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As gray wolves (Canis lupus) are removed from the federal Endangered Species List, management reverts to the states. Eventually most states will probably allow public wolf harvesting. Open seasons between about 1 November and 1 March accord more with basic wolf biology than during other times. Managers who consider wolf biology and public sensitivities, adapt public-taking regulations accordingly, and adjust harvest regulations as they learn will be best able to maximize the recreational value of wolf harvesting, minimize public animosity toward it, and meet their harvest objectives.
We examined and quantified the economic impact of grizzly bear (Ursus arctos) and gray wolf (Canis lupus) depredation on calves in the Upper Green River Cattle Allotment in western Wyoming, USA, using records of the number of animals grazed and number lost during 1990–2004. Our analysis indicated that increased calf losses coincided with grizzly bear and gray wolf arrival and population establishment, with the first confirmed depredation by grizzly bears in 1995 and the first confirmed wolf depredation in 2000. From 1995 through 2004, 29,693 calves grazed on the allotment, and of the 1,332 calves lost to all causes, an estimated 520 calves were lost to grizzly bear depredation and 177 calves to gray wolf depredation. We examined past and current grizzly and gray wolf compensation programs with respect to reimbursement of producers for costs associated with large-carnivore depredation. Estimated 1995–2004 uncompensated financial impacts from grizzly bear and gray wolf calf losses on the allotment were US$222,500. Our analysis suggested equitable compensation factors of 3.8∶1 for grizzly bear depredation and 6.3∶1 for gray wolf depredation. Inadequate compensation for livestock depredation results in resistance to large-carnivore recovery programs. Development of compensation programs that fairly reimburse livestock producers for losses is, therefore, a necessary component of carnivore recovery efforts. Our analysis also suggested that grizzly bear management actions were effectively targeting livestock-depredating grizzly bears on the allotment.
Assessing the impact of large carnivores on ungulate prey has been challenging in part because even basic components of predation are difficult to measure. For cougars (Puma concolor), limited field data are available concerning fundamental aspects of predation, such as kill rate, or the influence of season, cougar demography, or prey vulnerability on predation, leading to uncertainty over how best to predict or interpret cougar–ungulate dynamics. Global Positioning System (GPS) telemetry used to locate predation events in the field is an efficient way to monitor large numbers of cougars over long periods in all seasons. We applied GPS telemetry techniques combined with occasional snow-tracking to locate 1,509 predation events for 53 marked and an unknown number of unmarked cougars and amassed 9,543 days of continuous predation monitoring for a subset of 42 GPS-collared cougars in west-central Alberta, Canada. Cougars killed ungulates at rates near the upper end of the previously recorded range, and demography substantially influenced annual kill rate in terms of both number of ungulates (subad F [SAF] = 24, subad M [SAM] = 31, ad M = 35, ad F = 42, ad F with kittens <6 months = 47, ad F with kittens >6 months = 67) and kg of prey (SAF = 1,441, SAM = 2,051, ad M = 4,708, ad F = 2,423, ad F with kittens <6 months = 2,794, ad F with kittens >6 months = 4,280). Demography also influenced prey composition; adult females subsisted primarily on deer (Odocoileus spp.), whereas adult males killed more large ungulates (e.g., moose [Alces alces]), and subadults incorporated the highest proportion of nonungulate prey. Predation patterns varied by season and cougars killed ungulates 1.5 times more frequently in summer when juveniles dominated the diet. Higher kill rate in summer appeared to be driven primarily by greater vulnerability of juvenile prey and secondarily by reduced handling time for smaller prey. Moreover, in accordance with predictions of the reproductive vulnerability hypothesis, female ungulates made up a higher proportion of cougar diet in spring just prior to and during the birthing period, whereas the proportion of males increased dramatically in autumn during the rut, supporting the notion that prey vulnerability influences cougar predation. Our results have implications for the impact cougars have on ungulate populations and have application for using cougar harvest to manage ungulates.
