(Review) The Wolf’s Tooth, by Cristina Eisenberg

The Wolf's Tooth, cover (Island Press)

If I could use only three words to describe The Wolf’s Tooth, these are the ones I’d choose: elegant, forceful and fluid.

This is a story about how two intertwined ecological concepts — keystone predators and trophic cascades — leave their signatures upon entire landscapes. The Wolf’s Tooth is authored by Cristina Eisenberg, a PhD candidate at Oregon State University who studies conservation biology. Before graduate school, she was a journalist and editor. Her dual career paths collide in The Wolf’s Tooth, and the result is a remarkable and timely  story about her own research but also an entire mountain of literature that came before her.

Before I go on, some definitions may be helpful. Trophic cascades are a phenomenon whereby reactions cascade through a trophic web, or food web. Because trophic webs are really giant networks that process energy and nutrients through an ecosystem, when something causes a glitch or a change in the system it ripples through to other levels. Eisenberg studies this concept with a focus on the interactions between reintroduced gray wolves, elk and aspen and willows. This is a three level trophic web, where the wolves eat the elk which eat the aspen and willows. In this system, the wolves would also be known as a keystone species. By definition, these are carnivorous species that are the glue that bind their ecosystem together; without them, things have a tendency to fall apart or shift dramatically. Keystone species exert a disproportionately strong influence on the other species in their systems. For example, in the very real case of wolves being extirpated from Yellowstone National Park, the elk population swelled to great numbers and then ate the aspen and willow stands down to the point that new trees were not growing into mature trees because of over-browsing.

To tell the story of trophic cascades and how we know what we do about them, Eisenberg weaves fluid first-hand accounts of her PhD field work and personal experiences in nature with summaries of foundational studies. Her own field work entailed monitoring aspen and willow stands for herbivory patterns from elk, and correlating these patterns with the presence or absence of wolves and predators in the area. The scenes she bases on her field work transport the reader to the slopes and valleys she worked in Glacier and Yellowstone national parks, the H. J. Andrews Experimental Forest in Oregon and elsewhere. As a reader, you experience what she does: you discover a coyote carcass with its throat torn out by wolves, clear evidence of a territorial dispute; you tiptoe through a den site littered with the chew toys of wolf puppies; and you feel the hair on your neck raise when a moose is taken down by wolves only a few hundred yards from Eisenberg as she’s wrapping up a transect line. The sheer force of her narratives thrust you into the journey she’s embarked upon to understand how species interact in the web of life.

Sprinkled between these engaging field scenes, you are immersed in an elegant and detailed review of the basic science behind trophic cascades and keystone predators. Although Eisenberg leads with what she knows best, the Yellowstone ecosystem and wolves, she also dives deep into research of trophic cascades in aquatic ecosystems and old-growth rain forests. You learn about killer whales, sea otters, sea urchins and kelp; sharks and scallops; planktivorous and piscivorous fish and algae; cod, sea urchins, kelp and crabs; coyotes and songbirds. Discussing study after study may leave the more general readers yearning to fast-forward to the personal parts of her narrative, but one thing that helps these passages is the concise way that Eisenberg  imparts key concepts. She also introduces a good deal of literary references, making analogies to or comparing metaphors from Aldo Leopold’s A Sand County Almanac, Ray Bradbury’s short story, A Sound of Thunder and the movie Field of Dreams. You’ll even run into an analogy of how ecosystems unravel compared to the game of Jenga — a simple comparison that a non-scientist can easily grasp.

Perhaps the most engrossing scenes for me were the ones where she recounts talking to her father as he was losing his mind to dementia. Her father was raised in the Sierra Madre Occidental of Mexico and his father had won a huge ranch in a poker game. Her father spent his childhood summers tending to the cattle and protecting them from predators. His father impressed upon him that he was to shoot “anything with sharp teeth and claws: wolves, grizzly bears, cougars, and of course, coyotes.” Her dad told her stories of watching Mexican wolves weave through the herd on their way to somewhere else. He never shot them because they didn’t harass the herd. “There was something about them, in their eyes, in the way they carried themselves, that compelled him to let them go peacefully,” she recounted. When she told him she was going to study wolves for her PhD, he encouraged her, saying that there was so much we don’t know about these animals. It is these personal tidbits she imparts steadily throughout the book that make the overall story feel so powerful and forceful. She is not just a scientist communicating the findings of her field; she is, on a personal level, embedded within the structure of the story, and her family’s history is embedded deeper still. In a way, Eisenberg is custom-built to be the narrator of a book on trophic cascades and I almost wish this aspect were played up a little bit more.

One of the honest joys of reading Eisenberg’s tale is her mastery of language. I can’t recall the last time I was so pleasantly surprised by the word choices in a general science and nature book. For example, the opening sentence of chapter one reads: “We bushwhacked through an old burn at first light in a cold September rain mixed with snow, slipping on the blackened bones of downed lodgepole pines.” Her ability to evoke landscape imagery with just a few well-chosen words is a powerful tool that whisks the reader along. She also knows synecdoche when she sees it:

The wolf trails all led into a large lay. My daughter, Alana, in the field with me that day, photographed a bull elk skull. It had been there so long its cranial sutures had gone mossy and the scarlet leaves of a frost-singed geranium had sprung through an eye socket. Later I would be struck by the lyrical beauty and symbolism of that image —  the symbolism of life and death it contained and which coursed through the meadow like a leitmotif.

This is the power of her writing, to show the reader the effects of the trophic cascades she studies. In this case, symbolized by the dead elk and the newly growing and flowering plants popping up through its bones.

In general, I found The Wolf’s Tooth to be a delightful read. Most of the ecological concepts Eisenberg discussed were not new to me — though a few of the papers were — but the way she packaged and presented it was 100 percent fresh. If you’ve never taken any ecology courses or read ecology textbooks, then you’ll be in for a double treat because you’ll not only enjoy her lyrical and lucid writing, but the content will be new to you as well. If you are a nature lover, then I can’t recommend this book enough.

EXTRAS:
For another positive review written by a scientist, go here.
Island Press page for The Wolf’s Tooth.