Journal of Wildlife Management最新文献

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.

Photographic monitoring currently provides the most accurate means for identifying nest predators and eventually their role in bird population declines worldwide. However, previous studies have found that commercially available trail cameras represent an artificial structure that tend to negatively bias predation rates, likely through predator neophobia. Based on an experiment in Arctic tundra, involving 50 artificial nests and 30 cameras in each of 2 breeding seasons, we demonstrated that trail cameras attracted corvids (in particular ravens [Corvus corax]), which caused an extreme and positively biased predation rate that was consistent over a range of experimental and environmental conditions. We call for new technologies that allow for photographic monitoring of bird nests with minimal visual footprints, in the form of smaller cameras and more efficient internal batteries to minimize novel and conspicuous external features detectable by predators. However, even such improved devices need to be assessed with respect to potential effects on nest predation in each case.

Prairie dogs are notoriously difficult to enumerate, with previously methods including visual counts, mark-resight, burrow counts, and catch per unit effort. Unlike those methods, spatial capture-recapture (SCR) analyses allow for formal estimation of density along with associated estimates of uncertainty, detection probability, and the size of the average area over which an individual was detected during the study period (referred to as an activity center). Using SCR analyses, we compared density estimates as part of a field trial evaluating the effectiveness of an oral sylvatic plague vaccine in black-tailed prairie dogs (Cynomys ludovicianus), Gunnison's prairie dogs (C. gunnisoni), white-tailed prairie dogs (C. leucurus), and Utah prairie dogs (C. parvidens) at 11 study areas in the western United States. The study was designed as a matched pairs analysis that included 27 individual paired plots (54 plots), each consisting of a plot treated with vaccine baits and a plot treated with placebo baits. Overall, we captured >3,000 individuals each year on these plots, and recapture rates ranged from 5–87%. For black-tailed prairie dogs, density estimates ranged from 2.7 individuals/ha (95% CI = 2.2–3.3/ha) to 77.3/ha (63.2–94.4/ha), and for Gunnison's prairie dogs, estimates ranged from 11.7/ha (10.6–12.8/ha) to 15.4/ha (14.4–16.7/ha). White-tailed prairie dogs were at their lowest density (3.3/ha, 95% CI = 2.9–3.8/ha) during the first year of the study and their highest density (14.5/ha; 13.5–15.6/ha) during the last year of the study. Utah prairie dog density estimates ranged from a low of 4.0/ha (95% CI = 3.55–4.6/ha) to a high of 20.8/ha (16.8–25.8/ha). Best-fitting models of prairie dog density indicated increasing patterns of density over time on most study plots, negative effects of plague, and positive effects of vaccination. Finally, we found low correlations between catch per unit effort estimates from previous published literature at these sites and our densities estimates. Spatial capture-recapture estimates allowed us to consistently compare treatment effects across space and time, although some exceptions are noted where we observed significant movement between plots within a pair (3 pairs) and when trapping effort between plots or years was not consistent.

As wild boar populations and their distribution ranges increase, human–wild boar conflicts have become increasingly prevalent in numerous regions across the globe. These conflicts have a profound impact on human livelihoods, resulting in significant economic losses. Understanding the habitat requirements and relative abundance of wild boars is crucial prior to implementing any conservation measures. However, studies on wild boar habitat and population in the central and eastern regions of the Tianshan Mountains in China are lacking. We assessed the activity patterns and relative abundance of wild boars in these areas and evaluated habitat suitability using a combination of camera trapping, line transects, species distribution modeling (maximum entropy model), and hierarchical abundance modeling (Bayesian N-mixture model). We used 311 infrared cameras and 280 field-based line transects to cover approximately 31,000 km² from September 2022 to May 2023 in the east-central Tianshan Mountains. We used 240 wild boar distribution locations and 13 environmental predictors in the development of species distribution models. We also used species counts and associated environmental predictors in the N-mixture model to estimate the relative abundance of wild boar. Wild boars were most active during crepuscular hours (1800), and relatively active in the diurnal period compared to the nocturnal period. The probability of wild boar occurrence increased with higher normalized difference vegetation index (NDVI), the minimum temperature of the coldest month, and annual temperatures below 39°C. Boars were most likely to be found in closed deciduous-coniferous forests. The relative abundance of wild boars was positively affected by NDVI and negatively affected by the minimum temperature of the coldest month and temperature annual range. Based on our results, we suggest areas of management priority. In particular, extensive and intact habitat with substantial wild boar populations, such as the Banfanggou, the South Mountain of Urumqi, and the Hutubi, should be prioritized for long-term wild boar population monitoring and management so the adverse impacts of increasing wild boar populations in the study region can be minimized.

