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.
Highlights
Introduction: comparative biomechanics of striding bipedalism Humans walk and run bipedally, with two legs moving in an alternating pattern, a half-cycle out of phase (Alexander, 2004)
Do striding birds maintain dynamically similar gaits with variation in body size? Literature search and meta-analysis of scaling of avian bipedal gaits Here, we review literature data on avian walking and running to test the dynamic similarity hypothesis
The empirical scaling trends from our analysis across 21 species and a >2500-fold range in body mass reveals that large animals consistently use relatively higher stride frequencies and shorter stride lengths compared with small animals at equivalent dimensionless running speeds (Fig. 5, Table 4)
Summary
As a function of speed (Abourachid, 2001; Alexander, 2004, 1984; Gatesy and Biewener, 1991; Heglund et al, 1982; Maloiy et al, 1979). Considering the sparse sampling of species in previous scaling studies on bipedal gait, ranging from four to eight species (Gatesy and Biewener, 1991; Heglund et al, 1982; Maloiy et al, 1979), a single outlier could substantially skew scaling trends. We consider it timely to review the literature evidence for body mass scaling and leg postural factors in avian bipedal gaits. Dimensional analysis can be used to derive appropriate scaling factors to convert all physical quantities to dimensionless values from these base units (Table 2)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
