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At least 55 records · Page 3Linked to original sources
USGS2022

Interaction between transect design and animal distribution in distance sampling of deer

We conducted a simulation study to evaluate the consequences of violating statistical assumptions of distance sampling (DS) on the bias and precision of population estimates of white-tailed deer ( Odocoileus virginianus ). Distance sampling is a method for estimating the density of organisms using a distribution of observed distances to individuals. A key assumption of DS is that sampling transects are randomly located with respect to the population being sampled. Most DS transects used in National Parks follow roads and trails, which are not positioned randomly. We constructed spatially explicit simulations of surveys using 7 different types of deer spatial distributions and 3 survey designs. A significant interaction between survey type and deer distribution type explained most of the variation in population estimates across simulations and this interaction was also a significant predictor of the coefficient of variation (CV) of population estimates. Simulation results suggested that 1) non-road surveys were more robust to bias than were road surveys, 2) effectiveness of each of 3 survey types was dependent on the way deer were distributed across the landscape, and 3) non-road surveys produced unbiased estimates of populations affected by roads, whereas road surveys did not. The results of our study suggest that DS surveys using pre-existing roads and trails have potential biases resulting from study design, something that could be considered by land managers when constructing surveys.

Maryland↗
USGS2022

Availability of lesser prairie-chicken nesting habitat impairs restoration success

Regional populations of lesser prairie-chickens ( Tympanuchus pallidicinctus ) have been declining irregularly since the early 1900s (Jensen et al. 2000). Populations in the Sand Sagebrush Prairie Ecoregion of Kansas and Colorado, USA, have been experiencing declines during the last 2 decades. Ecoregion-wide declines included the Cimarron and Comanche National Grasslands in southwestern Kansas and southeastern Colorado, respectively, from which lesser prairie-chickens were nearly extirpated by 2016. In 2014, the United States Department of Agriculture (USDA)–Forest Service created a vegetation management plan to restore lesser prairie-chicken nesting habitat on the National Grasslands. We used management plan recommendations to evaluate available nesting habitat on National Grasslands and surrounding areas for 394 transmitter-marked lesser prairie-chickens translocated to the Sand Sagebrush Prairie Ecoregion during 2016–2019. We found that a small proportion of vegetation measurements met the USDA–Forest Service's 100% visual obstruction guidelines of 25.4 to 38.1 cm (Cimarron: 5.3–21.8% of observations among cover types; Comanche: 1.5–3.0%), and grass species with a high value for nesting were rare (Cimarron: 0.5–20.1% of observations within each cover type; Comanche: 1.5–3.0%). Lesser prairie-chickens selected for 2 of the 10 National Grasslands' cover types (shrubland state and warm season shortgrass state) during breeding season movements, but only shrubland state was selected for during nesting. Our results indicate that nesting habitat for lesser prairie-chickens is limited on Cimarron and Comanche National Grasslands. As private grassland was also avoided during nesting, lesser prairie-chickens in Baca and Morton counties are currently primarily relying on Conservation Reserve Program (CRP) grasslands to meet nesting habitat thresholds (Morton, KS: 17.7% CRP; Baca, CO: 16.6% CRP), which may be insufficient to sustain a viable population. Due to the impermanence of CRP, efforts to sustain local populations are likely to depend on increased improved lesser prairie-chicken nesting habitat on National Grasslands. Grazing strategies such as rest-rotation and year-long deferments may provide opportunities to restore lesser prairie-chicken habitat on sand sagebrush prairie.

Colorado, Kansas, New Mexico, Oklahoma, Texas↗
USGS2022

Adult white-tailed deer survival in hunted populations on public and private lands

