Naturalistic climbing reveals adaptive strategies for interlimb coordination in freely moving mice.

Multi-limb coordination is vital for mammalian locomotion. While coordination requires reliable organization of limb movements, it also requires flexibility to adapt to environmental demands. In natural settings, animals must navigate diverse terrains that impose unique challenges. Climbing, for example, introduces constraints due to gravitational load, substrate variability, and the need for behaviors like reaching and grasping. Understanding how animals accommodate these demands provides insight into the flexibility of motor systems supporting locomotion. To address this, we developed a naturalistic climbing assay to investigate multi-limb coordination in freely moving mice. Climbing gait emulated aspects of horizontal locomotion, including a speed-dependent decrease in duty factor. However, coordination between homologous limb pairs was asymmetric, with forelimbs favoring anti-phase movements and hindlimbs showing a tendency toward in-phase movements. Notably, mice adjusted this strategy to overcome vertical gaps. Our results reveal that mice engage unique coordination strategies during climbing and adapt them to navigate vertical challenges.