area had rapid, positive effects on Northern Spotted Owl survival and the rate of population change, supporting the hypothesis that, along with habitat conservation and management, Barred Owl removal may be able to slow or reverse Northern Spotted Owl population declines on at least a localized scale. USDA Forest ServiceUnited States Department of Agriculture (USDA)United States Forest Service; USDI Bureau of Land Management; USDI National Park Service; Green Diamond Resource Company; Plum Creek Timber Company; Louisiana Pacific Lumber Company; Hancock Forest Management; Hoopa Tribe; USDI Bureau of Land Management via a Cost Reimbursable Research Agreement with Oregon State University Funding for demographic studies of Northern Spotted Owls on federal lands was provided primarily by the USDA Forest Service, USDI Bureau of Land Management, and USDI National Park Service. Funding for studies on nonfederal lands came from the Green Diamond Resource Company, Plum Creek Timber Company, Louisiana Pacific Lumber Company, Hancock Forest Management, and the Hoopa Tribe. Funding for the workshop was provided by the USDA Forest Service and USDI Bureau of Land Management via a Cost Reimbursable Research Agreement with Oregon State University. The U.S. Geological Survey and USDA Forest Service required approval of the final manuscript before publication, but none of the funding agencies associated with this meta-analysis had any influence on the content of the submitted or published manuscript. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Ethics statement: All data from study areas in which K.M.D., E.D.F., and A.B.F. were principal investigators (CLE, OLY, COA, HJA, TYE, CAS, and NWC) were collected following protocols approved under animal care and use permits overseen by Oregon State University's and Colorado State University's Institutional Animal Care and Use Committees. These protocols were followed and all relevant state and federal permits were acquired and maintained for all study areas included in this meta-analysis. Public domain – authored by a U.S. government employee

The loss and modification of freshwater ecosystems has led to high rates of imperilment for freshwater species. The Giant Gartersnake (Thamnophis gigas) is among the species that have suffered declines in abundance and spatial distribution and is currently listed as a threatened species by the U.S. government and the State of California. Conservation and management of populations of T. gigas are hampered by a lack of information on its demography. Without estimates of demographic parameters, the status of the population is difficult to characterize, and identifying the parameters to target in management planning is problematic. We used capture–recapture data from two populations in the Great Central Valley of California to estimate annual survival probability. We also evaluated hypothesized causes of variation in survival probability among individuals and among years. Model-selection results for the population in the American Basin indicated that females have a higher survival probability than males and t...

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. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

The brown bear population on the Kenai Peninsula, Alaska, has not been empirically estimated previously because conventional aerial methods over this heavily forested landscape were infeasible. We applied a rapid field protocol to a DNA-based, mark-recapture approach on a large and tightly bounded sample frame to estimate brown bear abundance. We used lure to attract bears to barbed wire stations deployed in 145 9-km × 9-km cells systematically distributed across 10,200 km2 of available habitat on the Kenai National Wildlife Refuge and Chugach National Forest during 31 consecutive days in early summer 2010. Using 2 helicopters and 4 2-person field crews, we deployed the stations during a 6-day period and subsequently revisited these stations on 5 consecutive 5-day trap sessions. We extracted DNA to identify individual bears and developed capture histories as input to mark-recapture models. Combined with data from radio-telemetered bears, ≥243 brown bears were alive on the Kenai Peninsula in 2010, but we used only 99 females and 104 males in modeling. We used Akaike's Information Criterion selection and model averaging to estimate 428 (95% lognormal CI = 353–539) brown bears (including all age classes) on the study area. Despite low recaptures rates, we achieved reasonable precision by ensuring geographic and demographic population closure through a spatially comprehensive sample frame and very short sampling window. We reduced bias by including information from rub trees and telemetered females (i.e., occasion 0). Extrapolating the density estimate of 42 bears/1,000 km2 of available habitat on the study area to the Kenai Peninsula suggests a peninsula-wide population of 582 brown bears (95% lognormal CI = 469−719). Despite a density estimate that is low compared to other coastal brown bear populations in Alaska and genetic evidence that suggests this peninsular population is insular, harvest management has been liberalized since 2012. We recommend this population estimate serve as the benchmark for future management. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Radiocollared animals are frequently used to estimate detection probabilities in aerial surveys. The aircraft used to conduct these surveys may also have been used to aid in the capture of these animals, and recently captured animals may react to hearing or seeing the aircraft, changing their behavior in a way that calls into question the representativeness of estimated detection probabilities. We conducted a literature review and found 30 studies that used radiocollared animals to build sightability detection models; in ≥15 of these studies, the same aircraft was used to capture and survey animals. Although it is difficult to determine whether captured animals have different sighting probabilities than the rest of the target population, we used multiyear resighting data collected from moose (Alces alces) in Minnesota, elk (Cervus elaphus) in Washington, and mountain goats (Oreamnos americanus) in Washington and Alaska, to evaluate whether detection probabilities increased or decreased as a function of time since original capture. We did not detect statistically significant within-individual time trends in detection probabilities, although we could not rule out the possibility of biologically significant results because confidence intervals on effect sizes were relatively wide. The lone exception to this rule was for the cohort of radiocollared moose in Minnesota, which exhibited a slight decrease in detection probabilities over time. Differences in detection probabilities for marked and unmarked animals may not be a significant problem for sightability models, provided that the source of the variability can be captured by model covariates (e.g., heterogeneity is tied to an individual's propensity to be in heavy cover). Nonetheless, capture-related effects likely deserve greater consideration than currently afforded, and are critically important when applying simple mark–recapture abundance estimators (Lincoln–Petersen, mark–resight) that do not allow consideration of sighting covariates. © 2015 The Wildlife Society.

