Socio ecology of the blue monkeys (Cercopithecus mitis stuhlmanni) of the Kibale Forest, Uganda

Rasanayagam Rudran. Socioecology of the Blue Monkeys (Cercopithecus mitis stuhlmanni) of the Kibale Forest, Uganda. Smithsonian Contributions to Zoology, number 249, 88 pages, 34 figures, 58 tables, 1978. —This study was conducted between December 1972 and November 1974 and included some 2100 hours of observation. Blue monkeys usually lived in "one-adult male" social groups that included 13 to 27 animals (X = 20.8). The large disparity in the adult sex ratio of these groups was partly accounted for by the emigration of young males that lived as solitary individuals at least for a short period after leaving their parental groups. Blue monkeys frequently formed large mixed-species groupings with one or more of the other primates living in the study area and these associations probably functioned in the avoidance of predation. Associations with the folivorous red colobus (Colobus badius) probably enhanced the acquisition of invertebrate food, while other types of associations, particularly with redtails (Cercopithecus ascanius), may have resulted in efficient location of food resources. Polyspecific associations seemed to be avoided during the times blue monkeys fed on plant foods. Blue monkeys exploited a large number of food plants but tended to be selective feeders. Fruits were usually the most frequently used plant component, but foliar foods and invertebrates were periodically used at high frequencies. Spearman rank correlation tests indicated (1) a significant negative correlation between the frequency of use of fruits and indices of diet diversity computed on the basis of the Shannon-Wiener equation, and (2) a significant positive correlation between the frequency of use of foliar foods and indices of diet diversity. The use of food resources showed considerable intermonthly variations and depended on availability, relative abundance, and the dietary preferences of the blue monkeys. The frequency of food intake and the composition of the diet of four age /sex classes were found to differ. The adult male seemed to adopt a "time minimizing" feeding strategy and exploited a larger proportion of fruits and a smaller proportion of invertebrates than adult females, subadults, and juveniles. Blue monkeys of the Kibale Forest occupied relatively large home ranges. On a daily basis, however, they used only a small portion of their home range and the size of daily ranges varied appreciably during different sample periods. Overlaps in areas used on different days of a sample period were usually small. Thus on the average less than 5% of the area used during a sample period was used on all five days of the sample period, while about 66% was visited on only one day of the sample period. Phenological data collected during the study suggested that differential use of the home range was affected by variations in food abundance. Spearman rank correlation tests showed that ranging patterns were related to the location and exploitation of abundant food resources. In addition the ranging patterns appeared to be partially affected by climatic factors and the location of areas used for night resting. OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institution's annual report, Smithsonian Year. SERIES COVER DESIGN: The coral Montastrea cavernosa (Linnaeus). Library of Congress Cataloging in Publication Data Rudran, Rasanayagam Socioecology of the blue monkeys (Cercopithecus mitis stuhlmanni) of the Kibale Forest, Uganda. (Smithsonian contributions to zoology ; no. 249) Bibliography: p. 1. Cercopiihecus mitis —Behavior. 2. Social behavior in animals. 3. Animals, Food habits of. 4. Mammals—Ecology. 5. Mammals—Uganda—Kibale Forest Reserve. I. Title. II. Series: Smithsonian Institution. Smithsonian contributions to zoology ; no. 249. QL1.854 no. 249 [QL737.P93] 591'. 08s [599'. 82] 76-608404