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USGS2024

Duck hunters and difficulty complying with harvest regulations

Due to the steady decline of duck hunter participation, several studies have investigated means to bolster the duck hunter population. Researchers and wildlife professionals have assumed that simpler regulations would attract new and unconfident hunters to participate in duck hunting. In light of this, we sought to identify what portion of the duck-hunting population had difficulty understanding species-specific bag limits or complying with species-specific bag limits in the field. We also sought to describe hunters who had difficulty complying with specific bag limits and how their difficulties were associated with elements related to demography, attitude, and behavior. We found most hunters had no difficulty understanding (82%) or complying with (74%) species specific bag limits, but flyway (χ 2 = 35.06, P < 0.01), number of ducks harvested (χ 2 = 9.76, P < 0.01), number of years hunted (χ 2 = 9.20, P < 0.01), and gender (χ 2 = 4.14, P < 0.05), were important to predicting hunter difficulty with compliance. Hunters who can overcome their difficulties understanding and complying with species-specific bag limits may be more likely to be integrated into the duck hunting culture, and more likely to continue duck hunting in the future. More species identification tools and fewer species-specific bag limits may be appropriate for the 18% of the duck hunter population who indicated that bag-specific regulations were difficult to understand and the 26% who indicated that it was difficult to comply with species-specific bag limits in the field. A closer look may be warranted for how the trade-offs associated with the combination of species-specific bag limits in combination with the variety of duck season zone and split options states employ, license/stamp requirements, area-specific regulations, and trespass laws may influence duck hunter experiences.

Wildlife Society Bulletin↗

USGS2024

Developing a photography-based harvest survey to estimate age and subspecies composition of midcontinent sandhill cranes

Midcontinent sandhill cranes ( Antigone canadensis ) are managed as a single population, but hunting regulations are structured so harvest is targeted towards the more numerous lesser sandhill cranes ( A. c. canadensis ). However, research indicates that greater sandhill cranes ( A. c. tabida ) have been disproportionally exposed to harvest at a rate exceeding their proportion within the midcontinent population. In addition, harvest has increased 22% per year in the U.S. Central Flyway states. The midcontinent population appears to be growing in recent years, but variability in annual abundance estimates has increased substantially. With limited resources and harvest management uncertainty increasing, we developed methods for a citizen science, photography-based harvest survey to estimate age and subspecies composition of harvested midcontinent sandhill cranes. To develop survey methods, we collected physical parts from 284 sandhill cranes in North Dakota in 2019 and 2020. We manually measured the culmen and tarsus using calipers, and digitally measured these parts using photographs and computer software. All digitally derived measurements were 2.5% to 5.9% larger than manual measurements; therefore, we developed linear models that adjusted digital measurements, facilitating subspecies prediction using an existing morphometric-based technique. In 2021, we requested an equal number of hunters to participate using 2 data collection methods to test if hunters could reliably take photographs suitable for digital measurement. Collection method 1 involved photographing the head and leg simultaneously, and Collection method 2 involved photographing the head only. Hunters submitted a total of 239 photographs. Only 80 of these photographs were submitted using Collection method 1, and 72% were suitable for digital measurement. Conversely, hunters submitted twice as many photographs using Collection method 2, and 88% of these photographs were deemed suitable. Although obtaining the tarsus measurement slightly improved subspecies predictability, Collection method 2 increased participation and usable data. We believe our results could be used to develop an operational survey of age and subspecies composition of midcontinent sandhill cranes, wherein a sample of crane hunters throughout the midcontinent population range would be asked to electronically submit a photograph of the head of each bird they harvest. A time series of age and subspecies composition of this population would provide managers with valuable information and improve harvest management at minimal additional cost and burden, compared to a traditional parts collection survey administered by mail.

