Laura Juvany

Managing and conserving species in the face of the current biodiversity crisis requires consistent information on the status of wild animal populations across large spatiotemporal scales. Budgetary constraints, differences in national legislation, and the challenges of coordinating logistics transnationally often limit survey efforts to spatial extents that rarely encompass the full distribution of many species, and temporal extents that rarely exceed a few years. These limitations are particularly relevant in regions like Europe, where multiple countries often share and manage populations of the same wild species across national borders and under different legislative frameworks. Cooperation and collaboration can help overcome some of these challenges. Here, we present data from the first 2 years of Snapshot Europe, a collaborative, coordinated, and standardized European‐wide mammal survey conducted by camera‐trap experts working across the continent. Between mid‐August and mid‐November of 2021 and 2022, more than 160 researchers simultaneously collected camera‐trap data at 1198 and 967 locations across 81 and 55 arrays and 22 and 23 countries, respectively, for a total of 90,230 camera‐trap days (49,033 and 41,197 in 2021 and 2022, respectively), with 91% of the data collected in September and October. Thirty (28%) out of 106 arrays across the 2 years were sampled both in 2021 and 2022, allowing for comparisons of estimates over time. All data were managed and processed in Wildlife Insights ( https://www.wildlifeinsights.org/ ); each record was reviewed by at least one participant who confirmed or edited the initial classifications provided by the AI model integrated into the platform. The final dataset contains a total of 94,441 observations of 63 species of mammals and 5024 detections of 78 species of birds. These data capture a subsample of the European wildlife community and can be used to explore ecological questions related to drivers of distribution, abundance, and activity across the continent. We envision repeating this effort annually for the foreseeable future. Data for Snapshot Europe 2023, 2024, and 2025 are currently being revised and will be made publicly available soon. Collated, all the annual datasets will enable estimates of trends over time. Additionally, four sister initiatives, Snapshot USA (2019‐ongoing), Snapshot Japan (2023‐ongoing), Snapshot Brazil and Snapshot Chile (both started in 2025), annually collect data based on the same sampling protocol, enabling a new era of global‐scale comparisons. The images associated with the data accompanying this publication are available in Wildlife Insights. The data are available for reuse under CC BY‐SA 4.0 licensing. Please cite this data paper when reusing all or part of this dataset.

Shrubs of the genus Vaccinium serve as foundation species in boreal ecosystems as they define much of the structure of the ground vegetation and play key roles in many ecosystem services and processes. For example, Vaccinium myrtillus (bilberry) and Vaccinium vitis‐idaea (cowberry) constitute staple foods for several species of large herbivores (Cervidae, deer) in Northern Europe. However, changes to the tree layer from forestry practices have resulted in declines in habitat suitability and the abundance of these shrubs over recent decades. Here, we assess whether related changes to tree basal area and species composition also affect the macronutrient composition of these shrubs, and if so, how such alterations may influence food selection by moose ( Alces alces ). We sampled bilberry and cowberry twigs during wintertime in five study areas dispersed latitudinally in Sweden, using 65 forest stands dominated by Scots pine ( Pinus sylvestris ) or Norway spruce ( Picea abies ) that varied in age and site fertility, while also taking into account soil C:N, pH, and moisture. We found that the macronutrient composition of bilberry and cowberry forage was significantly altered by forest density and tree species composition. In denser and more spruce‐dominated forests (i.e., lower understory light), forage contained less nonstructural carbohydrates, but more protein and lignin, compared to shrubs growing in more open and pine‐dominated forests. We also found that the forage available in such shaded environments was closer to the presumed nutritional target balance of moose. Our results illustrate that management decisions influence the macronutrient composition of understory shrubs in a way that may be important for herbivore foraging choices. We suggest that a larger variation in forest structure, both within and among stands across the landscape, will provide cervids with greater variation in forage qualities, since even small differences in forest structure can increase the nutritional variation of the forage. We discuss our results in the context of plant resource allocation, herbivore nutritional balancing and game and forest management.

Climate change causes far‐reaching disruption in nature, where tolerance thresholds already have been exceeded for some plants and animals. In the short term, deer may respond to climate through individual physiological and behavioral responses. Over time, individual responses can aggregate to the population level and ultimately lead to evolutionary adaptations. We systematically reviewed the literature (published 2000–2022) to summarize the effect of temperature, rainfall, snow, combined measures (e.g., the North Atlantic Oscillation), and extreme events, on deer species inhabiting boreal and temperate forests in terms of their physiology, spatial use, and population dynamics. We targeted deer species that inhabit relevant biomes in North America, Europe, and Asia: moose, roe deer, wapiti, red deer, sika deer, fallow deer, white‐tailed deer, mule deer, caribou, and reindeer. Our review (218 papers) shows that many deer populations will likely benefit in part from warmer winters, but hotter and drier summers may exceed their physiological tolerances. We found support for deer expressing both morphological, physiological, and behavioral plasticity in response to climate variability. For example, some deer species can limit the effects of harsh weather conditions by modifying habitat use and daily activity patterns, while the physiological responses of female deer can lead to long‐lasting effects on population dynamics. We identified 20 patterns, among which some illustrate antagonistic pathways, suggesting that detrimental effects will cancel out some of the benefits of climate change. Our findings highlight the influence of local variables (e.g., population density and predation) on how deer will respond to climatic conditions. We identified several knowledge gaps, such as studies regarding the potential impact on these animals of extreme weather events, snow type, and wetter autumns. The patterns we have identified in this literature review should help managers understand how populations of deer may be affected by regionally projected futures regarding temperature, rainfall, and snow.