Fig. 1. Arboreal locomotion in Monodelphis domestica. (A) Resolution of substrate reaction forces (SRFs) into normal and shear components (F_normal,ML and F_shear,ML, respectively) as illustrated for a fore limb and its mediolateral SRF (F_ML). X_FL, Y_FL and Z_FL are coordinates of the estimated center of fore limb pressure. (B) Resolution of vertical SRFs into shear and normal components (F_normal,V and F_shear,V, respectively). (C) Cropped representative image of M. domestica on the arboreal trackway illustrating the limb landmarks: (1) distal tip of the third manual digit; (2) lateral aspect of the wrist joint; (3) distal tip of the fifth pedal digit; (4) lateral aspect of the metatarsophalangeal joint. Note that the heel (see arrow pointing to the ankle marker) was typically not in contact with the substrate during arboreal and terrestrial trials. Scale bar (4 cm) denotes the length and location of the arboreal force transducer.