Social organization of free-ranging ruffed lemurs, Varecia variegata variegata: mother-adult daughter relationship.

The relationship between a mother and an adult daughter is examined in a group of free-ranging ruffed lemurs (Varecia variegata) at the Duke University Primate Center (DUPC). Although the two females were affiliative during the birth season, interactions during the mating season were predominantly agonistic. The maturing daughter was dominant to the mother, as has been observed in many caged social groups at the DUPC. Although both mother and daughter produced offspring in the same group, the daughter subsequently aggressively evicted the mother from the enclosure. It was not possible to maintain more than one long-term resident breeding female in the same social group. This pattern contrasts with observations of affiliation among breeding females in the wild. © 1992 Wiley-Liss, Inc.

Activity Budgets, feeding behavior, and habitat use of pygmy chimpanzees at Lomako, Zaire.

Data from 250 hours of focal animal sampling in the Lomako Forest of central Zaire show pygmy chimpanzees spent 70% of feeding time on fruit and 25% on young leaves. Feeding and resting each accounted for about 40% and traveling less than 20% of the time. Sitting was the most frequent feeding posture. Locomotion was predominantly quadrupedal walking and quadrumanous climbing. Most feeding and resting occurred above 30 m. Pygmy chimpanzees spent most time in primary forest. Activity budgets varied with forest type. Most levels were used in each forest type. Pygmy chimpanzees spent most time in the canopy when in primary and slope (Bolafa) forests, and on the ground in secondary forest. These results show pygmy chimpanzees as arboreal, but habituation may have influenced the results. Pygmy chimpanzees at Lomako and Wamba have similar diets, despite differences in methods of data collection. At Wamba and Lomako, pygmy chimpanzees use secondary forest more and swamp forest less than expected given the abundance of each forest type at both sites.

Pygmy chimpanzee social organization: Variation with party size and between study sites.

Descriptions of social organization based on interactions are difficult for fission-fusion primates, such as pygmy chimpanzees, as interactions may depend on association in parties. Frequencies of male-male and male-female affiliative and female-male and female-female aggressive interactions among Lomako pygmy chimpanzees occurred in proportion to the presence of each sex in parties. Male-male aggression and female-male affiliation, however, were more frequent than expected on the basis of party membership. Females with small swellings received more grooming and less mating than expected. Patterns of interactions at Lomako also varied with party size. Female-female affiliation predominated in small parties, while male-female affiliation predominated in larger parties. This trend parallels observed differences between the Lomako and Wamba study sites. Male-female affiliation is more frequent at Wamba where party sizes are larger. Differences between study sites may also reflect provisioning, habituation, predator threat, and habitat. Provisioning at Wamba may result in higher frequencies of aggression among males and lower levels of aggression among females. Comparison between earlier and later Lomako studies suggests that increased habituation is associated with greater differences from, rather than more similarity to, results from Wamba. Differences between Lomako and Wamba in habitat, provisioning, and human (but not non-human) predation, by affecting party size and composition, most likely account for the observed differences in social organization between the two sites.