Estimates of sex- and age-specific survival are important for guiding population management decisions for white-tailed deer ( Odocoileus virginianus ). However, differences in deer survival between public and private lands can exist and, if unaccounted for, may affect wildlife agencies' ability to effectively manage statewide and local deer populations. From 2014 to 2016, we radiocollared and monitored survival of 79 adult white-tailed deer (141 deer-years; 62 male, 79 female) on 2 public and 2 private properties in Alabama, USA. We assessed the effects of sex, age, and landownership type (i.e., public or private) on adult white-tailed deer harvest and survival patterns using an information-theoretic approach. Hunter harvest accounted for 77% of observed mortalities ( n = 23/30), but harvest and survival rates varied by sex and age. Harvest and survival were similar between public and private property despite more restrictive hunting regulations for antlered deer on public areas. Similar harvest rates were likely due to self-imposed, quality deer management (QDM) harvest strategies on private land that emulated the effects of a state-mandated antler point restriction (APR) on public land. Our findings indicate survival rates of adult white-tailed deer may be applicable across landownership types where state-mandated harvest regulations with respect to males are more restrictive on public than private property, due to the popularity of QDM by private-land deer hunters. However, where regulations are similar across landownership types (e.g., no state-mandated APR), differences in harvest and survival rates may exist.

Alabama↗
USGS2022

Examining landowners’ preferences for a chronic wasting disease management program

Private landowners are key partners in chronic wasting disease (CWD) management, especially in landscapes where there is limited public ownership. In this study, we evaluated landowners' preferences for alternative hypothetical CWD management programs using a stated choice experiment. We were particularly interested in understanding preferences for the use of financial incentives to motivate white-tailed deer harvest and facilitate hunter access to private lands as potential CWD management tools. We used latent class analysis to characterize preference heterogeneity among landowners stemming from patterns of choice. We compared means and distributions of auxiliary variables related to landowners' perceived risks, trust, attitudes toward management, and sociodemographics across latent classes stemming from choice model results. The pooled model demonstrated that reducing deer population density, providing payments to landowners for CWD-positive deer taken from their property, the form of incentives for public access, and banning recreational deer feeding had a small positive effect on respondents' choice of CWD management program. However, providing financial payments to hunters for harvesting CWD-positive deer and the use of targeted culling had the opposite effect on choice. Latent class models revealed that a majority of respondents exhibited a pattern of preference where all forms of incentives exerted a negative effect on choice, but smaller subsets of landowners positively evaluate the use of some incentives. Post-hoc contrasts revealed relationships between patterns of preferences and trust, risk, and attitudes toward CWD management with small to medium effects. Results demonstrated limited support for the use of financial incentives as a tool to manage access and harvest in the southeast Minnesota CWD management zone

Minnesota↗
USGS2022

Efficacy of bear spray as a deterrent against polar bears

Although there have been few attempts to systematically analyze information on the use of deterrents on polar bears ( Ursus maritimus ), understanding their effectiveness in mitigating human-polar bear conflicts is critical to ensuring both human safety and polar bear conservation. To fill this knowledge gap, we analyzed 19 incidents involving the use of bear spray on free-ranging polar bears from 1986 to 2019 in Canada, Russia, and the United States to evaluate the effectiveness of bear spray as a polar bear deterrent. We found that bear spray was an effective deterrent in close-range encounters with polar bears, stopping undesirable behavior in 18 of 19 incidents. Bear spray effectively deterred both curious and aggressive polar bears, including polar bears attempting to attack people. The mean distance between user and bear at the time of spraying was 2 m (min–max = 0.2–10.0 m, mode = 1 m), though bears were usually first seen at greater distances. Bear spray was successfully deployed against polar bears in all 4 seasons. Wind affected spray performance in 1 of 19 of incidents. In 8 of 14 bear spray incidents, other deterrents were used without success before bear spray was used effectively to deter polar bears. No humans or polar bears were killed or injured in any of the incidents in which bear spray was used. We also analyzed 54 polar bear attacks and attempted attacks on humans where bear spray was not carried. The data suggest that in 93% of those incidents, the use of bear spray might have saved the lives of both the people and bears involved if it had been available and used. Our analysis improves our understanding of the effectiveness of bear spray for polar bear conflict mitigation.