We live-trapped American black bears (Ursus americanus) and sampled DNA from hair at White River National Wildlife Refuge, Arkansas, USA, to estimate annual population size (N), growth (λ), and density. We estimated N and λ with open population models, based on live-trapping data collected from 1998 through 2006, and robust design models for genotyped hair samples collected from 2004 through 2007. Population growth was weakly negative (i.e., 95% CI included 1.0) for males (0.901, 95% CI = 0.645–1.156) and strongly negative (i.e., 95% CI excluded 1.0) for females (0.846, 95% CI = 0.711–0.981), based on live-trapping data, with N from 1999 to 2006 ranging from 94.1 (95% CI = 70.3–137.1) to 45.2 (95% CI = 27.1–109.3), respectively, for males and from 151.4 (95% CI = 127.6–185.8) to 47.1 (95% CI = 24.4–140.4), respectively, for females. Likewise, mean annual λ based on hair-sampling data was weakly negative for males (0.742, 95% CI = 0.043–1.441) and strongly negative for females (0.782, 95% CI = 0.661–0.903), with abundance estimates from 2004 to 2007 ranging from 29.1 (95% CI = 21.2–65.8) to 11.9 (95% CI = 11.0–26.9), respectively, for males and from 54.4 (95% CI = 44.3–77.1) to 27.4 (95% CI = 24.9–36.6), respectively, for females. We attribute the decline in the number of females in this isolated population to a decrease in survival caused by a past translocation program and by hunting adjacent to the refuge. We suggest that managers restructure the quota-based harvest limits until these growth rates recover.
Noninvasive survey methods based on analyzing DNA extracted from feces can be useful for carnivores that are difficult to study by other methods. Changes in fecal deposition patterns associated with reproduction in kit foxes (Vulpes macrotis) might affect results of such surveys. We used a trained dog to collect fresh scats on 2-km transects in the home ranges of 11 radiocollared female kit foxes in January, February, and March 2008 and determined sex of the individual that deposited the scats by amplifying the zinc finger protein gene. Female foxes give birth in mid-February to mid-March. We found a similar number of scats each month. In January, the sex ratio of the scats was not different from the expected 1∶1. However, in February there were almost 2 male scats for every female scat and in March there were >8 male scats for every female scat. Comparing March to January, there were more male scats on all 11 transects and fewer female scats on 10 of 11 transects. Around the time pups are born, both sexes appear to show changes in fecal deposition patterns that make it easier to find male scats and harder to find female scats. Effects of these changes on survey results will vary depending on the purpose and design of the survey. Surveys to determine distribution and relative abundance would probably not be negatively affected by these changes. However, if surveys to estimate abundance are conducted during the reproductive season, they could result in an underestimate of population size unless the increased heterogeneity in scat detectability is taken into account.
The iconic plains bison (Bison bison) have been reintroduced to many places in their former range, but there are few scientific data evaluating the success of these reintroductions or guiding the continued management of these populations. Relying on mark–recapture data, we used a multistate model to estimate bison survival and breeding transition probabilities while controlling for the recapture process. We tested hypotheses in these demographic parameters associated with age, sex, reproductive state, and environmental variables. We also estimated biological process variation in survival and breeding transition probabilities by factoring out sampling variation. The recapture rate of females and calves was high (0.78 ± 0.15 [SE]) and much lower for males (0.41 ± 0.23), especially older males (0.17 ± 0.15). We found that overall bison survival was high (>0.8) and that males (0.80 ± 0.13) survived at lower rates than females (0.94 ± 0.04), but as females aged survival declined (0.89 ± 0.05 for F ≥15 yr old). Lactating and non-lactating females survived at similar rates. We found that females can conceive early (approx. 1.5 yr of age) and had a high probability (approx. 0.8) of breeding in consecutive years, until age 13.5 years, when females that were non-lactating tended to stay in that state. Our results suggest senescence in reproduction and survival for females. We found little support for the effect of climatic covariates on demographic rates, perhaps because the park's current population management goals were predicated from drought-year conditions. This reintroduction has been successful, but continued culling actions will need to be employed and an adaptive management approach is warranted. Our demographic approach can be applied to other heavily managed large-ungulate systems with few or no natural predators.