Wildlife Society Bulletin↗

USGS2024

Abundance estimates of Gunnison’s prairie dogs compared to the number of active burrows

Reliable estimates of prairie dog ( Cynomys spp.) population size and distribution are critical for assessing the status of prairie dogs and for selecting sites to reintroduce black-footed ferrets ( Mustela nigripes ). The density of active prairie dog burrows has commonly been used as an index of prairie dog abundance. Indices derived from active burrow counts were developed for black-tailed ( C. ludovicianus ) and white-tailed ( C. leucurus ) prairie dogs, but their efficacy has not been evaluated for all prairie dog species and studies affirming their validity with robust abundance estimators are few. We indexed or estimated the abundance of Gunnison's prairie dogs ( C. gunnisoni ) in the Aubrey Valley, Arizona, USA, in 2006 at 2 different time periods using 4 different methods—maximum above ground counts (MAGC), minimum number known alive (MNKA), capture-mark-recapture (CMR), and mark-resight—and compared these estimates to active burrow counts in 2005 and 2006. We found no positive relationship between active burrow counts and any abundance estimators. Mark-resight estimates of abundance were greater than the MNKA and were positively correlated with both the MNKA ( r 2 = 0.30) and CMR estimates ( r 2 = 0.49). Both CMR estimates and MAGC were typically below the MNKA and therefore biased low. Our results indicated that more rigorous estimation methods may be necessary to accurately estimate prairie dog abundance and assess habitat quality for ferret conservation.

Arizona↗

USGS2024

Evaluating satellite-transmitter backpack-harness effects on greater sage-grouse survival and device retention in the Great Basin

Wildlife tracking studies have become ubiquitous in ecology and now provide previously unobtainable data regarding individual movement, vital rates, and population demographics. However, tracking devices can potentially reduce survival of study subjects, generating biases in the vital rates they seek to measure. Previous studies have found that greater sage-grouse ( Centrocercus urophasianus ) fitted with Global Positioning System (GPS) tracking devices may experience reduced survival, relative to those tracked with traditional radio transmitters, and have documented skin abrasions and lacerations associated with typical backpack-style GPS harnesses. We implemented an experimental study comparing survival and harness retention between 2 different backpack-style GPS transmitter harnesses. We captured female sage-grouse at 3 study sites in the northwest Great Basin of Oregon, Nevada, and California during 2019–2021. We fit each individual, following previously published recommendations, with either a standard backpack harness or a modified harness hypothesized to reduce skin abrasion and laceration. We used known-fate models in Program MARK to model variation in survival and harness retention separately as a function of harness type, year, age, a linear effect of time, and the ratio of the device to individual body mass. Neither survival nor retention varied systematically by harness type, however retention decreased as a function of body mass ratio. We echo previous recommendations for standardized harness attachment protocols and studies designed to isolate and test potential mechanisms by which tracking devices and attachment methods might affect survival and well-being of sage-grouse and other tracked species.

California Nevada, Oregon↗

USGS2024

Evaluating habitat use and relative abundance of Iowa's river otter with harvest data

The North American river otter ( Lontra canadensis ) was extirpated from much of the United States in the early 20th century due to habitat loss, pollution of waterways, and overharvesting. The Iowa Department of Natural Resources began a river otter reintroduction effort in 1985, which placed otters in 14 sites across the state. Otters have since been known to occur in every county in Iowa and appear to have successfully repopulated their former range throughout the state. Our objective was to relate land cover characteristics and otter abundance using harvest data. We used data collected by agency staff to map the locations of otter harvest in Iowa from 2006 to 2016. We mapped otter harvest locations at the subwatershed level (also called 12-digit Hydrologic Unit Code or HUC-12). We related otter harvest to land cover variables and predicted otter abundance by land cover type. We found that roads, forests, larger waterways, and Ictaluridae (catfish) presence were negatively correlated with otter harvest. Variables positively correlated with otter harvest were areas with greater land cover diversity, wetland patch density, average stream density, and waterway and wetland areas. The land cover model predicted otters in equal or greater numbers than the harvest data in 62.8% of HUC-12s. The areas of greatest otter abundance estimates were located near recreation areas and urban areas, indicating the underutilization of these heavy-trafficked areas by trappers. Areas of fewer predicted otters were not concentrated in a single area of the state but occurred along the Interstate 80 corridor.

