I was out at the Carrizo Plain last week and did quite well, despite being limited to the paved road at the southern end, due to extremely wet and muddy conditions. I spent about 3 1/2 hours there, hiking and cruising, and conservatively saw 60+ rodents. There were at least 7 species, however I was only able to photograph 2.
I’m pretty sure these are San Joaquin Pocket Mice, Perognathus inornatus.
I think this is Peromyscus maniculatus.
I also saw the 3 K-rats, Southern Grasshopper Mouse, and a California Pocket Mouse.