Anny Peralta-Garcia | Geology Reports

USGS2018

Occurrence of Batrachochytrium dendrobatidis in anurans of the Mediterranean region of Baja California, México

Chytridiomycosis is caused by the fungal pathogen Batrachochytrium dendrobatidis ( Bd ) and is regarded as one of the most significant threats to global amphibian populations. In México, Bd was first reported in 2003 and has now been documented in 13 states. We visited 33 localities and swabbed 199 wild-caught anurans from 7 species (5 native, 2 exotic) across the Mediterranean region of the state of Baja California. Using quantitative PCR, Bd was detected in 94 individuals (47.2% of samples) at 25 of the 33 survey localities for 5 native and 1 exotic frog species. The exotic Xenopus laevis was the only species that tested completely negative for Bd . We found that remoteness, distance to agricultural land, and elevation were the best predictors of Bd presence. These are the first Bd -positive results for the state of Baja California and its presence should be regarded as an additional conservation threat to the region’s native frog species.

Baja California↗

USGS2016

Status of the California Red-legged Frog (Rana draytonii) in the State of Baja California, México

The California Red-legged Frog ( Rana draytonii ) is a threatened species in the United States that has undergone population declines, especially in southern California. Due to the lack of information on the status of Mexican populations, we surveyed for the presence of R. draytonii in Baja California and assessed possible threats to population persistence. Our study area extended from the U.S.-Mexican border to the southern end of the distribution of the species in the Sierra San Pedro Mártir. We found R. draytonii at six of 15 historical sites, none at five proxy sites (i.e., alternative sites chosen because the historical record lacked precise locality data), and four at 24 additional sites. The 10 occupied sites are within three watersheds in the Sierra San Pedro Mártir (two sites at Arroyo San Rafael, two sites at Arroyo San Telmo, and six sites at Arroyo Santo Domingo). We did not detect R. draytonii at 60% of historical sites, including the highest elevation site at La Encantada and multiple low-elevation coastal drainages, suggesting the species has declined in Baja California. The threats we noted most frequently were presence of exotic aquatic animal species, water diversion, and cattle grazing. Management of remaining populations and local education is needed to prevent further declines.

Baja California↗