Iowa↗

USGS2024

True metabolizable energy of foods consumed by lesser scaup (Aythya affinis)

The energy derived from available foods is an important factor used in conservation planning for migratory species. Estimating true metabolizable energy (TME) of available foods has become a common method for resource managers to increase reliability in energetic carrying-capacity estimates. Lesser scaup ( Aythya affinis ; hereafter scaup), have experienced a population decline concurrent with suspected decreases in foraging habitat quality and quantity at spring stopover sites in the upper Midwest, USA. Unfortunately, few TME estimates are available for common diet items of scaup. We estimated nitrogen-adjusted TME (TME N ) of 5 common foods of scaup by conducting feeding trials on wild females and males. True metabolizable energy varied by food taxa, but not by pretrial body mass or sex. Mean TME N (kcal/g[dry] ± SE) was greatest for wild millet ( Echinochloa crus-galli ; 2.20 ± 0.14), followed by chironomids ( Chironomus spp.; 1.41 ± 0.49), amphipods ( Gammarus spp .; 1.33 ± 0.23 ) , planorbid snails (Planorbidae; 0.17 ± 0.07), and fingernail clams (Sphaeriidae; −0.79 ± 0.27). Our results, combined with scaup diet literature indicated that the management of spring staging areas for high-energy invertebrates (i.e., chironomids and amphipods) would provide improved opportunity for energy acquisition during migration. Further study could help determine if the acclimation of scaup to particular diets, especially bivalves, increases their TME N values.

Wildlife Society Bulletin↗

USGS2024

Gray wolf breeders are more vulnerable to harvest during the breeding season

In cooperatively breeding carnivores, breeders are vital to perpetuating the group; the death or removal of an individual breeder can greatly affect group composition, genetic content, and short-term population growth. Understanding the number of breeders harvested and timing of harvest can increase our knowledge of how mortality affects groups of cooperative breeders. Gray wolves ( Canis lupus ) in Idaho, USA, are exposed to annual harvest and are an ideal species for studying the effects of harvest on breeder turnover. We combined genotypes from tissue samples of harvested wolves with parentage analyses and cementum annuli ages and estimated when and how many breeding wolves were harvested. We genotyped and aged 229 adults and 203 pups using tissue and tooth samples from wolves harvested between 2014 and 2016. We identified a minimum count of 33 breeders in the harvest and found that they were disproportionately harvested more during the breeding season. We estimated that a minimum of ~14.5% of adult wolves harvested annually, or approximately 1 in 7, were breeders. We posit their behavior during breeding season may increase their vulnerability to harvest. By linking animal life history with vulnerability to human-caused mortality we show that managers could structure harvest seasons so there is less overlap with wolves’ breeding season if there is concern about the demographic consequences of harvesting breeders.

Idaho↗

USGS2025

Development and evaluation of the remote passive integrated transponder tag reader for customizable monitoring of wildlife

Increasing the quantity and quality of mark-reencounter data can be important when individual identification data are needed to address research or management questions. Physical recapture methods tend to be labor-intensive and therefore expensive, while remote detection methods are not easily applied to all taxa or are proprietary and thus difficult to customize. However, partnerships between wildlife scientists and engineers have the potential to provide innovative solutions that improve data collection while reducing costs. We describe a collaborative effort to improve the collection of mark-reencounter data on an invasive reptile, the brown treesnake ( Boiga irregularis ). In laboratory trials conducted on Guåhan (CHamoru; Guam in English) in 2021, we assessed the feasibility of detecting snakes fitted with passive integrated transponder (PIT) tags using customized remote PIT-tag readers (RePTaR) paired with baited snake traps. We evaluated differences in scanning success as a function of snake traits, location of PIT tags within snakes, and the distance of the PIT tag from the reader. We successfully scanned all individuals, on average 529 times but ranging from 3 to 6,436 times, during 12-hour trials using a designed customizable RePTaR unit. Snake characteristics and marking location explained little of the variability in scanning success, with distance from the reader as the best-supported covariate. By building cross-disciplinary partnerships, we can develop customizable technological solutions and provide additional tools with which to address challenges in wildlife research and management.

