Depending on the species of animal the tail is attached to, it can have extraordinarily multi-functional purposes. Tails help the animals to navigate in challenging environments by providing more agility and maneuverability. For example, arboreal mammals like squirrels demonstrate impressive agility while jumping from branches to branches. In a recent YouTube video by Mark Rober, which went “viral”, squirrels voluntarily visiting the YouTuber’s garden cross parkour to earn a food reward. The squirrels were mechanically catapulted off of a track, inducing an initially uncontrolled rotation of the body. Interestingly, they skillfully stabilized themselves using tail motion, which ultimately allowed the squirrels to land successfully. We analyzed the mechanism by which the squirrels recover from significant body angular rates. From the analysis of videos, we observed that the squirrels first use their tail to stabilize their head to fix a landing site visually. Then the tail starts to rotate to help stabilize the body, preparing themselves for landing. To analyze further the mechanism of this tail use during mid-air, we built a multibody squirrel model as well as a squirrel robot and showed the righting strategy based on body inertia moment changes and active angular momentum transfer between axes.  

Another example of the amazing use of the tail is found in the fastest terrestrial animal; cheetah. Researchers have analyzed their hunting behavior in the wild and attributed their hunting success to their ability to change direction and decelerate rapidly. The tails play a crucial role in the maneuverability in running cheetahs using inertial and aerodynamic effects to counter the unwanted rotation it induces. Using two approaches, motion capture of the animal, and robotic imitation, the role of the cheetah’s tail in its maneuverability was studied (Fig. f).