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So excellent a survey, they’re conducting it again
Biologist Grinnell’s Yosemite fieldwork from 1914-20 is the basis for today’s research effort — minus the shotguns and snap traps

| 13 August 2003


This least weasel was one of many vertebrate specimens collected in Yosemite by Berkeley biologist Joseph Grinnell and his research team nearly a century ago. Campus researchers are revisiting the region this summer, in an effort to determine how wildlife populations may have changed — in numbers or distribution — over the decades.
Image courtesy of Museum Vertebrate Zoology

A party of Berkeley biologists is camping out around Yosemite National Park this summer, reprising a survey of park wildlife first conducted more than 80 years ago by an earlier generation of Berkeley scientists.

The survey by members of the Museum of Vertebrate Zoology follows the same transect — from Yosemite Valley to Mono Lake — that Joseph Grinnell and Tracey Storer surveyed in their landmark study of Sierra Nevada birds and mammals between 1914 and 1920. At the time, Grinnell was director of the museum and a zoology professor at UC Berkeley.

The National Park Service (NPS) last year asked the museum scientists to conduct a new survey, since no complete assessment of park wildlife had been done since Grinnell’s day. The team began its work in May.

“With this survey, we are hoping to get new baseline data to compare to the Grinnell and Storer surveys early in the 20th century. We want to see if there have been any changes in the abundance or distribution of species in the park,” said Yosemite’s lead wildlife biologist, Steve Thompson. The park service is committing $41,000 to the survey, Thompson said, while museum staff will donate about twice that amount in time and effort.

The survey, part of an NPS initiative to inventory and monitor wildlife in the national parks, coincides with the museum’s wish to commemorate its 100th anniversary with a major project of value to California. By the museum’s centennial in 2008, scientists there hope to have resurveyed many of Grinnell’s original transects around the state.

The survey of more than 20 sites in Yosemite will take about three years and involve most museum scientists and several students. It is being conducted concurrently with resurveys of Grinnell’s other transects, including Sequoia/Kings Canyon national parks, Lassen Volcanic National Park, the Trinity Alps, the Lower Colorado River, Death Valley, and the Mojave Desert.

An ‘astonishing’ legacy
Joseph Grinnell was an eminent biologist of the early 20th century, known for his concept of the ecological niche — the role an organism plays in the broader ecology of an area — and for his insistence on systematic and careful surveys of wildlife. Desiring to establish a research center that would rival the major natural history museums of the East Coast and Europe, he accepted an offer in 1908 to create the Museum of Vertebrate Zoology at UC Berkeley. He directed it until his death in 1939, realizing his dream and influencing generations of biologists in the areas of ecology, vertebrate systematics, and evolutionary biology.

“What’s astonishing about Grinnell’s work — and the only reason we can do this resurvey now — is the extent to which he kept highly detailed records. His field notes are extraordinary,” says museum director Craig Moritz, UC Berkeley professor of integrative biology. “He set up a whole system of taking field notes that’s been perpetuated through the history of the museum and has spread out to other places as well. What makes this museum special is that we have so much data per specimen and that it’s so well organized. That’s Grinnell’s legacy.”

The National Science Foundation just awarded the museum a grant to put all the field notes of Grinnell and his colleagues into a searchable online database. The notes themselves comprise 13,000 pages, and are accompanied by 2,000 photos and tens of thousands of specimens in the museum’s collections.

Among Grinnell’s legacies was the first field survey of Yosemite National Park, conducted at a time when the park’s unique and fragile habitat was feeling the pressure of increasing tourism. His survey led to recommendations for managing and preserving the park, among them elimination of agriculture and removal of a small zoo from the valley.

The Yosemite field notes generated by Grinnell, Storer, and their team alone number 2,000 pages, and the combined team put in about 1,000 hours of field work in the park.

“We’re going back through the field notes containing all the original information to do an exact comparison between today and 80 years ago, which is a remarkable thing,” says James Patton, who has been leading this summer’s survey teams. Patton is a curator in the museum, a Berkeley professor emeritus of integrative biology, and an expert on small mammals.

To make these comparisons, the team is initially revisiting about 10 of the 22 sites surveyed by Grinnell and Storer within the boundaries of Yosemite. Assuming funding comes through, museum scientists will revisit the remainder of the 22 “Grinnell” sites in the park, plus add some new ones in the northern tier, an area of the park Grinnell did not visit.

A vision of the future
“Soon after I arrived at the museum in 2000,” recalls Moritz, “I sat down and read a paper Grinnell wrote in 1910 on the uses of a research museum — in which he laid out really, really clearly the purpose of building a museum the way he did. He actually specified that his hope was that future curators and zoologists could come back in 100 years and look at the effect of human changes to the landscapes on the vertebrate fauna. As soon as I read that, it was clear what we had to do for our centenary — do what Grinnell told us to do and resurvey his transects.”

While the earlier biologists used shotguns, leg-hold traps, and snap traps to do much of their surveying and collecting, the current team will capture and release most of the animals. Bird populations will be assessed by observation and point counts, while mammals will be sampled through live trapping and release. A few small mammals will be taken to ensure correct identification and to provide reference material, as will some amphibians and reptiles.

This year so far, UC Berkeley biologists have made four trips to the park, often packing in their food and traps on mules. The first was in May to survey Yosemite Valley, followed by a trip in June to the northwest part of the park near Crane Flat and Merced Big Trees, one in early July to the Glacier Point area, and one in late July to Lyell Canyon. The team set off Aug. 5 for a 10-day survey near the Tuolumne area at Glen Aulin. During the summer the team is comprised of between four and eight people, including park service biologists, who are surveying mammals, birds, reptiles and amphibians. A separate team of herpetologists will descend on the park this fall and next spring to look for amphibians like frogs and salamanders.

A museum photographer will follow up by taking photos of the same areas as did Grinnell and his crew, ideally from the same spot.

Though the study is designed to assess the status of all vertebrates, there are some animals the park is specifically interested in because their status is currently unknown. These are not the obvious large or pervasive animals — bears, deer, owls, and others — that have been the subject of previous targeted studies. Instead, the list includes a pocket mouse, two species of grasshopper mouse, six species of shrews, six species of chipmunks, and reptiles like the Western fence lizard, Western skink, sagebrush lizard, night snake, and sharptailed snake.

“We’re learning there have been ecological changes within the park that until now we haven’t been able to document adequately,” says Leslie Chow, a Berkeley graduate now serving in Yosemite as a research wildlife biologist for the U.S. Geological Survey. “We view the park as relatively pristine because we don’t allow logging, but other actions — things like suppressing fires for a hundred years — have had an impact.”

While new data gathered this summer have not yet been thoroughly analyzed, a few surprises have already emerged. In Yosemite Valley, the formerly most abundant species of shrew has been supplanted by a species previously known only from higher elevations in the park. And, while looking at mammals in the northwest corner of the park around Merced Grove and Crane Flat, the scientists discovered that the golden mantled ground squirrel had disappeared from many areas, essentially moving to elevations 500 feet higher.

Moritz expects that other transects they survey will exhibit much greater change.”It’s our best protected landscape in California, so we are expecting Yosemite to be the benchmark against which we can compare other transects,” he says.

If Thompson and Chow have their way, museum scientists will regularly visit the park to document the changes occurring in species distribution and population.

“Grinnell established a baseline in the teens, and hopefully we can convince the park that this sort of monitoring needs to be done on a more regular basis,” says Chow. “We’d like to get the museum involved so it will come back every 20 years and do something like this.”

“I hope this cooperation is just a springboard for further work we can do with the Museum of Vertebrate Zoology,” Thompson says. “We do need the data.”