Snags (standing dead trees) are important components of forests that provide resources for numerous species of wildlife and contribute to decay dynamics and other ecological processes. Managers charged with managing populations of snags need information about standing rates of snags and factors influencing those rates, yet such data are limited for ponderosa pine (Pinus ponderosa) and especially mixed-conifer forests in the southwestern United States. We monitored standing rates of snags in 1-ha plots in Arizona mixed-conifer (n = 53 plots) and ponderosa pine (n = 60 plots) forests from 1997 through 2012. We used the Burnham live-dead, mark-resight model in Program MARK and multimodel inference to estimate standing rates during 5-year intervals while accounting for imperfect detection. Because snag standing rates may be influenced by plot characteristics, we used plots rather than snags as sampling units and conducted bootstrap analyses (500 iterations per model) to resample plots and estimate standing rates and associated parameters. We modeled standing rates in 3 discrete steps. First, we selected a parsimonious base model from a set of models including snag species, and then we evaluated models created by adding snag and plot covariates to the base model in steps 2 and 3, respectively. Snag standing rates differed among snag species and 5-year sampling intervals. Standing rates were positively related to snag diameter, negatively related to snag height, and were lower for snags with intact tops than for broken-topped snags. Standing rates also were positively related to topographic roughness, elevation, tree density, and an index of northness, and negatively related to slope and relative topographic exposure. Our results provide comparative data on standing rates of multiple species of snags based on a large and spatially extensive sample and rigorous analysis, and quantify the relative importance of several snag and plot characteristics on those rates. They indicate that modeling snag dynamics is complicated by both spatial and temporal variation in standing rates and identify areas where further work is needed to facilitate such modeling.

Wildlife managers often need tangible evidence of density dependence in populations to support decision making. Field experimentation to identify density dependent effects is often cost and time prohibitive. Thus, assimilation of existing knowledge into a balance of probabilities can serve as a surrogate for experimental research. A case study of such a process is found in the mule deer Odocoileus hemionus herds of Colorado. Wildlife managers and hunters expressed concern over a recent decline in western Colorado mule deer herds, yet the underlying cause of this decline is yet to be determined. In response to this management concern, we conducted a review of scientific evidence on Colorado's mule deer population dynamics. This review was done in the context of a conceptual model that portrays population growth as a function of population size, per capita growth rate and population carrying capacity. Similar declines that occurred during the 1960s and early 1990s resulted in similar reviews that identified...

The suite of demands competing for wildlife management funds necessitates direct assessment of management decisions, especially when these decisions have direct costs, as well as tangible opportunity costs. We conducted a mark–resight study that estimated mule deer (Odocoileus hemionus) density across multiple study units in southwest Colorado that had been exposed to different intensities of habitat treatments. Our treatments were comprised of common habitat management techniques including hydro-axe and roller-chopper disturbances as well chemical control of weeds and reseeding with desirable mule deer browse species. Reference study units received no habitat management treatments. Total deer densities varied between 20–84 deer/km2 in southern study units and 4–12 deer/km2 in northern study units. We did not observe a consistent pattern of higher deer density on advanced treatment study units despite it being the primary hypothesis of the study. We observed a wide range of variation in deer density among years. Resighting probabilities (range 0.070–0.567) were best modeled as an interactive function of study unit and year, although sampling method was also influential. We recommend that if population density is to be used as a population response variable, it be used in tandem with other, possibly more sensitive parameters such as overwinter survival or late winter body condition. © 2014 The Wildlife Society.

