Welcome to the jungle
From super rats to wildcats, towering oaks aren’t the only attractions in Sacramento County’s Tall Forest
“It’s like being in a cathedral. The trees tower over you; some of them are draped from top to bottom with [wild] grape. It looks tropical, very lush. It’s like a jungle.” That’s how Julian Wood, a biologist from the Point Reyes Bird Observatory, described the Tall Forest at the Cosumnes River Preserve in south Sacramento County. Wood is beginning his third year of studying the birds in the Tall Forest. He is not the only scientist in the cathedral.
Each spring, after the winter’s high waters begin to drain from the 160-acre riverside forest, the scientists flood in. Bugs, birds, fish, plants, bats, rats, the water, the mud and even the moist air that rises above the forest all are subjects of scientific study. Wood explained why the area is so popular with his fellow scientists: “The Tall Forest is the largest remaining tract of valley-oak-dominated, mature riparian forest. It’s extremely important, especially if you take into consideration that riparian [riverside] habitat has been reduced to about 2 percent of its original historic range.” The Tall Forest is officially recognized as a National Natural Landmark. This puts it in the same league with other California locations like Año Nuevo Island, the Anza-Borrego Desert and Mount Shasta.
I’m no scientist, and neither is my friend Mike Savino, but we appreciate the beauty and understand the importance of the Tall Forest. I help Savino with his wood-duck nest boxes. He’s in charge of 22 boxes in the Tall Forest, and we have special permission from the Cosumnes River Preserve to maintain and monitor them. The nesting boxes are mounted about 10 feet up the trunks of oak trees along a slough that runs about one-half mile through the forest. Every two weeks, we carry an aluminum ladder from tree to tree, count the duck eggs and record the information on a clipboard.
We often come across brightly colored plastic ribbons tied to the bushes and trees. Researchers use them to mark the locations of bird nests, animal trails and non-native plants as well as equipment like traps, solar-powered bat-counting instruments and motion-sensor cameras. Sometimes we meet scientists from places like Point Reyes; the University of California, Davis; or the University of California, Berkeley. It’s always interesting to talk to them about the various projects they are working on, but usually we’re alone in the quiet forest. We see lots of birds and sometimes an otter or a deer. Last year, we saw a mountain lion. I wonder if curious animals watch us from the shadows while we slog through the mud, slapping mosquitoes and dragging the ladder over fallen trees.
Sometimes I wonder if John Trochet is watching us—just for his own comic relief. Trochet is very serious, and he spends a great deal of time alone in the Tall Forest, silently observing wildlife. He knows the family, genus and species of everything that moves, and he knows the plants, too. Trochet is a great naturalist and is highly respected among birders, but he does not have an advanced degree in any of the natural sciences, and he is not even a member of the Audubon Society. “I’m not much of a joiner,” he told me.
Trochet was a medical doctor “in another life” but quit the profession to study zoology at UC Berkeley in 1986. Trochet pursued his academic career, and his wife pursued a medical career while they raised two children. It all became too much to handle, so Trochet quit school and has been a “househusband” ever since. He goes to the preserve three or four times a week, and his favorite place is the Tall Forest. He told me, “After I earned my spurs the first couple of years, I was kind of given carte blanche to do biological inventory anywhere on the preserve. I enjoy my time alone, and that’s what I do.”
I’ve seen Trochet at least a dozen times in the last two years, and one evening earlier this month, I was looking for him at a social event for the preserve’s volunteers and staff. I saw him across the crowded room, but I didn’t recognize him right away. He looked so strange. He wasn’t wearing his hat or glasses, and he didn’t have his binoculars. Strangest of all, he was indoors.
Trochet is the man to talk to for natural history, but for the Tall Forest’s human history, I went to Rick Cooper, the preserve’s manager. I learned that, with the exception of just a few trees, the entire Tall Forest was cut down in the 1890s. There was some farming and cattle grazing in the area, but the forest slowly grew back.
In the 1960s, the federal government, after years of studies and planning, decided not to build a dam farther up the river. Today, the Cosumnes is the one and only river flowing out of the western slope of the Sierra Nevada that makes it all the way to the ocean without a single dam in its way.
By the mid-1970s, the Tall Forest and some adjoining areas were being considered as a potential state park. “There was resistance by the private-land owners,” Cooper explained. “Some of the landowners went in and started cutting oaks down on their property to develop them into farmland. They were fearful that just because they had oaks, somebody was going to come in and condemn their land.” At that time, the state of California pushed for the inclusion of the Tall Forest in the federal National Natural Landmark program. It was officially designated the Cosumnes River Riparian Woodlands in 1976, and it remained in private ownership as part of the Crump Ranch.
In 1987, The Nature Conservancy, a nonprofit conservation organization, bought the Crump Ranch property and officially established the Cosumnes River Preserve. Cooper called the purchase of the Tall Forest a “starting point for the preserve.” The preserve grew in size throughout the years with the acquisition of wetlands, oak forests, sloughs, river bottomland and agricultural land. The preserve also formed partnerships with state, federal and private organizations like the Department of Fish and Game, the Bureau of Land Management and Ducks Unlimited. Today the preserve has about 40,000 acres, several partners and a mission to protect and restore riparian forest and freshwater seasonal wetlands.
