Understanding and saving big predators

![Figure][1] The public is fascinated by large carnivores because they seem dangerous, beautiful, intelligent, and secretive. Furthermore, they are rare and, like dinosaurs, no longer even a minor threat to the vast majority of North America's human population. This was not always the case; when Lewis and Clark set out across North America a mere two centuries ago, wolves and grizzly bears were a serious health hazard. How quickly things change. These days, when the public thinks about big carnivores in North America, typically the focus is one of trying to maintain or restore these species. Ecologists are fascinated by large carnivores for all of these same reasons but also because studying large carnivores is one of the few realms in which one gains insights into the ecological importance of not just a species or a population but the actual individual animal. Because of the combined (and interrelated) effects of their size, ranging habits, physiology, and diet, the presence of an individual large carnivorous animal is important—through its land use, or shifts in the whims of its behavior, the individual animal can have a drastic effect on a community. Having a handful of sea otters or wolves on the landscape can result in actual landscape change. Lose those carnivores, and the structure of the remaining plant and animal communities changes, often fundamentally. ![Figure][1] PHOTO: JUNIORS BILDARCHIV GMBH/ALAMY This narrative is a central underpinning of Cristina Eisenberg's new book, The Carnivore Way . Writing for both the researcher and the general public, Eisenberg uses her very personal experiences with large predators in western North America to establish the ecological basis for conserving these creatures. In the introduction, she writes “In the late 1990s, when wolves recolonized our valley, … deer and elk that used to stand around complacently mowing aspens and shrubs down to ankle height had to stay wary and on the move to avoid being eaten by wolves. And within five years, unbrowsed aspens and shrubs had filled our meadow.” Her observations are supported by extensive studies in a handful of (mainly) wolf-dominated sites, such as Yellowstone, Grand Teton, and Isle Royale national parks in the United States. The simplicity of these ecosystems in terms of numbers of species allows impacts of the loss or return of large predators to be relatively easily measured, and the picture derived from these measures is impressive. Ungulate, bird, butterfly, and plant communities change. Fluvial and biogeochemical processes are altered. It still is not clear if these insights are fully generalizable across the globe, including regions of high biodiversity such as the tropics, where the potential for buffering perturbations to food webs may be high, or to regions where interannual abiotic variation may overwhelm the top-down role of large predators in driving ecosystem function. Eisenberg's own research suggests nuance, and she attempts to impart this nuance. Nonetheless, the evidence from western North America, where Eisenberg focuses her attention, is such that the ecological importance of top predators has become something of a default framework for most researchers and the general public. “Large carnivores can help slow extinction because they increase biodiversity, thereby creating more resilient ecosystems.” The null hypothesis has seemingly become that large apex predators, through the top-down pressures they directly (by killing) or indirectly (by creating fear) impart, are the reason natural systems appear as they do and why researchers and conservationists alike should strive to aid the persistence of these taxa, not just in a few scattered locales but across vast landscapes. Eisenberg is a fine writer. She centers her attention on the linked rugged landscapes that run from the Sierra Madre Occidental of Mexico, along the Rocky Mountains of the United States and Canada, and into Alaska. This is the author's “Carnivore Way,” although clearly the phrase can mean something more. The book focuses on six species (gray wolves, grizzly bears, wolverines, lynx, jaguars, and cougars) and asks how carnivores inhabiting these regions live and die as they interact with increasing human populations and how we might overcome human-carnivore conflicts and gain, as the book jacket describes, a “peaceful coexistence.” Examining each species separately, Eisenberg is able to deftly touch on diverse themes: border fences; species life histories; ranching, hunting, and trapping; reintroduction efforts; drought and fire; public land availability and management; ranging and dispersal tendencies; and environmental laws and legal structures. The book, like its focal species, roams widely. The author is at her best when telling stories. By discussing how individual animals use their landscape, Eisenberg paints a picture of their trials and tribulations and how they make a living in an increasingly human-dominated environment. Collectively we gain a better understanding of the scale at which carnivore ecologists should be working. Yet the very wide-ranging nature of these animals means that in some ways Eisenberg's geographic Carnivore Way is a figment of human perspective. It is a glorious, rugged landscape. But these species once roamed far beyond it. Wolves and cougars were common in eastern deciduous forests, and grizzly bears once inhabited the Great Plains. These landscapes are the next frontier in carnivore conservation. [1]: pending:yes