Adaptive value of ambling gaits in primates and other mammals

Abstract

SUMMARY At speeds between the walk and the gallop, most mammals trot. Primates almost never trot, and it has been claimed that they transition directly from a walk to a gallop without any distinctive mid-speed running gait. If true,this would be another characteristic difference between the locomotion of primates and that of most other quadrupedal mammals. Presently, however, few data exist concerning the actual presence or absence of intermediate-speed gaits (i.e. gaits that are used between a walk and a gallop) in primates. Video records of running in twelve primate species reveal that, unlike most other mammals, all the primates studied almost exclusively adopt an `amble' -an intermediate-speed running gait with no whole-body aerial phase - rather than trot. Ambling is also common in elephants and some horses, raising the question of why ambling is preferred over trotting in these diverse groups of animals. Mathematical analyses presented here show that ambling ensures continuous contact of the body with the substrate while dramatically reducing vertical oscillations of the center of mass. This may explain why ambling appears to be preferable to trotting for extremely large terrestrial mammals such as elephants and for arboreal mammals like primates that move on unstable branches. These findings allow us to better understand the mechanics of these unusual running gaits and shed new light on primate locomotor evolution.

The three-dimensional locomotor dynamics of African (Loxodonta africana) and Asian (Elephas maximus) elephants reveal a smooth gait transition at moderate speed

“…We speculate that this may be because more compliant limb mechanics can attenuate transient impact forces on the feet (McMahon 1985;McMahon et al 1987;Blickhan 1989), and hence reduce the risk of limb injury incurred by the massive body weight. In addition, bouncing limb mechanics helps to modulate vertical CM oscillations Schmitt et al 2006), which may be particularly critical for the locomotor stability (and efficiency) of large quadrupeds.…”

“…As Gambaryan (1974) also noted, elephants have extraordinarily rigid bodies; hence, we expect that our assumption that the body is effectively rigid is more justifiable for them than for most other animals. The second gait of elephants could be called an amble, intermediate gait or run (Muybridge 1899;Gambaryan 1974;Alexander et al 1979;Ahn et al 2004;Schmitt et al 2006), and raises the question of whether gaits may be better defined by individual limb dynamics (e.g. vaulting or bouncing of particular limbs) rather than whole-body CM dynamics (Biewener 2006;Biknevicius & Reilly 2006).…”

Stability During Arboreal Locomotion

“…Many arboreal primates, the wooly opossum, and the kinkajou reduce the vertical oscillation of the center of mass while walking on branches (Schmitt, 1999;Schmitt and Lemelin, 2002;Schmitt et al, 2006;Young, 2009;Lemelin and Cartmill, 2010). A gait frequently employed to reduce vertical oscillation is the amble, first termed by Schmitt et al (2006).…”

“…A gait frequently employed to reduce vertical oscillation is the amble, first termed by Schmitt et al (2006). During ambling locomotion, the duty factor is less than 50% and the footfall pattern is trot-like or diagonal sequence, but there is no aerial phase.…”

Comparative morphometric analysis of the proximal femur of African hominids and felids

“…[4][5][6]10 All quadrupedal vertebrates are essentially hindlimb driven and, the unusual 'diagonal sequence' gait typical of primates notwithstanding, hindlimb drive is employed in recognition of the simple fact that the pelvic and proximal hindlimb musculature is the primary source of initial power input at commencement of the gait cycle from a static position of rest. [11][12][13][14] The principal function of the musculoskeletal components of the hip joint are akin to the stroke cycle of a piston rod (or main rod) which powers the main driving wheels in the propulsion of steam-powered locomotives. 15,16 Cyclical rotations and angular excursions of the spherical femoral head within its ball-and-socket joint and the shaft of the femur during contact phases of gait, particularly at optimal and peak velocities, are critical in maintaining momentum and direction of the centre of mass.…”