To improve understanding of snowshoe hare ecology in the Southern Rockies and enhance the ability of agency personnel to manage subalpine landscapes for snowshoe hares (Lepus americanus) and lynx (Lynx canadensis) in the region, we estimated snowshoe hare density, survival, and recruitment in west-central Colorado, USA from July 2006–March 2009. We sampled 3 types of forest stands that purportedly provide good habitat for hares: 1) mature Engelmann spruce (Picea engelmannii)–subalpine fir (Abies lasiocarpa), 2) early seral, even-aged lodgepole pine (Pinus contorta), and 3) mid-seral, even-aged lodgepole pine that had been pre-commercially thinned. In all forest types and all seasons, snowshoe hare densities were

Doak and Cutler critiqued methods used by the Interagency Grizzly Bear Study Team (IGBST) to estimate grizzly bear population size and trend in the Greater Yellowstone Ecosystem. Here, we focus on the premise, implementation, and interpretation of simulations they used to support their arguments. They argued that population increases documented by IGBST based on females with cubs-of-the-year were an artifact of increased search effort. However, we demonstrate their simulations were neither reflective of the true observation process nor did their results provide statistical support for their conclusion. They further argued that survival and reproductive senescence should be incorporated into population projections, but we demonstrate their choice of extreme mortality risk beyond age 20 and incompatible baseline fecundity led to erroneous conclusions. The conclusions of Doak and Cutler are unsubstantiated when placed within the context of a thorough understanding of the data, study system, and previous research findings and publications.

In the absence of natural or anthropogenic disturbance, many pinyon pine (Pinus edulis)–Utah juniper (Juniperus osteosperma) woodland habitats reach late seral stages that encroach into forest openings. This encroachment typically occurs at the expense of browse species that are preferred by mule deer (Odocoileus hemionus). Wildlife managers often treat habitat management as a tool to bolster mule deer populations, but documented changes in deer vital rates in response to habitat manipulations are lacking. We evaluated the effects of different levels of habitat improvement on pinyon pine–Utah juniper winter ranges in Colorado on mule deer overwinter survival. Mule deer fawns that overwintered on areas that received both a traditional mechanical treatment as well as follow-up chemical treatments experienced increased survival ( = 0.768, SE = 0.0851) over fawns on winter range that had only received traditional mechanical treatments or no habitat treatments ( = 0.675, SE = 0.112). When treatment intensity was partitioned into 3 levels: no treatment, traditional mechanical treatments, and advanced treatments comprised of both mechanical and chemical treatments, mule deer fawns inhabiting winter range subjected to advanced treatments experienced higher survival ( = 0.768, SE = 0.0849) than fawns on units that experienced only traditional mechanical treatments ( = 0.687, SE = 0.108), which in turn experienced higher survival than fawns in areas that had received no habitat treatments ( = 0.669, SE = 0.113). Our study provides evidence that habitat management on winter ranges can positively influence a key vital rate for mule deer in pinyon pine–Utah juniper ecosystems. We recommend that as habitat treatments are planned for benefit of mule deer, those plans include follow-up reseeding and weed control efforts. © 2014 The Wildlife Society.

Although telemetry is one of the most common tools used in the study of wildlife, advances in the analysis of telemetry data have lagged compared to progress in the development of telemetry devices. We demonstrate how standard known-fate telemetry and related nest-survival data analysis models are special cases of the more general multistate framework. We present a short theoretical development, and 2 case examples regarding the American black duck and the mallard. We also present a more complex lynx data analysis. Although not necessary in all situations, the multistate framework provides additional flexibility to analyze telemetry data, which may help analysts and biologists better deal with the vagaries of real-world data collection. © 2014 The Wildlife Society.

Information on population dynamics is key to gauging the status of threatened or endangered species. We monitored demography of a population of threatened Mexican spotted owls (Strix occidentalis lucida) in the Sacramento Mountains, New Mexico from 2003 to 2011. We estimated reproductive output for territorial pairs of owls; used mark-recapture methodology and Pradel's reparameterized Jolly-Seber models to estimate annual apparent survival rates, recapture rates, recruitment rates, and annual rate of population change (lRJS) for 2005-2009; and used estimates of lRJS to assess short-term population viability. Reproductive output was highly variable for 2004­2011, whereas annual apparent survival and recapture rates were less variable among years. Annual rates of population change exceeded 1.0 for both sexes from 2005 to 2009, and empirical observations of numbers of territorial owls supported the model-based trend estimate. Abundance of territorial owls was strongly related to reproduction within the study area, suggesting that population change was driven largely by internal processes. Population viability analyses suggested that population growth was likely to continue in the short term if current conditions persist. The positive growth rates observed in our study populations are encouraging, and may indicate that current recommendations for recovering this owl are succeeding. However, our estimates of lRJS covered a very short time period, given both the potential lifespan of Mexican spotted owls and the extent of temporal variability in weather typical of the southwestern United States. Longer studies of owl demography than we present will be required to understand long-term population trends, and such studies should extend across the range of the subspecies. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

