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US Fish & Wildlife Service FieldNotes

GUADALUPE-NIPOMO DUNES NWR: Invasion of the Toadlets!

Region 8, July 3, 2013
A recently metamorphed California toad at Myrtle Pond.
A recently metamorphed California toad at Myrtle Pond. - Photo Credit: n/a
Pieces of large woody debris were placed along the banks of both ponds to enhance wildlife habitat quality.
Pieces of large woody debris were placed along the banks of both ponds to enhance wildlife habitat quality. - Photo Credit: n/a
Part of a large congregation of California toad metamorphs at Myrtle Pond.
Part of a large congregation of California toad metamorphs at Myrtle Pond. - Photo Credit: n/a
Colorada Pond at completion, depicting the rust-colored water for which it was named.
Colorada Pond at completion, depicting the rust-colored water for which it was named. - Photo Credit: n/a
Excavating Colorada Pond.
Excavating Colorada Pond. - Photo Credit: n/a
Myrtle Pond at sunset.
Myrtle Pond at sunset. - Photo Credit: n/a

By Glenn Greenwald

After three-and-a-half years of planning, design, field analysis, permit preparation, and coordinating with neighbors, two wildlife ponds have been created on the Guadalupe-Nipomo Dunes National Wildlife Refuge.

The 2,553-acre refuge is located along the coast of San Luis Obispo County in Central California, and is a satellite of the Hopper Mountain National Wildlife Refuge Complex.

The two ponds were created as part of the Wildlife Ponds Project, an effort designed to provide high quality, long term habitat for the federally threatened California red-legged frog (Rana draytonii) and three federally endangered plants. These three plant species are marsh sandwort (Arenaria paludicola), Gambel’s watercress (Nasturtium gambelii), and La Graciosa thistle (Cirsium scariosum var. loncholepis).

Creating ponds in a coastal dunes environment proved to be a difficult undertaking. The primary hurdles to overcome with this project were 1) to find ground water lying close to the surface, and 2) to find such locations that were not located near the dozens of cultural resource sites that are located on the refuge.

Fifteen sites with groundwater located close to the surface were identified. Groundwater at these sites ranged from about 18 inches to five feet below the ground surface. From these 15 sites, the two sites that were ranked with the lowest probability of being in proximity to cultural or historic resources were selected for pond construction.

The first selected site, now known as Colorada Pond, is located about 2.5 miles inland from the ocean. The second selected site, now known as Myrtle Pond, is located about 300 yards inland from the ocean. Both sites were upland areas located near wetlands. With the help of heavy equipment, uplands were converted into wetlands.

Completed in February 2013, both ponds cover about 6,000 square feet of surface area, with an average depth of about four feet, and a maximum depth of about seven feet. The ponds were constructed with an irregular shape and designed to blend into the existing natural landscape.

To diversify habitat, efforts were made to incorporate small peninsulas and small coves along the shoreline of each pond. Large woody debris such as tree trunks, branches, stumps, and root wads were laid across or partially buried into the bank of each pond to add cover and basking habitat for wildlife. These materials were salvaged from downed willow trees that were located in refuge woodlands, and from driftwood found along the refuge beach.

Wildlife discovered the new ponds very rapidly. At both ponds, mule deer and coyote tracks were present at the water’s edge on the first morning after their creation. Within just a few days, both ponds possessed deafening evening choruses that were provided by dozens of Sierran treefrogs (Pseudacris sierra). Within one to two weeks after the ponds were created, northern raccoon, red-tailed hawk, great blue heron, mallard, mourning dove, red-winged blackbird, hooded oriole, and other wildlife species were observed or detected by their tracks.

About three weeks after Myrtle Pond was created, three pairs of California toad (Anaxyrus boreas halophilus) were observed breeding there, and within six weeks several thousand California toad tadpoles were present along its shoreline.

Ten weeks after Myrtle Pond was created, an invasion of toadlets(toad tadpole metamorphs) was in effect! California toadlet congregations were observed in several locations around the shoreline of Myrtle Pond in numbers that were too large to count. The large congregations of toadlets at the water’s edge resembled swarms of miniature locusts.

Ten weeks after Colorada Pond was created, thousands of Sierran tree frog tadpoles and froglets (frog tadpole metamorphs) were observed at this site.

Apparently, the local frogs and toads liked their new homes at both ponds.

The next phase of the project is planting La Graciosa thistle seeds and seed heads, and propagules of marsh sandwort and Gambel’s watercress. These activities will be conducted next fall as a joint operation by biologists from the Hopper Mountain National Wildlife Refuge Complex and Ventura Fish and Wildlife Office.

Hopefully, these three endangered plant species will adapt to their new homes as fast as the frogs and toads did.

Glenn Greenwald is the refuge manager at Guadalupe-Nipomo Dunes National Wildlife Refuge in Guadalupe, California.

Contact Info: Glenn Greenwald, 805-343-9151, glenn_greenwald@fws.gov