Journal of Wildlife Management最新文献

The Carolina heelsplitter Lasmigona [Platynaias] decorata is a federally endangered mussel endemic to North and South Carolina, USA. Captive propagation is aimed at bolstering wild populations via augmentation of juveniles, though factors affecting survival of captive-reared Carolina heelsplitter have not been evaluated. We compared survivorship of 100 captive-reared juvenile Carolina heelsplitters originating from two geographically isolated river basins (n = 50 of Pee Dee River basin origin; n = 50 of Catawba River basin origin) over 1 year (Oct 2021–Oct 2022). We retained a subset (n = 10 per origin) of mussels in a hatchery to serve as a control cohort and housed the remainder in concrete mussel silos deployed in one of four natural streams. We integrated a second species (eastern creekshell Villosa delumbis, n = 11 control and 20 in silos) in our study design to evaluate its potential use as a surrogate for assessing suitability of water quality for the Carolina heelsplitter at potential release sites, given the high rate of co-occurrence between the two species in South Carolina. We used known fate models to estimate weekly survival rates and ranked models to assess support for effects of species, basin of origin, release site, and time. Only 50 of 151 mussels (14% of all Carolina heelsplitters; 70.5% of eastern creekshells) survived the study. Eastern creekshell survival in the hatchery (100%) was higher than in natural streams (63%). However, we detected no evidence that Carolina heelsplitter survivorship was higher in the hatchery or varied by stream. Mussel survivorship increased with size at release but declined over time (except for eastern creekshell in the hatchery), with the most severe declines observed for the Carolina heelsplitter. Further, origin was a better predictor of Carolina heelsplitter survival than species alone or release site, with Catawba-origin juveniles having the lowest survivorship at most time points. Consistency in outcomes of Carolina heelsplitters in silos and the hatchery (control) provides strong evidence that their poor survivorship was due to an inherent attribute of our release cohort, rather than poor stream quality or cage effects. Further, the stark differences in species survivorship indicate the eastern creekshell may be a poor surrogate for investigating the resource requirements and release site suitability for Carolina heelsplitters of the size range we considered (25–38 mm). To improve propagation and release success for Carolina heelsplitters, we recommend investigating the species' basic requirements, the efficacy of rearing juveniles to a larger size prior to release, and whether extremely low rates of survival described here are consistent among first-generation (F1) offspring harvested from a wider range of wild adults in each natal river basin.

Invasive species management frameworks, such as the early detection of and rapid response to invasive species, use monitoring programs to detect new species occurrences. Resource managers use environmental DNA (eDNA) as one tool for these monitoring programs. An eDNA detection in a new location may lack perspective for resource managers and researchers because of the rarity of potential invaders and the randomness in their dispersal and detection. An example monitoring program is the eDNA-based sampling approach used by the U.S. Fish and Wildlife Service for bigheaded carps Hypophthalmichthys spp. in the upper Mississippi River and Great Lakes Basins that collects hundreds of water samples per event. The U.S. Fish and Wildlife Service detected a single positive sample for Bighead Carp Hypophthalmichthys nobilis during the spring 2021 sampling event in the Kinnickinnic River within the Milwaukee River Basin, and detected a second single positive sample for bigheaded carps during the fall 2021 sampling event in the Milwaukee River. The U.S. Fish and Wildlife Service did not detect any bigheaded carps in previous years (2015 to 2020) or in either the spring or fall 2022 sampling events. These detections lacked perspective, such as detection numbers for other species. We reanalyzed the 2021 and 2022 samples for four existing species of fish: two fairly common species (Common Carp Cyprinus carpio and Gizzard Shad Dorosoma cepedianum) and two fairly rare species (Burbot Lota lota and Grass Carp Ctenopharyngodon idella). We detected Common Carp during all four sampling events, Gizzard Shad during three of four sampling events, and Burbot and Grass Carp during two of four sampling events. These results demonstrated that current sampling efforts could detect other species, and bigheaded carp eDNA was not common in the Milwaukee River compared to these species. More specifically, this finding indicates bigheaded carp eDNA detections are as rare as, or rarer than, Grass Carp eDNA detections, a recent invader to the basin. Our findings also demonstrated how reanalyzing eDNA samples after positive detections for targeted species can help managers understand the context of the detections and provide perspective for the relative abundance of the targeted species. Additionally, our results highlight the importance of completing long-term eDNA-based monitoring rather than a single sampling or inventory event. These detections may have been missed in a single year or sampling event, whereas a multiyear monitoring program provides an opportunity to observe trends through time.

