Journal of Wildlife Management最新文献

Shorebird populations have experienced dramatic population declines worldwide. Reasons for these declines are varied, but one largely understudied threat at migratory shorebird non-breeding grounds is predation by introduced predators. High-tide roosting shorebirds may be vulnerable to ground predation, as they roost in a spatially clumped and temporally predictable manner in areas easily accessible to ground predators. We measured predation risk by the introduced red fox (Vulpes vulpes) at high-tide roosts within 2 internationally important shorebird estuaries in New South Wales, Australia, during a time when non-breeding shorebird numbers were at their annual peak, using a combination of camera trapping and environmental DNA (eDNA). Foxes were present at all study sites and were seen most frequently at sites encompassing the 2 largest high-tide roosts within the study estuaries, and least frequently nearest the roosts. Metabarcoding identified a broad range of avian taxa in fox scats collected at roosts, including ground-dwelling birds, native waterbirds, and introduced pigeons and doves, but no shorebird species. Bird prevalence in fox scats reached levels that far exceeded those reported in prior studies. Future studies should examine whether red foxes present a non-lethal, rather than lethal, predation threat to high-tide roosting shorebirds when feeding on other co-occurring food sources, potentially inducing energetically costly predator avoidance.

Breeding mallard (Anas platyrhynchos) populations in the Great Lakes region (Michigan, Minnesota, Wisconsin, USA) declined by >40% between 2000–2022 based on abundance data collected during spring aerial surveys. Mallards are an important waterfowl species in this region, where an estimated 60–80% of the mallard harvest is composed of locally banded birds. Extensive population monitoring datasets are available for mallards, presenting an opportunity to address complex questions such as estimating productivity at large spatial and temporal scales, identifying the effects of harvest on mallard demography, quantifying mechanisms for harvest compensation, and integrating multiple datasets to quantify the demographic drivers of population change. Our objective was to simultaneously examine factors affecting demographic parameters and their relative contribution to Great Lakes mallard population dynamics. We used 32 years of banding, band recovery, and aerial survey data collected for mallards from Michigan and Wisconsin to develop an integrated population model (IPM). We used age ratios at banding to estimate productivity, band recoveries from hunter-harvested birds to estimate annual survival and cause-specific mortality (i.e., harvest or non-hunting), and modeled abundance using aerial survey and demographic parameter estimates from 1991–2022. The IPM results indicated the decline in Great Lakes mallard abundance was caused by increased non-hunting mortality and a decline in productivity. Productivity varied spatially but temporally declined with the loss of Conservation Reserve Program area. Moreover, our productivity assessment provided evidence of density dependence in reproduction. Non-hunting mortality was 3.5–6.7 times and 1.3–4.2 times greater than harvest mortality for adult and juvenile female mallards, respectively, indicating environmental factors during spring and summer, not harvest, most greatly influenced annual mortality for female mallards. Our IPM reduced uncertainty in the factors affecting Great Lakes mallard population dynamics and indicated management actions that address non-hunting mortality and productivity would be most effective in increasing Great Lakes mallard abundance.

Agriculture can alter the nutritional landscape for herbivores in ways that can augment nutritional condition, reproduction, and survival. Ecological benefits associated with human modified landscapes, however, potentially alter environmental cues in ways that appear beneficial but ultimately have negative effects on fitness or population growth. We tested the hypothesis that the expected nutritional benefit of agriculture would come with a tradeoff associated with increased transmission of chronic wasting disease using a partially migratory population of mule deer (Odocoileus hemionus) in northern Wyoming, USA. Agriculture provided a substantial nutritional buffer to resident deer by augmenting nutritional condition in autumn and enhancing recruitment of offspring—a resident that spent 35% of its summer in agriculture had 1.2 percentage points more body fat in December and was 18 percentage points more likely to recruit offspring to December than a resident that spent 15% of its summer in agriculture. During winter, migrants and residents selected for home ranges closer to agriculture, but only residents selected for home ranges overlapping directly with agriculture. Proximity to agriculture in winter, however, decreased adult survival for migrants and residents (29 percentage points decreased probability of survival for every 1-km closer to agriculture) and increased the probability of having CWD at time of death. The nutritional benefits of agriculture likely increase the viability of a resident tactic, but the benefits may be offset if the nutrition gained from using agriculture does not outweigh the risks associated with disease.

