UC DAVIS (US) — Wet grass, not hungry cows, appears to be the cause for the steep decline of the Yosemite toad in the Sierra National Forest.
The findings could affect ranchers whose grazing allotments were restricted by the U.S. Forest Service in 2001 based on the assumption that grazing contributed to the toads’ decline. Officials will now use the study to develop plans that allow grazing within appropriate standards while conserving toads.
“A direct correlation between the intensity of cattle use and toad occupancy of meadows was not found for any portion of the grazing season—early, mid or late,” says Leslie Roche, a graduate student of plant sciences at the University of California, Davis, who worked on the study. “Results strongly indicate that toad presence is driven by meadow wetness rather than cattle utilization.”
The researchers had hypothesized that a reduction in grazing intensity would stop or even reverse the decline of the Yosemite toad but, no evidence to support that premise was found following the five-year study.
From 2005 to 2010, researchers conducted experiments on 39 meadows in the Sierra National Forest, analyzing the effects of different management practices including grazing across the entire meadow, fencing to exclude livestock from breeding areas, and no grazing within a meadow.
They examined the impact of these practices on tadpole density, breeding-pool occupancy, water quality, and other elements that support Yosemite toad survival.
The Yosemite toad was once one of the most prevalent amphibians in the high Sierra including Yosemite National Park, where it was first discovered and after which it is named. But its population and habitat has declined sharply since the early 1980s, disappearing from much of its historic range — meadows at elevations between 6,500 and 11,500 feet from Alpine to Fresno counties.
“The Forest Service is committed to using the best available science, such as this collaborative study, to achieve sustainable resource management,” says Anne Yost, the U.S. Forest Service Regional Rangeland Program Manager. “We will continue to monitor grazing and toad populations and adapt management if needed in the future.”
Researchers from University of California , Berkeley contributed to the study that was funded by the U.S. Forest Service.
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