The Effects of Cattle Grazing on Columbia Spotted Frogs (Rana Luteiventris) in the Owyhee Mountains, Idaho

Publication Date

7-2000

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Biology

Department

Biology

Supervisory Committee Chair

James C. Munger

Abstract

Two years of data was collected to measure the possible impacts of cattle grazing on the larval development and invertebrate prey base of the Columbia spotted frog (Rana luteiventris) in the Owyhee Mountains of Idaho. To assess the effects of cattle grazing on tadpoles, microcosm experiments were designed in which cattle wastes were added to water and tadpole growth was observed. Microcosm studies indicated that chronic exposure to high levels of waste could negatively impact the survivorship of these tadpoles. Conversely, the addition of high levels of waste increased the growth rate of tadpoles, suggesting waste could augment the larval food supply.

To assess the impacts of cattle grazing on the invertebrate prey base available to the frogs, I collected invertebrates in both grazed and artificially created ungrazed pond and stream sites for comparison. No significant differences in invertebrate biomass or diversity were found. It is possible that under the specific grazing regimes of these sites there is no effect of grazing on the invertebrate community, but a small sample size and very general taxonomic identification may have masked any true differences. A companion stomach-flushing study was conducted to determine the diet and assess possible impacts of grazing on feeding. Surprisingly, no stomach contents were found in adult frogs suggesting that they do not feed in early fall or extraneous factors prevented them feeding.

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