Many wildlife studies develop habitat models based on spatially limited, ground-based surveys. These surveys cannot adequately measure forest canopy features or characterize features at landscape scales, nor can these models be applied at larger extents, making them less useful for conservation. Lidar offers the opportunity to objectively measure habitat features across landscape-level extents, making it possible to predict landscape suitability at the level of entire states. We measured structural diversity of forest vegetation at 179 plots across Indiana, USA, at 3 radii (50 m, 100 m, and 300 m) to explore species associations with forest characteristics at different spatial scales. We developed occupancy models at each scale to predict species presence by relating detection–non-detection of wildlife species from camera traps (2019–2020) to indices of forest structure derived from aerial lidar (2016–2020). We quantified the relationship between the presence of 7 wildlife species and the 3 forest structure metrics. The effect sizes for each metric varied depending on the plot extent and species, often displaying opposite trends at different radii. Deep gap fraction had a strong positive association with species like eastern cottontail (Sylvilagus floridanus) at the 100-m and 300-m extents (95% credible intervals did not cross zero), but weaker relationships at 50 m. Some species also used areas with higher vegetation diversity, such as coyote (Canis latrans), which was positively associated with higher values for Gini foliage diversity at the 300-m extents. Habitat generalists did not show strong evidence of selection for specific metrics. Our study demonstrates that lidar shows great promise for habitat modeling based on its ability to characterize forest structure at landscape scales across large geographic extents. These models identify patterns of space use that are difficult and expensive to capture through traditional survey methods and have clear conservation and management applications owing to their extensive spatial coverage.

Military installations are important refuges for sensitive species and are charged with conducting conservation measures for species’ habitat protection. The federally endangered Indiana bat Myotis sodalis was first documented at Fort Knox in northcentral Kentucky in 1998. We monitored this first documented colony and additional colonies on base from 2005–2021. By conducting multiple simultaneous emergence counts and banding bats at both natural and artificial roosts (e.g., BrandenBark®), we documented the two largest Indiana bat maternity colonies in the range of the species and two additional colonies that require additional study. An average of 102.5 ± 5.2 bats emerged per roost during 449 counts of 104 roosts. Emergence counts from BrandenBark® ($��\; ��\overline{x}��$ = 122.7 ± 8.0 bats per roost) were significantly greater than those from natural roosts ($��\; ��\overline{x}��$ = 71.6 ± 9.3 bats per roost), and 16 emergence events exceeded the published maximum emergence count of 384 bats. We tracked bats to 190 natural and artificial roosts. Most of the 158 natural roosts were green ash Fraxinus pennsylvanica or silver maple Acer saccharinum trees. There were no significant differences in roost tree diameter at breast height (dbh) or height compared to the dbh and height of trees in the plot around the roost, and there were no differences in roost dbh or height among reproductive periods. Home range sizes between the two main colonies were similar: 5,003.8 ha at the Cundiff Lake colony and 4,501.8 ha at the HA6 colony. We found that federal bounding dates for reproductive periods did not align with actual dates of reproduction at Fort Knox for pregnancy or post-lactation, but there was no difference for the lactation period. The contiguous managed deciduous forest, abundant water sources, and proximity to large hibernacula make the roosting and foraging habitat at Fort Knox ideal for supporting large colonies of bats.

