Surveys for arroyo toad have been conducted across San Diego County by various biologists from federal and state agencies, educational institutions, and non-governmental organizations. For over 20 years the U.S. Geological Survey (USGS) has been one of the agencies conducting various arroyo toad studies throughout San Diego County in collaboration with other agencies and academic partners. Since 2000, USGS has conducted various monitoring and inventory surveys to determine the status of the species on conserved lands (Brown and Fisher 2002, Ervin, Hathaway, and Fisher 2002, Meyer et al. 2003, Hitchcock, Backlin, and Fisher 2004a, 2004b, Madden-Smith Ervin, and Fisher 2005). USGS has expanded studies on the arroyo toad to assess impacts from disturbance, management operations, and naturally occurring disturbance such as wildfires and drought (Madden-Smith et al. 2003, Madden-Smith, Ervin, and Fisher 2005, Mendelsohn, Madden-Smith, and Fisher 2005, Brown et al. 2020, Gallegos et al. 2021, Hitchcock et al. 2022). USGS has also continued to refine and improve survey methods, data collection, and analysis methods to better inform status and trends, threats and stressors, and responses of arroyo toads to habitat and water management (Brehme et al. 2006, 2011, 2019).

This project builds on this previous work by USGS and partners to develop and implement a monitoring plan for arroyo toad across San Diego County. 

Background:

The arroyo toad (Anaxyrus californicus) is a habitat specialist endemic to the coastal plains and mountains of central and southern California and northwestern Baja California (Jennings and Hayes 1994). It has a life span of seven to eight years (Fisher et al. 2018). The species primarily inhabits low gradient streams and rivers composed of sandy soils and containing sandy streamside terraces (Sweet 1992 and 1993, Barto 1999). Reproduction depends on availability of shallow, still, or low flow pools in which breeding, egg laying, and tadpole development occur over 65–85 days (Sweet 1992). These habitat requirements are largely determined by natural hydrological cycles and scouring flood events (USFWS 1999, Madden-Smith et al. 2003).  

In 1994, the U.S. Fish and Wildlife Service (USFWS) listed the arroyo toad as endangered in response to a decline of 75% of its historic distribution within the United States (Jennings and Hayes 1994, USFWS 1994) due to extensive habitat loss, human modification to natural water flow regimes, and introduction of non-native predators. The USFWS released a recovery plan for the arroyo toad in 1999 (USFWS 1999) and reviewed its classification status in 2014, which remained as endangered (USFWS 2015). Arroyo toads were detected in 80% of the 25 his