Scaling of avian bipedal locomotion reveals independent effects of body mass and leg posture on gait

Abstract

Birds provide an interesting opportunity to study the relationships between body size, limb morphology and bipedal locomotor function. Birds are ecologically diverse and span a large range of body size and limb proportions, yet all use their hindlimbs for bipedal terrestrial locomotion, for at least some part of their life history. Here, we review the scaling of avian striding bipedal gaits to explore how body mass and leg morphology influence walking and running. We collate literature data from 21 species, spanning a 2500× range in body mass from painted quail to ostriches. Using dynamic similarity theory to interpret scaling trends, we find evidence for independent effects of body mass, leg length and leg posture on gait. We find no evidence for scaling of duty factor with body size, suggesting that vertical forces scale with dynamic similarity. However, at dynamically similar speeds, large birds use relatively shorter stride lengths and higher stride frequencies compared with small birds. We also find that birds with long legs for their mass, such as the white stork and red-legged seriema, use longer strides and lower swing frequencies, consistent with the influence of high limb inertia on gait. We discuss the observed scaling of avian bipedal gait in relation to mechanical demands for force, work and power relative to muscle actuator capacity, muscle activation costs related to leg cycling frequency, and considerations of stability and agility. Many opportunities remain for future work to investigate how morphology influences gait dynamics among birds specialized for different habitats and locomotor behaviors.

Growth Dependent Changes in Pressure Sensing Walkway Data for Turkeys

“…When velocity remains relatively constant duty factor is calculated: contact time/gait cycle time with a duty factor >0.5 indicating a support phase or the fraction of a stride in which the foot is in contact with the ground ( 22 , 23 ). In the current study, duty factor did increase linearly from 0.65 to 0.79 as the birds aged in the right leg ( P = 0.02).…”

Endochondral ossification and the evolution of limb proportions

“…Alternatively, the available evidence suggests that proliferation and cell number may be evolutionarily ancient determinants of limb bone allometry shared between birds and mammals, while modulation of chondrocyte hypertrophy, or the ability for extreme chondrocyte hypertrophy, is an evolutionary innovation among mammals. This may explain, for example, why extreme hypertrophy has been documented in several mammalian species with divergent limb proportions (Figure ), but not so far in avian species, even in the relatively elongated tarsometatarsus of storks and the flightless rheas (Daley & Birn‐Jeffery, ; Kember et al, ). Further phylogenetic analyses comparing mammals and birds with extreme limb proportions to their “normally” proportioned relatives (e.g., tarsiers vs. other haplorrhine primates, macropods vs. possums) will be necessary to test this hypothesis.…”

Spring-loaded inverted pendulum goes through two contraction-extension cycles during the single stance phase of walking

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