Irwin S. Bernstein
A field study of the Lutong, (Presbytis cristatus) was conducted in Malaya. Lutong troops were observed for more than 1000 hours and were found to be markedly territorial. Only one control male lives in each troop and he actively defends the territory against incursions by other lutong males. Each troop moves slowly through its territory feeding and resting and comes into frequent visual contact with adjacent troops. Each troop is a well organized social unit but only the control males show consistent hostility to one another when troops meet. Grooming, play, sexual responses, maternal behavior and agonistic episodes are described as well as travel, feeding and diurnal patterns. These patterns appear similar to those reported in other Presbytis species, but contrast markedly with macaque and baboon reports. Differences in behavior between species of Presbytis do not exceed differences reported in the same species by different observers in different areas.
Lawrence G. Sharpe and Irwin S. Bernstein
A group of eleven rhesus monkeys selected to approximate a small natural group were allowed to establish a social organization and to live with minimal disturbance in a specially designed compound. Observations were made on a variety of social and individual activities with some manipulation of feeding used to get at specific behavior patterns. Quantitative data on the frequency of activities for each member of the group was obtained. Individual animals were found to fall into subgroup classification in terms of activity patterns observed. This role differentiation was consistent despite minor modifications observed in some individuals. The subgroups correspond by the large to morphological divisions of size and sex, but status also contributed to the differentiation of roles. The role of the dominant male was analyzed in detail and found to supercede that of simple preempting of incentives. Less elaborate analyses were made for other clearly differentiated roles in the group.