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Migration is a striking behavioral strategy by which many animals enhance resource acquisition while reducing predation risk. Historically, the demographic benefits of such movements made migration common, but in many taxa the phenomenon is considered globally threatened. Here we describe a long-term decline in the productivity of elk ( Cervus elaphus ) that migrate through intact wilderness areas to protected summer ranges inside Yellowstone National Park, USA. We attribute this decline to a long-term reduction in the demographic benefits that ungulates typically gain from migration. Among migratory elk, we observed a 21-year, 70% reduction in recruitment and a 4-year, 19% depression in their pregnancy rate largely caused by infrequent reproduction of females that were young or lactating. In contrast, among resident elk, we have recently observed increasing recruitment and a high rate of pregnancy. Landscape-level changes in habitat quality and predation appear to be responsible for the declining productivity of Yellowstone migrants. From 1989 to 2009, migratory elk experienced an increasing rate and shorter duration of green-up coincident with warmer spring-summer temperatures and reduced spring precipitation, also consistent with observations of an unusually severe drought in the region. Migrants are also now exposed to four times as many grizzly bears ( Ursus arctos ) and wolves ( Canis lupus ) as resident elk. Both of these restored predators consume migratory elk calves at high rates in the Yellowstone wilderness but are maintained at low densities via lethal management and human disturbance in the year-round habitats of resident elk. Our findings suggest that large-carnivore recovery and drought, operating simultaneously along an elevation gradient, have disproportionately influenced the demography of migratory elk. Many migratory animals travel large geographic distances between their seasonal ranges. Changes in land use and climate that disparately influence such seasonal ranges may alter the ecological basis of migratory behavior, representing an important challenge for, and a powerful lens into, the ecology and conservation of migratory taxa.

Populations of woodland caribou (Rangifer tarandus caribou) are declining throughout their range and many are at risk of extirpation, yet the role of nutrition in these declines remains poorly understood, in part owing to a lack of information about available nutritional resources during summer. We quantified rates of intake of digestible protein and digestible energy by tame caribou foraging in temporary enclosures in the predominant plant communities of northeastern British Columbia, Canada, during summer–autumn and compared intake rates to daily requirements for protein and energy during lactation. We tested hypotheses related to the nutritional adequacy of the environment to support nutritional requirements during lactation (with and without replenishment of body reserves) and simulated scenarios of foraging by caribou in these plant communities to better understand how wild caribou could meet nutritional demands on these landscapes. Nutritional resources varied among plant communities across seasonal, ecological, and successional gradients; digestible energy intake per minute and per day were significantly greater in younger than older forests; dietary digestible energy and per-minute and daily intake of digestible protein were greater, though not significantly so, in younger than older forests; and dietary digestible protein was greater in older than younger forests, though differences were not significant. Tame caribou were unable to satisfy protein and energy requirements during lactation, even without replenishment of body reserves, at most sites sampled. Further, foraging simulations suggested widespread nutritional inadequacies on ranges of wild caribou. Selection for habitats offering the best nutrition may mitigate some nutritional inadequacies, but given low availability of vegetation communities with high nutritional value, performance (e.g., calf production, growth, replenishment of body fat and protein) of caribou may be depressed at levels of nutrition documented herein. Our results, coupled with recent measurements of body fat of wild caribou in northeastern British Columbia, refute the hypothesis that the nutritional environment available to caribou during summer in northeastern British Columbia is adequate to fully support nutritional demands of lactating caribou, which has implications to productivity of caribou populations, recovery, and conservation.

Foraging by animals is hypothesized to be state-dependent, that is, varying with physiological condition of individuals. State often is defined by energy reserves, but state also can reflect differences in nutritional requirements (e.g., for reproduction, lactation, growth, etc.). Testing hypotheses about state-dependent foraging in ungulates is difficult because fine-scale data needed to evaluate these hypotheses generally are lacking. To evaluate whether foraging by caribou (Rangifer tarandus) was state-dependent, we compared bite and intake rates, travel rates, dietary quality, forage selection, daily foraging time, and foraging strategies of caribou with three levels of nutritional requirements (lactating adults, nonlactating adults, subadults 1–2 years old). Only daily foraging times and daily nutrient intakes differed among nutritional classes of caribou. Lactating caribou foraged longer per day than nonlactating caribou—a difference that was greatest at the highest rates of intake, but which persisted even when intake was below requirements. Further, at sites where caribou achieved high rates of intake, caribou in each nutritional class continued foraging even after satisfying daily nutritional requirements, which was consistent with a foraging strategy to maximize energy intake. Foraging time by caribou was partially state-dependent, highlighting the importance of accounting for physiological state in studies of animal behavior. Fine-scale foraging behaviors may influence larger-scale behavioral strategies, with potential implications for conservation and management.