In capture–recapture studies, the estimation accuracy of demographic parameters is essential to the efficacy of management of hunted animal populations. Dead recovery models based upon the reporting of rings or bands are often used for estimating survival of waterfowl and other harvested species. However, distance from the ringing site or condition of the bird may introduce substantial individual heterogeneity in the conditional band reporting rates (r), which could cause bias in estimated survival rates (S) or suggest nonexistent individual heterogeneity in S. To explore these hypotheses, we ran two sets of simulations (n = 1000) in MARK using Seber's dead recovery model, allowing time variation on both S and r. This included a series of heterogeneity models, allowing substantial variation on logit(r), and control models with no heterogeneity. We conducted simulations using two different values of S: S = 0.60, which would be typical of dabbling ducks such as mallards (Anas platyrhynchos), and S = 0.80, which would be more typical of sea ducks or geese. We chose a mean reporting rate on the logit scale of −1.9459 with SD = 1.5 for the heterogeneity models (producing a back-transformed mean of 0.196 with SD = 0.196, median = 0.125) and a constant reporting rate for the control models of 0.196. Within these sets of simulations, estimation models where σS = 0 and σS > 0 (σS is SD of individual survival rates on the logit scale) were incorporated to investigate whether real heterogeneity in r would induce apparent individual heterogeneity in S. Models where σS = 0 were selected approximately 91% of the time over models where σS > 0. Simulation results showed < 0.05% relative bias in estimating survival rates except for models estimating σS > 0 when true S = 0.8, where relative bias was a modest 0.5%. These results indicate that considerable variation in reporting rates does not cause major bias in estimated survival rates of waterfowl, further highlighting the robust nature of dead recovery models that are being used for the management of harvested species.

Summary When estimating demographic parameters for wild populations, using multiple data sources can increase robustness through greater precision, reducing bias and permitting the estimation of otherwise confounded parameters. We present a method that combines recapture data from marked individuals, collected at a single study site, under a robust design framework, with dead recoveries and auxiliary resightings collected at any time and place. This model permits the joint modelling of survival, permanent and temporary emigration from the study area. We demonstrate that the usefulness of this model is compelling in the case of long-lived species with substantial rates of temporary emigration, to mitigate bias in survival at the end of the time series and to permit conservation decisions based on more current information. We use the case of Florida manatees as an example. Our model can easily be extended to account for an arbitrary number of phenotypic states and account for state uncertainty. The increase in precision overall in vital rates, and the mitigation of bias in survival estimation in the final years of a time series, permits managers to base resource decisions on more robust and timely information. The model also provides the ability to adapt monitoring to changing conditions or specific management objectives, via dynamic allocation of effort to auxiliary resightings.

Mark-resight designs for estimation of population abundance are common and attractive to researchers. However, inference from such designs is very limited when faced with sparse data, either from a low number of marked animals, a low probability of detection, or both. In the Greater Yellowstone Ecosystem, yearly mark-resight data are collected for female grizzly bears with cubs-of-the-year (FCOY), and inference suffers from both limitations. To overcome difficulties due to sparseness, we assume homogeneity in sighting probabilities over 16 years of bi-annual aerial surveys. We model counts of marked and unmarked animals as multinomial random variables, using the capture frequencies of marked animals for inference about the latent multinomial frequencies for unmarked animals. We discuss undesirable behavior of the commonly used discrete uniform prior distribution on the population size parameter and provide OpenBUGS code for fitting such models. The application provides valuable insights into subtleties of implementing Bayesian inference for latent multinomial models. We tie the discussion to our application, though the insights are broadly useful for applications of the latent multinomial model.

