Adaptive management is a powerful means of learning about complex ecosystems, but is rarely used for recovering endangered species. Here, we demonstrate how it can benefit woodland caribou, which became the first large mammal extirpated from the contiguous United States in recent history. The continental scale of forest alteration and extended time needed for forest recovery means that relying only on habitat protection and restoration will likely fail. Therefore, population management is also needed as an emergency measure to avoid further extirpation. Reductions of predators and overabundant prey, translocations, and creating safe havens have been applied in a design covering >90,000 km2. Combinations of treatments that increased multiple vital rates produced the highest population growth. Moreover, the degree of ecosystem alteration did not influence this pattern. By coordinating recovery involving scientists, governments, and First Nations, treatments were applied across vast scales to benefit this iconic species.

We investigated the consequences of simulated grazing and browsing on net primary production and chemical composition (nutrients, fiber, and total nonstructural carbohydrates) of some plant types available to caribou on Southampton Island, Northwest Territories, Canada. Clipping experiments were conducted in three large exclosures (22 × 22 m) on one deciduous (Salix lanata), one evergreen (Cassiope tetragona), and one semi-evergreen (Dryas integrifolia) shrub species and two types of sedges (Carex scirpoidea and wet-meadow sedges). The impact of various clipping regimes was analyzed in the growing season during which the treatments were applied and at the end of the following growing season. Clipping, for the most part, reduced plant net production. Responses differed among and within plant types according to the timing and intensity of clipping. In some cases maximum net production of plants was not restored during the recovery year, although grazing and browsing pressure was lifted. Clipping modified the chemical composition of S. lanata, D. integrifolia, and the two types of sedges investigated. In clipped sedges, nitrogen, magnesium, potassium, and phosphorus levels in regrowth were above the maximum obtained from controls at any point during the growing season. These chemical changes possibly enhanced the quality of these plants as food for herbivores. Because plant types that showed a high degree of compensatory growth also showed an increase in quality following clipping, herbivores might benefit if they reselect these plants over the course of the growing season. Growth of S. lanata is negatively affected by clipping and represents an important component of the caribou's summer diet, therefore willows are expected to decrease in abundance as the caribou population increases. The decrease in abundance of deciduous shrubs may have important consequences for the caribou's range use and population dynamics.

Increasingly, measures of glucocorticoid levels (e.g., cortisol), key components of the neuroendocrine stress axis, are being used to measure past hypothalamic-pituitary-adrenal (HPA) activity to index psychological and physiological stress exhibited by wildlife for assessing individual and population-level well-being. However, many intrinsic and extrinsic factors affect HPA activity in animals. Using American black bears (Ursus americanus; n = 116) as an ecological model and hair cortisol concentration (HCC) as an integrative measure of past HPA activity, we evaluated the influence of diet, sex and the social environment on black bear HCC in a free-ranging population that spanned adjoining ecoregions with differing densities of potential conspecific and heterospecific competitors. HCC varied by sex, with female HCC ranging from 0.6 to 10.7 pg/mg (median = 4.5 ± 1.2 mean absolute deviation [MAD]) and male HCC ranging from 0.5 to 35.1 pg/mg (median = 6.2 ± 2.6 MAD). We also observed a three-way interaction among sex, δ14C and ecoregion, which may indicate that some differences in HCC between female and male black bears results from variability in the nutritional needs of larger-bodied males relative to smaller-bodied females, slight differences in food resources use between ecoregions as well as sex-based differences regarding the social environment. Once we understand what drives sex-specific differences in HCC, HCC may aid our understanding of the physiological responses by bears and other wildlife to diverse environmental challenges.

Both top-down and bottom-up processes influence herbivore populations, and identifying dominant limiting factors is essential for applying effective conservation actions. Mountain caribou are an endangered ecotype of woodland caribou (Rangifer tarandus caribou) that have been declining, and unsustainable predation has been identified as the proximate cause. To investigate the role of poor nutrition, we examined the influence of sex, season, age class, and available suitable habitat (i.e., old-growth forest>140 years) per caribou on bone marrow fat content of caribou that died (n = 79). Sex was the only strong predictor of marrow fat. Males that died during and post rut had lower marrow fat than females or males at other times of year. Old-growth abundance per caribou, season, and age class did not predict marrow fat. Caribou killed by predators did not have less marrow fat than those that died in accidents, suggesting that nutritionally stressed caribou were not foraging in less secure habitats or that predators selected nutritionally stressed individuals. Marrow fat in endangered and declining populations of mountain caribou was similar to caribou in other, more viable populations. Our results support previous research suggesting that observed population declines of mountain caribou are due to excessive predation that is not linked to body condition.

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