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Knowledge of the diet ecology of apex predators in insular island ecosystems has direct applications to the conservation of endemic species at risk of extinction. We used stable isotopes of carbon and nitrogen to infer resource-use strategies of an indigenous predator, the Pacific marten (Martes caurina (Merriam, 1890)), in a highly modified ecosystem on Haida Gwaii, British Columbia, Canada. We used Bayesian isotopic mixing models to estimate the relative contributions of different food sources to marten diet across seasons and during overall lifetime, and to determine how diet varied with different levels of access to marine resources. Isotopes of carbon and nitrogen measured in hair and muscle tissue suggested that marten consumed salmon (3%-17%) and berries (25%-37%) seasonally; these diet groups were relatively minor components of the lifetime diet. Analysis of bone collagen suggested that terrestrial fauna--including birds, deer, small mammals, and invertebrates--contributed the most to diet (41%-55%), and marine invertebrates (38%-48%), not salmon (0%-3%), were the main allochthonous marine nutrient subsidy to lifetime diet. Plasticity in foraging ecology, combined with a broad dietary niche, introduced prey, notably the invasive Sitka black-tailed deer (Odocoileus hemionus sitkensis Merriam, 1898), as well as abundant marine resources, may allow marten to outcompete other indigenous and endemic carnivores on Haida Gwaii. Key words: Pacific marten, Martes caurina, Haida Gwaii, stable isotopes, diet ecology, mesocarnivore, apex predator, island ecosystem, species at risk. Les connaissances sur l'écologie alimentaire des prédateurs de niveau trophique supérieur dans les écosystèmes insulaires ont des applications directes pour la conservation d'espèces endémiques en danger de disparition. Nous utilisons des isotopes stables de carbone et d'azote pour inférer les stratégies d'utilisation des ressources d'un prédateur indigène, la marte du Pacifique (Martes caurina (Merriam, 1890)), dans un écosystème fortement modifié dans l'archipel Haida Gwaii (Colombie-Britannique, Canada). Nous utilisons des modèles de mélange isotopique bayésiens pour estimer les apports relatifs de différentes sources de nourriture au régime alimentaire des martes pour différentes saisons et sur toute la durée de vie, et pour déterminer les variations du régime alimentaire en fonction de différents degrés d'accès à des ressources marines. Les isotopes de carbone et d'azote mesurés dans les poils et les tissus musculaires indiqueraient que les martes consomment des saumons (3% - 17%) et des baies (25% - 37%) sur une base saisonnière; ces groupes alimentaires sont des composantes relativement mineures du régime alimentaire sur la durée de vie. L'analyse du collagène osseux donne à penser que la faune terrestre--dont des oiseaux, cerfs, petits mammifères et invertébrés--fait le plus grand apport au régime alimentaire des martes (41% - 55%), et que les invertébrés marins (38% - 48%), et non les saumons (0% - 3%), constituent le plus grand apport allochtone de nutriments marins à ce régime alimentaire sur toute la durée de vie. La plasticité de l'écologie de l'alimentation, combinée à une large niche alimentaire, des proies introduites, notamment le cerf de Sitka (Odocoileus hemionus sitkensis Merriam, 1898), une espèce envahissante, ainsi que d'abondantes ressources marines, pourraient permettre aux martes de prévaloir sur d'autres carnivores indigènes et endémiques dans l'archipel Haida Gwaii. [Traduit par la Rédaction] Mots-clés : marte du Pacifique, Martes caurina, archipel Haida Gwaii, isotopes stables, écologie alimentaire, mésocarnivore, prédateur de niveau trophique supérieur, écosystème insulaire, espèce en péril., Introduction The spread of invasive species through human activities has contributed to the majority of recent vertebrate extinctions and is one of the most significant threats to global biodiversity across [...]

Moose are an iconic symbol of northern forests. In many jurisdictions, the management of moose has focused on regulating harvest with less emphasis on understanding moose–habitat relationships. We reviewed the literature and summarised the effects of forest harvest and management on the ecology of moose. Greater than 50 years of scientific studies document both positive and negative effects of forest harvest and associated activities such as silviculture and road building. Moose require spatially adjacent patches of younger plant communities for forage and older forests for thermal and security cover. Extensive and rapid forest harvest can result in the prevalence of young forest with a corresponding reduction in the fitness of moose populations. A warming climate likely will exacerbate the negative effects associated with the broad-scale removal of forest cover. Resource roads can create edge habitat that may serve as forage, but those features result in increased hunting and collisions with vehicles and facilitate the movement of predators. Post-harvest silviculture, including the application of herbicides, can create stand conditions that provide very little or low-quality forage. The ecological and societal benefits of moose are dependent on forest management that provides a mix of old and young forest, employs silviculture that retains adequate cover and forage plants, and minimises the development of roads. [ABSTRACT FROM AUTHOR]

Conservation strategies for imperiled species are frequently based on identifying and addressing the probable causes of population decline, an approach known as the declining population paradigm. Causes, however, are frequently linked to demographic outcomes by multiple mechanisms, and failing to target the primary mechanisms can reduce the effectiveness and efficiency of conservation actions. Increasingly, conservation strategies also need to consider emerging threats, such as climate change. Here, we use boreal caribou (Rangifer tarandus caribou), a threatened ecotype of woodland caribou, as a case study to illustrate how landscape disturbance and climate change can each exert negative demographic effects on caribou through multiple and complex mechanisms. We reviewed the extensive literature focused on woodland caribou to identify and assess the relative importance of each putative mechanism. While disturbance‐mediated apparent competition, the expansion of novel predators, and altered predator behavior appear to be primary mechanisms dictating past and current declines of caribou, climate change has increasing potential to exert strong direct and indirect effects now and in the future. Predicted climate effects may prevent some populations from regaining self‐sustaining status, despite local conservation actions. Our review revealed several knowledge gaps, notably a lack of clarity on the spatial extent of undisturbed habitat required for caribou populations to be stable. We used outcomes from our review to demonstrate how a mechanistic understanding of population decline can inform habitat‐based conservation strategies for caribou. For populations residing within highly disturbed ranges, habitat restoration is a key recommendation of current conservation strategies, yet the large spatial extent of disturbances will require prioritization of areas for restoration. Maximizing the conservation return‐on‐investment for caribou will require a mechanistically informed prioritization process that targets conservation actions toward the primary mechanisms underlying population decline. [ABSTRACT FROM AUTHOR]