Wildlife managers often manipulate hunting regulations to control deer populations. However, few empirical studies have examined the level of hunting effort (hunter-days) required to limit population growth and demographic effects through harvesting of females. Moreover, the relative importance of density effects on population growth has not been quantified. We reconstructed a sika deer [Cervus nippon] population over a period of 12 years (1990–2001) using age- and sex-specific harvest data. Using cohort analysis, we analyzed population dynamics, focusing on 1) the relationship between hunting effort and hunting-induced mortality rate, 2) relative contributions of hunting mortality and recruitment of yearlings to annual changes in population growth rate, and 3) annual variation in recruitment rate. Population size increased until 1998 and declined thereafter. The population growth rate changed more in response to annual changes in recruitment rate than hunting mortality rate. Temporal variation in recruitment rate was not controlled by birth rate alone; direct density dependence, intensities of hunting mortality for fawns, and for females (≥2 yr of age), which accounted for the fawn survival rate, were required as factors to explain temporal variation. Density effects on the recruitment rate were not strong enough to regulate the population within the study period; high hunting mortality, with intensive female harvesting, was necessary to prevent population growth. Hunting effort was a good predictor of the hunting mortality rate, and female harvest had a negative effect on the recruitment rate through fawn survival. We suggest that >3,500 hunter-days and prioritization of female harvesting are required to prevent increases in this deer population.
Surgical sterilization by tubal ligation has been proposed as a technique for controlling white-tailed deer (Odocoileus virginianus) populations in urban or suburban areas where other forms of population control are impractical, but little is known about demographic rates in populations under management with surgical sterilization. We analyzed seasonal movement and mortality data collected during a 4-year study of surgical sterilization in suburban Chicago, Illinois, USA. We calculated 323 home range size estimates for 62 individual females within season and year. Non-gravid females without young exhibited home range sizes 52% larger than gravid females and females with fawns. Mortality rate was positively correlated with home range size. We suggest that the increased mortality rate observed in surgically sterilized females may be due to greater movement by non-maternal females. Population managers will need to account for potential effects of maternal status on movement and mortality when considering the use of sterilization for management of suburban populations of white-tailed deer.
To provide habitat for late-successional wildlife species, new ecosystem-based forest management practices aim to retain elements of complex stand structure, including live residual trees, dead wood legacies, and advanced regeneration, within managed stands. Predicting the effectiveness of these strategies is a challenge for species whose habitat relationships may involve multiple factors and can vary among sites. For 2 years, we live-trapped a common, late-successional microtine rodent, the southern red-backed vole (Myodes [formerly Clethrionomys] gapperi), in 40 1.4-ha boreal mixedwood sites in Ontario, Canada. Using a neighborhood-scale modeling approach, we related red-backed vole capture locations to spatially referenced measures of overstory trees, shrubs and saplings, downed woody debris (DWD), and forest floor substrate. We further assessed how associations with these features varied with availability of the features within a site and as a function of stand management history. In spring, red-backed voles were associated with trap stations that had, within a 26-m radius, a dense shrub layer, abundant late-decay DWD, coniferous understory and litter, and possibly, understory vegetation associated with moist conditions. Positive associations with shrub cover, late-decay DWD, and a moisture-associated understory were most apparent in sites in which these elements were scarce (e.g., <1,500 stems/ha of hardwood saplings and short shrubs; <0.8% projected ground cover of late-decay DWD). The importance of late-decay DWD; shade-tolerant, coniferous understory composition; and substrate varied depending on a site's management history, with each feature having a strong positive effect in 47–64-year-old stands that were harvested using horse skidding and weaker effects in both 31–40-year-old stands that were clearcut with mechanical skidding and >80-year-old fire-origin stands. Our models of fine-scale habitat relationships for red-backed voles may be useful in establishing structural retention guidelines suitable for wildlife species dependent on late-successional habitat structure. In this regard, retaining abundant DWD and 10–30% live trees at harvest may be effective management strategies for providing favorable habitat conditions at localized scales.
Low adult marten (Martes americana) survival may be one factor limiting their population growth >30 yr after their reintroduction in Wisconsin, USA. We estimated annual adult marten survival at 0.81 in northern Wisconsin, with lower survival during winter (0.87) than summer–fall (1.00). Fisher (Martes pennanti) and raptor kills were infrequent, and each reduced marten adult annual survival <10%. Annual adult survival was similar to or higher than survival in other areas, suggesting that it was not unusually low and therefore did not limit recovery of marten populations in northern Wisconsin. We captured few juvenile martens, suggesting low reproduction or reduced juvenile survival.
Wildlife population models are potentially valuable for conservation planning. Validation is necessary to ensure that models are sufficiently robust for predicting management outcomes consistent with conservation objectives. Sorensen et al. (2008) produced a model of woodland caribou (Rangifer tarandus) population growth rate that was recently modified and used as a predictive tool at several scales. We computed confidence intervals and evaluated the performance of this model using novel data. Confidence intervals were wide, and results suggested that the model may have a positive bias, resulting in over-estimation of population growth rates, as well as low predictive power. Wide confidence intervals mean that current understanding of factors governing woodland caribou herd dynamics is not sufficient for wildlife managers to make reliable projections of responses to management.