Wildlife Society Bulletin↗
USGS2022

Optimizing surveys of fall-staging geese using aerial imagery and automated counting

Ocular aerial surveys allow efficient coverage of large areas and can be used to monitor abundance and distribution of wild populations. However, uncertainty around resulting population estimates can be large due to difficulty in visually identifying and counting animals from aircraft, as well as logistical challenges in estimating detection probabilities. Photographic aerial surveys can mitigate these challenges and can allow flight at higher altitudes to minimize disturbance of birds and improve safety for surveyors. We evaluated a photographic aerial survey that incorporated a systematic sampling design with automated photo capture and processing for fall-staging geese at Izembek Lagoon, Alaska, in 2017–2019. Ocular aerial surveys have been completed at Izembek Lagoon for >40 years. For the new photo survey, we used a commercial system to automatically trigger cameras at preset points. We then applied a machine-learning algorithm trained to automatically identify and count geese in our photos, manually corrected those counts, and quantified the algorithm's accuracy. We translated corrected counts into density and extrapolated mean density across the entire lagoon to estimate total population size for Pacific brant ( Branta bernicla ) and cackling geese ( B. hutchinsii ). The automated algorithm undercounted geese, but successfully identified the small subset of photos containing geese. Manual correction was therefore needed only for photos automatically identified as containing geese, allowing substantial reduction of workload. Manually-corrected, photo-based estimates of Pacific brant and cackling goose population sizes were larger and more precise than ocular estimates in all 3 years. To reduce costs with little penalty for variance around population estimates, the photographic survey design could be optimized by reducing the number of transects to ~67% of the current number while still manually correcting all photos in which the automated algorithm detected geese. Further years of both ocular and photo surveys would be needed to calibrate the photo estimates against the >40-year timeseries of the ocular survey, after which the photo series could successfully guide management of Pacific brant. As technologies continue to advance, we expect photographic surveys with automated counting to be easily implemented and advantageous to many monitoring programs.

Alaska↗
USGS2023

Influence of camera model and alignment on the performance of paired camera stations

The probability of obtaining images of target species may vary across camera models or relative position of cameras at survey locations. Alignment of cameras within paired camera stations (hereafter, stations) could affect species detection due to issues with image exposure. We quantified effects of 3 camera models and alignment (staggered, offset by a perpendicular distance of 4.6 m, and aligned, directly facing one another) on camera performance in a station design. Mean exposure events (flash from one camera overexposes or underexposes pictures) at aligned stations was 3.93 (SE = 1.01; n = 40), whereas no exposure events were documented at staggered ( n = 36) stations. Overall frequency of exposure events of mammal images at aligned cameras was 44% (68 exposure events/153 images). On average, 8% (range 0−35%) of mammal images from aligned stations were exposure events. We detected no difference ( P = 0.88) in exposure events among paired camera models. Further, we detected no overall differences ( P ≥ 0.07) in paired camera performance (i.e., number of mammal images over survey interval) between aligned or staggered stations, though reliability (i.e., percentage of camera stations that lasted entire survey interval) varied ( P ≤ 0.001) between model types. Research deploying 2 cameras within a camera station framework can eliminate exposure events by using a staggered camera alignment without affecting the number of usable mammal photos. Rigorous field testing prior to deployment of stations is warranted to optimize reliability. One of our low-cost models performed as well as a more expensive model within our paired camera stations at collecting mammal images, and thus could be incorporated into study designs without compromising quality of camera photo data. We suggest a pilot study before large-scale deployment to evaluate reliability and performance of cameras, particularly when deploying multiple models.

Illinois↗
USGS2023

Landowner and biologist perceptions of game bird predators and management

Nest survival has been identified as one of the most influential vital rates causing population change in game birds, and depredation, often influenced by habitat loss and fragmentation, is the primary cause of nest failure of upland game birds. We were interested in quantifying and comparing the perspectives of landowners and biologists in South Dakota regarding complex predator-prey interactions to improve communication and management efficacy. We developed a questionnaire regarding the following: 1) general attitude statements about game bird species; 2) perceived impacts of 9 factors (e.g., development, pollution, predators) and 13 potential predators on game bird abundances; and 3) attitude statements regarding use of lethal predator control and nesting habitat management practices. A cluster analysis using landowner attitude statements about predator management identified 3 landowner segments that had strong (most supportive; 37%), moderate (moderately supportive; 35%), or weak (least supportive; 28%) attitude statements about lethal predator control. Landowner segments most supportive and moderately supportive of predator control rated predators as the primary negative factor impacting game bird abundances and agreed that predators were the primary cause of game bird abundance declines, whereas the landowner segment least supportive of predator control rated habitat loss as the top factor and disagreed that predators were the primary cause of game bird declines. Biologists rated habitat loss as the top factor negatively impacting game bird abundances and disagreed that predators were the primary cause of game bird abundance declines. Thus, when considering the effectiveness of strategies to reduce nest depredation, most landowners focused on the direct cause of nest failures (predators), whereas biologists focused on an indirect cause (habitat loss). Perception differences among these groups emphasizes the need for better communication on proximate and ultimate factors affecting game bird populations and how these differences may impact management decisions.