Relatively little is known about red fox (Vulpes vulpes) spatial ecology on barrier islands, where semi-linear habitat distribution and aquatic barriers may affect terrestrial movements. Because red foxes often are a predator of imperiled shorebirds in these ecosystems, and predation is often managed along with other factors such as habitat limitation, this information is needed to inform effective holistic management. The goals of this study were to describe red fox spatial ecology in a barrier island ecosystem and compare these findings to the existing literature on red fox space use in other coastal settings. We used global positioning system (GPS) collar data collected from 2015–2018 from 31 red foxes to estimate sizes of home ranges and core-use areas, describe daily activity patterns, and investigate within-home-range resource selection among red foxes on Fire Island, New York, USA. Twenty-two of 31 red foxes maintained distinct home ranges throughout the monitoring period, while 9 were transient, regularly traveling through the home ranges of other red foxes and among management units across the island. Observed GPS-collared red fox home range sizes (95% time local convex hull [t-LoCoH] isopleths) ranged from 10 ha to 659 ha, averaging 59 ± 7 ha (SE) among resident foxes and 447 ± 46 ha among transient foxes. Core-use areas (50% t-LoCoH isopleths) ranged from <1 ha to 268 ha, averaging 10 ± 1 ha among resident foxes and 67 ± 27 ha among transient foxes. Hourly minimum movement rates varied across the diel cycle and among individuals, averaging 216 m/hour ± 9 m/hour, and were highest 13–22 hours after sunrise. Within-home-range resource selection varied among activity periods. For example, red foxes selected areas closer than expected to vegetation based on availability during the daytime and twilight hours but farther than expected from vegetation at night. We recommend vegetation management in and around shorebird nesting areas to reduce daytime resting sites and hunting cover for red foxes while improving suitability for use by nesting shorebirds. We also suggest coordination of predator management activities across agencies in this situation and in others where predators regularly cross management unit boundaries. Overall, we found that many aspects of red fox space use in the study area, such as smaller average home ranges compared to those in other ecosystems, were similar to that of red foxes in other coastal settings; additional research is needed to determine whether this holds true in other barrier island systems.

The Arctic wolf (Canis lupus arctos) is a predator of muskoxen (Ovibos moschatus), Arctic hares (Lepus arcticus), and endangered Peary caribou (Rangifer tarandus pearyi) in the Canadian High Arctic. Although Arctic wolves potentially affect the dynamics of muskoxen and Peary caribou populations, knowledge about their abundance, distribution, and predation patterns is limited. Inuit and Inuvialuit communities value these species for sociocultural and subsistence reasons, and community members are concerned about how interactions among these species and their environment may change in a warming, unpredictable Arctic. We conducted a study from 2014–2018 of wolves in the rolling tundra of central Ellesmere Island (Fosheim Peninsula) and eastern Axel Heiberg Island. This area supported relatively high densities of muskoxen and Arctic hares, and previously supported Peary caribou, although caribou were mostly absent in the area during our study. We deployed global positioning system (GPS) radio-collars on 10 adult wolves in 6 packs on Ellesmere and Axel Heiberg islands to describe wolf density and predation patterns. Wolves were neither nomadic nor migratory; they remained on territories year-round, with summer densities of 2.5–8.0 adult wolves/1,000 km² and 3.7–10.4 wolves/1,000 km² including pups. Based on a ground search of 312 of 868 location clusters over a 340-day period, wolves in a focal study pack killed approximately 0.12 muskoxen/day, equivalent to a predation rate of 5.5–17.0% of the estimated muskox population (older than 10 months old). This predation rate is likely sustainable given that calves and yearlings rather than reproductive adults comprised most documented kills, and that muskox populations can increase at rates up to 20%. The kill rate for this pack also implied a biomass intake deficit of 0.82–1.63 kg/wolf/day that could have been offset by each wolf consuming 115–228 Arctic hares annually. The decline of Peary caribou in the study area precluded any assessment of wolf predation influences on their population, but annual telemetry data confirming the year-round presence of a wolf–ungulate–hare system with relatively high wolf densities suggests that apparent competition could present a challenge to Peary caribou recovery efforts.

Harvest sustainability is a primary goal of wildlife management and conservation, and in a changing world, it is increasingly important to consider environmental drivers of population dynamics alongside harvest in cohesive management plans. This is particularly pertinent for harvested species that acutely experience effects of climate change. The Pacific walrus (Odobenus rosmarus divergens), a crucial subsistence resource for Indigenous communities, is simultaneously subject to rapid habitat loss associated with diminishing sea ice and an increasing anthropogenic footprint in the Arctic. We developed a theta-logistic population modeling-management framework to evaluate various harvest scenarios combined with 4 potential climate and disturbance scenarios (ranging from optimistic to pessimistic, based largely on sea ice projections from general circulation models) to simulate Pacific walrus population dynamics to the end of the twenty-first century, focusing on the independent-aged female subset of the population. We considered 2 types of harvest strategies: 1) state-dependent harvest scenarios wherein we calculated harvest as a percentage of the population and updated annual harvests at set intervals as the population was reassessed, and 2) annually consistent harvest scenarios wherein annual harvest levels remain consistent into the future. All climate and disturbance scenarios indicated declines of varying severity in Pacific walrus abundance to the end of the twenty-first century, even in the absence of harvest. However, we found that a state-dependent annual harvest of 1.23% of the independent-aged female subset of the population (e.g., 1,280 independent-aged females harvested in 2020, similar to contemporary harvest levels) met our criterion for sustainability under all climate and disturbance scenarios, considering a medium risk tolerance level of 25%. This indicates that the present rate of Pacific walrus harvest is sustainable and will continue to be—provided the population is assessed at regular intervals and harvest is adapted to match changes in population dynamics. Our simulations indicate that a sustainable annually-consistent harvest is also possible but only at low levels if the population declines as expected. Applying a constant annual harvest of 1,280 independent-aged females failed to meet our criterion for sustainability under 3 of the 4 climate and disturbance scenarios we evaluated and had a higher probability of quasi-extinction than an equivalent state-dependent harvest scenario (1.23%). We highlight the importance of state-dependent management strategies and suggest our modeling framework is useful for managing harvest sustainability in a changing climate.