Shrubland birds are declining throughout the eastern United States. To manage scrub-shrub habitats for birds, managers need information on avian habitat relationships. Past studies have produced contradictory results in some cases and may be of limited generality because of site- and habitat-specific factors. We studied shrubland birds across 6 habitats in 3 New England states to provide more general information on habitat relationships than has been possible in past studies. Our study sites included all major scrub-shrub habitats in New England: wildlife openings, regenerating clear-cuts, beaver ponds, utility rights-of-way, pitch pine (Pinus rigida) woodlands, and scrub oak (Quercus ilicifolia) barrens and ranged from Connecticut to northern New Hampshire, with research conducted from 2002 to 2007. Using N-mixture models of repeated point counts, we found that 6 of 12 shrubland birds preferred areas with greater shrub cover. An additional 4 species appeared to prefer areas with lower-stature vegetation and greater forb cover. Eight of 10 bird species showed relationships with cover of individual plant species, with Spiraea spp., willows (Salix spp.), alders (Alnus spp.), and invasive exotics being the most important. We recommend that shrubland management for birds focus on providing 2 distinct habitats: 1) areas of tall (>1.5 m) vegetation with abundant shrub cover and 2) areas of lower (<1.5 m) vegetation with abundant forb cover but fewer shrubs.
Northern saw-whet owls (Aegolius acadicus) are secondary cavity-nesters and their dependence on snags has potential repercussions on forest management practices. Descriptive studies exist regarding habitat characteristics around saw-whet nest and roost areas, yet few studies have examined associations within larger areas or relative to snag characteristics (e.g., density). We conducted owl broadcast surveys and snag sampling during the spring and summer of 2006 and 2007 in the Lake Tahoe Basin of the central Sierra Nevada; we measured additional habitat variables from Geographic Information System layers. We modeled detection and occupancy probabilities for saw-whets using sampling and site covariates at survey sites. In addition, we used stepwise logistic regression to compare habitat characteristics at owl use sites and nonuse sites at 2 spatial scales. Detection probability was low in 2006 and decreased throughout the survey period; detection probability was slightly higher in 2007 and unaffected by day of survey. Probability of occupancy was affected by elevation and dominant tree species in 2007. Similarly, stepwise logistic regression indicated saw-whet occurrence was negatively correlated with the percentage of area dominated by white fir (Abies concolor) at both the macrohabitat (approx. 260 ha) and microhabitat (approx. 20 ha) scales and was positively correlated with the percentage of area containing open canopy at the microhabitat scale. We did not find correlations between saw-whet occurrence and snag characteristics. Current restoration projects in areas of the Sierra Nevada aim to decrease relative abundance of white fir and the number of snags in forest stands. We recommend continued monitoring of saw-whets to understand potential effects of these restoration activities. Our estimates of saw-whet occupancy and detection probabilities can be used by forest managers to determine necessary survey effort for reliable results when developing monitoring protocols.
Loss of quality brood rearing habitat, resulting in reduced chick growth and poor recruitment, is one mechanism associated with decline of greater sage-grouse (Centrocercus urophasianus) populations. Low chick survival rates are typically attributed to poor-quality brood rearing habitat. Models that delineate suitability of sage-grouse nesting or brood rearing habitat at the landscape scale can provide key insights into the relationship between sage-grouse and the environment, allowing managers to identify and prioritize habitats for protection or restoration. We used Southwest Regional Gap landcover types to identify early and late greater sage-grouse brood rearing in east-central Nevada. We conducted an Ecological Niche Factor Analysis to 1) examine the effect these landcover types and other ecogeographical variables have on sage-grouse selection of brood rearing habitat, and 2) generate landscape-scale suitability maps. We also evaluated if incorporating a fitness component (brood survival) in landscape spatial analyses of habitat quality influenced our assessment of habitat suitability. Because 36% of our 6,500-km2 study area was identified as early brood rearing habitat, we believe this habitat may not be limiting greater sage-grouse populations in east-central Nevada, USA, at least in wet years. We found strong selection for particular landcover types (e.g., higher elevation, moist sites with riparian shrubs or montane sagebrush) during late brood rearing. Late brood rearing habitat on which broods were successfully reared represented only 2.8% of the study area and had a restricted distribution, suggesting the potential that such habitat could limit sage-grouse populations in east-central Nevada.
