Bone structure adapts to locomotor behavior. This thesis focuses on comparing the effects of burrowing behavior on appendicular bone structure in two Peromyscus (deer mouse) subspecies, P. eremicus and P. polionotus. P. polionotus characteristically creates multiple complex burrows in their territories, while P. eremicus is a nesting mouse and does not burrow. Museum specimens of lab-reared and wild-caught mice of the two subspecies, were scanned using a µCT and analyzed to quantify their bone structure. Wild P. polionotus mice were found to have cortical ulna and tibia bones that suggest better adaptation to bending than their captive-reared counterparts. Notably, the deltoid tuberosity in the humerus of the wild P. polionotus was larger and more distal compared to the lab reared counterpart, possibly indicating greater usage of the deltoid muscles from burrowing behavior. Wild P. polionotus also had larger section modulus, moment of area, and cross-sectional area in the tibia than wild P. eremicus. Trabecular bone analysis shows wild P.polionotus have lower trabecular spacing than wild P. eremicus and a lower trabecular thickness than wild P. eremicus and lab reared P. polionotus, properties that suggest adaptation to high loads from digging. Results lay the groundwork for future exploration of the ontogenetic and phylogenetic basis of mechanoadaption in Peromyscus.