Guam↗

USGS2025

Informing adaptive management to reduce ungulate aggregations: A case study involving winter feeding of elk

In the United States, wildlife managers are entrusted with preserving culturally and economically important ungulate populations in the face of the ongoing spread of chronic wasting disease (CWD). The U.S. Fish and Wildlife Service established an adaptive management plan to reduce the reliance of elk ( Cervus canadensis ) on supplemental winter feeding on the National Elk Refuge. The end goal of reducing the unnaturally high aggregation of elk during the winter is to mitigate the threat of disease outbreaks and to meet the objectives of sustainable populations of elk on the refuge. In this case study, we evaluated 6 years (2017–2022) of data from GPS-collared elk to determine the efficacy of shortening the length of the annual feeding period on the refuge to reduce elk aggregation. We measured aggregation using proximity rates, based on pairwise interactions over time, in both raw form as an index as well as predicted proximity as a function of other abiotic influences. We created a new R package, wildagg , to help with the process of computing the metrics from our study and to increase reproducibility in the future. Aggregation declined in years with less feeding on the refuge according to raw aggregation metrics when examined in isolation and dependent on the baseline feeding year used for comparison. However, accounting for abiotic factors while modeling proximity rates suggested in some years the decision to shorten the feeding period had less influence on aggregation than predicted. Our results underscore the complexity of measuring management outcomes and the usefulness of multiple approaches to evaluation.

Wyoming↗

USGS2025

Observability of eastern massasauga (Sistrurus catenatus) during visual encounter surveys in Michigan, USA

Visual encounter surveys are commonly used to document site occupancy for the eastern massasauga ( Sistrurus catenatus ; EMR). Efficacy of surveys depends on visual and auditory cues, with basking behavior and burrow use strongly affecting detection. Our goal was to predict body exposure and probability of burrow use from telemetered EMR to better inform implementation of visual encounter surveys. We collected body exposure and burrow use from 23 EMR (14 females [12 gravid], 9 males) from April through September (i.e., active season) at 2 sites in south central Michigan, USA, 2020–2022. Average body exposure for observed snakes was 42% (SE = 3%) and ranged from 0–100%. Percent body exposure during the active season was positively influenced by air temperature, where body exposure increased from ~25% at ~15°C to ~50% at ~35°C. We did not find an effect of cloud cover, hour of day, humidity, or sex on EMR body exposure. Of 176 observations of EMR during the active season, we found EMR using burrows 20 times (~11% of observations). Julian date and air temperature affected the probability of EMR burrow use early in the active season. Probability of EMR burrow use was <0.10 from the end of May through the end of October and was almost 0.00 after mid-July. The probability of using a burrow was generally low (i.e., <0.25) across the range of air temperatures measured in our study, but approached 0.00 as temperatures exceeded 30°C. We did not find an effect of cloud cover, time of day, humidity, or sex on probability of EMR burrow use. Our results indicated that EMR observability in southern Michigan was greatest when air temperatures were 30°C to 35°C, corresponding to when EMR were visible and aboveground.

Michigan↗

USGS2025

Monitoring Pacific walrus coastal haulouts by satellite to estimate herd abundance and distribution

The Pacific walrus ( Odobenus rosmarus divergens ) has a single, panmictic stock that ranges across the Bering and Chukchi Seas. However, its seasonal distribution is incompletely described, particularly in autumn when herds gather on shore, and abundance is of interest to management entities. We monitored walrus herds using satellite imagery on shore across their summer and autumn range in the Chukchi Sea to provide insights on seasonal distribution and abundance. During each study year (2017–2024), we documented walrus herd abundance at 8 Chukchi Sea haulouts based on the herd area detected in satellite imagery multiplied by herd density estimates derived from aerial survey data. In contrast to historical seasonal use, we found large herds on shore at only 3 sites, 1 in Alaska and 2 in northern Chukotka (Russia). In 2022, we observed a very large herd with an abundance (and 90% prediction interval) of 184,000 (min–max = 153,000–214,000) northwest of the Bering Strait, which enabled us to estimate a minimum population size (N min ) by correcting the abundance estimate by the proportion of walruses that may be hauled out and available for detection. Our estimate of 250,000 was commensurate with the N min estimate (214,000) from a 2013–2017 Pacific walrus genetic mark-recapture study.

Alaska↗

USGS2025

A framework for analyzing wild turkey summer sighting data.