Considering habitat selection at multiple scales is essential to fully understand habitat requirements and management needs for wildlife species of concern. We used a hierarchical information-theoretic approach and variance decomposition techniques to analyze habitat selection using local-scale habitat variables measured in the field and landscape-scale variables derived with a Geographic Information System (GIS) for nesting greater sage-grouse (Centrocercus urophasianus) in the Powder River Basin (PRB), Montana and Wyoming, USA, 2003–2007. We investigated relationships between habitat features that can and cannot be mapped in a GIS to provide insights into interpretation of landscape-scale–only GIS models. We produced models of habitat selection at both local and landscape scales and across scales, yet multiscale models had overwhelming statistical and biological support. Variance decomposition showed that local-scale measures explained the most pure variation (50%) in sage-grouse nesting-habitat selection. Landscape-scale features explained 20% of pure variation and shared 30% with local-scale features. Both local- and landscape-scale habitat features are important in sage-grouse nesting-habitat selection because each scale explained both pure and shared variation. Our landscape-scale model was accurate in predicting priority landscapes where sage-grouse nests would occur and is, therefore, useful in providing landscape context for management decisions. It accurately predicted locations of independent sage-grouse nests (validation R2 = 0.99) and showed good discriminatory ability with >90% of nests located within only 40% of the study area. Our landscape-scale model also accurately predicted independent lek locations. We estimated twice the amount of predicted nesting habitat within 3 km of leks compared to random locations in the PRB. Likewise we estimated 1.8 times more predicted nesting habitat within 10 km of leks compared to random locations. These results support predictions of the hotspot theory of lek placement. Local-scale habitat variables that cannot currently be mapped in a GIS strongly influence sage-grouse nest-site selection, but only within priority nesting habitats defined at the landscape scale. Our results indicate that habitat treatments for nesting sage-grouse applied in areas with an unsuitable landscape context are unlikely to achieve desired conservation results.
A bioenergetic approach has been adopted as a planning tool to set habitat management objectives by several United States Fish and Wildlife Service North American Waterfowl Management Plan Joint Ventures. A bioenergetics model can be simplified into 2 major components, energetic demand and energetic supply. Our goal was to estimate habitat-specific food availability, information necessary for estimating energy supply for black ducks (Anas rubripes) wintering on Long Island, New York, USA. We collected both nektonic and benthic samples from 85 wetland sites dispersed among 5 habitat types (salt marsh, mud flat, submersed aquatic vegetation, brackish bay, and freshwater) commonly used by black ducks in proportion to expected use. Biomass varied among habitats (F4,5 > 7.46, P < 0.03) in 2004–2005, but there was only marginal variation in 2005–2006 (F3,4 = 5.75, P = 0.06). Mud flats had the greatest biomass (1,204 kg/ha, SE = 532), followed by submersed aquatic vegetation (61 kg/ha, SE = 18), and salt marsh (34 kg/ha, SE = 6). In the second year of the study, freshwater had the greatest biomass (306 kg/ha, SE = 286), followed by mud flats (85 kg/ha, SE = 63), and salt marsh (35 kg/ha, SE = 4). Our results suggest food density on wintering grounds of black ducks on coastal Long Island is considerably lower than for dabbling ducks using inland freshwater habitats, indicating black duck populations are more likely than other species of dabbling ducks to be limited by winter habitat. We recommend targeting preservation, restoration, and enhancement efforts on salt marsh habitat.
Common reed (Phragmites australis) forms dense stands with deep layers of residual organic matter that negatively affects plant diversity and possibly habitat use by wetland birds. We sought to determine whether seasonal relative abundance and species richness of birds varied among 3 habitat types in Great Lakes coastal wetland complexes recently invaded by common reed. We used fixed-distance point counts to determine species relative abundances and species richness in edge and interior locales within common reed, cattail (Typha spp.), and meadow marsh habitats of various sizes during 2 summers (2001 and 2002) and 1 autumn (2001) at Long Point, Lake Erie, Ontario, Canada. We found that total relative abundance and species richness of birds were greater in common reed habitat compared to cattail or meadow marsh habitats. However, we also found that relative abundance of marsh-nesting birds was greater in meadow marsh habitat than in cattail and common reed during summer. Lastly, we found that, irrespective of habitat type, habitat edges had higher total relative abundance and species richness of birds than did habitat interiors. Our results show that common reed provides suitable habitat for a diversity of landbirds during summer and autumn but only limited habitat for many marsh-nesting birds during summer. Based on these results, we recommend restoration of meadow marsh habitat through reduction of common reed in Great Lakes wetlands where providing habitat for breeding marsh-nesting birds is an objective. Managers also might consider reducing the size of nonnative common reed stands to increase edge effect and use by birds, possibly including wetland birds.