Estimation of animal density is fundamental to ecology, and ecologists often pursue density estimates using grids of detectors (e.g., cameras, live traps, hair snags) to sample animals at a study site. However, under such a framework, reliable estimates can be difficult to obtain because animals move on and off of the site during the sampling session (i.e., the site is not closed geographically). Generally, practitioners address lack of geographic closure by inflating the area sampled by the detectors based on the mean distance individuals moved between trapping events or invoking hierarchical models in which animal density is assumed to be a spatial point process, and detection is modeled as a declining function of distance to a detector. We provide an alternative in which lack of geographic closure is sampled directly using telemetry, and this auxiliary information is used to compute estimates of density based on a modified Huggins closed-capture estimator. Contrary to other approaches, this method is free from assumptions regarding the distribution and movement of animals on the landscape, the stationarity of their home ranges, and biases induced by abnormal movements in response to baited detectors. The estimator is freely available in Program MARK.

Estimation of animal density is fundamental to wildlife research and management, but estimation via mark–recapture is often complicated by lack of geographic closure of study sites. Contemporary methods for estimating density using mark–recapture data include (1) approximating the effective area sampled by an array of detectors based on the mean maximum distance moved (MMDM) by animals during the sampling session, (2) spatially explicit capture–recapture (SECR) methods that formulate the problem hierarchically with a process model for animal density and an observation model in which detection probability declines with distance from a detector, and (3) a telemetry estimator (TELEM) that uses auxiliary telemetry information to estimate the proportion of animals on the study site. We used simulation to compare relative performance (percent error) of these methods under all combinations of three levels of detection probability (0.2, 0.4, 0.6), three levels of occasions (5, 7, 10), and three levels of abundanc...

We explored the relationship between Sprague's Pipit (Anthus spragueii) nest (n = 125) survival and the distance from their nests to grassland edge and other linear features on Bowdoin National Wildlife Refuge in north-central Montana from 1997 to 2007. Specifically, we studied the effect of distance to roads (secondary paved road and tertiary improved and unimproved dirt roads), an agriculture field, an active railroad right-of-way, and lacustrine shoreline on nest daily survival rate (DSR). The overall DSR was 0.95 ± 0.0057 (SE) with a 95% confidence interval of 0.94–0.96. We considered how models with distance thresholds (within 50, 100, 200, or 300 m) affected DSR while controlling for important covariates. None of the distance models improved the model over the minimum AICc model containing only non-distance covariates. There was no support for distance to any of the edges, including roads, having an effect on DSR relative to the minimum AICc model that contained three non-distance covariates.

Wolverines (Gulo gulo) in the conterminous United States have experienced range contraction, are uncommon, and have been designated as warranted for protection under the United States Endangered Species Act. Data from the southern edge of the wolverine's circumpolar distribution is sparse, and development of effective conservation strategies would benefit from a more complete understanding of the species' ecology. We captured and radio-monitored 30 wolverines in the Greater Yellowstone Ecosystem (GYE), tested for seasonal habitat selection by elevation band, and examined a suite of spatial characteristics to clarify our understanding of the wolverine's niche. Wolverines in GYE selected for areas >2,600 m latitude-adjusted elevation (LAE; n = 2,257 wolverine locations [12 F, 6 M]). Wolverines avoided areas 75% the size of their multi-year home range in an average of 32 days (n = 7 [5 F, 2 M]). Average movement rates of 1.3 km/2-hr indicated that both sexes move distances equivalent to the diameter of their home range every 2 days or the circumference of their home range in 2,150 m LAE (95% CI = 2.8–9.6). Dispersal movements extended to at least 170 km for both sexes (n = 5 F, 2 M). At the southern edge of distribution, where suitable and unsuitable conditions exist in close proximity, wolverines selected high-elevation areas near alpine tree-line where a mix of forest, meadow, and boulder fields were present, deep snow-cover existed during winter, and low temperatures near freezing can occur throughout the year. Persistence in these areas where the growing season is brief requires large home ranges that are regularly patrolled, a social system that provides exclusive access to resources, and low densities. These characteristics, along with low reproductive rates, are prevalent throughout the species range, indicating that wolverines are specialists at exploiting a cold, unproductive niche where interspecific competition is limited. The vulnerability inherent in occupying this unproductive niche was likely influential in previous declines within the conterminous United States and will remain a factor as wolverines encounter modern human influences. Conserving wolverines in the conterminous United States will require collaborative management over a large geographic scale. © 2011 The Wildlife Society.

