Journal of Wildlife Management最新文献

Anthropogenic infrastructure has contributed to increasing common raven (Corvus corax) abundance across the Great Basin region of the United States, particularly in sagebrush ecosystems, where high raven densities are correlated with reduced sage-grouse (Centrocercus urophasianus) nest survival. Our understanding of how raven reproductive behavior affects sage-grouse nest predation is limited, especially considering their overlapping breeding seasons. Understanding differences in space use and resource selection between breeding and non-breeding ravens could help identify high-use areas and corresponding predation risk for sage-grouse nests. We analyzed space use and resource selection of breeding (n = 13) and non-breeding (n = 32) global positioning system (GPS)-marked ravens in Nevada, USA (2017–2022) during the breeding season (1 March–31 June). We compared home-range size, core area size, step lengths, and resource selection within a Bayesian framework with inference made by comparing Bayesian credible intervals (CRI). We generated home range and core area estimates using autocorrelated kernel density methods. We did not find a difference in home range size between breeding (469.33 km², 95% CRI = 228.79–709.45 km²) and non-breeding (525.26 km², 95% CRI = 410.71–654.10 km²) ravens. However, breeding ravens had smaller core areas (10.77 km², 95% CRI = 3.16–35.78 km²) and shorter step lengths (1,160.33 m/hr, 95% CRI = 1,087.78–1,277.17 m/hr) than non-breeding ravens (core area = 279.50 km², 95% CRI = 206.77–363.72 km²; step length = 1,953.74 m/hr, 95% CRI = 1,898.42–2,009.56 m/hr). Ravens in both breeding classes selected high normalized difference vegetation index (NDVI) and low annual grass and shrub cover, but non-breeding ravens showed stronger selection for low annual grass and shrub cover areas. We found strong differences in selection between breeding classes for 6 of our 9 covariates: distance to road, solar radiation, distance to natural water, distance to forest edge, percent annual grass cover, and percent shrub cover. Non-breeding ravens concentrated activity near forest edges, natural water sources, and anthropogenic features, whereas breeding ravens focused activity close to their nests. Our findings suggest that raven management could be more effective if it targeted areas with high NDVI and low annual grass and shrub cover, especially in anthropogenically modified landscapes and near forest edges, and prevented raven nest establishment near prey populations of concern.

Understanding ecological niche is critical to the management and conservation of any species or population. For herbivores, dietary niche is critical for understanding habitat suitability, carrying capacity, and population and community viability. In closely related species with similar morphologies, dietary niches can diverge depending on environmental and seasonal factors. Elk Island National Park in Alberta, Canada, contains populations of both American bison (Bison bison) subspecies—plains bison (B. b. bison) and wood bison (B. b. athabascae)—in similar but separate habitats located at the historical confluence of the subspecies' distributions. Using generalized additive models and nutritional geometry, we compared the subspecies' dietary niches in terms of content and quality continuously for one year (Dec 2020 – Nov 2021). Both subspecies consumed primarily graminoids during winter, spring, and fall and incorporated a variety of forbs and woody plants during summer. Plains bison diets contained more upland grasses and digestible organic matter in their diet and less wetland graminoids (e.g., sedges) throughout the year. We also found differing dietary niches between the subspecies during the spring and summer months. Our unique, continuous analysis of annual diet content and quality can deliver insight into the similarities and differences between subspecies' dietary niches that should help improve management decisions, such as better matching between source populations and release areas for future translocations.