We tested whether presence of white-winged doves (Zenaida asiatica) and mourning doves (Z. macroura) in South Texas, USA, was associated with any of the land cover types recorded in the 2001 National Land Classification Database. We used the point-transect method to conduct presence–absence surveys for both species at 236 points encompassing 744 observations. Within predefined land cover types surrounding each survey point, we used Geographic Information Systems to determine the proportions of each land cover type present. We used randomization tests to compare proportions of land cover types present at points with and without doves. We used Program DISTANCE to estimate dove densities at survey points and to test whether certain land cover types were associated with greater dove densities. Our results indicated white-winged dove occurrence in South Texas was positively associated with urban land and cropland, whereas mourning dove occurrence was positively associated with cropland. For land cover types found to be associated with dove presence, estimated density for each dove species increased as the proportion of associated land cover type increased. These results can assist wildlife biologists in the development of a more efficient and targeted protocol for censusing doves. In addition, our methods can be applied to other species across several geographic areas and landscape scales.
We developed a method for predicting wood duck (Aix sponsa) harvest rates in eastern North America using waterfowl banding and recovery data, annual indices of hunter numbers, and harvest survey data from the United States and Canada. We predicted that under the current season length (60 days), if hunter numbers remain unchanged, increasing the wood duck bag limit from 2 to 3 would increase harvest of adult male wood ducks in the Atlantic and Mississippi flyways by 12.3%, causing an increase in harvest rate of 7.1% from 0.087 to 0.093. The Flyway Councils and the United States Fish and Wildlife Service can consider this information to predict the impacts of regulatory changes.
Conservation and management of native species on landscapes managed for intensive wood production represents an ongoing challenge to forest managers. Previous research suggests that impacts of forest practices on stream-associated amphibians (SAA; giant [Dicamptodon spp.], torrent [Rhyacotriton spp.], and plethodontid [Plethodon spp.] salamanders and coastal tailed frogs [Ascaphus truei]) in Oregon and Washington, USA, vary spatially and temporally as a result of biotic and abiotic factors, some of which can be influenced by management treatments. Although individual harvest units can encompass multiple stream reaches and entire second-order basins, nearly all published research studies used stream reaches of various lengths as sample units. To address this discrepancy between research and operational scales, we sampled first-, second-, and third-order streams in 70 randomly selected third-order basins in Oregon and Washington in 2007 and 2008 to estimate detection and occupancy parameters for SAA and to develop basin-level density estimates for different species and genera. We estimated occupancy probabilities of 0.99 (95% CL = 0.96–1.00) for torrent and giant salamanders, 0.93 (95% CL = 0.76–0.92) for Dunn's salamanders (Plethodon dunni), and 0.60 (95% CL = 0.46–0.72) for tailed frogs. Our estimates can be compared with estimates for unmanaged third-order basins in Oregon and Washington to provide a relative measure of potential impacts of forest management on these taxa. In addition, our estimates provide baseline information with which to assess potential effects of future environmental changes on the 4 genera.
State wildlife agencies often use input obtained through public meetings to develop management policies. Because public meetings can be dominated by single stakeholder groups, these policies may not reflect the attitudes of new wildlife stakeholders. In 2000 the Utah Wildlife Board, after a series of public meetings, adopted a statewide policy for winter-feeding mule deer (Odocoileus hemionus). The policy was implemented by the Utah Division of Wildlife Resources from 2001 to 2007 in Cache County of northern Utah, USA. In 2007, we surveyed Utah households representing metropolitan, nonmetropolitan, and Cache County residents (n = 1,800) to evaluate whether the winter-feeding policy reflected the attitudes of all wildlife stakeholders. Survey respondents, regardless of residence strata, believed winter-feeding programs were essential for managing mule deer in Utah (χ26 = 7.02, P = 0.32). However, most respondents were reluctant to support feeding programs at the expense of habitat restoration projects (χ26 = 11.64, P = 0.07). Our results suggest that the winter-feeding policy represented the attitudes of the Utah residents surveyed, though few had participated in its development. Respondents' strong utilitarian attitudes toward wildlife (e.g., strong support for hunting and feeding) influenced those respondents' perceptions of the policy. Given the effects of increased urbanization on utilitarian attitudes toward wildlife in many parts of the United States, coupled with decreasing numbers of traditional wildlife stakeholders, state wildlife agencies should continually reevaluate their public involvement processes to ensure new wildlife stakeholders' attitudes and concerns are represented.