Elk (Cervus elaphus) in the western United States are an economically and socially valuable wildlife species. They have featured species status for federal land management planning; hence, considerable modeling focused on habitat evaluation and land management planning has been undertaken for elk. The extent to which these and other habitat models for large ungulates account for influences of nutritional resources varies greatly, probably because of varying recognition of the importance of nutrition and uncertainty about how to measure and model nutrition. Our primary goals were to 1) develop greater understanding of how habitat conditions influence foraging dynamics and nutrition of elk in summer and autumn; and 2) illustrate an ecological framework for evaluating and predicting nutritional resources so that nutritional needs of elk can be integrated within landscape-scale plans, population models, and habitat evaluation models. We evaluated foraging responses of elk to clearcut logging and commercial thinning, forest succession, and season across ecological site potentials. We also identified the extent to which plant communities satisfied nutritional requirements of lactating female elk and their calves. Our study was conducted in the temperate rainforests of the Pacific Northwest on industrial and public timberlands. We evaluated relations between habitat conditions and elk nutrition in plant communities representing a range in stand age and ecological conditions at 3 study areas, 1 near the Canadian border in the north Cascades Mountains (Nooksack), 1 in the Coast range southwest of Olympia, Washington (Willapa Hills), and the third in the central Cascades near Springfield, Oregon (Springfield), from late June to November, 2000–2002. In 98–143 macroplots per study area, we measured forage abundance by plant species, digestible energy content by plant life-form group, and forest overstory. In a subset of these macroplots (∼30 per study area), we held 4 tame lactating elk with calves in electrified pens (n = 15–25 adult elk per year), and sampled activity budgets, dietary composition, forage selection, and other measures of foraging behavior; dietary digestible energy (DE; kcal/g) and protein (DP; %) levels; and intake rates of these nutrients. In 15 of these pens, we held elk for extended periods (13–21 days) to monitor changes in body fat of adults and growth of calves. We developed equations to predict dietary DE and DP and per-minute intake rates of each in a nutrition prediction model that reflected vegetation attributes and ecological site influences. Total abundance of forage in the western hemlock series after clearcut logging in low to moderate elevations (≤1,000 m) ranged from a peak of 3,000–4,500 kg/ha in 5- to 10-year-old stands to 100–300 kg/ha in 20- to 50-year-old stands with only moderate increases through late succession. Patterns were similar in higher elevation forests (1,000–1,800 m), although peaks and troughs in forage abundance developed more slowly. Deciduous shrubs, forbs, and graminoids were abundant in early seral stages after stand disturbance, but these were rapidly replaced by shade-tolerant evergreen shrubs and ferns as conifer overstories closed 15–20 years later in low-elevation forest zones, and 20–40 years later in high-elevation zones. Digestible energy within plant life-form groups generally declined with season and with advancing succession, increased with elevation, and was highest in forbs and deciduous shrubs and lowest in evergreen shrubs and shade-tolerant ferns. Levels of DE in elk diets exhibited a strong asymptotic relation with abundance (kg/ha) of plant species that were eaten in proportions equal to or greater than availability (i.e., accepted species). Marked declines in dietary DE occurred in stands containing <400 kg/ha to 500 kg/ha of accepted species, largely because elk began to increase consumption of avoided species, and these typically contained low levels of DE. The asymptotic pattern was generally consistent among seasons, study areas, and habitat types (potential natural vegetation categories), although the asymptote averaged 10–12% greater in high- versus low-elevation forests. Abundance of accepted species in early seral stands averaged 7–10 times that in mid and late seral stages, and dietary DE levels varied accordingly. Dietary DE was little influenced by thinning in 20- to 60-year-old stands. In contrast, levels of dietary DP were unrelated to forage composition and abundance of accepted or avoided species, and varied little between low and high-elevation forests. Dietary DP increased with overstory canopy cover, was higher in thinned and hardwood stands, particularly those hardwood stands with saturated soils in late summer, declined with season, and was lowest in the driest forest communities in our study. Overall, soil moisture regime and season accounted for the majority of variation in dietary DP. Relations between nutrient intake rate and vegetation conditions varied among study areas and habitat types. Nevertheless, elk maintained about double the intake rate of DE in early seral stages versus closed-canopy forests. Intake rate of DP was similar between early seral versus closed-canopy forests, despite modestly lower dietary DP in early seral stages. Protein intake rate was greater in thinned and hardwood-riparian stands. In early seral stages, dietary DE typically met the requirement of 2.7 kcal/g of ingested forage (necessary to maintain body fat levels of lactating elk in summer) in the low-elevation forest zones and exceeded that level in high-elevation forest zones. In closed-canopy forests, dietary DE averaged below requirements, markedly so in low-elevation forests (2.25–2.5 kcal/g) and moderately so in high-elevation forests (2.4–2.65 kcal/g). Evidence of deficiencies based on DE intake rate was greater, averaging about 50% of requirements (28 kcal/min; 21,000 kcal/day) in closed-canopy forests and 