Abstract Animals in northern environments contend with seasonally variable resources and have evolved life histories to cope with the flush of nutrients in summer and scarcity in winter. Ungulates cope with seasonal variation in resources by accreting fat stores when resources are plentiful during the growing season and then mobilizing these stores to meet nutritional requirements when resources are more limited during winter. While this generalization makes sense, previous work has suggested that caribou ( Rangifer tarandus spp.) may break this rule; however, previous works have suffered various limitations that leave this question unanswered. As part of a larger study to understand the role of nutrition as a potential factor limiting the Mulchatna Caribou Herd (MCH) in southwestern Alaska, we initiated a longitudinal study in which we captured the same individual caribou twice annually in autumn and late winter. We aimed to test the hypothesis that winter nutrition limited the MCH and predicted that caribou would lose fat between late autumn and late winter. During captures, we determined body fat percentage of lactating, adult females using validated ultrasonography and manual palpation techniques, and determined pregnancy status in late winter using transabdominal ultrasonography. Repeated measures indicated lactating females gained body fat over winter, averaging ~2.8 percentage points from 6.1% ± 0.1% (mean ± SE) in autumn to 8.9% ± 0.4% in late winter ( z = 5.425, p < 0.001), with maximum individual gains of up to 8.5 percentage points. Our findings provide empirical support for overwinter gains in fat among caribou and indicate that winter nutrition is not limiting the MCH. Our findings illustrate the value of longitudinal studies in ecology, have implications for research designs for studies of nutrition in northern ungulates, and highlight important considerations for caribou relative to unique nutritional aspects of their life history.

Abstract Many salamander populations are declining, and methods to determine how best to allocate limited resources to slow or reverse these declines could support land managers in their decision‐making processes. Multiple types of uncertainty may delay management decisions, including when (1) knowledge of a species' ecology is incomplete, (2) climate change effects on environmental covariates are uncertain, and (3) the efficacy of management alternatives is unknown. For management decisions, a value‐of‐information analysis can identify which uncertainties are critical to reduce in order to identify an optimal strategy from a set of possible management actions. If the same management action is optimal across the full range of uncertainties, then resources for research can be redirected toward active management. Using value‐of‐information analyses, we examine the effect of uncertainty on identifying optimal management to maximize the future expected occupancy of Plethodon shenandoah , a Federally Endangered high‐elevation endemic salamander that is threatened by climate change. Out of 11 management actions proposed by National Park Service managers, those that increase environmental moisture are expected to maximize occupancy, and we find that the selection of this action is robust to all the identified uncertainties. We show that, even in systems with multiple sources of large uncertainty, value of information analyses discriminate among investments in species management.

Abstract The feeding ecology of apex carnivores is affected by multiple intrinsic (e.g., sex and age) and extrinsic (e.g., prey density, habitat availability, presence of dominant competitors) factors, yet little research has explored how these factors affect the temporal use of resources. We placed video camera traps at puma ( Puma concolor ) kill sites and used a series of comparative analyses to understand if pumas varied in their diel activity at kill sites. We found that the diel activity of male pumas at kill sites peaked around midnight, but the diel activity of females and family groups peaked just after sunset, supporting our hypothesis that other sex/age classes would shift diel activity to avoid the potential risk posed by male pumas. We also observed changes in diel activity according to whether pumas fed during the visit to a kill site or not, their visit duration, and the number of days since the kill was made—suggesting that pumas adjusted the diel aspect of feeding to minimize competition risk while maximizing energy/nutrient intake as carcass quality degraded. Finally, contrary to our predictions, human activity had a greater impact on puma diel activity at kill sites than the human footprint, suggesting that pumas are more sensitive to short‐term anthropogenic disturbances near their kills than proximity to permanent structures. Our study highlights how both intrinsic and extrinsic factors lead to diel variation in kill sites by pumas. Better understanding the dynamics of the feeding ecology of apex carnivores—including how they balance the competing forces of feeding efficiency, safety, and competition—will facilitate developing more effective conservation strategies to minimize costly disturbances while feeding for apex carnivores.

