Journal of Wildlife Management最新文献

Before implementing nontoxic shot requirements for hunting waterfowl and American coots Fulica americana in the United States in 1991, the U.S. Fish and Wildlife Service monitored lead poisoning in waterfowl on federal and state wildlife hunting areas during 1983–1986. Federal and state collaborators collected gizzards and livers from 9,029 hunter-killed waterfowl (10 species of dabbling ducks Anatinae, 9 diving ducks Aythyinae, 5 geese Anserinae, and tundra swans Cygnus columbianus) across the four flyways. At the U.S. Fish and Wildlife Service National Wildlife Health Center, Madison, Wisconsin, waterfowl gizzards were examined for ingested lead and nontoxic shot and livers were analyzed for lead concentrations. Diving ducks had the greatest frequency (8.7%) of one or more ingested lead shot, followed by dabbling ducks (5.5%) and geese (1.3%). Ingested shot was not found in tundra swans. The frequency of elevated (≥2.0 mg/kg wet weight) liver lead concentrations was also greatest in diving ducks, followed by dabbling ducks and geese. Within each species group, the frequency of elevated liver lead concentrations was greater than ingested lead shot, an indication that lead shot ingestion alone underrepresents lead exposure. Thus, lead in the liver may remain elevated after the erosion and excretion of lead pellets from the gizzard. Our results provide historical baseline data and summarize a nationwide study of lead exposure, using both ingested lead shot and liver lead concentrations, in waterfowl in the United States before the implementation of nontoxic shot regulations in 1991. These data can be compared with previous studies of lead exposure in waterfowl, as well as current and future assessments to evaluate the success of nontoxic shot regulations nationwide and specifically within previously sampled waterfowl management areas.

American black ducks Anas rubripes (hereafter, black ducks) are an important game species in the eastern United States and Canada that declined between the 1950s and 1990s, resulting in the implementation of restrictive hunting regulations in the United States and Canada. Black duck harvest is managed by the Black Duck International Adaptive Harvest Management (BDAHM) strategy that was developed between Canada and the United States. The strategy requires that the black duck population be maintained at a level that is commensurate with legal mandates, provides for use appropriate for the habitat carrying capacity, and is managed in a manner that maintains equitable access (between Canada and the United States) to the black duck resource. Fulfilling these mandates requires unbiased country-specific harvest probability estimates, which in turn require estimates of band reporting probability, that is, the probability that a hunter who harvests a banded bird will report it to the North American Bird Banding Program (NABBP) through either the United States Bird Banding Lab (BBL) or the Canadian Bird Banding Office (BBO). We conducted a reporting probability study during the 2017–2018, 2018–2019, and 2019–2020 hunting seasons, using reward bands to estimate continental and country-specific band reporting probabilities. The continental (pooled) band reporting probability was 0.80 (95% CI = 0.660–0.945). Band reporting probability was lower in Canada (0.65, 95% CI = 0.487–0.821) than in the United States (1.00, 0.978–1.022) but increased in both countries since they were last estimated in the 2000s. Increased reporting probability and the difference in reporting between the two countries should be accounted for to most effectively meet the objectives of the BDAHM strategy.

We describe the results of long-term population monitoring of the island night lizard Xantusia riversiana on San Nicolas Island, California, following the species' removal from the U.S. Endangered Species list in 2014. Monitoring activities were carried out from October 2014 through November 2023, but we also incorporate data from earlier work dating back to 1993. Because of habitat loss on the western part of the island, the island night lizard is almost entirely confined to the island's eastern half. The species' distribution remains largely the same since studies in the 1990s, though small increases in distribution were noted at the island's west end. Numbers at most long-term monitoring sites appeared to show a slight decrease associated with a multi-year drought, with numbers returning to previous levels by the end of the monitoring period. Models fit to counts of newly recruited lizards suggested a positive association between winter precipitation and abundance; however, we found a simpler model including constant abundance throughout the study to be more parsimonious. Two monitoring sites showed marked decreases in numbers, with one site declining to zero following infestation of the area by non-native Argentine ants Linepithema humile. The island's vegetation and natural communities continue to gradually recover from a century of overgrazing by sheep and the widespread introduction of aggressive non-native plants. Habitat restoration efforts by U.S. Navy natural resources staff on the island may lead to increasing population numbers and genetic connectivity, but persistent threats remain for the island night lizard on San Nicolas Island.

