Resourcefulness, Robustness, and Recovery: Tail Use during Climbing in Rats

Tails serve diverse evolutionary functions across species, but their mechanical role during complex climbing maneuvers remains understudied. We investigated how Long-Evans rats (Rattus norvegicus) use their tails when climbing up and over a ledge with a climbing bar positioned 23-32 cm above a bottom platform. Using force measurements and motion tracking, we quantified tail-generated impulse during climbing and found that tail usage followed an inverse relationship between the impulse they imparted to the bottom platform and the usage of their tail: a higher initial jumping impulse required less assistance from the tail, while a lower initial momentum required a greater compensatory force from the tail. When climbing from greater depths (up to 32 cm), rats maintained consistent jumping impulse but significantly increased tail usage, suggesting a preference for a reliable strategy with mid-climb adjustments rather than pre-calibrated jumping force. Rats demonstrated one-shot learning when the forelimb torque was eliminated by covertly unlocking the climbing bar. After a single near-failure, they shifted from a dynamic, ballistic climbing style to a more controlled, quasistatic approach. This new method involved increased tail usage and adjusted body positioning to reduce gravitational moments. These findings reveal that rats employ their tails as actively controlled limbs that contribute substantial forces during complex maneuvers, adapting usage based on initial conditions and mechanical constraints.