With increased human populations and tourism in coastal areas, there is greater potential for disturbance of marine wildlife. Because of their high metabolic rates, sea otters (Enhydra lutris) are at particular risk of increased energetic costs due to human disturbance. We used scan surveys to monitor southern sea otter (E. l. nereis) activity and potential disturbance stimuli over 5 years (2015–2020) at 3 California, USA, study sites: Monterey, Moss Landing, and Morro Bay. We developed a process-based, hierarchical model of sea otter behavior, which we fit to survey data to examine how activity varies in response to the occurrence of and proximity to disturbance stimuli, while controlling for location, group size, pup-to-adult ratio, and presence-absence of kelp or eelgrass canopy. We combined model results with published estimates of activity-specific metabolic rates, translating estimated activity change into corresponding energetic costs. We found that effects of disturbance stimuli on sea otter behavior were location specific and varied non-linearly with distance from disturbance stimuli. Our model results suggest that, on average, the likelihood of a group of sea otters being disturbed is <10% when stimuli are >29 m away, although this threshold varies by location, group size, and several other covariates. Based on the observed frequency and magnitude of disturbance at Cannery row in Monterey, we estimated that energetic costs were increased by 7.2%, 5.4%, and 5.4% for adult males, females, and females with large pups, respectively. We observed similar cost increases at the wildlife platform in Moss Landing (5.8%, 4.4%, and 4.3%) and T-pier in Morro Bay (5.2%, 4.0%, and 3.9%). Our analyses represent a novel approach for estimating behavioral responses and energetic costs of human disturbance, furthering understanding of how human activities affect sea otters and providing a sound scientific basis for management.

The isolated and endangered Columbian population of fishers (Pekania pennanti) is thought to be declining in central interior British Columbia, Canada, yet little is known about the distribution and abundance of the species in several regions. We conducted DNA-based mark-recapture surveys to estimate the density of fishers in 2 spatially distinct ecosystems where current data were lacking, and evaluated which factors best explained the distribution of fishers in each ecosystem. We found the density of fishers varied substantially between study areas, likely because of the level of trapping mortality during each survey season. The density of fishers in the Chilcotin study area west of Williams Lake was among the highest ever reported for the province (21.3 ± 3.8 [SE] fishers/1,000 km²), whereas density in the Enterprise study area southeast of Williams Lake was among the lowest (8.9 ± 2.7 fishers/1,000 km²). Density estimates for both study areas, however, were orders of magnitude lower than those reported for eastern North America and the western United States and thus are at levels worthy of concern. Forested stands with wet soil moisture regimes composed of older deciduous and spruce trees were most strongly related to higher densities in both study areas; these stands also were known to contain higher densities of the denning and resting structures fishers require to survive and reproduce. This study provided wildlife managers with a snapshot of the density of fishers in 2 areas of central interior British Columbia that will help refine the estimate for the endangered Columbian population. Additionally, this work suggests that reducing trapping mortality within the Columbian population of fishers and increasing the protection of high-value denning and resting habitats may both be necessary to promote the recovery of the species over the longer term.

The decline of semi-natural open ecosystems after land abandonment is a conservation issue in many industrialized countries. Large herbivores, such as horses (Equus ferus), are excellent candidates for rewilding activities, as they can contribute to reducing loss of open landscapes. However, their presence could affect the spatio-temporal distribution of sympatric species, especially if the reintroduction is unplanned and uncontrolled. La Calvana, central Italy, is a protected area with a mammalian community that has never been systematically monitored, and its grasslands, which are a high conservation priority, are disappearing. The area hosts a population of feral horses that originated about 40 years ago from a few released domestic individuals, and their unplanned presence could represent a unique rewilding opportunity for the restoration of the abandoned landscape. Yet nothing is known about their distribution or relationships with sympatric mammals. By deploying 40 camera traps in May-July 2022, we systematically monitored the area to investigate spatio-temporal patterns of feral horses and their relationships with environmental, biotic, and anthropogenic factors. We detected 12 wild mammal species and estimated that horses were present in 40% of the study area. None of the environmental variables tested affected the occupancy of horses, although modeling of site-use intensity revealed that this species used upper-ridge grasslands more frequently. This suggests the area is suitable to support the population and that their presence at higher elevations can be an asset to preserving grasslands by limiting forest and shrub encroachment. Horses occupancy was not related to the relative abundance of wild ungulates, suggesting minimal competition for resources at present. However, the lower temporal overlap at sites with greater vegetation cover during the hottest hours indicated dominance of horses. Feral horses seem unaffected by human proximity, although they are occasionally subject to poaching. Lastly, the 7-year-long population census revealed a 12% annual growth rate that may lead to exceeding the carrying capacity of the ecosystem in the future. We recommend continued monitoring of this population and implementation of conservation and management programs.