The Hawaiian common gallinule (Gallinula galeata sandvicensis) is endemic to Hawai‘i and is state and federally listed as endangered. Capture provides an opportunity to measure individual morphometrics and, through marking, monitor survival and movement. This paper describes a technique for capturing adult and juvenile Hawaiian common gallinules using a baited remote-operated cage trap. The primary advantages of this technique are its ability to selectively capture birds, low injury rate, and minimal training requirements for the operator. The method can be adapted to related rallids with similar behavior and habitat use.

The Pascagoula map turtle Graptemys gibbonsi and the Pearl River map turtle G. pearlensis are endemic to their respective river drainages, the Pascagoula River and Pearl River. Both species are considered imperiled, with anthropogenic activities (e.g., impoundments, pollution) differentially impacting these river systems and their respective species. Genetic assessments have already been completed for the sympatric, federally threatened yellow-blotched sawback G. flavimaculata of the Pascagoula River and ringed sawback G. oculifera of the Pearl River, pursuant to the Endangered Species Act; however, the megacephalic Pascagoula map turtle and Pearl River map turtle occupy different ecological niches and may show different patterns of genetic structure than the microcephalic sawbacks. We used up to 11 microsatellite loci to analyze the population genetic structure and effective population size of the Pascagoula map turtle and Pearl River map turtle sampled throughout their ranges. For the Pascagoula map turtle, the STRUCTURE results indicated two well-supported groups (Upper Leaf River and Upper Chickasawhay River) and a third moderately supported group (Pascagoula River). However, the Pearl River map turtle lacked strong genetic structure throughout the Pearl River system. Although a single genetic population was recovered for the Pearl River map turtle, it is not entirely panmictic, as there were private alleles at some sites and evidence of isolation by distance. The genetic structure of both species mirrors the findings of the sympatric yellow-blotched map turtle and ringed map turtle, possibly reflecting the influence of their respective river drainage's hydrological histories or dendritic structure. Our study provides the first genetic assessment for the Pascagoula map turtle and Pearl River map turtle, which can be used to inform potential reintroduction needs in the future and inform management plans to maintain current levels of genetic diversity and connectivity.

In the rain-snow transition zone of the Pacific Northwest, climate change is expected to alter the incidence of rain-on-snow and freeze-thaw events, which will change snow density and hardness dynamics. In winter, the ability of economically and ecologically important wildlife species, such as deer (Odocoileus spp.), to efficiently move through the landscape and access forage is mediated by snow conditions. Therefore, snow properties such as density and hardness can directly affect how energetically costly it is for these animals to survive. However, little is known about whether and how ungulates use habitats based on snow density and hardness. We deployed a stratified network of remote camera stations in complex forested terrain in Latah County, Idaho, USA, to remotely measure snow depth and detect deer. We also collected snow density and hardness measurements throughout the winter. We used these data to determine the degree to which the probability of deer presence at cameras could be explained by snow conditions and air temperature. Snow depth and density had negative relationships with the probability of deer presence, while ram resistance (a proxy for snow hardness) had a marginal positive effect. We were able to estimate snow conditions important to deer in winter 2020–2021 primarily using data obtained from cameras. This provides an important proof-of-concept that can be applied at different sites and climate conditions to gain a deeper understanding of how deer are affected by snowpack properties. These methods can be used by managers to determine how ungulates are affected by snow depth, density, and hardness collectively and subsequently inform ungulate management in a changing climate.

