San Francisco

Zoologists in California are repeating an 80-year-old ecological survey of the Sierra Nevada as part of a scheme to measure the effect of human activity on the state's wildlife. The first phase of the project, which takes place in Yosemite National Park, is also expected to help guide the region's policy for dealing with forest fires.

From 1914 to 1920, the biologist Joseph Grinnell led one of the most extensive wildlife surveys ever conducted in the western United States. His team collected tens of thousands of animal specimens, took about 2,000 photographs, and produced some 13,000 pages of meticulous notes that are still used by biologists today.

Yosemite contains one-fifth of Grinnell's original survey sites, and this summer it once again played host to wildlife survey teams. The US National Park Service has commissioned biologists at the Museum of Vertebrate Zoology at the University of California, Berkeley, to do the work.

Whereas Grinnell relied mainly on the snaptrap — an oversized mousetrap that kills instantly — museum zoologist Craig Moritz, the head of the project, and his team are using live-trapping methods. A few animals will be kept as specimens; the rest will be counted and released.

The team has already found some changes from Grinnell's findings. Several small mammals, such as squirrels, now seem to be living at higher elevations than they used to. One possibility is that warmer average temperatures have driven them higher; another is that fire suppression has caused a build-up of undergrowth and pushed these species uphill.

Berkeley zoologist David Wake, the team's amphibian expert, hopes that the survey will lead to the discovery of new species of salamander. Grinnell's party discovered the first Californian species, the Mount Lyell salamander (Hydromantes platycephalus), in Yosemite. Wake suspects that Yosemite is crawling with salamanders — but Grinnell was less interested in amphibians, and no one has looked carefully since his time.

Moritz hopes to revisit all of Grinnell's survey sites, which range throughout California from the mountains to the coast. “Yosemite will be our benchmark,” he says.