Wildlife agencies collect data on productivity (e.g., proportion of hens with poults and number of poults per hen) of wild turkey ( Meleagris gallopavo ) to monitor population status and trends. However, sampling protocols to collect productivity data rely on opportunistic observations reported by wildlife agency personnel and the public and have changed over time and differed among agencies. A protocol to standardize data collection was adopted by most state wildlife agencies in 2019, but long-term historical datasets exist that cannot be analyzed readily to make inferences about spatial and temporal patterns in wild turkey productivity. We developed statistical models to allow comparisons and model trends in productivity among and within states even though data collection protocols changed over time and differed among states. We found greater spatial variation in the proportion of hens with poults than the number of poults per brood, which may reflect how environmental factors influence wild turkey productivity. Our models can also provide inferences about productivity when data are limited or temporally discontinuous for some spatial units. Additionally, we found that temporal and spatial variation in data collection, even under the new protocol, can affect inferences about trends in productivity. The statistical models we developed address the uncontrolled nature of when and where data are collected and offer the ability to investigate long-term patterns of productivity in relation to factors such as changing climate or habitat conditions.

Maryland, New Jersey, New York, Ohio, Pennsylvania↗

USGS2025

Passive acoustic monitoring is a cost-effective approach to conduct inland surveys for marbled murrelets

The marbled murrelet ( Brachyramphus marmoratus ) is a seabird of conservation concern that nests in late-successional, old-growth forests in Oregon, Washington, and California, USA. Traditional audio-visual surveys have been the standard method for detecting murrelets in forests. Given that murrelets can be extremely cryptic in forest environments, audio-visual surveys are difficult, time consuming, and expensive to conduct. Passive acoustic monitoring (PAM) may be a useful and cost-effective alternative. Using a paired murrelet survey design, we compared detection probabilities across 88 survey points in forests of Oregon and Washington. We conducted 2–4 early morning audio-visual surveys and 13–53-day PAM surveys from 14 June through 5 August 2022 and 2023, when murrelets typically make the most frequent inland flights during the nesting season. We found the average detection probability for murrelets on any given day was higher for an audio-visual survey visit (0.40, SD = 0.17) than for a PAM survey day (0.19, SD = 0.10). However, the cumulative detection probability for PAM surveys was 0.98 (95% CI = 0.96–1.0) after 19 survey days, whereas the same cumulative detection probability would require 9 audio-visual survey visits. Using simulations to compare the cost-effectiveness of both methods, we found audio-visual surveys cost more when compared with PAM surveys in 61–91% of scenarios because they require specialized personnel training and additional pre-dawn visits. Further, PAM per survey costs decreased as the number of survey days per point increased and over time after initial costs were incurred, particularly when autonomous recording units were reused for multiple years. While audio-visual surveys are the standard method for murrelet surveys in forest habitats, PAM represents a more cost-effective approach to determine the presence of murrelets.

Oregon, Washington↗

USGS2012

A modified night-netting technique for recapturing quail

Difficulties in recapturing radiomarked birds often prevent wildlife researchers from replacing transmitters and continuing to collect data over long time periods. We developed an effective, inexpensive capture technique for radiomarked mountain quail (Oreortyx pictus). Twenty-three of 25 mountain quail in south-central Idaho, USA, in 2006 and 2007 were recaptured for transmitter replacement. This technique will provide researchers with an opportunity to recapture relatively small birds, particularly those in dense vegetation, to help conduct long-term studies.

Wildlife Society Bulletin↗

USGS2012

Shifting foundations and metrics for golden-cheeked warbler recovery

Using the golden-cheeked warbler (Setophaga chrysoparia) as a case study, this paper discusses what lessons can be learned from the process of the emergency listing and subsequent development of the recovery plan. Are the metrics for recovery in the current warbler plan appropriate, including population size and distribution (recovery units), migration corridors, and wintering habitat? In other words, what happened, what can we learn, and what should happen (in general) in the future for development of such plans? We discuss the number of recovery units required for species persistence and estimate the number of male warblers in protected areas across the breeding range of the species, using newly published density estimates. We also discuss future monitoring strategies to estimate warbler population trends and dispersal rates.