Occupancy estimation is an effective analytic framework, but requires repeated surveys of a sample unit to estimate the probability of detection. Detection rates can be estimated from spatially replicated rather than temporally replicated surveys, but this may violate the closure assumption and result in biased estimates of occupancy. We present a new application of a multi-scale occupancy model that permits the simultaneous use of presence–absence data collected at 2 spatial scales and uses a removal design to estimate the probability of detection. Occupancy at the small scale corresponds to local territory occupancy, whereas occupancy at the large scale corresponds to regional occupancy of the sample units. Small-scale occupancy also corresponds to a spatial availability or coverage parameter where a species may be unavailable for sampling at a fraction of the survey stations. We applied the multi-scale occupancy model to a hierarchical sample design for 2 bird species in the Black Hills National Forest: brown creeper (Certhia americana) and lark sparrow (Chondestes grammacus). Our application of the multi-scale occupancy model is particularly well suited for hierarchical sample designs, such as spatially replicated survey stations within sample units that are typical of avian monitoring programs. The model appropriately accounts for the non-independence of the spatially replicated survey stations, addresses the closure assumption for the spatially replicated survey stations, and is useful for decomposing the observation process into detection and availability parameters. This analytic approach is likely to be useful for monitoring at local and regional scales, modeling multi-scale habitat relationships, and estimating population state variables for rare species of conservation concern. © 2011 The Wildlife Society.

Reintroductions are a common strategy to restore ecosystem integrity, especially when top predators are involved. Reintroductions are often time consuming, expensive, and controversial, and thus understanding what aspects are important for a successful program is needed. Focusing on the example of the reintroduction of Canada lynx (Lynx canadensis) to Colorado, we investigated how different release protocols (RP) affected mortality within the first year post-release. We found that average monthly mortality in the study area during the first year decreased with time in captivity from 0.205 (95% CI = 0.069, 0.475) for lynx having spent up to 7 days in captivity to 0.028 (95% CI = 0.012, 0.064) for lynx spending >45 days in captivity before release. Our results also suggest that keeping lynx in captivity beyond 5–6 weeks accrued little benefit in terms of monthly survival. We found that, on a monthly average basis, lynx were as likely to move out (P = 0.196, SE = 0.032) as well as back onto (P = 0.1...

Estimation of stream fish abundance using removal electrofishing is common and allows sampling of fish populations during a single site visit. However, recent evaluations have demonstrated that removal estimators can substantially underestimate fish abundance, raising concerns about using this method. We evaluated removal estimates of trout (family Salmonidae) abundance using night electrofishing in 200–300-m reaches of 8 Rocky Mountain streams and analyzed the data using new methods in Program MARK to account for potential sources of bias. The removal estimates were validated using populations of previously captured and marked resident fish. Overall, removal estimates were accurate estimates of the number of marked fish in study reaches (mean bias, −2.4% [

One challenge an analyst often encounters when dealing with complex mark–recapture models is how to limit the number of a priori models. While all possible combinations of model structures on the different parameters (e.g., ϕ, p) can be considered, such a strategy often results in a burdensome number of models, leading to the use of ad hoc strategies to reduce the number of models constructed. For the Cormack–Jolly–Seber data type, one example of an ad hoc strategy is to hold a general ϕ model structure constant while investigating model structures on p, and then to hold the resulting best structure on p constant and investigate structures on ϕ. Many comparable strategies exist. The effect of following ad hoc strategies on parameter estimates as well as for variable selection and whether model averaging can ameliorate any problems are unknown. By means of a simulation study, we have investigated this informational gap by comparing the all-combinations model building strategy with two ad hoc strategies and with truth, as well as considering the results of model averaging. We found that model selection strategy had little effect on parameter estimator bias and precision and that model averaging did improve bias and precision slightly. In terms of variable selection (i.e., cumulative Akaike’s information criterion weights), model sets based on ad hoc strategies did not perform as well as those based on all combinations, as less important variables often had higher weights with the former than with the all possible combinations strategy. Increased sample size resulted in increased variable weights, with an infinite sample size resulting in all variable weights equaling 1 for variables with any predictive influence. Thus, the distinction between statistical importance (dependent on sample size) and biological importance must be recognized when utilizing cumulative weights. We recommend that all-combinations model strategy and model averaging be used. However, if an ad hoc strategy is relied upon to reduce the computational demand, parameter estimates will generally be comparable to the all-combinations strategy, but variable weights will not correspond to the all-combinations strategy.

The California spotted owl (Strix occidentalis occidentalis) is the only spotted owl subspecies not listed as threatened or endangered under the United States Endangered Species Act despite petitions to list it as threatened. We conducted a meta-analysis of population data for 4 populations in the southern Cascades and Sierra Nevada, California, USA, from 1990 to 2005 to assist a listing evaluation by the United States Fish and Wildlife Service. Our study areas (from N to S) were on the Lassen National Forest (LAS), Eldorado National Forest (ELD), Sierra National Forest (SIE), and Sequoia and Kings Canyon National Parks (SKC). These study areas represented a broad spectrum of habitat and management conditions in these mountain ranges. We estimated apparent survival probability, reproductive output, and rate of population change for spotted owls on individual study areas and for all study areas combined (meta-analysis) using model selection or model-averaging based on maximum-likelihood estimation...