The role of scavenging species in disease transmission is inherently complex, as their interactions at and with carcasses can either mitigate or facilitate pathogen spread. Chronic wasting disease (CWD) is a transmissible prion disease afflicting cervids, a taxon that is important to multiple stakeholder groups. The disease is invariably fatal after the onset of clinical symptoms, and the agent is highly resistant to degradation. Scavengers have been implicated in the transmission of CWD, and recent studies have begun to quantify the extent of their involvement. We explored scavenger activity at 20 cervid carcasses in northern Colorado, USA, using data gathered from cameras from January 2022 to May 2023. Specifically, we characterized the species community at cervid carcasses, described carcass use patterns, identified landscape factors associated with scavenger diversity at carcass sites, and determined the correlates of scavenger foraging duration. Black-billed magpies (Pica hudsonia) and coyotes (Canis latrans) comprised 63.9% of species detections at carcasses. Site-level species diversity decreased as human modifications to the landscape increased, and foraging bout duration decreased as carcasses aged and as temperatures increased. Foraging time at carcasses varied by species, with common ravens (Corvus corax) and black bears (Ursus americanus) spending the greatest time foraging on carcasses. While observability of carcass tissues consumed was limited, most scavengers consumed muscle (tissue with relatively low prion loads), except for turkey vultures (Cathartes aura), who preferred abdominopelvic cavity organs. Our study underscores the complex interplay between temporal, environmental, and species-specific factors in determining scavengers' roles in transmission dynamics, with broader implications for understanding the cascading effects of scavenger activity on ecosystem health.

We undertook a study to evaluate the effect of electroshock-induced spinal injury on survival and growth of adult Northern Pike Esox lucius. Our study was conducted on 210 (140 treatment, 70 control) wild adult fish. We exposed treatment fish to 5 s of 120-Hz pulsed DC, then length-measured, x-rayed, double-marked, and released them into 0.04-ha ponds. X-ray images of all fish were evaluated for spinal injury. Of the 140 shocked fish, 28% were injured. After 37 days (9 May–15 June 1991), the ponds were drained, and 193 surviving fish collected for estimates of short-term survival. Most of these fish (154) were deemed healthy and relocated to a 25-ha lake. After 290 days (15 June 1991–1 April 1992), we used gill nets to obtain recaptures for estimates of growth and long-term survival. For both shocked and control fish, short-term survival was in the low 90-percent range and long-term survival was in the low 40-percent range with no difference in survival between shocked and control fish. After 290 d, growth of shocked and control fish was not different. Long-term survival was significantly length-dependent: of the 154 fish released, 42% survived and were significantly larger at initial measurement than the 58% that did not. Despite electroshock and injury having no apparent effect on survival and growth, it is essential that injury be minimized. Based on our results, we advise against using 120-Hz pulsed DC electrofishing of Northern Pike. Based on results in other studies, we recommend using 60-Hz pulsed DC.

A piscicide delivery method was designed to selectively target Black Carp Mylopharyngodon piceus, an invasive fish species in North America, which possesses pharyngeal teeth adapted for crushing mollusk prey. Many North American mollusks exist in small, fragmented populations susceptible to local extirpation. A Black Carp-selective toxic bait deployed properly could be used to protect those populations. Results represent initial efforts to construct an effective single-dose species-selective toxic bait. We prepared a bait by attaching a glass vial containing toxicant (antimycin A) to the exterior of a Corbicula fluminea clam valve. We designed the vial to break from the force of the fish's pharyngeal teeth when attempting to crush and consume the clam. We tested suitable vial sizes for encapsulating piscicide and two attachment materials, an aquarium epoxy and ultraviolet light-cured attachment material. The aquarium epoxy was rigid and reinforced vials. The ultraviolet light-cured attachment material was softer, resulting in more vials broken at 3- and 24-h post feeding. In a second trial, toxic baits consisting of antimycin A piscicide were administered in pure ethanol and acetone carriers to Black Carp in assembled baits with vials attached to live clam valves at three concentrations (40.0 mg/mL in ethanol, 170.8 mg/mL and 341.5 mg/mL in acetone). We selected aquarium epoxy for assembled baits based on the bond between the epoxy and glass vial, which allowed a greater surface area to be exposed and broken. While Black Carp successfully broke vials containing piscicide, no treatment caused carp mortality. The delivery method was unsuccessful as a single dose antimycin A piscicide bait for Black Carp. Additional considerations for this approach are provided.