Plague is a zoonotic vector-borne disease caused by the bacterium Yersinia pestis that impacts humans and wildlife around the world. One of the most well-studied species in North America negatively impacted by plague is the black-tailed prairie dog Cynomys ludovicianus. Black-tailed prairie dogs are colonial, ground-dwelling sciurids that live in territorial family groups called coteries. Previous plague transmission models have assumed that prairie dogs rarely move outside of their coteries and hence have little interaction with individuals outside of their family groups. Consequently, they would not contribute appreciably to intracolonial transmission of plague among coteries. We examined this assumption by attaching global positioning system (GPS) radio-collars to document prairie dog spatial use, their coterie boundaries, and whether they move outside of their coteries. We recovered five out of six collared yearling male prairie dogs in Scotts Bluff National Monument in Nebraska, USA, and estimated their coterie boundaries using 95% minimum convex polygons and kernel density estimation. We found evidence suggesting that all five individuals made exploratory movements outside of their coteries, with two moving >100 m from their estimated boundary. Exploratory movements provide opportunities for direct contact with prairie dogs from other coteries or with their fleas. Our work provides a baseline for future studies of unknown aspects of prairie dog movement ecology that could alter how we model intracolonial plague transmission.

Bull Trout Salvelinus confluentus is a federally threatened species in the conterminous United States. Although some populations are stable or increasing, Bull Trout in the United States Fish and Wildlife Service's designated Coeur d'Alene Core Area in Idaho have experienced substantial declines in abundance. Today, the remaining extant population in the Coeur d'Alene Core Area returns to the headwaters of the St. Joe River to spawn. The population has been monitored annually since 1992 using spawning ground surveys, but little is known about early life stages in the system. The objective of our research was to evaluate the distribution and abundance, age and size structure, habitat associations, and outmigration characteristics of juvenile Bull Trout in the upper St. Joe River basin. In 2022–2023, we sampled 200 stream reaches on the mainstem St. Joe River and four tributaries (Heller, Medicine, Sherlock, and Wisdom creeks). We sampled 1,529 Bull Trout varying in length from 29−257 mm in total length (TL; mean ± SD; 108 ± 44 mm). Population estimates suggested there were 1,841 (95% CI = 1,188−2,494) juvenile Bull Trout in the study area in 2022 and 2,388 (1,646−3,130) in 2023. Regression models indicated that abundance was positively related to canopy cover, amount of large substrate, amount of large woody debris, and amount of gravel, and negatively related to water temperature. We tagged 1,142 fish with passive integrated transponders (PIT) and detected 163 (14%) of these fish using a stationary tag array that was operational during June or July through October. Peak autumn outmigration occurred in October of both sampling years. Of the fish that were detected moving, age varied from 1−4 years, but age-1 and age-2 fish were more commonly detected moving downstream compared to other age classes. This study provides important information on the ecology of juvenile Bull Trout that can be used to guide conservation and recovery efforts in montane ecosystems. Furthermore, juvenile Bull Trout in the upper St. Joe River basin were present at similar densities and experienced growth rates similar to more robust adfluvial populations (e.g., Lake Pend Oreille, Idaho), thereby indicating that factors contributing to the low abundance of adults are not likely occurring in the headwaters of the St. Joe River. Thus, conservation efforts may be more successful if they are focused on the migration corridor and Coeur d'Alene Lake.

A formal framework for the adaptive management of duck harvests (Adaptive Harvest Management; AHM) was adopted by the U.S. Fish and Wildlife Service in 1995. In addition to concomitantly facilitating management decision making and reducing uncertainty, the process can reduce conflict among stakeholders within the regulation-setting process. However, evidence for reductions in conflict due to adaptive management has been largely anecdotal. We examined Federal Register documents to characterize and quantify the number and types of conflicts that occurred before and after the implementation of AHM for setting annual duck hunting regulations. We used Poisson regression models to test the effects of AHM implementation, habitat quality, and duck abundance on the number of conflicts documented in the regulation-setting process. Exponentiated coefficients from the best model indicated a 38% decrease in conflicts per additional one million ponds and a 9% decrease per additional one million total ducks. The number of annual conflicts before AHM was adopted was 1.72-fold greater than after its implementation.

