Why Create Novel
Overall, gestures foster more efficient social relations. At the beginning of my observations the 13-year-old silverback male Kubie and the 8-year-old female Zura performed the great majority of gesturing in the San Francisco group. Zura was Kubie's playmate primarily while Bawang, his preferred mate, was pregnant and nursing her first baby (by Kubie). Kubie showed sexual interest in Zura, but her response was sometimes a rather uncooperative or teasing one. Kubie often had to find ways to persuade her to play and to keep her from running away. Kubie’s gestures provided gentle enticement to a relatively inexperienced and uncooperative partner, and Zura’s gestures communicated her level of receptivity or reluctance. (Though mating has been seen, Zura has never become pregnant).
The gesturing of Kubie and Zura also served to reduce male-male conflict between Kubie and his father Bwana, both mature silverbacks. Their novel gestures were silent and did not attract attention from Bwana. In addition, gestures may be a way to save energy. Kubie was twice the size of Zura, and for the large male body gestures used less energy than chasing and forceful action. Gestures promoted male-female cooperation in a physical environment where females could leave if they desired (up trees safe only for the lighter female body, or indoors through a door too small for the males).
Ultimately, gestures improve social interaction and perhaps enhance reproductive success.
Gesture appears to be a response to necessities in the social and physical environment, therefore, gesturing changes. As we continued to observe the gorillas after the initial period of study of Kubie and Zura's elaborate gesturing, suddenly almost all gesturing stopped for several years. This was quite curious, considering previous copious gesturing. Several factors seemed to be in play: Kubie's preferred mate, Bawang, came back into estrus after her first baby, Shango, stopped nursing, and Kubie began to pursue her obsessively, ignoring Zura. Bawang would often exit into the indoor quarters where he could not follow, and her interest or lack of interest in Kubie was uncompromising and did not involve playful interaction. Around the same time, there was a period of major building and construction at the Zoo, and the noise from this also seemed to inhibit and stress the gorillas' playful behavior.
Then, another period of much gesturing began as Kubie's two sons, Shango and Barney, began to grow up. From the age of five years onward, Shango played wildly with both his father, Kubie, and younger brother, Barney. Shango took an interest in Zura and their play involved positioning gestures as well as others. Barney began to develop his own favorite gestures, which differed from Shango's favorites in both quantity and usage.
And at present the story goes on; the death of Kubie and the transfer of Shango and Barney to another zoo in 2004 was soon followed by the introduction of a new silverback, OJ (Oscar Jonesy). Bawang and her third offspring, the female Nneka, both interact in fascinating ways with OJ, including some new gesturing. In 2006, another young female, Monifa, was introduced to the group. Monifa and OJ produced a male offspring, Hasani, born in December 2008. Monifa rejected the baby, who was reared by human caregivers for a few months. He was subsequently adopted by experienced mother Bawang and by age 6 months was successfully integrated into the whole group. To be continued!
(For more detailed information see Tanner, Joanne E. & Byrne, Richard W. (1999). The development of spontaneous gestural communication in a group of zoo-living lowland gorillas. In: The Mentalities of Gorillas and Orangutans: Comparative Perspectives, pp. 211-239. Ed. Parker, S.T., Mitchell, R.W., and Miles, H. Lyn. Cambridge University Press, Cambridge, UK.)