Type: report

Article abstract: Observations of the federally endangered arroyo toad (Bufo californicus) within Cuyamaca Rancho State Park in 1999 created the need for a park-wide study of this endangered amphibian. At that time it was not known what the current distribution of the arroyo toad was or how much suitable habitat for this amphibian occurred on state park properties in this general area. USGS San Diego Field Station was contracted to address both issues. Surveys were conducted in 2002 and 2003 in Cuyamaca Rancho State Park and in 2003 in the adjacent Lucky 5 Ranch properties in Anza-Borrego Desert Sate Park. Habitat assessment surveys were conducted during daylight hours, and follow-up presence surveys were conducted after dark from June through September to clarify distribution. We used a habitat quality rating system to classify habitats (i.e., drainage reaches) as high, good, marginal, or poor quality for this endangered species. The presence/absence of physical features, known to be highly correlated to the presence of arroyo toad populations were used to score each drainage reach resulting in an overall habitat quality score. Four individual habitat patches were identified as high or good quality within Cuyamaca Rancho State Park; no suitable habitat was located within the Lucky 5 Ranch properties. Because high and/or good quality habitat was found only in Cuyamaca Rancho State Park, focused surveys for arroyo toads were only conducted there. For each arroyo toad observation we report the specific location (latitude / longitude), environmental parameters, age class, and time of observation. Only two observations of were made in 2002, while 43 individual observations were made in 2003. The greater number of observations in 2003 than in 2002 was attributed to the greater amount of rainfall and warmer nighttime temperatures in 2003. In addition, we documented breeding (larvae) and recruitment (recent metamorphs) at two of the four high quality habitat patches. It was also noted that this high-elevation arroyo toad population bred later in the season than the coastal and foothill population in the same region. Introduced species including, hatchery-stock rainbow trout (Oncorhynchus mykiss var.), threespine stickleback (Gasterosteus aculeatus microcephalus), goldfish (Carassius auratus), and wild turkey (Meleagris gallopavo var.) were all documented within Cuyamaca Rancho State Park and were found to co-occur with the endangered arroyo toads. The po