Is there a unifying principle underpinning animal locomotion in its rich diversity? A thermodynamic analysis performed by a Skoltech professor and his French collaborators at Université Paris Diderot, Université Paris Saclay, and the Muséum national d'Histoire Naturelle, shows why and how waste minimization prevails on efficiency or power maximization when it comes to free locomotion irrespective of the available mode and gaits. The research is published in the Physical Review Letters.