Development of quadrupedal locomotion on level surfaces in Japanese macaques.

Longitudinal comparisons of high-speed quadrupedal locomotion on level surfaces were made on 4 infant Japanese macaques (Macaca fuscata) with normal mother-infant relationships. Compared to adults, infants exhibited considerable variation in each step of locomotion. Braking components of foot force tended to be larger in the forelimb than in the hindlimb during the infant stage of development. Conversely, accelerating components were larger in the hindlimb than in the forelimb. In 1- and 2-month-old infants, vertical components in the hindlimb were not significantly larger than those of the forelimb. Fore- and hindlimb differentiation in infant Japanese macaques resembles that of adult macaques even at this early stage of development.