The salt marsh harvest mouse, Reithrodontomys raviventris, is an endangered specialist, exclusively confined to the marshes of San Francisco. Understanding the morphology and conferred locomotor capabilities of the salt marsh harvest mouse is increasingly important as climate change induces vegetative and sea level fluctuations. The western harvest mouse (Reithrodontomys megalotis) also inhabits the San Francisco wetlands as a portion of its expansive range. The ability to climb vegetation rooted in the marsh to avoid tidal surges may be an important factor of R. raviventris survival. Conversely, R. megalotis likely avoids inundation by travelling upland, away from the bay edge. R. raviventris tends to employ its tail as a prehensile appendage during climbs, a behavior akin to arboreal/scansorial species. Long, prehensile tails are composed of a higher number of cranial-caudally shorter vertebrae, permitting flexibility and increasing torsion tolerance. Prehensile tail muscularization may lead to vertebral process lengthening to facilitate muscle attachment. Higher phalangeal indices are also associated with increasing arboreality in mammals. Relatively long digits allow climbers to wrap feet fully around the substrate, thereby increasing correctional torque abilities. To understand if the climbing activity of R. raviventris observed in the marsh is accompanied by skeletal adaptations, I will use micro computed tomography of carcasses to compare its post-cranial skeletal anatomy to that of R. megalotis. I predict that R. raviventris will exhibit higher phalangeal indices, longer vertebral processes, and a higher number of caudal vertebrae than its comparator, indicative of specialization within its dynamic habitat.