South Dakota↗
USGS2023

Policy comparison of lead hunting ammunition bans and voluntary nonlead programs for California condors

The endangered California condor ( Gymnogyps californianus ) is negatively affected by lead poisoning from spent lead-based hunting ammunition. Because lead poisoning is the primary mortality factor affecting condors, the California Fish and Game Commission banned lead hunting ammunition during 2008 in the southern California condor range followed by a statewide ban implemented in 2019. In contrast, the Arizona Game and Fish Department instituted an outreach and awareness program encouraging voluntary use of nonlead hunting ammunition in the northern portion of the state during 2005 and a similar program was launched in Utah during 2012. The juxtaposition of policy tools provided a unique opportunity to evaluate the intended efforts to mitigate lead exposure in condors and their respective positive and negative effects. Herein we reflect upon the effectiveness of lead policy actions in the 3-state region on the basis of condor blood-lead levels, population status, and hunter awareness of the issue and use of nonlead hunting ammunition.

California↗
USGS2012

Aerial surveys adjusted by ground surveys to estimate area occupied by black-tailed prairie dog colonies

Aerial surveys using line-intercept methods are one approach to estimate the extent of prairie dog colonies in a large geographic area. Although black-tailed prairie dogs ( Cynomys ludovicianus ) construct conspicuous mounds at burrow openings, aerial observers have difficulty discriminating between areas with burrows occupied by prairie dogs (colonies) versus areas of uninhabited burrows (uninhabited colony sites). Consequently, aerial line-intercept surveys may overestimate prairie dog colony extent unless adjusted by an on-the-ground inspection of a sample of intercepts. We compared aerial line-intercept surveys conducted over 2 National Grasslands in Colorado, USA, with independent ground-mapping of known black-tailed prairie dog colonies. Aerial line-intercepts adjusted by ground surveys using a single activity category adjustment overestimated colonies by ≥94% on the Comanche National Grassland and ≥58% on the Pawnee National Grassland. We present a ground-survey technique that involves 1) visiting on the ground a subset of aerial intercepts classified as occupied colonies plus a subset of intercepts classified as uninhabited colony sites, and 2) based on these ground observations, recording the proportion of each aerial intercept that intersects a colony and the proportion that intersects an uninhabited colony site. Where line-intercept techniques are applied to aerial surveys or remotely sensed imagery, this method can provide more accurate estimates of black-tailed prairie dog abundance and trends

Colorado↗
USGS2023

Actualizing Indigenous Knowledge in tribal wildlife management: Basic preconditions

Indigenous Knowledge (IK) is increasingly involved in the contemporary management of natural resources. Tribal wildlife management programs in the United States may be uniquely positioned to effectively and ethically integrate their IK. While a narrow focus on the body of IK and a particular management activity may suffice for project-level integration efforts, herein we consider how IK integration at the programmatic level may be best supported. We propose a holistic conceptual framework of preconditions including sovereignty, the North American Model management, funding, cultural resources, stakeholder support, and programmatic leadership. We assess the current status and common challenges with each precondition and illustrate their potential roles for a more lasting and pervasive integration of IK into tribal wildlife management programs.

