Alligatorascension: climbing performance of Alligator mississippiensis

Abstract

In tetrapedal locomotion, whether horizontal or during climbing, interactions between the foot and the contact surface or substrate influence the locomotor performance. Multiple previous studies of tetrapedal squamates (lizards) have reported that the animals used the same locomotor velocity, regardless of the angle of ascension. The present study was performed to determine if the American alligator (Alligator mississippiensis) would exhibit a stable climbing velocity and to determine to what degree, if any, this climbing velocity could be modified by substrate differences. Sub-adult Alligator mississippiensis, with body lengths around 170 cm, used the same stride velocity when moving at angles of 0°, 30°, and 55°. During these trials, both the sub-adult and juvenile alligators used a “low walk” gait, rather than a distinctive climbing gait. When the alligators traversed an open grate, their stride duration increased (and stride velocity decreased) presumably due to the insertion (and retraction) of their claws and digits into the grate. When climbing at 55° the juvenile and sub-adult alligators used the same stride duration; the sub-adults used a stride length that was significantly larger in absolute terms, but significantly shorter in relative terms. Despite their large size, and their more caudal center of mass, the climbing performance of Alligator mississippiensis is similar to what has been described in the previously-studied tetrapedal squamates.