Alternative Futures for the Region of Camp Pendleton, California
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Arroyo Southwestern Toad Potential Habitat

The arroyo southwestern toad, Bufo microscaphus californicus, is sensitive to changes in hydrology and riparian vegetation. It is a federally listed endangered species. This species was described by Sweet (1991) as an animal specialized for life in an intrinsically unstable habitat. Breeding sites and areas for adults are drainages of an intermediate size range, typically third- or fourth-order streams in decomposed granite, or fifth-order streams in sedimentary rock where stream gradients are low. Bars and low sandy terraces bordering the stream channel are important as are higher terraces of fine alluvium. Summer stream flow or the persistence of shallow pools until at least July is essential.

Adult arroyo toads feed almost exclusively on a variety of insects. Juvenile toads feed on small insects such as ants, beetles, and ladybugs. Tadpoles are detritus feeders, gleaning organic matter from the sand or gravel substrate.

Adult arroyo toads are primarily nocturnal, and thus darkness is one component of cover. They remain buried during the day and emerge nightly from late March to early July. The tadpoles frequent open bars and flats along the stream edge. Algae mats that form in quiet shallows are an important cover type.

Breeding pools for the arroyo southwestern toad require minimal stream current, a majority of pools less than 0.3m deep, pool substrate of sand and gravel with virtually no silt, and a gently sloping shoreline or central bar nearby.

As shown in figures 55 and 56, there will be few changes in Arroyo Toad habitat that are directly caused by development between 1990+ and Plans Build-Out. This is because of the relative difficulty of building in riparian corridors and existing protective regulations. However, there may be important indirect impacts due to decreasing soil moisture in upland areas and increased flooding and scouring of riparian zones at lower elevations.


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