The Wildlife Society Bulletin↗
USGS2023

Evaluation of replicate sampling using hierarchical spatial modeling of population surveys accounting for imperfect detectability

Effective species management and conservation benefit from knowledge of species distribution and status. Surveys to obtain that information often involve replicate sampling, which increases survey effort and costs. We simultaneously modeled species distribution, abundance and spatial correlation, and compared the uncertainty in replicate abundance estimates of the endangered palila ( Loxioides bailleui ) using hierarchical generalized additive models with a soap film smoother that incorporated random effects for visit. Based on survey coverage and detections, we selected the 2017 point-transect distance sampling survey on Mauna Kea, Hawai‘i Island, for our modeling. Our modeling approach allowed us to account for imperfect detections, control the effects of boundary features, and generate visit-specific density surface maps. We found that visit-specific smooths were nearly identical, indicating that little information was gained from a subsequent visit, and that most of the estimator uncertainty was derived from within-visit variability. Scaling back the palila survey to a single visit would halve the survey effort and logistical costs and increase efficiencies in data management and processing. Changing the sampling protocol warrants careful consideration and our findings may help management and regulatory agencies by maximizing efficiency and minimizing costs of surveying protocols, while providing guidelines on how to best collect information critical to species' conservation.

Hawai'i↗
USGS2023

Virtual snow stakes: a new method for snow depth measurement at remote camera stations

Remote cameras are used to study demographics, ecological processes, and behavior of wildlife populations. Cameras have also been used to measure snow depth with physical snow stakes. However, concerns that physical instruments at camera sites may influence animal behavior limit installation of instruments to facilitate collecting such data. Given that snow depth data are inherently contained within images, potential insights that could be made using these data are lost. To facilitate camera-based snow depth observations without additional equipment installation, we developed a method implemented in an R package called edger to superimpose virtual measurement devices onto images. The virtual snow stakes can be used to derive snow depth measurements. We validated the method for snow depth estimation using camera data from Latah County, Idaho, USA in winter 2020–2021. Mean bias error between the virtual snow stake and a physical snow stake was 5.8 cm; the mean absolute bias error was 8.8 cm. The mean Nash Sutcliffe Efficiency score comparing the fit of the 2 sets of measurements within each camera was 0.748, indicating good agreement. The edger package provides researchers with a means to take critical measurements for ecological studies without the use of physical objects that could alter animal behavior, and snow data at finer scales can complement other snow data sources that have coarser spatial and temporal resolution.

Idaho↗
USGS2023

Evaluation of fall-seeded cover crops for grassland nesting waterfowl in eastern South Dakota

The Prairie Pothole Region (PPR) is the primary breeding ground for many species of North American waterfowl. The PPR was historically dominated by mixed and tallgrass prairies interspersed with wetlands, but >70% of the native grassland area has been lost due to widespread conversion to croplands. Cover cropping is a reemerging farming technique that may provide suitable nesting cover for grassland nesting waterfowl in active croplands, but waterfowl nest survival in fall cover-cropped fields has not been evaluated. We studied use (nest abundance and density) and nest survival of breeding waterfowl in fall-seeded cover crops and perennial cover during 2018 and 2019. We searched 2,094 ha of cover crops and 1,604 ha of perennial cover and found 123 and 304 duck nests, respectively, in each cover type. Estimated nest success (34-day interval) was 3.7% and 16.6% in cover crops during 2018 and 2019, respectively, versus 22.1% in 2018 and 24.9% in 2019 in perennial cover, with increased success of cover-crop fields in 2019 resulting from precipitation that prevented most fields from being planted to row crops. In a model that included effects of planting, daily nest survival in perennial cover was 0.944 (SD = 0.026) in 2018 and 0.960 (SD = 0.019) in 2019. Estimated daily nest survival was 0.912 (SD = 0.040) in 2018 and 0.960 (SD = 0.019) in 2019 during intervals when planting did not occur, but was only 0.417 (SD = 0.124) in 2018 and 0.612 (SD = 0.117) in 2019 on the day that planting occurred. Estimated nest densities in 2018 and 2019, adjusted for nests that failed prior to discovery, were 5.1 (SE = 1.1) and 11.0 (SE = 3.1) nests 100-ha −1 in perennial cover, but only 2.1 (SE = 0.8) and 2.6 (SE = 0.7) in cover crops, respectively. Based on observed nest initiation and planting dates, about 70% of duck nests in cover crops would experience planting events in a typical growing season. Our results suggest that under current management techniques, fall-seeded cover crops offer poor nesting habitat for waterfowl; however, the important benefits cover crops provide to soil health, water quality, and other ecosystem services remain.

