biostudies-literatureLee SDArmy Research Officejeb249934https://www.ebi.ac.uk/biostudies/studies/S-EPMC11993264biostudies-literatureUnknown228(7)For gap-crossing agility, arboreal animals require the ability to stabilize dynamic landings on branches. Despite lacking a prehensile grip, squirrels achieve stable landings using a palmar grasp. We investigated the landing dynamics of free-ranging fox squirrels (Sciurus niger) to uncover strategies for stable, above-branch landings. Using high-speed video and force-torque measurements in the sagittal plane, we quantified landing kinetics across gap distances. Squirrels rapidly managed >80% of the landing energy with their forelimbs. With larger gaps, peak leg force and foot torque increased. Alignment between forelimbs, velocity and force also increased, likely reducing joint moment. We tested control hypotheses based on an extensible pendulum model used in a physical, hopping robot nameThe Journal of experimental biologyFree-ranging squirrels perform stable, above-branch landings by balancing using leg force and nonprehensile foot torque.PMC11993264W911NF-1810327ARO #W911NF-1810327 and ARO #W911NF-17-S-002Kuang DWang EKWang SFull RJFearing RSLee SDHunt NHYim JKStuart HSfalseFree-ranging squirrels perform stable, above-branch landings by balancing using leg force and nonprehensile foot torque.For gap-crossing agility, arboreal animals require the ability to stabilize dynamic landings on branches. Despite lacking a prehensile grip, squirrels achieve stable landings using a palmar grasp. We investigated the landing dynamics of free-ranging fox squirrels (Sciurus niger) to uncover strategies for stable, above-branch landings. Using high-speed video and force-torque measurements in the sagittal plane, we quantified landing kinetics across gap distances. Squirrels rapidly managed >80% of the landing energy with their forelimbs. With larger gaps, peak leg force and foot torque increased. Alignment between forelimbs, velocity and force also increased, likely reducing joint moment. We tested control hypotheses based on an extensible pendulum model used in a physical, hopping robot name2025-01-01T00:00:00Z2025 Apr2025-07-13T03:05:01.284Z2025-07-13T03:05:01.284ZS-EPMC119932644001358010.1242/jeb.249934