Bigheaded carps (i.e., Silver Carp Hypophthalmichthys molitrix and Bighead Carp H. nobilis) are non-native species that continue to expand their ranges throughout North American river systems, including the Tennessee and Cumberland river systems in the southeastern United States. These species are known to have deleterious effects on native fishes. Management efforts have focused on reducing upstream passage at dams coupled with intensive removal of individuals occupying upstream reaches. Understanding mechanisms affecting the success of upstream fish passage through lock chambers is critical to determining immigration rates into upstream habitats, the likelihood of success for upstream removal efforts, and potential effects of upstream passage reduction using deterrents. We used acoustic telemetry to examine the timing of Silver Carp upstream and downstream dam passages, patterns of fish movement throughout the river systems, and the relationship between fish size and upstream passage through the lock chamber. During 2016–2019, 465 Silver Carp were surgically implanted with transmitters within the two river systems. We documented 37 upstream passages and 57 downstream passages of Barkley, Kentucky, and Pickwick dams. During the two years in which dam passages were observed, most upstream dam passages (89%) occurred during April–August when water temperature ranged from 12–31°C. Most downstream passages (89%) occurred from late-February through July. The relatively small portion of Silver Carp tagged in Pickwick Lake (11% of total tagged), the uppermost reach of the study area, accounted for nearly two-thirds of all dam passages. Our findings may help managers model Silver Carp populations and inform decisions regarding fish deterrent placement and operation.

Management plans with clear priorities can help to achieve brown pelican Pelecanus occidentalis conservation objectives in the northern Gulf of America (Gulf of Mexico). Efforts to establish clear priorities can be hindered by information gaps, especially those related to the uncertainty associated with changing conditions that influence brown pelican populations. We addressed these gaps by creating a model that uses island-specific conditions (e.g., geomorphology; predator-related conditions; brown pelican terrestrial nesting, roosting, and loafing habitats) to predict the nest count as a proxy for breeding pairs on the island. We used the model and 2000–2015 brown pelican nest count data to estimate if breeding pair targets that we identified or estimated for 10 U.S Fish and Wildlife Service Gulf Coast Biological Planning Units were met while accounting for uncertainty. Our results indicate that breeding pair targets were met in 7 of the 10 units by existing conditions. Our confidence in judging nest deficits tended to decrease from west to east because the model over-predicted total nests in the east Gulf Coast. Using an island from our data, we show how the model could be used to quantify the uncertainty of nest count outcomes under simulated changes in island conditions. The model indicated that the island's existing conditions most probably result in nests (probability = 0.51) and that increasing the area of nesting habitat (shrubs) could increase the probability of nests from 49% to 70%. Increasing shrub habitat in the model also increased nest count uncertainty by 60%, but this was due to a greater probability of larger nest counts. Our model suggests that nest count uncertainty could be reduced by improving data on island size, shrub area, and predator presence, depending on the unit and how isolated the island is from the mainland. These tools could help managers understand and incorporate the uncertainty associated with creating island conditions that are intended to help achieve brown pelican conservation objectives.

Eastern and Great Lakes populations of mallards (Anas platyrhynchos) have experienced a significant decline in recent years. These subpopulations are increasingly wild × game-farm mallard hybrids because of widespread releases of game-farm individuals. Concurrent with an increasing prevalence of releases, a near 50% decline in mallard populations in the United States occurred, while abundances remained stable in Canada. We aimed to refine our understanding of the metapopulation dynamics of eastern North American and Great Lakes mallards to provide information useful in population and harvest management. We used stable isotope and genetic techniques during pre-hunting season (July–September) banding to determine if banding location was representative of hatch or molt origin of mallards and if wild mallards captured and banded had more northern origins than wild × game-farm hybrids. Mallards are expected to be largely of local origin during the pre-hunting season, but nearly 50% of our sample had an origin north of their banding site, suggesting substantial movements during the banding period. We detected a similar percentage of wild × game-farm hybrid prevalence for the eastern mallard population (~89%), but a substantial increase in the Great Lakes region (~75%) compared to prior studies. However, we did not detect strong evidence for geographic or temporal variation in isotopic values (i.e., origins) of wild and hybrid mallards, which suggests that genotypes of mallards occurred together throughout the sampling period. Our results suggest that banding location of mallards in eastern North America does not equate to breeding ground origin or genotype (wild or hybrid), and we recommend investigation of other methods to understand if vital metrics differ among regions and genotypes. The movement we inferred during the banding season could potentially violate important assumptions that birds do not move among banding units and confound population vital rates estimated using banding returns. Thus, we recommend that current integrated population models consider eastern mallards as a single population because their movement throughout the banding period makes assessment at smaller geographic units invalid.