South Dakota↗
USGS2023

Potential impacts of land-management schedules on grassland bird nests and fledglings

Trade-offs exist between timing of grassland habitat management activities (e.g., weed and brush control) while also ensuring other conservation objectives (e.g., grassland bird reproductive success) are met. On land set aside for grassland conservation (e.g., lands enrolled in the U.S. Department of Agriculture Conservation Reserve Program and some state and federal wildlife management areas), federal and state agencies set time frames for land management based on avoiding disturbance of grassland bird nests. However, recent calls for considering the needs of dependent fledglings in conservation plans imply a need to evaluate whether current time frames are adequate. We used initiation and end dates for 3,257 nests of 8 obligate grassland bird species in Illinois and Wisconsin and a simulation approach for fledgling survival to estimate the potential proportion of active nests at risk when management (e.g., mowing, fire) occurred on the 1st and 15th day of May, June, July, and August during the breeding season. Management during June had the potential to impact 24–61% of nests, depending on the species. Management during July had the potential to impact 4–52% of nests, depending on the species. If disturbance occurred during August, proportionately few active nests were at risk for any species (0–9% of nests on 1 August, 0–<0.5% on 15 August). Potential proportions of fledglings at risk from management were greatest in July for 7 of the 8 species (7–18%). Our study suggests that on lands where a primary conservation objective is to increase or ensure survival of grassland birds, delaying management activities until August could be beneficial for protecting both grassland bird nests and fledglings.

Illinois, Wisconsin↗
USGS2023

Assessment of lesser prairie-chicken translocation through survival and lek surveys

Translocation is a management tool used to restore or augment wildlife populations, but outcomes of translocations are often poorly documented and can have varying levels of success for improving wildlife population declines. The lesser prairie-chicken (Tympanuchus pallidicinctus) is a prairie grouse endemic to the southern Great Plains. In response to declining abundance and distribution, in 2023 lesser prairie-chickens were listed as threatened or endangered under the Endangered Species Act in different states. Translocation is a potential management response to population declines when there is an availability of unoccupied habitats, but translocation efficacy has not been evaluated for lesser prairie-chickens. We translocated 411 lesser prairie-chickens seasonally from 2016-2019 and monitored the translocated lesser prairie-chicken population from 2017–2022. To assess translocation as a management tool for lesser prairie-chickens, we estimated survival for 2017–2020 and conducted lek surveys during 2017–2022. Over a fifth (22.8%, n = 94) of translocated birds either died or went missing within the first 2 weeks following release. Survival rates of translocated birds during the breeding (0.44 ± 0.02 [SE]) and nonbreeding (0.55 ± 0.03 [SE]) seasons were relatively low compared to nontranslocated lesser prairie-chickens in other studies (0.63–0.93 for breeding season; 0.43–0.87 for non-breeding season). Twenty-seven percent of translocated birds survived to the breeding season after release (i.e., >1 year). Translocated lesser prairie-chickens initiated 28 lekking sites over the study period. We estimated 77% of males available >2 weeks post release participated in lekking activity. The number of leks and male high counts on leks in the study area increased after translocation, peaking one year post-translocation (an overall increase of 250% and 340%, respectively). However, both the number of leks and male high counts decreased (48% and 39%, respectively) within 3 years after translocation cessation. Establishment of leks and increasing lek attendance directly following translocation initially suggested that translocation could be a viable management tool. However, survival rates after translocation and declining lek counts following translocation indicates that the increased population abundance and occupied range from this translocation effort may be unsustainable. Our results highlight the necessity of monitoring to determine outcomes of a large lesser prairie-chicken translocation. Other management strategies, such as targeted grassland restoration and management in areas of greatest lesser prairie-chicken density, could be more beneficial for conservation of lesser prairie-chicken populations.

