In this study, the locomotor activity of a nocturnal prosimian, the slow loris (Nycticebus coucang), was monitored under an experimentally varied light regime. During the process of reversing their day-night cycle, activity was monitored for a light-dark cycle roughly correlating to the external day-night, a free-running period in total darkness followed by a reversed day- night light regime. Under constant conditions an endogenous cycle was shown to be present. During the artificial light regimes, locomotor activity became synchronized to the period of darkness.

Communication and. social behavior of a prosimian primate, Nycticebus coucang, were studied to gain a better understanding of communication and social behaviors of the Order Primates. Four adult females, two adult males, and one juvenile male were the subjects for the study. The focal animal technique was used to observe communicative and social behavior. Vocal behaviors were sonagraphically analyzed. Probability of occurrence was calculated for all behavior categories observed. Conditional probabilities were calculated for the eight most frequently occurring behaviors in a lag sequential analysis. Results of the probability of occurrence analysis showed that agonistic behaviors occurred rarely or not at all, depending on the individual, and that there were few differences between the behavior of males and females. Results of the lag sequential analysis showed that there were no clear sequences of behavior. Results of the sonagraphic analysis showed that vocal behaviors could reach ultra-sonic levels. Differences between the present data and comparative data presented in other studies of prosimians are discussed, as are problems with the lag sequential analysis.