Abstract # 29:

Scheduled for Thursday, June 21, 2007 02:45 PM-03:00 PM: Session 5 (North Main Hall E) Oral Presentation

Reproductive Behavior of Male Mountain Gorillas Living in Multi-male Groups (Gorilla beringei beringei)

T. S. Stoinski1,2, S. Rosenbaum2 and K. A. Fawcett2
1Zoo Atlanta, 800 Cherokee Ave. SE, Atlanta, GA 30315-1440, USA, 2Dian Fossey Gorilla Fund International
     In the last decade, the mountain gorilla groups monitored by the Karisoke Research Center have experienced a threefold increase in the number of subadult and adult males and a two- to four-fold increase in the number of adult females. The current study examined reproductive behavior of males under these unique demographic conditions. Subjects included 27 subadult and adult males ranging in age from 8 to 30 years living in three groups in the Parc National des Volcans, Rwanda. Data on copulations were collected using focal animal and all occurrence sampling (N=580 hours). Copulation patterns varied as a function of both individual- and group-level factors. Rank was a significant predictor of total copulations [Spearman Rank Order Correlations, N=27 for all, r=0.49; p=0.01] and those with cycling females [r=0.57, p<0.01] but not of those with pregnant [r=0.21; p=0.3] or subadult females [r=0.17; p=0.4]. Specifically, the three top-ranking silverbacks bred equally with cycling females but at much higher frequencies than subordinate silverbacks and blackback males [c2(4)=158.2, p<0.001]. Relatedness influenced copulation patterns, with males copulating more frequently with paternal than maternal relatives [c2(1)=15.6, p<0.001]. The results will be compared to those of previous studies to highlight the flexibility of gorilla reproductive behavior and the importance of demographic influences on behavior. Support provided by the Leakey Foundation.