Abstract Lagomorphs are selective herbivores that can strongly influence rangeland condition if their population densities increase through predator release. However, the effect size of lagomorph herbivory has not previously been quantified for the semiarid rangelands of the southwestern United States, where their predators are suppressed. We used a differential exclosure experiment replicated across 20 sites in a public rangeland in southern Utah to quantify the effect of lagomorph herbivory (jackrabbits and cottontails) for comparison with ungulate herbivory (cattle and bison). Across our 11‐year study, we measured aboveground net primary productivity (ANPP; 3 × 1‐year data sets) and long‐term standing crop (SC; 1 × 8‐year data set). We also measured nutrient concentrations in grass and soil samples in plots with complete exclosure (lagomorphs and ungulates out), partial exclosure (lagomorphs in and ungulates out), and no exclosure (open control plots) for 8 years. From the grass data, we calculated the effect size of lagomorph grazing as a 26.6% reduction in ANPP and an 11.3% reduction in SC, compared to ungulate grazing as a 24.9% reduction in grass ANPP and a 72.2% reduction in SC. We found lagomorphs had no effect on forb ANPP but actually increased forb SC, which is consistent with previous evidence that lagomorphs facilitate noxious weeds on these rangelands. There were no significant effects of either lagomorph or ungulate herbivory on plant and soil nutrient levels. Using the effect sizes of lagomorph herbivory on grass ANPP and SC, applied to the animal unit months (AUMs) prescribed for that rangeland, we calculated that lagomorphs currently impose an annual economic cost of between US$30.16 km −2 (SC) and US$70.64 km −2 (ANPP) in the Henry Mountains region of southern Utah, USA. We recommend that managers consider the lagomorph effect on rangeland resources in relation to the costs and benefits of conserving their predators, which are currently suppressed indirectly through various anthropogenic effects (raptors) and directly by agency‐funded control programs (coyotes).

Abstract Resilient ecosystems maintain similar species diversity and composition despite extreme environmental variation, while ecosystem collapse can be characterized by high mortality rates and decreased species diversity. Submerged aquatic macrophytes often support species diversity by providing habitat, shelter, food, and oxygen for fish and invertebrates. Can submerged macrophytes cause extreme chemical fluctuations, high mortality, and rapid ecosystem collapse in a small floodplain pond in the temperate zone? We measured fish survival from spring to fall and used mesocosms to assess diel fluctuations of dissolved oxygen (DO) and pH during spring, summer, and fall in patches of aquatic macrophytes (metaphyton, Chara , Potamogeton foliosus , and Lemna minor ). Submerged macrophytes (metaphyton, Chara , and P. foliosus ) dominated in spring and summer before being overgrown by a floating macrophyte in fall ( L. minor ). Of the four fish species, only western mosquitofish survived from spring to fall. In spring, high rates of photosynthesis in submerged macrophytes led to long periods of supersaturation (12–16 h/day) and basicity (2–10 h/day of pH >9.0). High rates of microbial respiration in summer were driven by elevated temperatures (≈35°C), high nutrient levels (average TN and TP = 4.4 and 0.17 mg/L), and decaying submerged macrophytes, resulting in long durations of hypoxia (4.8–19.6 h/day of DO < 1.0 mg/L). In fall, cooler temperatures (≈10°C) diminished extreme fluctuations in DO and pH beneath a floating mat of L. minor . All macrophytes died back in winter. This seasonal cycle of colonization during spring runoff and ecosystem collapse in summer was not a transition to an alternative stable state dominated by floating macrophytes as in other lentic ecosystems. Warm temperatures and nutrient enrichment can produce extreme diel fluctuation in DO and pH in patches of submerged macrophytes, resulting in high rates of mortality in floodplain ponds, one of the most common types of wetlands in the world.

