From the individual-based records of hunting practice for 1,633 hr in total and from the hunters' visual acuity and grip strength observed among the Gidra Papuans in lowland Papua New Guinea, this paper aims to analyze the relationship between the hunting activity and aging. The sensori-motor functions determine the range of age in which the individuals act as active or productive hunters: determined to be from the late teen-age years to about 45 years among the present subjects. In this age range, hunting efficiency increases with age. In terms of weight of animals killed per hunting time, the efficiency of the elder married (aged about 35 to 45 years) was almost four times higher than that of the unmarried (16-17 to late 20s). This aging effect is judged to depend on behavioral abilities that increase in accordance with experience and cumulative knowledge. Simultaneously, the comparison of individual hunters' records in 1971-72 and in 1981 reveals that hunting efficiency is associated with the individualities of the hunters.