80% of requirements in early seral stages. In contrast, dietary DP and DP intake rates generally approached or exceeded estimated requirements (6.8% DP; 380 g/day) in many habitat types that we sampled, with the greatest potential for deficient DP intake rates in relatively dry, low-elevation forests. Body fat dynamics and growth of calves confirmed nutritional deficiencies suggested by our data on DE intake. Adult elk lost body fat during all trials at rates generally in accordance with expectations at the dietary DE levels they consumed, and rate of change in body fat was inversely related to abundance of accepted species. Calves grew at about half the rate of which they are capable (1 kg/day) if summer nutrition is sufficient. Daily calf growth was positively related to their mother's dietary DE and protein intake levels. Elk compensated for limited foraging options in many plant communities via several behavioral strategies. Selection was generally strong for plants with higher DE levels, where selected species composed nearly 5 times more of the diet than did species that elk avoided, yet avoided species were 10 times more abundant. As abundance of accepted species declined below approximately 400 kg/ha, elk increased intake of avoided species. This strategy delayed declines in per-minute forage and DE intake rate as long as abundance of accepted species remained above roughly 200 kg/ha, despite declining dietary DE levels apparent at <400 kg/ha to 500 kg/ha of accepted species. Elk traveled faster while foraging to compensate for plant communities with very low abundance of total forage, increased bite rate as bite mass declined, increased time spent feeding at night in pens with low abundance of total forage or relatively low dietary DE levels, and increased rumination time particularly as dietary fiber levels increased. Dietary DE, DP, and intake rates of these nutrients therefore were robust to substantial variation in overall forage quality and quantity. Nevertheless, these strategies were insufficient to compensate for low abundance of high-quality forage typically present under closed forest canopies. Our nutrition model included nonlinear and multiple regression equations to predict 1) dietary DE (kcal/g of ingested forage), based primarily on abundance of accepted species (r2 = 0.49–0.62); and 2) dietary DP (% of ingested forage), based primarily on abundance of accepted species, overstory canopy cover, and site characteristics intended to index soil moisture (r2 = 0.60). Additional equations to predict intake rates per minute included the same covariates, but the variance explained was modestly lower (DE intake: r2 = 0.43; DP intake: r2 = 0.45–0.54). With these equations, we created nutrition-succession profiles to illustrate dietary DE and DP intake dynamics across the successional sequence for each habitat type and study area. These profiles may serve as inputs for spatially explicit maps of nutritional resources for elk. Because they were developed using nutrition data from foraging elk, they should help alleviate much of the uncertainty arising from proxy variables often used as indices of nutritional resources. Our data demonstrated that nutritional resources in forests of western Oregon and Washington are generally deficient for lactating elk in summer and early autumn. They provided evidence that inadequate nutritional resources are largely responsible for low body fat in autumn and reduced pregnancy rates reported for many elk herds in the Pacific Northwest. Our data also illustrated that nutritional value of habitats is highly variable depending on ecological context, disturbance, and succession. Thus, how, if, and where forested elk habitats are managed can greatly influence the nutritional suitability of an area. Finally, our data indicate a considerable need for integrating nutritional assessments in landscape planning processes where maintaining abundant and productive elk populations is one of several

Adult female survival and calf recruitment influence population dynamics, but there is limited information on calving and neonatal mortality of boreal woodland caribou (Rangifer tarandus caribou; caribou) in Ontario, Canada. We identified calf parturition sites and 5-week neonatal mortality using a movement-based approach across 3 northern Ontario study regions (Pickle Lake, Nakina, and Cochrane) that vary in their capacity to support caribou populations. In comparing 22 caribou-years of video-collar footage during 2010–2013 to predictions of the movement-based approach, we found live parturition events were 100% correctly classified, date of parturition was within 1.08±0.28 (x̄ ± SE) days, and mortality events up to 5 weeks postpartum were 88% correctly classified. Across study regions, 87% of 186 caribou were pregnant and 76% of 107 caribou-years indicated birth events with median parturition dates a week later in Cochrane (23 May) than in Pickle Lake (17 May) and Nakina (16 May). Based on selection ratios of caribou-years with calves-at-heel (n=80), caribou consistently selected for lowlands and closed-canopied forests and mostly against early-seral stands (<20 yrs old) and areas near linear features during the neonatal and the post-neonatal period (up to 35 days postpartum). Based on the video footage and movement models, 30% of 81 caribou-years that indicated live births also showed females lost their calf within the first 5 weeks postpartum, with higher risk of neonatal mortality associated with increased use of lowlands and greater postpartum movement rates. This study provides informative metrics of caribou reproduction across northern Ontario that will contribute to future population modeling and identifies important landscape features to be considered in future industrial development and land use planning for caribou conservation.

[This corrects the article DOI: 10.1093/jmammal/gyaa003.].[This corrects the article DOI: 10.1093/jmammal/gyaa003.].