Extensive agricultural development in the United States over the last century and subsequent restoration efforts through the Conservation Reserve Program (CRP) have led to many wildlife species occupying landscapes comprising a mix of natural and developed cover types. Understanding how species like mule deer (Odocoileus hemionus) move through and select resources in those landscapes is important for effectively managing populations and habitat. We examined seasonal resource selection, migration, and survival of female mule deer in the Columbia Plateau Ecoregion of southeastern Washington, USA, which is dominated by row-crop agriculture. We acquired global positioning system locations at 4-hour intervals from 57 adult females during 2018-2022. We used Migration Mapper 3.0 to detect migration, resource selection functions to evaluate resource selection, and Cox proportional hazards to quantify survival. Thirty percent of deer migrated for an average distance of 30 km each year. Residents and migrants had the same annual survival of 0.86 (SE = 0.03), similar to survival of adult female mule deer across their range. When selecting home ranges within the study area in summer and winter, CRP and grassland were the highest-ranked cover types, and selection for cereal agriculture and fallow fields was low to moderate. Within their home ranges, deer selected shrublands (including CRP) followed by tree-covered areas in summer. Cereal agriculture and fallow fields ranked lowest in summer, whereas grasslands and agriculture ranked highest in winter. Survival rates of residents and migrants were not related to their use of CRP or agriculture cover types. Mule deer used different components of the landscape mosaic seasonally, selecting vertical cover during summer fawn rearing and areas with young wheat and broad-leaved forbs during winter. Regardless of season and scale, intact (grassland and shrubland) or restored (CRP) cover types were most selected, demonstrating the importance of increasing both CRP and native cover for deer in agricultural landscapes.

Federal and state agencies within the United States have recently issued directives prioritizing the conservation of ungulate migration corridors and winter ranges. The ability to identify and delineate the spatial distribution of seasonal ranges underpins these policies. While such delineations are often derived from global positioning system (GPS) collar data collected for a few years on a focal population, they are being used in long-term conservation planning. Our objectives were to quantify consistency in migration corridors from year to year and cumulatively across multiple years and identify which aspects of the sampling design of GPS collar deployment will delineate a consistent and relatively complete migration corridor. We used data from 6 sub-herds of mule deer (Odocoileus hemionus), a species known to have high migratory fidelity, located in Wyoming and northern New Mexico, USA, monitored for 5–7 years (510 unique individuals). We calculated 2 types of migration corridors over time: cumulative corridors where each new year of data was added to all previous years and yearly corridors where each year was based only on data collected in that year. We then calculated the year-to-year consistency in the 2 types of migration corridors by calculating the percent overlap between corridors calculated in sequential years. We found that collaring a higher proportion of a sub-herd increased the consistency in migration corridors, whereas collaring new individuals via redeployments in a subsequent year of monitoring caused corridors to shift. To obtain a corridor with ≥90% consistency (i.e., approaching the complete area used by a population in our data), our results suggest that biologists should strive to collar ≥6% of a sub-herd for a minimum of 2 years. However, if ≥6% of a sub-herd cannot be collared, monitoring for longer (3–4 years) will provide roughly 90% consistency in a migration corridor estimate for mule deer. Furthermore, adding 16–25% new individuals each year will help capture variation among individuals while maintaining corridor consistency of ≥90%, leading to a more accurate delineation of the corridor. Our results provide managers with a logistical framework for collaring projects aimed at delineating migration corridors that are durable into the future.