Matrilineal distribution of louse egg-handling techniques during grooming in free-ranging Japanese macaques.

Grooming behavior of which the primary function appears to be the removal of lice on other (Tanaka and Takefushi [1993] Anthropological Science 101:187-193) was studied in Japanese maceques at Jigokudani Monkey Park, Japan, June 1990-July 1993. Several louse egg-handling techniques used during grooming were identified (with differences in efficiency) in a free-ranging group. In the low-ranking maternal lineages, the distribution of these techniques is quite homogeneous, suggesting social transmission with goal emulation (one form of social learning) based on maternal kin. However, there is considerable variation in the high-ranking matriline. The social system of dominance--the tendency of subordinates to groom more often than to be groomed--may result in oblique transmission of more effective techniques from low-ranking monkeys to some offspring of high-ranking females.