CUTE, AREN'T THEY? The red fox, with its endearing
face; the fat, masked raccoon; skunks (if you ignore their potential) -- fluffy little things you want to take home with you. And look at the austere great horned owl and northern harrier, with a dignity and aloofness that humbles flightless man.

Years ago, I spent time with such animals at a wildlife rehabilitation center, where I learned of the need for wild ecosystems and of man's crimes against nature. I also discovered the rewards of volunteering. So when an old friend offered me an opportunity to work without pay for the U.S. Fish and Wildlife Service and the California Coastal Conservancy last summer, I eagerly accepted.

Leaving undergrad lecture halls behind me, I got into the hands-on, dirty, and intensely satisfying work of tidal marsh restoration at the Service's San Pablo Bay National Wildlife Refuge, on Mare Island. I learned to do many things: survey, track, and call animals, find my way around the marshes, balance full-sized pickup trucks on narrow and eroding levees, and help feed and entertain international delegates.

I also learned that real life doesn't always follow the rules they teach you in class. Take the concept of biodiversity, a magic word to an ecologist and anyone else interested in nature. Throughout my four-plus years in Evolution, Ecology, and Anthropology at the University of California, Davis, professors pounded into my brain the many ways that a healthy ecosystem depends on a variety of plant and animal species. Without the complex food pyramid in place, everything quickly goes haywire. One case I have recited on multiple exams makes a good example. If the big fish in the lake are fished out, the smaller fish population explodes, eating all the plankton that normally abound. The microscopic plant populations normally kept in check by grazing plankton grow exponentially, leading to algal blooms that cloud the entire lake and threaten to suffocate other aquatic life. Although not all examples are as extreme as this, it seems sufficiently clear that the task of a conservationist is to strive for a well-balanced system at all levels of the food chain. Right?

Not necessarily. If you want to protect and restore species on the brink of extinction, you sometimes have to create an exception to the rule. The U.S. Fish and Wildlife Service restoration projects in the North Bay (between Vallejo and Novato) focus on preserving endangered, threatened, and sensitive San Francisco Bay species, especially the salt marsh harvest mouse, the California clapper rail, and the California black rail. Fields once farmed for fodder are being converted to pickleweed tidal marsh, human disturbances have been reduced by limiting public access, and (this is where I come in) exotic and natural predators of threatened species will be discouraged. Theoretically, predators help to keep prey populations healthy by ridding them of aged and sick individuals. But in this case, when a fox, say, consumes two or three endangered mice each week, the effect on the remnant species can be devastating.

Both mice and rails -- secretive, ground-dwelling birds -- are prey species, and both are endangered, so the Fish and Wildlife Service is required to protect them and aid in their recovery. To do this, we may have to control other species. We've taken care of humans the best we can, by directing public access to specified areas. To discourage birds of prey, we will remove trees and fence posts. We hope that without perch sites, these birds will leave. Ground-dwelling predators present a much more difficult problem. Among them are cats (domestic and feral), foxes, coyotes, skunks, opossums, raccoons, and even ground squirrels which are known to eat eggs. How can we control them all, efficiently and, if possible, nonfatally?

A particularly troublesome predator is the red fox, which was imported from Europe at a time when fox fur was elegant wear. Today, escapees from fox farms thrive along the coast and are moving slowly but inexorably northward. Because five to seven pups are born to a vixen each year, red fox populations grow and spread quickly. This fox eats almost anything: eggs, adult birds, rodents, reptiles -- you name it. It swims, digs, climbs, runs, and jumps, so barricades are out of the question. It is also among the few predators that cache their prey, killing and storing more than they eat. Because its range is small and concentrated, it can devastate local prey populations.

Something has to be done to control this predator. Past attempts to live-trap foxes and relocate them have usually succeeded only in moving the problem elsewhere. The only answer seems to be euthanasia. But because foxes are undeniably endearing, with their roguish grins and legendary cleverness, people don't want them killed. So wildlife managers face the task of trying to persuade the public to accept plans to trap and kill foxes as humanely as possible. Once they have determined if and where the red fox poses a threat to the recovery of native species, they have a duty to do so.

My job with the Service focused on this problem. As endangered species recovery programs are still in the early stages, I worked to gather preliminary data on which predators are present at the Refuge so we will know what to look for during later censuses. With the help of many knowledgeable individuals, I went to work armed with binoculars and a camera and learned the rudiments of tracking, animal calling, and other hunting skills. With interns and fellow volunteers, I set up scent stations designed to attract predators with smelly lures. Tracks, left on the carefully swept ground by visiting animals, are later used for identification. We drove the levees at night, at 5 mph with huge spotlights, looking for nocturnal animals and herding skunks and jackrabbits with our truck till early morning. It's satisfying knowing that you're spending your time on something worthwhile, helping to put something back the way it once was -- the way it should be.

But the best part of it all is the exploring. Searching for new locations for scent stations or following tracks, I have been able to wander areas rarely disturbed by humans. My favorite spot is wet with mud (makes for easy tracking) and decomposing plants. The water is falling back from the levees, evaporating quickly so there's a different scene every week, and it smells of the rich dark decaying wetland soil. Maybe I'm selfish, but I take pleasure in being one of the few allowed to visit. No matter what happens to these lands in the future, whether they are opened to the public or flooded with saltwater and made impenetrable to humans, they are mine for a time, while I hunt for the hunters.

I think perhaps the most lasting lesson of the summer is that the classroom and the field don't, in fact, conflict. We learn what should be, in an ideal world, while we're in school: of the way things once were and how we have changed them. In the field we learn how to mesh our teachings with reality. Some things you just can't put back after you've played with them. We have to accept that and realize that although we can't undo what's been done, the real fight lies in protecting and learning about what we still do have, like San Francisco Bay's own salt marsh harvest mouse and California clapper and black rails.

Katie Chapple, who remembers that she first discovered the beauty of earthworm eggs when she was two, has studied nature ever since. She is currently in her fifth year at U.C. Davis, and will graduate in March.