Conservation Northwest

Getting wilder Joe Scott International conservation director, joe@conservationnw.org of Apex Predators The enforcers Release of the little guys Similarly, apex predators are the neighborhood enforcers. They keep the so-called mesopredators in check—these are the skunks, opossums, raccoons, and house cats, and in some systems, coyotes and foxes. Not to villainize any wild animal, but unchecked mesopredators are like the small-time crooks and petty thieves of the neighborhood, who steal old ladies' pocketbooks and break into houses. Absent controls by greater powers, they can devastate the "little guy." In an ecological context, the little guys are the neotropical migrant songbirds and the native rodents, which play critical ecological roles, including insect control, soil aeration, and the spreading of spores of fungi or seeds of native plants. Some of these changes are often at first invisible and the effects only become apparent over time, especially as they are exacerbated by the over browsing and behavioral changes of big ungulates once these deer, elk, and others are freed from the "ecology of fear" as the big predators are lost from the system. The combination of "mesopredator release" and over-population of ungulates can have devastating ecological consequences for overall ecosystem productivity, richness, and diversity. Ecosystem productivity, diversity (the numbers of niches or "jobs" available), and richness (number of different species in a given area) are the building blocks and health of ecosystems. It's not so difficult to imagine how influential predators are when you think about how natural systems work. Because prey species eat plants and their seeds, predation on the herbivores shapes plant communities, which in turn influences plant abundance and distribution. This affects interactions not only between the trees and plants themselves but also between the birds, insects, and mammals in a given system. When the fur trade in the North Pacific very nearly wiped out sea otters, Keeping the Northwest wild the otters primary marine invertebrate prey, sea urchins, grew unchecked, devastating their main food, the kelp forests, as well as the other invertebrates, fish, sea birds, and raptors that depend on the kelp beds. In essence, the top dog sea otter is the "keystone species" to the kelp beds, and its removal makes the neighborhood a lot less biologically diverse, functional, and interesting. Insidious extinction Loss of apex predators Ecologists refer to the process following the loss of apex predators as "trophic downgrading," a process that reaches further into the machinery of ecosystems than anyone ever suspected. Trophic downgrading is an unbalancing of the stable, pyramidal structure of the ecosystem or trophic levels, with plant communities at the large base, herbivores in the steady middle, and carnivores at the smallest top. Recent research has shown that apex consumers affect "processes as diverse as the dynamics of disease, wildfire, carbon sequestration, invasive species and biogeochemical cycles." ("Trophic Downgrading of Planet Earth," James A. Estes, et al, Science 333, 301 - 2011) Even salmon habitat and the prospects for recovering them in the long term could be partly dependent on The Alpha male of the beleaguered Lookout Pack left tracks along this ridge in the Washington Cascades. His female mate disappeared the year prior, likely a victim of poaching. © David Moskowitz healthy predator populations and natural predator/prey systems. In a retrospective study, researchers from Oregon State University found that salmon streams on the Olympic Peninsula may have undergone profound changes since wolves were eliminated early in the 20th century. The researchers postulate that freed Continued next page Coyote, a "mesopredator" whose prelevance has increased following the loss of wolves from an ecosystem. © Alan Bauer Fall 2011 5

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