Ontogenetic Scaling of Fore- and Hind Limb Posture in Wild Chacma Baboons (Papio hamadryas ursinus)

Abstract

Large-scale interspecific studies of mammals ranging between 0.04–280 kg have shown that larger animals walk with more extended limb joints. Within a taxon or clade, however, the relationship between body size and joint posture is less straightforward. Factors that may affect the lack of congruence between broad and narrow phylogenetic analyses of limb kinematics include limited sampling of (1) ranges of body size, and/or (2) numbers of individuals. Unfortunately, both issues are inherent in laboratory-based or zoo locomotion research. In this study, we examined the relationship between body mass and elbow and knee joint angles (our proxies of fore- and hind limb posture, respectively) in a cross-sectional ontogenetic sample of wild chacma baboons (Papio hamadryas ursinus) habituated in the De Hoop Nature Reserve, South Africa. Videos were obtained from 33 individuals of known age (12 to ≥108 months) and body mass (2–29.5 kg) during walking trials. Results show that older, heavier baboons walk with significantly more extended knee joints but not elbow joints. This pattern is consistent when examining only males, but not within the female sample. Heavier, older baboons also display significantly less variation in their hind limb posture compared to lighter, young animals. Thus, within this ontogenetic sample of a single primate species spanning an order of magnitude in body mass, hind limb posture exhibited a postural scaling phenomenon while the forelimbs did not. These findings may further help explain 1) why younger mammals (including baboons) tend to have relatively stronger bones than adults, and 2) why humeri appear relatively weaker than femora (in at least baboons). Finally, this study demonstrates how field-acquired kinematics can help answer fundamental biomechanical questions usually addressed only in animal gait laboratories.

Kinematics and spatiotemporal parameters of infant‐carrying in olive baboons

“…Concerning limb posture, according to Biewener's (1989) theory on mammals, and Polk (2002) and Patel et al (2013) on monkeys, we predicted that loaded females would extend their hind limbs more while carrying an infant, and that, given the range of infant body mass, this would become more significant as the infant becomes heavier. However, our results show that, on average, the hind limbs are no more extended when the female is loaded.…”

Segmental morphometrics of the olive baboon (Papio anubis): a longitudinal study from birth to adulthood

“…Rose, ; Raichlen, ; Patel et al. ). Our results support this assumption in the sense that the CoM (linear effects) and RG (rotational effects) are always more distally positioned, relative to limb lengths, in the forelimbs than in the hindlimbs.…”

“…We used a typical body posture (quadrupedal standing) observed in the wild with an average elbow joint angle of 155° and knee joint angle of 138° for all morphotypes (see Patel et al. ). We calculated the position of the whole body centre of mass (BCoM) in this posture, as well as the fore‐ and hindlimb centre of mass (CoM1 and CoM2, respectively).…”

“…) and in their biomechanics (see hindlimb compliance in Patel et al. ). With regard to morphometrics, we hypothesized that females would have a lower rate of mass gain and that this pattern would end earlier than in males.…”

Bipedalism in non-human primates: a comparative review of behavioural and experimental explorations on catarrhines

“…With regard to the kinematics of primary locomotor modes, this can be done by means of video recordings (see e.g. [132] on quadrupedal baboons). However, bipedal behaviour has never been investigated experimentally in the wild; its occasional nature and the constraints due to natural environmental conditions drastically limit the possibilities for experimental investigations of animals in the wild.…”