Asymmetrical gaits of juvenile Crocodylus johnstoni, galloping Australian crocodiles

Abstract

Seven juvenile individuals of the Australian species Crocodylus johnstoni from the Frankfurt Zoological Park were ®lmed on high-speed video, at 250 ®elds s 71 , whilst freely moving at various speeds in a long corridor. The sequences of locomotion were analysed to determine the various space and time parameters to characterize limb kinematics. We found that the animals use diverse patterns of asymmetrical gait, revealing great¯exibility in limb co-ordination. In all these gaits, the forelimb strikes the ground ®rst, in the couple made by diagonally opposite fore-and hindlimbs. Among these gaits, rotary gallop offers probably a high level of manoeuvrability, whereas transverse gallop resulted in a higher level of stability. Speed increase is achieved by half-bound and bound, the latter being the only gait used at velocities > 2 m s 71 . Speed was increased mainly by increasing the stride length of the fore-and hindlimbs by simultaneously increasing both its components, the step and swing lengths. However, in bound, the step length of each forelimb increased more than the swing length, resulting in a stronger thrust action, whereas swing length increased more than step length for the hindlimb, causing the centre of mass to accelerate forwards during its ballistic phase. The asymmetrical gaits of crocodiles such as Crocodylus johnstoni are probably not functionally equivalent to the transitional asymmetrical gaits exhibited by lizards when building up into a bipedal run. These gaits are also not entirely equivalent to mammalian gaits, despite the use of vertical movements of the vertebral axis in these crocodiles, favouring an erect dynamic posture.

Biomechanical determinants of transverse and rotary gallop in cursorial mammals

“…However, both transverse and rotary gallop patterns can be displayed by species that have a sprawling limb posture, like some crocodiles (Renous et al, 2002) and seals (A.E.M., personal observation). Nevertheless, in these species there is neither a clear relationship between the type of gallop and the speed, like we have observed in cursorial mammals, nor a difference in gait parameters other than the footfall pattern (Renous et al, 2002).…”

“…Indeed, cursoriality and asymmetrical patterns of limb coordination seem to have appeared in different lineages of terrestrial vertebrates (Carrano, 1999;Renous et al, 2002;Stein and Casinos, 1997).…”

Bipedal locomotion in Tropidurus torquatus (Wied, 1820) and Liolaemus lutzae Mertens, 1938

“…Dorsiflexion of the tail in lizards, such as in Calissaurus draconoides and Uma scoparia, may stretch the caudofemoralis muscle, thereby enhancing the muscle's ability to generate propulsive force (Irschick and Jayne, 1999). Even large reptiles, such as Crocodylus, also elevate their tail during quick galloping bouts, presumably to improve their running mechanics (Renous et al, 2002). Basilisks, on the other hand, drag their tails behind them while running through water.…”

Trackways of the American Crocodile (Crocodylus acutus) in Northwestern Costa Rica: Implications for Crocodylian Ichnology

“…The functional morphology and kinematics of crocodylian terrestrial locomotion have received considerable attention (von Huene, 1913;Schaeffer, 1941;Zug, 1974;Brinkman, 1980;Parrish, 1987;Frey, 1988;Gatesy, 1991;Reilly and Elias, 1998;Biewener, 1999, 2001;Salisbury and Frey, 2000;Renous et al, 2002;Richardson et al, 2002;Meers, 2003;Reilly and Blob, 2003;Willey et al, 2004;Reilly et al, 2005;Hutchinson, 2006;Carpenter, 2009;Allen et al, 2010;Kubo and Ozaki, 2009;Kubo, 2010b;Hutson and Hutson, 2012, 2013Baier and Gatesy, 2013;Grigg and Kirshner, 2015). Several features of our American crocodile trackways clearly are consistent with the results of kinematic analyses of high-walking.…”

“…Crocodylians use different gaits during terrestrial locomotion, and may travel considerable distances overland (von Huene, 1913;Cott, 1961;Zug, 1974;Bustard and Singh, 1977;Parrish, 1987;Frey, 1988, Whitaker andAndrews, 1988;Gatesy, 1991;Richardson et al, 2002;Renous et al, 2002;Campos et al, 2003;Baier and Gatesy, 2013;Grigg and Kirshner, 2015). In this study we will be concerned mainly with the high walk of crocodiles on land, but will offer brief comments about aquatic locomotion as related to possible underwater traces.…”