Comparative myology of the ankle of Leopardus wiedii and L. geoffroyi (Carnivora: Felidae): functional consistency with osteology, locomotor habits and hunting in captivity.

Leopardus wiedii (margay) is the only arboreal Neotropical felid able to climb head-first down trees, due to its ability to rotate its tarsal joint 180°. A closely related, similar-sized species, L. geoffroyi (Geoffroy's cat) exhibits more typical terrestrial habits and lacks the arboreal capabilities of L. wiedii. There is osteological evidence that supports a mechanical specialization of L. wiedii's tarsal joint for inversion, but there have been no studies on the myology of this specialization. Based on comparative gross-anatomy dissections of zeugo- and autopodial muscles related to the ankle joint of one margay specimen and two Geoffroýs cats, we identified myological specializations of L. wiedii that support its arboreal abilities. In addition, we documented both species hunting the same prey (domestic pigeon Columba livia, Aves: Columbidae) in captivity, to complement. We report differences in the origin, insertion and belly in 8 of the 10 dissected muscles. At least 3 of these interspecific variations can be associated with strengthening of the main muscles that command inversion/eversion movements of the tarsal joint and support the body weight in the head-down climbing position typical of L. wiedii. Frame-by-frame video reconstructions depict the sequence of movements in these species while hunting and highlight the advantages of the arboreal abilities of L. wiedii.