Abstract Vertebrate herbivores require symbiotic gastrointestinal (GI) microbes to extract energy and nutrients from fibrous and sometimes toxic plant diets. Because GI microbes vary in their relative abundance, function, and degree of specialization, the microbial community depends on both the characteristics of plants consumed and the anatomical, physiological, and behavioral characteristics of the herbivore host. To tease apart the relative contribution of diet and herbivore phylogeny to the microbiome, we leveraged a unique study system in which mule deer ( Odocoileus hemionus ) and white‐tailed deer ( O. virginianus ) had been hand‐raised from neonates to adulthood in identical conditions on a pelleted ration, then transitioned over 2 weeks in the spring onto natural plant diets as they foraged together in the same habitats across summer, then transitioned back onto the pelleted ration in late summer. We determined the plant composition and nutritional quality of the deers' diets using bite count techniques and analyzed 16S rRNA genes of their feces to determine microbial diversity and composition. Our experiments demonstrated that the GI microbial community of congeneric deer responded to characteristics of both diet and deer species. Alpha and beta microbial diversity and microbial composition differed when deer consumed the pelleted ration versus natural browse and varied with other dietary characteristics including plant diversity, composition of plant functional groups, and nutritional constituents. Microbial communities of the two deer species responded differently to dietary changes, but most strongly when deer selected different natural plant diets. Despite controlling early experience, innate behavior and physiological differences between species likely influenced the GI microbiome. Our findings underscore the potential disruption in GI microbial communities with rapid diet changes and the importance of diverse, high‐quality forages for wild ruminants. A better understanding of how sympatric herbivores use the same available resources is crucial for predicting the consequences of increasing overlap in wildlife distributions with climate change and human disturbances.

Abstract Widespread declines in North American birds have elevated the need for proactive conservation planning and delivery to promote recovery. Long‐term monitoring at large spatial and temporal extents has been critical to identifying declines, but there is also a need for monitoring designs that can track species at scales relevant to management activities, which often occur within smaller jurisdictions. We highlight Integrated Monitoring in Bird Conservation Regions (IMBCR), a rigorous monitoring program in the western United States providing population estimates at multiple spatial scales from individual management units to state and region‐wide. Additionally, we publicize the availability of program trend estimates to management professionals via the Rocky Mountain Avian Data Center (RMADC). Here, we explore contemporary IMBCR trends in three western states, Colorado, Montana, and Wyoming, and document the continued decline of grassland bird species as well as declines in common generalists. We also provide an example of spatial heterogeneity in trends among management boundaries and discuss potential applications of fine‐resolution trend data, such as evaluating the effects of management. Finally, we provide an example application demonstrating the value of regional IMBCR trends in species prioritization efforts by state management agencies as a part of State Wildlife Action Plan (SWAP) revisions.

Abstract Alpine areas such as the headwaters of California's Sierra Nevada are increasingly imperiled by climate change and other human‐induced stressors. For one, the introduction of non‐native fishes into over 60% of its historically fishless watersheds has profoundly restructured the aquatic food web, depressed the abundance, biomass, and diversity of native invertebrates, and endangered endemic vertebrate taxa. Lakes and their surrounding land are reciprocally connected through flows of organic matter, such as emerging aquatic insects; however, the extent to which trout introductions disrupt such flows to the terrestrial environment is poorly understood. Emerging aquatic insects are a potentially important prey source for birds; thus, we hypothesized that the community composition, diversity, and abundance of birds differ between fishless lakes and those stocked with trout due to reduced emerging aquatic insect biomass and diversity. We conducted lakeside bird surveys in headwater lake basins in Sequoia and Kings Canyon National Parks for three summers (2014–2015, 2020) at a total of 39 lakes and quantified the emergence of mayflies between lake types using sticky traps. In addition to major reductions in mayfly densities, we documented lower overall bird abundance at stocked lakes, as well as turnover in avian community composition between stocked and fishless lakes. A fish eradication project at one lake between 2016 and 2019 allowed us to conduct a multiple‐control before‐after‐control‐impact (M‐BACI) case study to assess changes in the avian community following fish removal. After fish were removed, bird abundance was two times higher than at the control lake. Given the global decline of insect populations and their importance in bird diets, this study reinforces the importance of studying aquatic and terrestrial habitats as interdependent systems and motivates the restoration of naturally fishless habitats impacted by introduced fishes.