Maintaining Basking Sites for California Red Legged Frog at Big Gun Conservation Bank

Back in 2010 we announced the approval by U.S. Fish and Wildlife Service of our Big Gun Conservation Bank.  The Bank, located in Michigan Bluff, outside Foresthill, is home to what may be the largest remaining documented population of California red-legged frogs (CRLF) in the Sierra Nevada.  The California red-legged frog, made famous by the Mark Twain story of the “The Celebrated Jumping Frog of Calaveras County”, is listed as endangered by the U.S. Fish and Wildlife Service. This species once spread far and wide throughout western California and northwest Baja, however mining activities, intensive agriculture and development has limited the range of the species. Historically, the 48-acre site was hydraulically mined for gold in the late 19 century and as a result large pools were formed and have since become prime habitat for the CRLF.  Since 2010, Westervelt Ecological Services (WES) has been working diligently to maintain the site and the population of the species. 

One of our most recent maintenance activities included the removal of dense vegetation in several locations around some of the ponds to increase basking sites for the CRLF.  Each of the areas selected for vegetation removal was selected based on several factors.  First, CRLF’s had been observed in the pond during previous surveys.  The pond edge had a gentle slope and shallow water, allowing the water to warm quickly in the late spring.  Finally, vegetation or other escape cover was immediately adjacent to the basking site, acting as a nearby retreat from predators.  All vegetation removed from the basking sites was removed by hand in the late spring under the supervision of a biological monitor.

Why is this critical for the frogs?  Basking is important for absorbing solar energy and raising the body temperature of the adults and tadpoles.  This helps a frog have a temperature higher than its environment.  An increased body temperature accelerates growth, digestion and produces fat deposits.

You can see from the photos posted below the difference in vegetation from 2010 to 2011 – after the vegetation has been removed.

Here at WES we are just weeks away from the first round of sampling for California Tiger Salamander (CTS) larvae at our Burke Ranch Conservation Bank, assuming the rains continue.  The California Tiger Salamander is listed both as a federally threatened and California State threatened species.  It is a terrestrial salamander with a broad, rounded snout.  The adults are black and can have white or pale yellow spots on its back and sides. The belly varies from almost uniform white or pale yellow to a variegated pattern of white or pale yellow and black. The salamander's small eyes protrude from its heads and a yellow pattern along the upper edge of its mouth makes it look as if it is smiling.  Salamander larvae look very different than the adults. They are yellowish-gray with a broad dorsal fin extending well onto the back. The head is large and broad with feathery gills on each side. The larvae are what we hope to find during this stage of monitoring.

CTS monitoring on  the Bank is an activity outlined in our long-term management and monitoring plan which gives us the opportunity to understand the status and trends of the species population on the Bank.  It also allows us to document that the site continues to provide food, shelter, and breeding areas for the animal over time and to document and evaluate any changes in the salamander population over time.  Monitoring results also provide important information for the habitat management feedback loop where management activities on the Bank may be adjusted to promote the species life history needs.

Sampling for CTS larvae is conducted under a Section 10(A)(1)(a) of the federal Endangered Species Act by a biologist who has received a special permit from the U.S. Fish and Wildlife Service to sample for this species.   Sampling is conducted in aquatic breeding pools where the larvae live until they develop legs, lungs, and the ability to survive in upland areas. Each pool with the appropriate ponding characteristics for the larval study is systematically sampled using seines and dip nets. Seines are best used to sample first the perimeter and then the remaining portion of the pool.  Dip nets are used in areas where seining is too challenging due to water depth or proximity to pool edges.  One- to two-seines can be used in each pool, depending on the size of the feature being sampled.  The contents of the seines and dip nets are examined after each sweep.  All CTS larvae observed are measured and are development stage cataloged on field data sheets along with any other species of interest such as vernal pool fairy shrimp or tadpole shrimp.  After recordation, each captured larvae is quickly placed in buckets that have been filled with water from the pool being sampled and kept there until the entire sampling effort for that pool has been completed.  This prevents the same CTS from being counted twice and also reduces the stress to that animal. As soon as the last net has been emptied, all CTS are quickly returned back into the same wetland where they were captured. As the pools dry down the larvae develop their legs and soon begin their terrestrial life.

Pictures are the results of last years monitoring of the larvae. Enjoy! -Matt Gause, Senior Ecologist