Studies of habitat selection and use by wildlife, especially large herbivores, are foundational for understanding their ecology and management, especially if predictors of use represent habitat requirements that can be related to demography or fitness. Many ungulate species serve societal needs as game animals or subsistence foods, and also can affect native vegetation and agricultural crops because of their large body size, diet choices, and widespread distributions. Understanding nutritional resources and habitat use of large herbivores like elk (Cervus canadensis) can benefit their management across different land ownerships and management regimes. Distributions of elk in much of the western United States have shifted from public to private lands, leading to reduced hunting and viewing opportunities on the former and increased crop damage and other undesired effects on the latter. These shifts may be caused by increasing human disturbance (e.g., roads and traffic) and declines of early-seral vegetation, which provides abundant forage for elk and other wildlife on public lands. Managers can benefit from tools that predict how nutritional resources, other environmental characteristics, elk productivity and performance, and elk distributions respond to management actions. We present a large-scale effort to develop regional elk nutrition and habitat-use models for summer ranges spanning 11 million ha in western Oregon and Washington, USA (hereafter Westside). We chose summer because nutritional limitations on elk condition (e.g., body fat levels) and reproduction in this season are evident across much of the western United States. Our overarching hypothesis was that elk habitat use during summer is driven by a suite of interacting covariates related to energy balance: acquisition (e.g., nutritional resources, juxtaposition of cover and foraging areas), and loss (e.g., proximity to open roads, topography). We predicted that female elk consistently select areas of higher summer nutrition, resulting in better animal performance in more nutritionally rich landscapes. We also predicted that factors of human disturbance, vegetation, and topography would affect elk use of landscapes and available nutrition during summer, and specifically predicted that elk would avoid open roads and areas far from cover-forage edges because of their preference for foraging sites with secure patches of cover nearby. Our work had 2 primary objectives: 1) to develop and evaluate a nutrition model that estimates regional nutritional conditions for elk on summer ranges, using predictors that reflect elk nutritional ecology; and 2) to develop a summer habitat-use model that integrates the nutrition model predictions with other covariates to estimate relative probability of use by elk, accounting for ecological processes that drive use. To meet our objectives, we used 25 previously collected data sets on elk nutrition, performance, and distributions from 12 study areas. We demonstrated the management utility of our regional-scale models via application in 2 landscapes in Washington. The elk nutrition model predicts levels of digestible energy in elk diets (DDE; kcal DE/g of consumed forage) during summer. Model input data were from foraging experiments using captive female elk and field measurements of site characteristics at fine scales (∼0.5 ha). The nutrition model included a set of equations that predicted forage biomass as a function of site characteristics and a second set that predicted DDE primarily as a function of forage biomass. We used the nutrition model to develop a DDE map across the Westside. We then evaluated performance of the model by comparing predicted DDE to nutritional resource selection by elk and to population-level estimates of autumn body fat and pregnancy rates of lactating elk. To model elk habitat use, we compiled 13 unique telemetry data sets from female elk (n = 173) in 7 study areas (data collected June–August 1991–2009). We used a generalized linear model with 5 of the data sets, coupled with ecologically relevant covariates characterizing nutrition, human disturbance, vegetation, and physical conditions, to estimate intensity of use with the negative binomial model. We evaluated model performance by mapping predicted habitat use with the regional model and comparing predictions with counts of elk locations using 8 independent telemetry data sets. The nutrition model explained a reasonably high amount of variation in forage biomass (r² = 0.46–0.72) and included covariates of overstory canopy cover, proportion of hardwoods in the canopy, potential natural vegetation (PNV) zone, and study area. Dietary DE equations in the model explained about 50% of the variation in DDE (r² = 0.39–0.57) as a function of forage biomass by PNV zone and study area. Broad-scale application of the nutrition model in the Westside region illustrated the predominance of landscapes that failed to meet nutritional needs of lactating females (≤2.58 kcal/g) and their calves, especially at moderate elevations in closed-canopy forests in both the Coast Range and the southern Cascades. Areas providing DDE at (>2.58–2.75 kcal/g) or in excess (>2.75 kcal/g) of the basic requirement of lactating females were uncommon (<15% of area) or rare (<5% of area), respectively, and primarily occurred in early-seral communities, particularly at higher elevations. Wild elk avoided areas with DDE below basic requirement and selected for areas with DDE >2.60 kcal/g. Percentage of elk ranges providing DDE levels near or above basic requirement was highly correlated with pregnancy rates of lactating females. Autumn body fat levels were highly correlated with percentage of elk ranges providing DDE levels above basic requirement. The regional model of elk habitat use with greatest support in the empirical data included 4 covariates: DDE, distance to nearest road open to motorized use by the public, distance to cover-forage edge, and slope. Elk preferred habitats that were relatively high in DDE, far from roads, close to cover-forage edges, and on gentle slopes. Based on standardized coefficients, changes in slope (−0.949) were most important in predicting habitat use, followed by DDE (0.656), distance to edge (−0.305), and distance to open road (0.300). Use ratios for the regional model indicated these changes in relative probability of use by elk: a 111.2% increase in use for each 0.1-unit increase in DDE; a 22.7% increase