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US Fish & Wildlife Service FieldNotes
REGION 8: Giant Garter Snake Habitat Restoration Project: Yellow Water Primrose (Ludwigia peploides) Removed on the Cosumnes River Preserve. 
Region 8, September 30, 2008
Giant garter snake traps are set within invasive yellow water primrose in pilot restoration area at Snake Marsh, prior to excavation to create open water habitat. (photo: USFWS)
Giant garter snake traps are set within invasive yellow water primrose in pilot restoration area at Snake Marsh, prior to excavation to create open water habitat. (photo: USFWS) - Photo Credit: n/a
Newly excavated open water area at Snake Marsh within pilot restoration area. (photo: USFWS)
Newly excavated open water area at Snake Marsh within pilot restoration area. (photo: USFWS) - Photo Credit: n/a

by Cesar Blanco
The Central Valley Project Improvement Act (CVPIA) Habitat Restoration Program (HRP) is a grants program which annually funds a variety of acquisition, restoration, research, and other projects such as outreach and planning.  For Fiscal Year 2008, the HRP funded the Cosumnes River Preserve (Preserve) to implement a recovery action for one of the 13 sub-populations of giant garter snakes (Thamnophis gigas) recognized by the U.S. Fish and Wildlife Service (Service); the giant garter snake is a federally listed threatened species.  The project is located at the Preserve’s Badger Creek Unit, near the intersection of Highway 99 and Arno Road, in Sacramento County, California.  The quality and quantity of aquatic habitat in Snake Marsh and Badger Creek, has been degrading over the past several years due, in part, to the highly invasive plant species, yellow water primrose (Ludwigia peploides).  It was anticipated that if primrose continued to grow and expand into the last remaining limits of Snake Marsh and Badger Creek, the habitat would no longer support the snake or its prey species; therefore, the project included both a monitoring and restoration component.

The monitoring component of the restoration project includes baseline and post-project giant garter snake trapping to determine presence, distribution, and relative density of the species.  Determining changes in the species population dynamics in response to changing conditions will help determine if creating additional foraging habitat for the species was a success.  The restoration component included a 1-acre pilot restoration project to restore open-water habitat in Snake Marsh and was initiated in mid-September of 2008.  Open-water habitat was re-created by removing the existing primrose from the 1-acre pond and by excavating an area along the edge of the northwest end of the marsh deep enough to prevent future colonization and complete occlusion of the open-water habitat by primrose.

Excavated material was dumped within a designated stockpiling area, leveled, and contoured to create a new 1-2-acre high-ground area that could be used as over-wintering habitat for giant garter snakes and their prey species.  Following the first rain of the year, the newly created high-ground will be seeded with a native seed mixture.  Giant garter snakes will continue to be monitored during the 2009 active season (about April 1 through September/October 2009), and this information will be used to evaluate the species’ immediate response to the pilot restoration effort, and to formulate a long-term management strategy for the marsh.

Additional information about the HRP Program Manager is available from Caroline Prose:  (916)  414-6575.

 

Contact Info: Cesar Blanco, 916-978-6190, cesar_blanco@fws.gov