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Technology Associates International Corporation (TAIC), assisted by the San Diego Natural History Museum, conducted baseline biological surveys at Hellhole Canyon Preserve on behalf of the County of San Diego Department of Parks and Recreation. The purpose of these baseline surveys is to provide the County with information on existing biological conditions to develop a Resource Management Plan (RMP) including Area Specific Management Directives (ASMDs). The Preserve is located approximately six miles northeast of Escondido in Valley Center, east of Valley Center Road and north of Santee Lane in San Diego County, California, and is owned and managed by the County of San Diego.

Baseline surveys were conducted in the winter, spring, and summer of 2008. Biologists conducted the following surveys to assess the current status of biological resources onsite: (1) mapping of vegetation communities, (2) a floral inventory including rare plant surveys, (3) checklist butterfly surveys, (4) pitfall trapping to sample amphibians, reptiles, and small mammals, (5) focused arroyo toad surveys, (6) aquatic herpetofauna surveys, (7) diurnal avian point count surveys, (8) nocturnal avian surveys, (9) acoustic sampling and roost and foraging surveys for bats, (10) small mammal trapping using live Sherman traps, and (11) track and camera station surveys for medium and large mammals. Due to a series of drought years and recent wildfires that have burned much of the Preserve, results of these surveys may under-represent the diversity of plant and wildlife species that occupy the Preserve. Nine vegetation communities were mapped within the Preserve and consist of southern coast live oak riparian forest, Diegan coastal sage scrub, southern mixed chaparral, mafic southern mixed chaparral, non-native grassland, coast live oak woodland, eucalyptus woodland, disturbed habitat, and urban/developed. The most abundant vegetation community on the Preserve is southern mixed chaparral. Floristic surveys documented 337 plant taxa occurring in the nine vegetation communities. These include both native and non-native species along with seven sensitive plant species: Brewer?s calandrinia, Humboldt?s lily, Cleveland?s bush monkey flower, felt-leaved monardella, Fish?s milkwort, Robinson?s pepper-grass, and Engelmann oak. A total of 150 animal species were documented from the Preserve during the 2008 baseline surveys. These include 16 species of butterflies, three species of amphibians, 16 species of reptiles, 78 species of birds, and 37 species of mammals. No federally or state listed species were detected; however, 13 non-listed sensitive species were detected during baseline surveys.