Thaele 1958 Species account. Microtus californicus Dec.23 San Pablo Creek (Saltmarsh), Richmond, Contra Costa Co., Calif. This A.M.: I had 25 mice. After checking my traps I decided I had enough so I pulled the line, and picked up another 8 mice. George Fisher had another 12; again almost all young individuals. I discarded 4 ?? and 3 ??? under thirty grams. While picking up my traps I realized for the first time that the fifty traps along the ditch were almost all in an area that was regularly flooded by high tides. As I picked them up all but half a dozen were in water. Even with the water covering much of the marsh I never saw any Microtus. They must either succeed in hiding in the Salicornia & much of which is still above water or live under water as one approaches. We released a young Microtus from one of George's live traps. She seemed quite at home climbing in the Salicornia above the level of the water. She managed to elude us in about 40 sec.