The waning of dependence in infant free-ranging yellow baboons (Papio cynocephalus) of Mikumi National Park.

Development toward independence during the early years of baboon life is reflected in the infant's transition from riding on its mother to walking on its own during progressions from one location to another. This transition was studied during the first year of life in 55 infants from two differently sized troops living in Mikumi National Park, Tanzania. There was a nearly linear transition in the first year from almost 100% ventral riding to almost 100% walking. The amount of dorsal riding started near zero, reached a plateau lasting from about the 15th to the 26th wk of life, and then gradually declined to zero. Dorsal riding did not replace ventral; rather, dorsal riding increased in frequency until it occurred about as often as ventral riding. Prolonged ventral riding by infants of the smaller of the two troops may have been due to spacing differences or to greater nervousness among members of the smaller troop. There were no significant differences in riding or walking associated with the time of day or the infant's sex. The rate of transition from riding to walking was greatest from about the fifth to the seventh months, which may be especially significant time in the early development of independence.