| Western lowland gorillas (Gorilla gorilla gorilla) primarily live in single-male, multi-female troops. Group cohesion is maintained through female preference for the same male. When multiple females exhibit proceptive behavior, males choose to mate with high-ranking females even when those females are not in estrous to our knowledge. No studies examine male preference outside of reproductive contexts, but these are likely in group-living species. Proximity is often used as an indicator of social preference in gorillas. Using 2-minute scan sampling, we measured proximity (≤5m) between silverbacks and females in four gorilla troops at three zoos (three females/group, 1553-6384 observations/male). We used two-proportions Z-tests to determine if there were significant differences between time spent alone versus with a female, and between time spent with each female. Overwhelmingly, males preferred to be alone (p<0.0005), with each male spending less than a quarter of their time in proximity with females. At Louisville Zoo, the silverback spent 91.6% (p<0.0005) of his social time with one female. The silverback from Omaha's Henry Doorly Zoo spent almost equal time between two females (35% and 37%; p=0.335) but spent 10% less time with the third (p<0.0005). At the Columbus Zoo, both silverbacks showed a preference for one female (p<0.0002). While males spend most of their time away from females, these results suggest males do exhibit preference for particular females outside of mating. |