Status and trends of gopher tortoise (Gopherus polyphemus) populations are a critical information need for natural resource managers, researchers, and policy makers. Many tortoise populations are small and isolated, which can present challenges for deriving population estimates. Our objective was to compare abundance and density estimates for a small tortoise population derived using a total burrow count versus estimates obtained with line transect distance sampling (LTDS) using repeated surveys. We also compared results of the 2 survey methods using standard burrow-to-tortoise correction factors versus assessing occupancy of all burrows with a camera scope. In addition, we compared LTDS data obtained using a compass and measuring tape to define transects to those obtained using a Global Positioning System (GPS) and Personal Data Assistant (PDA) field computer to navigate transects. Line transect distance sampling with repeated surveys (both with a measuring tape and compass and with a GPS–PDA) yielded sufficient observations of tortoises to calculate population estimates. From 18% to 31% of burrows were occupied by tortoises as determined with the burrow camera. We found 25 burrows during the LTDS survey that we did not find in the total count survey, which demonstrated that the assumption of 100% detection for the total count was not met; hence, density or abundance measurements derived with this method were underestimates. We recommend using GPS–PDA technology, scoping all burrows detected, and using LTDS with repeated surveys to estimate abundance and density for small gopher tortoise populations.
American mink (Neovison vison) are an ecologically damaging invasive species where they have been introduced in Europe. Effectiveness of mink population control by trapping has been difficult to assess, without knowing how efficiently mink are caught by traps or detected by other methods. Use of track-recording rafts to detect mink and guide trapping effort has proved efficient and leads to a supposition that no detection indicates absence of mink. To draw this conclusion with any confidence requires a measure of detectability. We applied occupancy models to data from an earlier study to estimate detectability of individual American mink on track-recording rafts. Estimated detectability of individual mink, per raft, and 2-week check period varied between 0.4 in late summer and 0.6 in late autumn. By inference, risk of failing to detect a mink that was present would be <5% given 4–6 independent opportunities to detect it. These opportunities could be created either by using a raft spacing that ensured multiple detections of each mink or by monitoring rafts through a succession of check intervals. Within certain simple constraints, raft location did not contribute substantially to detection probability. These findings will allow field operators, strategists, and funders to assess with confidence the success of efforts to control mink density. We expect the estimation of individual detectability to be similarly valuable in population control or eradication of other species.
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 mark–resight approaches when statistically rigorous population estimates are required for management and conservation of lekking species.
Unmanned aircraft systems (UASs) are proposed as a useful alternative to manned aircraft for some aerial wildlife surveys. We described the components and current capabilities of a small UAS developed specifically for wildlife and ecological surveys that is currently in field use for a variety of applications. We also reviewed government regulations currently affecting the use of UASs in civilian airspace. Information on capabilities and regulations will be valuable for agencies and individuals interested in the potential UASs offer for monitoring wildlife populations and their habitat. Descriptions of current uses and recommendations for future employment will be helpful in implementing this technology efficiently for aerial surveys as the civilian sector begins to adopt UASs for peacetime missions.
Rapidly deployable and effective methods are needed to contain free-ranging deer (Odocoileus spp.) during acute disease outbreaks. We evaluated efficacy of a 2.1-m-tall polypropylene mesh (poly-mesh) fence for containing ≥15 free-ranging white-tailed deer (O. virginianus) within a 42-ha area in eastern Nebraska, USA. We observed a 99% decrease in deer leaving the enclosure area after we installed fencing (1 deer jumped; 0.02 deer/hr) compared with prefence rates (5.26 deer/hr). However, 8 deer (53% of censused population) escaped the enclosure during a census drive after our study. Poly-mesh fencing may be effective in temporarily containing free-ranging deer during minimally disruptive deer removal actions such as trapping or sharpshooting.