American black bear (Ursus americanus) populations are increasing throughout much of North America. Use of multiple harvest methods, including hunting over bait, is intended to increase harvest success rates to meet harvest and population management objectives. However, black bear population growth can be influenced by food availability, and some speculate the use of bait may inadvertently increase bear abundance through food resource supplementation. We collected hair from black bears captured from 2005–2019 and a selection of potential food items, including those used as bait from 3 study areas in Maine, USA, with different levels of human influence. We used stable isotope analysis of the black bear hair and food item samples to evaluate the contribution of different identified food groups to the diet of individual bears. We found no evidence that greater contribution of human food resources, including bait, increased the number of cubs per litter for reproductive females or that human foods comprised a greater part of the diet in years when natural food resources were less abundant. Approximately 69% of black bear harvest occurred over bait. We found the probability of reproductive-age females to be harvested increased with average representation of human foods with high carbon enrichment (including bait) in their diet, but the relationship was weak, likely because of sampling constraints. Additionally, the probability of being harvested was greater in years when natural food resources were scarce. We conclude that bait is not available on the landscape in large enough amounts or for a sufficient amount of time in Maine to substantially influence female reproduction. Our results indicate hunting over bait is an effective tool in a state that is attempting to maintain a stable bear population via harvest, and dispels conjecture that hunting over bait may increase cub production and offset the intention of harvest.

Many large-herbivore populations are regulated at least in part by bottom-up forces, and thus relationships between herbivores and their habitat are of fundamental importance to wildlife managers. Variation in nutritional resources—and how herbivores respond to that variation—influences rates of nutrient intake, which directly affect nutritional condition, pregnancy rates, timing of parturition, offspring birth mass, and survival. Accordingly, nutrition-focused research holds great potential for uncovering the mechanisms that govern population performance of large herbivores and for assessing the nature and magnitude of bottom-up limitations. We quantified relationships between the foodscape (i.e., spatiotemporal variation in forage quality and abundance) in southwestern Oregon, USA, and black-tailed deer (Odocoileus hemionus columbianus) behavior and performance, with a focus on the influence of maternal nutrition on fawn survival. We hypothesized that black-tailed deer performance (i.e., fawn birth mass and survival) is influenced by the availability of high-quality forage during spring and summer and patterns of foodscape use exhibited by individual deer. From 2016–2023 we monitored movement and survival of adult female black-tailed deer and their offspring. We also conducted intensive vegetation sampling and used generalized additive modeling to map the foodscape available to deer in spring and summer. Suitable forage biomass (i.e., maximum biomass of forage that together exceeded quality thresholds for supporting one fawn) was highly variable across space and time, and our top foodscape model explained 70% of the variation in suitable biomass (adjusted R² = 0.70). We observed a strong, positive relationship between use of the foodscape by maternal females prior to parturition and fawn birth mass. Although maternal foodscape use after parturition did not influence the probability of fawn survival, survival increased with increasing birth mass. These results suggest that the effects of nutrition on fawn survival in our study system are indirectly mediated by maternal behavior (i.e., use of the foodscape) and the corresponding effects on birth mass of fawns. Our study adds to a growing body of literature supporting a fundamental link between foodscape use and population performance of large herbivores. Wildlife managers can use the dynamic models we developed to assess habitat quality and to make quantitative predictions about how different management actions (e.g., forest thinning) are likely to influence habitat quality and performance of black-tailed deer.