With the decline of many lekking species, the need to develop a rigorous population estimation technique is critical for successful conservation and management. We employed mark–resight methods to estimate population size for 2 lekking species: greater sage-grouse (Centrocercus urophasianus) and Gunnison sage-grouse (Centrocercus minimus). We evaluated 2 different estimators: Bowden's estimator and the mixed logit-normal mark–resight model. We captured and marked 75 greater sage-grouse. We counted marked and unmarked birds as they attended 15 known leks. We used 36 and 37 marked Gunnison sage-grouse to estimate population size in 2003 and 2004, respectively. We observed marked and unmarked Gunnison sage-grouse daily as they attended 6 leks in 2003 and 3 leks in 2004. Based on our examination of the assumptions of each mark–resight estimator, relative to behavior and biology of these species, we concluded the mixed logit-normal mark–resight model is preferred. We recommend wildlife managers employ...

We used tag–recapture data to estimate apparent survival and capture probability for 119,129 hatchery-reared, federally endangered razorback suckers Xyrauchen texanus stocked into upper Colorado River basin streams during 1995–2005. Effects investigated included reach, year, and season of stocking; fish total length (TL) at time of stocking; survival in the first year after stocking versus in subsequent years; and sampling effort. Recapture data were also used to describe poststocking movement. First-year survival rate for stocked razorback suckers of average TL (252.5 mm) was low: 0.05 (95% confidence interval [CI], 0.042–0.071). Total length at stocking and first-year survival were positively correlated; survival approached zero for fish smaller than 200 mm TL but increased to 0.75 or higher for the few fish larger than 500 mm. Season of stocking had a large effect on razorback sucker first-year survival; the predicted rate for average-length fish stocked in summer was less than 0.02 (CI, 0.012...

During the past 2 decades, the grizzly bear (Ursus arctos) population in the Greater Yellowstone Ecosystem (GYE) has increased in numbers and expanded its range. Early efforts to model grizzly bear mortality were principally focused within the United States Fish and Wildlife Service Grizzly Bear Recovery Zone, which currently represents only about 61% of known bear distribution in the GYE. A more recent analysis that explored one spatial covariate that encompassed the entire GYE suggested that grizzly bear survival was highest in Yellowstone National Park, followed by areas in the grizzly bear Recovery Zone outside the park, and lowest outside the Recovery Zone. Although management differences within these areas partially explained differences in grizzly bear survival, these simple spatial covariates did not capture site-specific reasons why bears die at higher rates outside the Recovery Zone. Here, we model annual survival of grizzly bears in the GYE to 1) identify landscape features (i.e., foods, land management policies, or human disturbances factors) that best describe spatial heterogeneity among bear mortalities, 2) spatially depict the differences in grizzly bear survival across the GYE, and 3) demonstrate how our spatially explicit model of survival can be linked with demographic parameters to identify source and sink habitats. We used recent data from radiomarked bears to estimate survival (1983-2003) using the known-fate data type in Program MARK. Our top models suggested that survival of independent (age L yr) grizzly bears was best explained by the level of human development of the landscape within the home ranges of bears. Survival improved as secure habitat and elevation increased but declined as road density, number of homes, and site developments increased. Bears living in areas open to fall ungulate hunting suffered higher rates of mortality than bears living in areas closed to hunting. Our top model strongly supported previous research that identified roads and developed sites as hazards to grizzly bear survival. We also demonstrated that rural homes and ungulate hunting negatively affected survival, both new findings. We illustrate how our survival model, when linked with estimates of reproduction and survival of dependent young, can be used to identify demographically the source and sink habitats in the GYE. Finally, we discuss how this demographic model constitutes one component of a habitat-based framework for grizzly bear conservation. Such a framework can spatially depict the areas of risk in otherwise good habitat, providing a focus for resource management in the GYE.

