Ito’s CCI Plan

Interactions among Chimpanzee (Pan troglodytes) Infants

Noriko Ito
(Japan Monkey Centre)

Abstract

Researchers in primatology have often recognized the transition from infancy to adulthood as the progression from an immature to a mature state. This perspective is broadly applicable to most domains of research, from physical organs to societies. For example, the infant body is regarded as immature whereas the adult body is regarded as mature. However, this perspective is insufficient for fully understanding infancy. Indeed, a small infant body is needed to enable the mother to carry the infant. The same argument holds for the study of primate societies, but little research in this domain has been conducted from the aforementioned perspective (as an exception, see King, 2002).

This study examines how chimpanzee infants interact with each other, focusing on vocalizations known as “pant grants”. In primatology, the pant grant has been used as an indicator of a dominant/subordinate relationship among individuals. It has been assumed that subordinate individuals express pant grants to dominant individuals, and researchers have used this indicator to understand the hierarchy among adult males. Moreover, females and infants are usually viewed as subordinate to males. However, research has also recognized that interactions among males are qualitatively different from those between males and females. Furthermore, interactions between infants and adults are qualitatively different from the two kinds of interactions noted above. Although researchers have implicitly presumed that interactions among infants are “immature,” this presumption requires further examination.

It is not known exactly when infants start producing pant grants. However, I observed that wild chimpanzee infants living in Mahare Mt. National park (in Tanzania) uttered pant grants shortly after the birth. Using both cross-sectional and longitudinal methods, this study examines: (1) the situations in which chimpanzee infants produce pant grants, and (2) how vocalization and relational patterns change. Infants do not perform actions in isolation; these actions are always embedded in the social environment in which surrounding adults, including their mothers, engage in various activities. Some previous experiments have been notorious for eliminating the social environment of chimpanzees and then attempting to claim that chimps learn language in isolation (Fouts 1997). In this study, I will collect and analyze data derived from the social environment to overcome this individualistic perspective (i.e., development from immature infant to mature adult) and explicate the process by which the social environment itself changes.

References

• Fouts, R. 1997. Next of kin: What chimpanzees have taught me about who we are. New York: William Morrow.
• King B. 2002. On patterned interactions and culture in great apes. In: Richard G Fox & Barbara J King (eds). Anthropology Beyond Culture. New York: Berg.