in use for each kilometer away from an open road; an 8.1% decrease in use for each 100-m increase in distance to edge; and a 5.3% decrease in use for each percent increase in slope. The regional model validated well overall, with high correlation between predicted use and observed values for the 4 Washington sites (rs ≥ 0.96) but lower correlation in southwestern Oregon sites (rs = 0.32–0.87). Our results demonstrated that nutrition data collected at fine scales with captive elk can be used to predict nutritional resources at large scales, and that these predictions directly relate to habitat use and performance of free-ranging elk across the Westside region. These results also highlight the importance of including summer nutrition in habitat evaluation and landscape planning for Westside elk. The models can inform management strategies to achieve objectives for elk across land ownerships. The regional model provides a useful tool to understand and document spatially explicit habitat requirements and distributions of elk in current or future landscapes. The 2 examples of management application demonstrated how effects of management on elk nutrition and habitat use can be evaluated at landscape scales, and in turn how animal performance and distribution are affected. Results further illustrated the importance of managing for nutrition in combination with other covariates (i.e., roads, slope, cover-forage edges) that affect elk use of nutritional resources to achieve desired distributions of elk. Our meta-analysis approach to habitat modeling provides a useful framework for research and management of wildlife species with coarse-scale habitat requirements by identifying commonalities in habitat-use patterns that are robust across multiple modeling areas and a large geographic range. Use of such methods in future modeling, including application in monitoring programs and adaptive management, will continue to advance ecological knowledge and management of wildlife species like elk. © 2018 The Authors. Wildlife Monographs published by Wiley on behalf of The Wildlife Society. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. Los estudios de selección y uso de hábitats por la vida silvestre, especialmente herbívoros grandes, son fundamentales para comprender su ecología y gestión, especialmente si los predictores de uso representan requisitos de hábitat que pueden estar relacionados con la demografía o aptitud física. Muchas especies de ungulados sirven a las necesidades de la sociedad como animales de caza o alimento sustancial, y también pueden afectar la vegetación nativa y los cultivos agrícolas debido a sus grande opciones de dieta de tamaño corporal y su amplia distribución. El entendimiento de los recursos nutricionales y el uso de hábitat de grandes herbívoros como el alce (Cervus canadensis) puede beneficiar su gestión en diferentes propiedades de la tierra y regímenes de gestión. Distribuciones de alce en gran parte del oeste de los Estados Unidos han cambiado de tierras públicas a privadas, conduciendo a oportunidades a la caza y observación reducidas en la primera y el aumento del daño a los cultivos y otros efectos no deseados en este último. Estos cambios pueden ser causados por el aumento de la perturbac

ABSTRACT Demographic data show many populations of Rocky Mountain (Cervus elaphus nelsoni) and Roosevelt (Cervus elaphus roosevelti) elk have been declining over the last few decades. Recent work suggests that forage quality and associated animal nutritional condition, particularly in late summer and early autumn, influence reproduction and survival in elk. Therefore, we estimated seasonal nutritional condition of 861 female elk in 2,114 capture events from 21 herds in Washington, Oregon, Wyoming, Colorado, and South Dakota from 1998 to 2007. We estimated ingesta‐free body fat and body mass, and determined age, pregnancy status, and lactation status. We obtained estimates for most herds in both late winter–early spring (late Feb–early Apr) and in autumn (Nov–early Dec) to identify changes in nutritional condition of individuals across seasons. Body fat levels of lactating females in autumn were consistently lower than their non‐lactating counterparts, and herd averages of lactating elk ranged from 5.5% to 12.4%. These levels were 30–75% of those documented for captive lactating elk fed high‐quality diets during summer and autumn. Body fat levels were generally lowest in the coastal and inland northwest regions and highest along the west‐slope of the northern Cascades. Adult females in most herds lost an average of 30.7 kg (range: 5–62 kg), or about 13% (range: 2.6–25%) of their autumn mass during winter, indicating nutritional deficiencies. However, we found no significant relationships between spring body fat or change in body fat over winter with winter weather, region, or herd, despite markedly different winter weather among herds and regions. Instead, body fat levels in spring were primarily a function of fat levels the previous autumn. Thinner females in autumn lost less body fat and body mass over winter than did fatter females, a compensatory response, but still ended the season with less body fat than the fatter elk. Body fat levels of lactating females in autumn varied among herds but were unrelated to their body fat levels the previous spring. Within herds, thinner females exhibited a compensatory response during summer and accrued more fat than their fatter counterparts over summer, resulting in similar body fat levels among lactating elk in autumn despite considerable differences in their fat levels the previous spring. Level of body fat achieved by lactating females in autumn varied 2‐fold among herds, undoubtedly because of differences in summer nutrition. Thus, summer nutrition set limits to rates of body fat accrual of lactating females that in turn limited body condition across the annual cycle. Pregnancy rates of 2‐ to 14‐year‐old females ranged from 68% to 100% in coastal populations of Washington, 69% to 98% in Cascade populations of Washington and Oregon, 84% to 94% in inland northwestern populations of Washington and Oregon, and 78% to 93% in Rocky Mountain populations. We found evidence of late breeding, even in herds with comparatively high pregnancy rates. Mean body mass of calves (n = 242) in 3 populations was 75 kg, 81 kg, and 97 kg, representing 55–70% of potential mass for 6‐ to 8‐month‐old calves on high‐quality