Summary 1. Reintroducing carnivores has become a widely used technique to restore the natural integrity of ecosystems. Accurate estimates of demographic parameters for reintroduced populations are essential to evaluate the success of the reintroduction programme, assess the need to release additional animals and to develop management recommendations. 2. In an effort to establish a viable population of Canada lynx Lynx canadensis in Colorado, USA, the Colorado Division of Wildlife released 218 wild-caught lynx from 1999 to 2006. All lynx were released with very high frequency (VHF) and/or satellite transmitters from which locations, mortality, reproduction, habitat use and movement patterns were documented. We present estimates of mortality. 3. Known-fate models could not be applied here to estimate mortality due to excessive missing location data because of either extensive movement outside of the study area or transmitter failure. Instead we employed a multistate model to address these issues. 4. We describe how the more general multistate mark–recapture model can accommodate missing data to estimate monthly mortality rates of released lynx both inside and outside the study area. We also explored factors possibly affecting lynx survival such as sex, time spent in pre-release captivity, movement patterns and origin. 5. Monthly mortality rate was lower inside the study area than outside, and slightly higher for males than for females, although 95% confidence intervals overlapped for sexes. Mortality was higher immediately after release [first month = 0·0368 (SE = 0·0140), and 0·1012 (SE = 0·0359) respectively, inside and outside the study area], and then decreased according to a quadratic trend. Annual survival was 0·9315 (SE = 0·0325) within the study area and 0·8219 (SE = 0·0744) outside the study area. 6. Synthesis and applications. For those contemplating lynx, or other carnivore reintroductions, we suggest identifying a high-quality release site to minimize mortality. We recommend that managers consider the demography of animals separately within and outside the reintroduction area for valid assessment of the reintroduction. Movements of reintroduced animals and their subsequent loss through death or permanent emigration may require the need for additional individuals to be released for a successful reintroduction effort.

Mark–resight methods can be a less expensive and less invasive alternative to traditional mark–recapture for estimating abundance and related demographic parameters. This is because only a single marking event is required, and subsequent sighting data from both marked and unmarked individuals are used for estimation. Mark–resight is therefore particularly appealing when working with limited budgets or sensitive species. These methods have been applied to many taxa, including avians such as Bald Eagles (Haliaeetus leucocephalu), Sage Grouse (Centrocercus urophasianus), and New Zealand Robins (Petroica australis). However, previous model and software development overwhelmingly focused on abundance estimation and did not extend much beyond classic Lincoln–Petersen methods. For this purpose, Program NOREMARK provided a convenient, but limited, means for analysis. To address these limitations, a new suite of likelihood-based mark–resight estimators has been developed and implemented within Program MARK. Unlike the estimators in NOREMARK, these new models provide a theoretical basis for model selection and multimodel inference, the incorporation of spatio-temporal and individual covariate information, full utilization of the robust design (including the estimation of survival and state transition probabilities), and all the other analysis tools that MARK provides. In addition, MARK no longer requires that the exact number of marked individuals available for sighting be known, thereby greatly extending the potential use of mark–resight methodology for population monitoring. Here, we provide a review of mark–resight methodology and present the various mark–resight estimators that are implemented in Program MARK.

Count data with means 1.2. Thus, managers can use simple statistical methods with which they are likely already familiar to analyze the kinds of count data we described here.

We used band-recovery data from 2 populations of greater sage-grouse (Centrocercus urophasianus), one in Colorado, USA, and another in Nevada, USA, to examine the relationship between harvest rates and annual survival. We used a Seber parameterization to estimate parameters for both populations. We estimated the process correlation between reporting rate and annual survival using Markov chain Monte Carlo methods implemented in Program MARK. If hunting mortality is additive to other mortality factors, then the process correlation between reporting and survival rates will be negative. Annual survival estimates for adult and juvenile greater sage-grouse in Nevada were 0.42 6 0.07 (x ¯ 6 SE) for both age classes, whereas estimates of reporting rate were 0.15 6 0.02 and 0.16 6 0.03 for the 2 age classes, respectively. For Colorado, average reporting rates were 0.14 6 0.016, 0.14 6 0.010, 0.19 6 0.014, and 0.18 6 0.014 for adult females, adult males, juvenile females, and juvenile males, respectively. Corresponding mean annual survival estimates were 0.59 6 0.01, 0.37 6 0.03, 0.78 6 0.01, and 0.64 6 0.03. Estimated process correlation between logit-transformed reporting and survival rates for greater sage-grouse in Colorado was r 5 0.68 6 0.26, whereas that for Nevada was r 5 0.04 6 0.58. We found no support for an additive effect of harvest on survival in either population, although the Nevada study likely had low power. This finding will assist mangers in establishing harvest regulations and otherwise managing greater sage-grouse populations. The notion that mortality associated with predation might be compensated by reduced mortality from other causes dates at least to Errington's ideas about the threshold of security (Errington and Hammerstrom 1935, Errington