Wildlife Society Bulletin↗

USGS2012

Using structured decision making to manage disease risk for Montana wildlife

We used structured decision-making to develop a 2-part framework to assist managers in the proactive management of disease outbreaks in Montana, USA. The first part of the framework is a model to estimate the probability of disease outbreak given field observations available to managers. The second part of the framework is decision analysis that evaluates likely outcomes of management alternatives based on the estimated probability of disease outbreak, and applies managers' values for different objectives to indicate a preferred management strategy. We used pneumonia in bighorn sheep (Ovis canadensis) as a case study for our approach, applying it to 2 populations in Montana that differed in their likelihood of a pneumonia outbreak. The framework provided credible predictions of both probability of disease outbreaks, as well as biological and monetary consequences of management actions. The structured decision-making approach to this problem was valuable for defining the challenges of disease management in a decentralized agency where decisions are generally made at the local level in cooperation with stakeholders. Our approach provides local managers with the ability to tailor management planning for disease outbreaks to local conditions. Further work is needed to refine our disease risk models and decision analysis, including robust prediction of disease outbreaks and improved assessment of management alternatives.

Montana↗

USGS2013

Anthropogenic impacts to the recovery of the Mexican gray wolf with a focus on trapping-related incidents

Concerns regarding the potential negative impacts of regulated furbearer trapping to reintroduced Mexican gray wolves (Canis lupus baileyi), led to an executive order prohibiting trapping in the New Mexico, USA, portion of the Blue Range Wolf Recovery Area. This ban was to last for 6 months and required an evaluation of the risk posed to wolves by traps and snares legally permitted in New Mexico. We reviewed potential threats to wolves in the Blue Range Wolf Recovery Area, including threats associated with regulated furbearer trapping. One hundred Mexican gray wolf mortalities have been documented during the reintroduction effort (1998–2011). Of those mortalities with a known cause, >81% were human-caused resulting from illegal shooting (n = 43), vehicle collisions (n = 14), lethal removal by the United States Fish and Wildlife Service (USFWS; n = 12), non-project-related trapping (n = 2), project-related trapping (n = 1), and legal shooting by the public (n = 1). Ten wolves died due to unknown causes. The remaining 17 mortalities were a result of natural causes (e.g., starvation, disease). An additional 23 wolves were permanently, but non-lethally, removed from the wild by the USFWS. Of 13 trapping incidents in New Mexico that involved non-project trappers (i.e., trappers not associated with USFWS or U.S. Department of Agriculture-Wildlife Services), 7 incidents are known to have resulted in injuries to wolves: 2 wolves sustained injuries severe enough to result in leg amputations and 2 additional wolves died as a result of injuries sustained. Foothold traps with rubber-padded jaws and properly set snares may reduce trap-related injuries to Mexican gray wolves; however, impacts caused by trapping are overshadowed by other anthropogenic impacts (e.g., illegal shooting, non-lethal permanent removal, and vehicle collisions).

New Mexico↗

USGS2013

Do singing-ground surveys reflect american woodcock abundance in the western Great Lakes region?

The Singing-ground Survey (SGS) is the primary monitoring tool used to assess population status and trends of American woodcock ( Scolopax minor ). Like most broad-scale surveys, the SGS cannot be directly validated because there are no independent estimates of abundance of displaying male American woodcock at an appropriate spatial scale. Furthermore, because locations of individual SGS routes have generally remained stationary since the SGS was standardized in 1968, it is not known whether routes adequately represent the landscapes they were intended to represent. To indirectly validate the SGS, we evaluated whether 1) counts of displaying male American woodcock on SGS routes related to land-cover types known to be related to American woodcock abundance, 2) changes in counts of displaying male American woodcock through time were related to changes in land cover along SGS routes, and 3) land-cover type composition along SGS routes was similar to land-cover type composition of the surrounding landscape. In Wisconsin and Minnesota, USA, counts along SGS routes reflected known American woodcock-habitat relations. Increases in the number of woodcock heard along SGS routes over a 13-year period in Wisconsin were related to increasing amounts of early successional forest, decreasing amounts of mature forest, and increasing dispersion and interspersion of cover types. Finally, the cover types most strongly associated with American woodcock abundance were represented along SGS routes in proportion to their composition of the broader landscape. Taken together, these results suggest that in the western Great Lakes region, the SGS likely provides a reliable tool for monitoring relative abundance and population trends of breeding, male American woodcock.

Minnesota, Wisconsin↗