A salt marsh harvest mouse is release to the wild. (Photo: California Dept. of Water Resources)

Joelle Buffa - Don Edwards National Wildlife Refuge

The salt marsh harvest mouse was listed as endangered by the Fish and Wildlife Service in 1970, and by the California Department of Fish and Game in 1971.  A recovery plan, published by the Service in 1984, addressed both the salt marsh harvest mouse and the California clapper rail.

The harvest mouse is endemic to the common pickleweed dominated habitat along the fringes of the tidal marshes of the San FranciscoBay estuary in California.  The destruction and modification of over 80% of the marsh habitat around the estuary resulted in the listing of the animal as endangered.  Protection of remaining habitat along with salt marsh restoration and enhancement are considered key to the recovery of the salt marsh harvest mouse.  The efforts of many public and private groups around the Bay Area have made noticeable gains in protecting and, in some cases, restoring the mouse’s habitat.

One positive step in the mouse’s road to recovery was illustrated at a small parcel on the Don Edwards San Francisco Bay National Wildlife Refuge over the past two years.  Refuge specialists managed to convert agricultural land into salt marsh wetland covered with pickleweed by making some flow adjustments to the muted tidal regime that occurred on the parcel.  Trans-locating mice trapped from an off-refuge parcel that was being sacrificed to the development of a nearby business park, was undertaken.  After two years a follow-up survey was undertaken to assess the status of the relocation effort. 

The numbers (see below) are remarkable and speak for themselves, but some things just don't show up in the cold hard numbers.....such as the several male-female pairs of harvest mice captured in the same trap!  Evidently, one couple had done more than just eat seeds overnight, as indicated by the reproductive status of both animals.  Without going into the scandalous details, let’s just say that the biologists nicknamed trap D-22 the "Honeymoon Suite".  Several other salt marsh harvest mice were either pregnant or reproductively active, so the translocation of mouse from the business park project, and the natural re-colonization of harvest mice appear to be successful, and the recovery of the harvest mouse another step closer.

Species                                                New     Recaptures

Salt Marsh Harvest Mouse                   25               3

Western Harvest Mouse                        6                0

Salt Marsh Intermediate                       15               1

California Vole                                       6               1

House Mouse                                       18