and along the west slopes of the Sierra/Cascade mountain ranges in most of central and northern California. Other isolated populations have been reported in the Baja California Norte, in southern California, and at Sutter Buttes in Butte County, California. The species is found at elevations ranging from sea level to in Baja California Norte. In California, foothill yellow-legged frog have been recorded in the Sierra as high as near McKesick Peak, Plumas National Forest and at Snow Mountain at the boundary of Lake and Colusa Counties. They are found in flowing streams and rivers with either rocky substrate or sunny banks. Chemical defense R. boylii uses a chemical defense to protect itself from fungal infections, such as the Batrachochytrium dendrobatidis. The frog secretes a peptide through the skin and the hydrophobic (water repellent) sections of the peptide access to fungi that want to attach to the amphibian. This ability can also be found in other Rana species, including the Cascades frog and the moor frog. The former secretes a milky substance that fights against fungal infections and the latter uses its capability to have males turn blue during mating season. Still, the foothill yellow-legged frog's chemical defense has not been fully examined. Although not much is known about it, this ability of the species has been of interest to many companies because of its overall antifungal effectiveness. However, current pesticide use has caused problems for the frog. Exposure to carbaryl, a substance found in common pesticides, has been shown to not kill the frogs but does lower the peptides' abilities to defend the species against invaders like the chytrid, B. dendrobatidis. More research is being done to see the full effects pesticides may have on R. boylii. Environmental issues Along with the problems associated with pesticides being washed into this frog's habitat, in Trinity County, California, a dam on the major river of the frog's home has affected about 94% of the possible procreation areas for the frogs, which has endangered the population. One study suggests the "data from a comparably sized undammed river fork in the same system ... demonstrated that both the number of potential sites and the total number of egg masses were…higher on this fork than in our main stem", so the unseasonal flooding required by the dam was negatively affecting the mating behavior of the frog. The temperature of the water in Trinity County is