Small mammal population change in a central California restoration site

An important aspect to habitat restoration is the repopulation of the site by animal species. This study was initiated in 2003 to investigate how small mammals naturally repopulate an area being actively restored. The study site was in the San Joaquin National Wildlife Refuge (SJRWNR) in the central valley of California. SJRNWR was established in 1987. Additional purchases of adjacent flood-prone farmlands in 1999 added to the refuge area. Refuge personnel and River Partners are actively restoring many areas within SJRNWR. For this study, a grid of 100 Sherman live traps was run for five nights approximately every three months (May, August, November). In 2003, the site was basically a plowed field with rows of newly planted native trees and bushes. At that time, only very low numbers of Peromyscus maniculatus and Mus musculus were caught.  In 2004 and 2005 as the site developed and ground cover was introduced, Reithrodontomys megalotis and Microtus californicus were also caught in the grid.  In general during 2004 and 2005, P. maniculatus decreased, M. musculus dramatically increased, and R. megalotis stayed in low numbers.  M. californicus also increased substantially by the end of 2005. In 2006, a major flood inundated the area from April through July. While most of the trees survived, the ground cover was lost.  The rodent populations found in the site postflood were again low numbers of P. maniculatus and M. musculus.