diets. Mean mass of 11 yearling females caught in autumn was 162 kg, approximately 70% of potential for autumn, and pregnancy rate was 27%. Mean mass of 28 yearlings caught in spring was 163 kg and pregnancy rate was 34%. Our data suggest widespread occurrence of inadequate summer nutrition. Summer ranges of just 3 herds supported relatively high levels of autumn body fat (11–13% body fat) and pregnancy rates (>90%) even among females that successfully raised a calf year after year. Most other summer ranges supported relatively low autumn levels of body fat (5–9% body fat), and reproductive pauses were common (<80% pregnancy rates). Overall, our data failed to support 2 common assumptions: 1) summer and early autumn foraging conditions are typically satisfactory to prevent nutritional limitations to adult fat accretion, pregnancy rates, and calf and yearling growth; and 2) winter nutrition and winter weather are the principal limiting effects on elk productivity. Instead, a strong interaction existed among level of summer nutrition, lactation status, and probability of breeding that was little affected by winter conditions—adequacy of summer nutrition dictated reproductive performance of female elk and growth as well as growth and development of their offspring in the Northwest and Rocky Mountains. Our work signals the need for greater emphasis on summer habitats in land management planning on behalf of elk. © 2013 The Wildlife Society. RESUMEN Los datos demográficos disponibles muestran que las poblaciones de alce de las Montañas Rocosas (Cervus elaphus nelsoni) y de alce de Roosevelt (Cervus elaphus roosevelti) han ido disminuyendo en las últimas décadas. Estudios recientes sugieren que la calidad del forraje y el estado nutricional del alce, especialmente a finales del verano y principios del otoño, influyen en su reproducción y supervivencia. En consecuencia, se decidió estimar el estado nutricional de 861 hembras de alce, en 2114 eventos de captura, de 21 rebaños en Washington, Oregón, Wyoming, Colorado y Dakota del Sur desde 1998 al 2007. Se estimó la grasa corporal (sin incluir el bolo alimentario) y la masa corporal y también se determinó la edad, el estado de embarazo y el estado de lactancia de estos animales. Estas estimaciones fueron obtenidas, para la mayoría de los rebaños, a finales del invierno y principios de la primavera (finales de febrero y principios de abril) así como en otoño (noviembre y principios de diciembre) con el fin de identificar los cambios en el estado nutricional de los individuos a través de las estaciones. En otoño, los niveles de grasa corporal de las hembras que daban de lactar fueron consistentemente más bajos que aquellos de las hembras que no daban de lactar y el promedio de hembras en estado de lactancia varió entre 5.5% y 12.4%. Estos niveles equivalen al 30–75% de aquellos documentados en la literatura para hembras en cautividad, en estado de lactancia y alimentadas con dietas de alta calidad durante el verano y el otoño. Los niveles de grasa corporal fueron generalmente más bajos en regiones costeras y al interior del Noroeste americano, mientras que los niveles más altos fueron observados a lo largo de la ladera occidental de las Cascadas del Norte. Durante el invierno, las hembras adultas en la mayoría de los rebaños perdieron un promedio de 30.7 kg (rango: 5–62 kg), o alrededor del 13% (rango: 2.6–25%) de la masa corporal registrada en otoño, lo que es indicativo de deficiencias nutricionales. Sin embargo, no se encontraron correlaciones significativas entre la grasa corporal registrada en primavera, o el cambio en la grasa corporal durante el invierno, y el clima invernal, la región o el rebaño, a pesar de los diferentes climas invernales entre los rebaños y las regiones. Por otro lado, se observó que los niveles de grasa corporal en la primavera fueron principalmente una función de los niveles de grasa del otoño precedente. Las hembras más delgadas perdieron menos grasa corporal y masa corporal durante el invierno que las hembras más gordas—lo que podría interpretarse como una respuesta compensatoria—pero aún así terminaron la temporada con menos grasa corporal que las hembras más gordas. Los niveles de grasa corporal de las hembras que daban de lactar en otoño variaron entre los rebaños, pero no guardaron ninguna relación con los niveles de grasa corporal de la primavera anterior. Dentro de los rebaños, las hembras más delgadas mostraron una respuesta compensatoria durante el verano y acumularon más grasa que las hembras más gordas a lo largo del verano, dando lugar a similares niveles de grasa corporal entre las hembras que daban de lactar en otoño a pesar de las considerables diferencias en sus niveles de grasa de la primavera anterior. El nivel de grasa corporal adquirido por las hembras que daban de lactar en otoño varió el doble entre los rebaños, sin duda debido a las diferencias en la alimentación durante el verano. Así, el nivel de nutrición alcanzado durante el verano parece haber establecido restricciones en las tasas de acumulación de grasa corporal de las hembras que daban de lactar, lo que a su vez limitó su condición física a través del ciclo anual. Las tasas de embarazo de las hembras de entre 2 a 14 años de edad varió entre 68% y 100% en las poblaciones costeras de Washington, entre 69% y 98% en las poblaciones de Cascade de Washington y Oregón, entre 84% a 94% en las poblaciones del interior del noroeste de Washington y Oregón, y entre 78% y 93% en las poblaciones de las Montañas Rocosas. Se encontró evidencia de reproducción tardía incluso en rebaños con tasas de embarazo relativamente altas. La media de masa corporal de los terneros (n = 242) en tres poblaciones fue de 75, 81 y 97 kg, es decir entre 55% y 70% de la masa potencial de terneros de 6 a 8 meses de edad alimentados con dieta de alta calidad. La media de masa corporal de 11 becerras atrapadas en otoño fue de 162 kg, lo que equivale aproximadamente a 70% de su masa potencial en otoño; su tasa de embarazo fue del 27%. La media de masa corporal de 28 becerras atrapadas en primavera fue de 163 kg y su tasa de embarazo fue del 34%. Nuestros datos sugieren una amplia incidencia de malnutrición durante el verano. Las zonas de alimentación de verano de sólo tres rebaños sustentaron niveles relativamente altos de grasa corporal de otoño (11–13%) y tasas de embarazo (>90%) incluso entre las hembras que lograron criar un ternero año tras año. La mayoría de las otras zonas de alimentación de verano sustentaron niveles de grasa corporal relativamente bajos (5–9%) y en esas zonas las pausas reproductivas fueron comunes (tasas de embarazo <80%). En general, nuestros datos no apoyan dos supuestos comunes: 1) las condiciones de búsqueda de forraje durante el