Colorado, Kansas↗
USGS2023

Comparing methods to estimate feral burro abundance

Obtaining precise and unbiased estimates of feral burro ( Equus asinus ) abundance in the western United States is challenging due to their cryptic pelage and the rugged terrain they inhabit. Management agencies employ helicopter-based, simultaneous double-observer sightability surveys (hereafter denoted as DOS) to estimate abundance of burros; but the DOS method routinely produces negatively biased estimates due to residual heterogeneity in detection probability. Consequently, testing alternative methods to improve upon current procedures is warranted. Residual heterogeneity in DOS surveys can be minimized by including radio-collared individuals in the population. Alternatively, if distance measurements are recorded, residual heterogeneity can also be reduced via a mark-recapture distance sampling (MRDS) approach. Aerial infrared (IR) surveys offer a safer alternative than helicopter-based surveys because they can be flown at a higher altitude and require fewer observers in the aircraft. Further, IR surveys using a distance sampling approach have been shown to generate accurate and precise estimates of feral horse ( E. caballus ) populations. Accordingly, we compared results of surveys using aerial IR distance sampling, the standard DOS survey, a DOS survey incorporating detections of radio-collared individuals, and an MRDS analysis of a feral burro population with a known minimum population size in central Utah, winter 2015–2016 and spring 2016. The minimum number of burros known alive during the winter and spring surveys were 236 and 136, respectively. The average detection probability of IR surveys was P = 0.88 (SE = 0.16) and distance models produced estimates of 127 burros (95% CIs = 99–175) for the winter survey, and 94 burros (CIs = 72–134) for the spring survey. Mean detection probability of the standard DOS surveys was P = 0.78 (SE = 0.09), and model-generated abundance estimates were 155 burros (CIs = 133–227) in winter, and 92 burros (CIs = 79–139) in spring. Incorporating detections of radio-collared individuals in the DOS survey resulted in a decreased detection probability ( P = 0.46; SE = 0.06) and increased abundance estimates to 267 (CIs = 169–571) and 155 (CIs = 128–263) for winter and spring, respectively. Mark-recapture distance sampling produced a mean detection probability of P = 0.48 (SE = 0.12) and resulted in estimates of 282 (CIs = 178–385) and 169 (CIs = 73–310) burros in winter and spring, respectively. Our study demonstrated that aerial IR surveys conducted using standard distance sampling can produce precise estimates of burro population sizes; however, estimates were negatively biased relative to the known population size. Small sample size limits generalization of our results, but the IR-based distance approach did not improve upon DOS surveys. Accounting for residual heterogeneity through use of radio-collars and mark-recapture distance sampling eliminated the negative bias from the standard DOS survey but decreased survey precision. Managers will need to decide whether unbiased but less precise abundance estimates are preferable compared to a more precise, but biased, estimate.

Utah↗
USGS2012

Archive eggs: a research and management tool for avian conservation breeding

Worldwide, approximately 168 bird species are captive-bred for reintroduction into the wild. Programs tend to be initiated for species with a high level of endangerment. Depressed hatching success can be a problem for such programs and has been linked to artificial incubation. The need for artificial incubation is driven by the practice of multiclutching to increase egg production or by uncertainty over the incubation abilities of captive birds. There has been little attempt to determine how artificial incubation differs from bird-contact incubation. We describe a novel archive (data-logger) egg and use it to compare temperature, humidity, and egg-turning in 5 whooping crane (Grus americana) nests, 4 sandhill crane (G. canadensis) nests, and 3 models of artificial incubator; each of which are used to incubate eggs in whooping crane captive-breeding programs. Mean incubation temperature was 31.7&deg; C for whooping cranes and 32.83&deg; C for sandhill cranes. This is well below that of the artificial incubators (which were set based on a protocol of 37.6&deg; C). Humidity in crane nests varied considerably, but median humidity in all 3 artificial incubators was substantially different from that in the crane nests. Two artificial incubators failed to turn the eggs in a way that mimicked crane egg-turning. Archive eggs are an effective tool for guiding the management of avian conservation breeding programs, and can be custom-made for other species. They also have potential to be applied to research on wild populations.

Wildlife Society Bulletin↗