Only a few months after the preserve was established, the riparian restoration program began. Word went out that people were needed to plant oaks and uproot weeds. Volunteers showed up to donate their labor, and the Habitat Restoration Team (HRT) was born. Everyone was welcome to join the HRT, and it still meets twice a month on Saturday mornings. Team members sweat and get dirty, sunburned and bitten by mosquitoes, yet they keep showing up month after month—some of them for more than a decade. (April 3 is the HRT’s annual Spring Workday Extravaganza. Visit www.cosumnes.org or call (916) 684-2816 for info.)
I’ve been showing up for HRT workdays, off and on, for two years. Last fall, we were removing some fig trees and weeds from the Tall Forest when we met Bill Rainy. Rainy is a bat expert from Berkeley, and he knows Trochet from when Trochet was a zoology grad student in the 1980s. Rainy explained how his solar-powered bat-counting instruments work, and he told us about the dozen or so species of bats that live on the preserve, including a maternal colony of 40,000 Mexican free-tailed bats. The bats are doing well.
The rats, meanwhile, are doing far too well. In the Tall Forest, the mammal with the largest population by far is the non-native black rat. Andy Engilis, from UC Davis, has been studying the rat problem for three years and said, “Using our methods to extrapolate populations, we found an infinite population of black rats.” He explained, “The floodwaters don’t impact them as greatly as they do all the terrestrial mammals. These rats are arboreal; they live in the trees, and they can climb out of the floodwaters. So, what happens every time there’s a big flood? All of the terrestrial
mammal populations are basically
brought back down to near zero, and the black rats are still high, so there’s no competition. The system is just really out of whack.”
The wacky ecosystem has played havoc with nesting birds. The arboreal rats eat their eggs. Engilis said, “I think our reproductive success there is about 8 percent. In order to maintain populations of birds, you have to have somewhere between 20 and 30 percent.” Engilis fears that the Tall Forest may actually be a biological “sink,” working like a magnet to pull in birds from surrounding areas to nest—only to feed the rats.
In the last two years, Engilis has made some startling discoveries. By mounting cameras in trees, above fake bird nests filled with artificial eggs, he found that “nearly 100 percent of predation has been by black rats.” He also put radio collars on rats to get a look at rat society.
“Nobody had ever done radio-collar tracking of black rats in a natural habitat,” he said. Results indicated that female and young rats “tend to have fairly discrete territories in the forest. Some males have larger territories that overlap several females—and then you have these super males. They are big, and they weigh more than others, and they can range over the territories of all the animals. The super males are inserting their genes into the system no matter where they are in the forest.” Engilis said that “nothing can control the black rat, and there is nothing that will compete with black rats; they’re basically the top mammal in that system.”
Engilis’ group only studied “open cup” nesting birds, not cavity nesters like flickers, woodpeckers and wood ducks. Savino’s 22 wood-duck nesting boxes produced 96 ducklings last year, so maybe the cavity nesters are at least a little better off than the other birds.
Engilis’ study ends this year, and he said, “We’ll be finishing it up and
writing our papers and getting the preliminary information out in the literature so that others can hopefully follow up on it and get at this problem. At least now we’ve identified it. It’s kind of like a disease. You identify a disease, and scientists work to try to find a cure.”
In addition to Tall Forest scientific studies on rats, birds and bats, scientists currently are looking at the rate of growth of salmon and phytoplankton, sediment deposition, forest regeneration and the transpiration rates of trees. Keith Whitner, project ecologist for the preserve, is especially interested in a UC Berkeley project that brings everything
together. He called it an “umbrella study.” He said, “It’s taking a lot of
the research that everybody else has done, from bugs to fish to birds to bats, and trying to get a bigger perspective of the whole productivity cycle of the flood plain.”
As to the bigger perspective on the future of the river, Cooper sees a 13-mile riparian corridor from the mouth of the Cosumnes all the way up to and past Highway 99: “We would have a continuous riparian band along there. You might have pockets of bigger forests in some locations and very narrow strips at other locations along the river, but I think it’s certainly achievable in a 20-year time frame.”
As for this year in the Tall Forest, Trochet will be helping to wrap up the rat project, and he occasionally will assist the Point Reyes group with its bird study. I’ll be helping Savino carry the aluminum ladder around to his wood-duck boxes. I think everyone out there feels very fortunate to be able to be in the forest.
The Tall Forest is normally closed to the public, except for monthly bird walks led by Trochet. He said, “It’s the only opportunity for the public to see the Tall Forest, and, in my opinion, that’s the plum parcel of the preserve.” He added, “I don’t require that people necessarily be interested in birds. If they’ve got a natural-history knowledge of any sort, they’re welcome, and they can teach me something.”
Somehow, I doubt that last part.