Article abstract: To address the problems associated with large variations in adult toad activity, we employed a spatial and temporal monitoring approach that tracks the presence of arroyo toad breeding populations by documenting the presence of eggs and tadpoles. In 2011, surveys did not officially start until early July due to a delay in the contract, which was later than optimal for full documentation of breeding. Under this circumstance, the contract and protocol were modified to adjust for the remaining available survey period. Sites were surveyed up to two times to detect breeding activity and the resulting occupancy modeling is limited to single- year analysis. During 2011, seasonal rainfall totaled 320.5 millimeters (12.62 inches), which is 17% above to the historical normal average rainfall. Approximately 80% of suitable habitat contained water during the arroyo toad breeding season. Where surface water was present, we documented arroyo toad breeding at a majority of sites (82.5%), including those in the ephemeral watersheds. Even though surface water availability was highly variable (34-95%) from 2003-2011, the overall extent of breeding toads in wetted areas remained relatively stable (77-95%) with no significant change over the nine-year period. Single-year models showed negative associations between occupancy of non-native aquatic species and arroyo toad tadpoles in 2011. Co-occurrence of arroyo toads and non-natives is largely within the Santa Margarita River. We previously documented negative associations in detection probability from 2004 to 2008, with a large peak in 2007. This association weakened in 2008 and disappeared in 2009. We attribute this partly to our bullfrog removal efforts in 2008, and to MCBCP base-wide efforts to remove bullfrogs, crayfish, and non-native fish, particularly in the Santa Margarita River since 2009. The increased association between presence of non-native aquatic species and absence of arroyo toads during 2010 and 2011 indicates that continued removal efforts support persistence of the arroyo toad in the river. We continue to demonstrate an important feedback loop between monitoring and management for this endangered species.
Number of pages: 44
Authors: Brehme, Cheryl; Matsuda, Tritia; Fisher, Robert N.;
Purpose: Data Summary
Prepared for: Marine Corps Base Camp Pendleton;
Prepared by: U.S. Geological Survey, Western Ecological Research Center;
Keywords: arroyo toad; monitoring;
Species: Arroyo toad