Understanding bottom-up, top-down, and abiotic factors along with interactions that may influence additive or compensatory effects of predation on ungulate population growth has become increasingly important as carnivore assemblages, land management policies, and climate variability change across western North America. Recruitment and population trends of elk (Cervus canadensis) have been downward in the last 4 decades across the northern Rocky Mountains and Pacific Northwest, USA. In Oregon, changes in vegetation composition and land use practices occurred, cougar (Puma concolor) populations recovered from near-extirpation, and black bear (Ursus americanus) populations increased. Our goal was to provide managers with insight into the influence of annual climatic variation, and bottom-up and top-down factors affecting recruitment of elk in Oregon. We conducted our research in southwestern (SW; Toketee and Steamboat) and northeastern (NE; Wenaha and Sled Springs) Oregon, which had similar predator assemblages but differed in patterns of juvenile recruitment, climate, cougar densities, and vegetative characteristics. We obtained monthly temperature and precipitation measures from Parameter-elevation Regressions on Independent Slopes Model (PRISM) and estimates of normalized difference vegetation index (NDVI) for each study area to assess effects of climate and vegetation growth on elk vital rates. To evaluate the nutritional status of elk in each study area, we captured, aged, and radio-collared adult female elk in SW (n = 69) in 2002–2005 and NE (n = 113) in 2001–2007. We repeatedly captured these elk in autumn (n = 232) and spring (n = 404) and measured ingesta-free body fat (IFBF), mass, and pregnancy and lactation status. We fitted pregnant elk with vaginal implant transmitters (VITs) in spring and captured their neonates in SW (n = 46) and NE (n = 100). We placed expandable radio-collars on these plus an additional 110 neonates in SW and 360 neonates in NE captured by hand or net-gunning via helicopter and estimated their age at capture, birth mass from mass at capture, and sex. We monitored their fates and documented causes of mortality until 1 year of age. We estimated density of cougars by population reconstruction of captured (n = 96) and unmarked cougars killed (n = 27) and of black bears from DNA analysis of hair collected from snares. We found evidence in lactating females of nutritional limitations on all 4 study areas where IFBFautumn was below 12%, a threshold above which there are few nutritional limitations (9.8% [SE = 0.64%, n = 17] at Toketee, 7.9% [SE = 0.78%, n = 17] at Steamboat, 7.3% [SE = 0.33%, n = 46] at Sled Springs, and 8.9% [SE = 0.51%, n = 23] at Wenaha). In spring, of females known to have been lactating the previous autumn, 48% (SE = 3.3%, n = 56) had IFBFspring <2%, a level indicating severe nutritional limitations, compared to 20% (SE = 1.7%, n = 91) of those not lactating the previous autumn. These low levels of IFBFspring of lactating females likely resulted from a carry-over effect of inadequate nutrition during summer and early autumn. We found a positive relationship between summer precipitation and IFBFautumn in NE, and that IFBFautumn of pregnant females was inversely related to birth date of their neonates the following spring (F 1, 52 = 20.37, P < 0.001, R²adj = 0.27). Mean pregnancy rates of lactating females were below 0.90, a threshold indicating nutritional limitations, at Toketee (0.67, SE = 0.12, n = 15), Wenaha (0.70, SE = 0.10, n = 23), and Sled Springs (0.87, SE = 0.05, n = 47) but not Steamboat (0.93, SE = 0.07, n = 14). Of elk where we sampled femur fat during winter in NE, we saw evidence of imminent starvation in 3 of 21 juveniles (12%) with all 3 killed by cougars, and 2 of 12 adult elk (17%) that both died from non-predation events. Birth mass was <13 kg for 6.5% and 2% of VIT neonates in SW and NE, respectively, a mass associated with reduced probability of survival in previous studies. Birth mass of VIT neonates was greater in Sled Springs (x̄ = 18.3 kg, SD = 2.5, n = 59) than Steamboat (x̄ = 16.3 kg, SD = 2.1, n = 21) or Toketee (x̄ = 16.1 kg, SD = 2.8, n = 24) but not Wenaha (x̄ = 17.1 kg, SD = 2.8, n = 36; F 3, 132 = 7.63, P < 0.001). Median and mean birth date (29 May) for VIT neonates did not differ between regions (F 1, 136 = 0.33, P = 0.56), but NE had greater variation around the mean, indicating a longer parturition interval. We documented 293 mortalities of juveniles across study areas and years, and predation was the proximate cause of mortality in 262 cases primarily from cougar (n = 203), black bear (n = 34), and other or unknown predation (n = 25). We also documented causes of mortality as unknown (n = 16), human-caused (n = 8), and disease or starvation (n = 7). We recorded abandonment of 2 (1.4%) and predation mortality of 4 (2.7%) VIT neonates prior to being collared. We found 4-fold differences between regions of subadult female and adult cougar densities (0.90–4.29/100 km²) and 2-fold differences within study areas across years, with cougar density lower in SW than NE. Black bear densities varied from 15–20/100 km² across our study areas. We estimated survival of neonates to 30 days, 16 weeks, and 12 months using known fates models in Program MARK. Survival of neonates born to females with VITs was associated with cougar density, IFBFspring, and female mass but not female age or neonate birth date or birth mass. Survival was higher for juveniles born to females with lower IFBF and mass in spring, opposite of what we predicted. In a post hoc analysis, we found females successful in raising their neonate to recruitment were more likely to be successful the following year compared to those not successful the previous year, which may explain this unexpected finding. As cougar density increased, survival of juveniles born to females of known nutritional condition declined. We conducted separate analyses of survival by region for all neonates captured to evaluate effects of climate, bottom-up (but not maternal condition), and top-down factors. In NE, juvenile survival was little affected by annual