Parks in this Network
Amphibian & Reptile (Herpetofauna) Monitoring
- Aquatic Herpetofauna
- Terrestrial Herpetofauna
The Pacific Treefrog can be found in streams in the Santa Monica Mountains
Urbanization is the most significant source of land use change in southern California. Urban development that results in habitat fragmentation, spread of non-native species, and degraded water and air quality can have measurable impacts on natural open space and the plants and animals that inhabit these areas. Several species of amphibians are widespread throughout the Santa Monica Mountains and Simi Hills. The permeability of their skin and long life (more than 10 years in some species) makes amphibians especially vulnerable to cumulative changes in airborne and waterborne ecosystem stressors.
In 2000, park biologists at the Santa Monica Mountains National Recreation Area began an inventory of aquatic amphibians to assess population status and reproductive success. This inventory effort provided experience and baseline data that guided the development of a long-term monitoring strategy for aquatic amphibians in the Santa Monica Mountains.
Biologists conduct a stream survey
- Ten "sentinel" sites were retained from the initial inventory effort, conducted between 2000 and 2005, and are sampled annually. In addition, we also sample 36 randomly-selected sites over a three-year rotation (12 per year).
- Sampling occurs from April to July to coincide with the amphibian breeding season. Each sampling location is visited twice during the season: once when a full suite of biological and environmental data are collected, and again to determine the presence or absence of target aquatic amphibians and nonnative species.
- Determine status and long-term trends in the distribution and relative abundance of aquatic amphibians.
- Determine environmental and physical features that may influence amphibian populations in the Santa Monica Mountains.
- Monitoring the status of native amphibians in the Santa Monica Mountains helps us to detect changes over a broad landscape involving multiple watersheds subjected to various levels of urbanization, pollution and non-native species, which can help to inform resource management decisions and actions.
- Invasive species, such as crayfish, fish, and New Zealand mud snails, have a detrimental effect on our native amphibians. Pacific treefrog tadpole density is severely reduced in streams with crayfish, as compared to streams without.
- New Zealand mud snails have recently invaded many of our streams, and it is unknown how their presence will affect native species. Studies from other areas of the U.S. have shown that native aquatic invertebrates, prey for amphibian larvae
Pacific treefrogs persist in almost all streams in the Santa Monica Mountains, suggesting that non-native predators do not severely affect the distribution of this species. However, the presence of non-native crayfish appears to affect abundance as shown in the graph above depicting the proportion of stops averaged over streams with or without crayfish that contained the various categories of Pacific treefrogs.
The Monterey Ensatina (Ensatina eschscholtzii) is one of thirty-four species of herpetofauna that can be found in Santa Monica Mountains
For more information contact: Katy Delaney
A diverse assemblage of reptiles and amphibians collectively referred to as herpetofauna, can be found in a variety of habitats in southern California. More than thirty species can be found in the Santa Monica Mountains and Point Loma peninsula. Of the five species that occur at Channel Islands National Park, two have been recognized as being an endemic subspecies.
Pitfall trap arrays have been established in various habitats within the Santa Monica Mountains and Point Loma peninsula.
Unfortunately, much of the habitat in the southern California area has been significantly altered or destroyed by urban development, habitat fragmentation and land use changes. Evaluation of historic data and past studies suggest that a number of reptile species in the Santa Monica Mountains and on Point Loma are in decline. In the Santa Monica Mountains National Recreation Area, 13 of the 34 species of herpetofauna are state- or federally-listed as rare, threatened or endangered. Seven of the 19 species of herpetofauna historically known to occur at Cabrillo National Monument or on Point Loma peninsula are now thought to have been extirpated. Because of their diversity, dependence on multiple habitats, and sensitivity to environmental perturbations, reptiles and amphibians are being monitored by the Mediterranean Coast Network as indicators of ecosystem health.
- Monitoring was initiated at Cabrillo National Monument in 1995 by the United States Geological Survey (USGS) using pitfall trap methodology. Similar monitoring was initiated in the Santa Monica Mountains in 2001. Logistic constraints restricted the use of pitfall trap arrays on the Channel Islands. A series of coverboards along a transect line are used instead.
- Pitfall trap arrays consist of bucket traps (pits) embedded in the ground connected by "drift" fencing. Supplemental funnel snake-traps are laid alongside the fence line.
- In the Santa Monica Mountains and Point Loma peninsula, pitfall trap sampling sites were chosen to represent a variety of habitats. Six permanent transect lines have been established on six different islands at Channel Islands National Park.
- Pitfall trap arrays are visited monthly for five consecutive days. Coverboard transect lines are sampled in the spring and fall.
- Determine long-term trends in terrestrial reptile and amphibian diversity, distribution, and abundance using pitfall trap arrays.
- Monitoring the status of native terrestrial herpetofauna in the Santa Monica Mountains helps us to detect changes over a broad landscape area, which can help to inform resource management decisions and actions.
- A recent study showed that common lizards sampled from across a highly fragmented area in the Simi Hills and Santa Monica Mountains showed large genetic divergences across urban barriers, such as development and roads. Essentially, lizards were isolated in "habitat islands" surrounded by intense development, which did not allow for effective migration and gene flow.