Taxonomy and Distribution of Sigmodon in California
Cotton rats, genus Sigmodon, occur commonly in grassland habitats throughout the southern United States and Mexico. The most widespread species is S. hispidus, which is known to occur in California, although previous studies give reason to believe 5". arizonae also occur in the state. Cotton rats were studied in California using a combination of karyology and skull morphology. Results indicate two species of Sigmodon occur in California: S. hispidus in extreme southeastern California and the Imperial Valley and S. arizonae along the Col- orado River north of the Palo Verde Mountains.
Blood, Brad R.
"Taxonomy and Distribution of Sigmodon in California,"
Bulletin of the Southern California Academy of Sciences:
Available at: http://scholar.oxy.edu/scas/vol89/iss2/4