variation in climate but decreased as cougar densities increased and as birth date became later. For SW, survival was higher with less April–May precipitation and for later born neonates but less affected by cougar density than observed in NE. Across our 4 study areas, survival varied annually from 0.61 (SE = 0.08) to 1.00 during the first 30 days, 0.41 (SE = 0.11) to 0.90 (SE = 0.09) the first 16 weeks, and 0.18 (SE = 0.06) to 0.57 (SE = 0.11) through 12 months (recruitment) with survival higher in SW than NE. Survival of juvenile elk was inversely related to cougar density through 30 days (F 1, 18 = 16.59, R²adj = 0.45, P < 0.001), 16 weeks (F 1, 18 = 21.07, R²adj = 0.51, P < 0.001), and 12 months (F 1, 11 = 18.94, R²adj = 0.60, P = 0.001). We found that as rates of cougar-specific mortality increased, juvenile survival declined (β̂ = −0.63, 95% CI = −0.84 to −0.42) suggesting cougar predation was partially additive mortality because the estimated regression coefficient was significantly less than 0 but greater than −1. We did not observe a similar relationship with rates of black bear-specific mortality because the estimated regression coefficient overlapped 0, suggesting predation by black bears on juvenile elk was compensatory. Our results suggest that recruitment in NE but not SW was primarily limited by predation from cougars, which was partially additive mortality. Given that we observed nutritional limitations that influenced juvenile survival in all 4 study areas, we were unable to explicitly quantify how much of the cougar predation was additive mortality. Thus, we caution that a reduction in cougar density may not result in an equivalent increase in recruitment, and maintaining or enhancing summer and winter ranges of elk in our study areas is also vitally important for sustaining populations and distributions. In SW, where cougar densities were lower, maintaining, and enhancing existing elk habitat may be the only management option to improve recruitment. Given the differences we found between regions monitored, basing management on an incomplete understanding of causative factors affecting elk population dynamics may result in ineffective actions to address low recruitment. La comprensión de los factores de abajo hacia arriba, de arriba hacia abajo y abióticos, junto con las interacciones que pueden influir en los efectos aditivos o compensatorios de la depredación sobre el crecimiento de la población ungulada, se ha vuelto cada vez más importante como asociaciones de carnívoros, políticas de manejo de la tierra y cambios en la variabilidad del clima en el oeste de América del Norte. El reclutamiento y las tendencias poblacionales de los alces (Cervus canadensis) han disminuido en las últimas 4 décadas en el norte de las Montañas Rocosas del Norte y el Pacífico Noroeste, EE. UU. En Oregón, se produjeron cambios en la composición de la vegetación y en las prácticas de uso de la tierra, las poblaciones de pumas (Puma concolor) se recuperaron de la casi extirpación y aumentaron las poblaciones de osos negros (Ursus americanus). Nuestro objetivo era proporcionar a los gerentes información sobre la influencia de la variación climática anual y los factores de abajo hacia arriba y de arriba hacia abajo que afectan el reclutamiento de alces en Oregón. Llevamos a cabo nuestra investigación en el suroeste (SW, Toketee y Steamboat) y en el noreste (NE, Wenaha y Sled Springs) Oregon, que tenían ensamblajes de depredadores similares pero diferían en los patrones de reclutamiento juvenil, clima, densidades de puma y características vegetativas. Obtuvimos medidas mensuales de temperatura y precipitación a partir de Regresiones de Elevación de Parámetros en el Modelo de Pendientes Independientes (PRISM) y estimaciones del Índice de Vegetación de Di

Because they do not require sacrificing animals, body condition scores (BCS), thickness of rump fat (MAXFAT), and other similar predictors of body fat have advanced estimating nutritional condition of ungulates and their use has proliferated in North America in the last decade. However, initial testing of these predictors was too limited to assess their reliability among diverse habitats, ecotypes, subspecies, and populations across the continent. With data collected from mule deer (Odocoileus hemionus), elk (Cervus elaphus), and moose (Alces alces) during initial model development and data collected subsequently from free-ranging mule deer and elk herds across much of the western United States, we evaluated reliability across a broader range of conditions than were initially available. First, to more rigorously test reliability of the MAXFAT index, we evaluated its robustness across the 3 species, using an allometric scaling function to adjust for differences in animal size. We then evaluated MAXFAT, rump body condition score (rBCS), rLIVINDEX (an arithmetic combination of MAXFAT and rBCS), and our new allometrically scaled rump-fat thickness index using data from 815 free-ranging female Roosevelt and Rocky Mountain elk (C. e. roosevelti and C. e. nelsoni) from 19 populations encompassing 4 geographic regions and 250 free-ranging female mule deer from 7 populations and 2 regions. We tested for effects of subspecies, geographic region, and captive versus free-ranging existence. Rump-fat thickness, when scaled allometrically with body mass, was related to ingesta-free body fat over a 38–522-kg range of body mass (r2  =  0.87; P < 0.001), indicating the technique is remarkably robust among at least the 3 cervid species of our analysis. However, we found an underscoring bias with the rBCS for elk that had >12% body fat. This bias translated into a difference between subspecies, because Rocky Mountain elk tended to be fatter than Roosevelt elk in our sample. Effects of observer error with the rBCS also existed for mule deer with moderate to high levels of body fat, and deer body size significantly affected accuracy of the MAXFAT predictor. Our analyses confirm robustness of the rump-fat index for these 3 species but highlight the potential for bias due to differences in body size and to observer error with BCS scoring. We present alternative LIVINDEX equations where potential bias from rBCS and bias due to body size are eliminated or reduced. These modifications improve the accuracy of estimating body fat for projects intended to monitor nutritional status of herds or to evaluate nutrition's influence on population demographics.