![]() ![]() Thus, the dynamics of taxonomically and functionally distinct plants, fishes, invertebrates, and ungulates are linked by apex omnivores that serve as hubs of interaction effects. americanus) are often the most important predators of ungulate neonates ( Supplementary Table 1 Zager and Beecham, 2006) but ungulates comprise a minor energetic resource for bears, which can subsist on alternatives such as fruit, seed mast, invertebrates, and fishes. For example, in North America, brown and American black bears ( Ursus arctos and U. This broad trophic position can lead to highly asymmetric interactions. While apex predator populations are limited by prey availability, apex omnivores can switch among a wider array resources. Owing to the reticulate nature of omnivorous interactions in food webs, the effects of apex omnivores on ecosystems could be more varied and widespread than those of apex predators. However, nature is more complex, and some of Earth’s most iconic predators are omnivores that forage across trophic levels from plants to large herbivores, with broad ecosystem effects. This paradigm focuses on relatively simple predator-herbivore-plant and apex predator-mesopredator-prey interactions. Although nature is rarely so black and white, the “big things run the world” paradigm has been well supported by a large body of literature on the direct and indirect effects of top predators, including trophic cascade and mesopredator release theory ( Ritchie and Johnson, 2009 Levi and Wilmers, 2012). John Terborgh countered that in fact big things such as large-bodied ungulates and top predators run the world ( Terborgh, 1988). Wilson famously postulated that little things – invertebrates – run the world ( Wilson, 1987). Our review and empirical data highlight key knowledge gaps and research opportunities to understand the complex ecosystem effects related to bear-salmon interactions. First, deer densities appear to be consistently higher on islands with abundant brown bears than adjacent islands with black bears and wolves, and moose calf survival is higher at low bear densities (25 bears per 100 km 2). ![]() In addition to our review of the literature, we present original data to demonstrate two community-level patterns that are currently unexplained. Here we review the biogeography of bear-salmon interactions and the role of salmon-subsidized bears in (1) resource provisioning to plants and scavengers through the distribution of salmon carcasses, (2) competition among bears and other large carnivores, (3) predation of ungulate neonates, (4) seed dispersal, and (5) resource subsidies to rodents with seed-filled scats. In coastal temperate ecosystems throughout much of the Northern Hemisphere, anadromous salmon once supported abundant bear populations, but both taxa have declined or been extirpated from large parts of their former ranges with limited research on the consequences of diminished or absent interactions among species. 12Department of Environmental Studies, University of California, Santa Cruz, Santa Cruz, CA, United StatesĪpex predators play keystone roles in ecosystems through top-down control, but the effects of apex omnivores on ecosystems could be more varied because changes in the resource base alter their densities and reverberate through ecosystems in complex ways.11Oregon Department of Fish and Wildlife, Salem, OR, United States.10Department of Forest Ecosystems and Society, Oregon State University, Corvallis, OR, United States.9Department of Fish and Wildlife Sciences, University of Idaho, Moscow, ID, United States.8Raincoast Conservation Foundation, Sidney, BC, Canada.7Department of Geography, University of Victoria, Victoria, BC, Canada. ![]() 6Hakai Institute, Heriot Bay, BC, Canada. ![]()
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