Cathemerality in the mongoose lemur, Eulemur mongoz

Results of a 10 month study of the mongoose lemur (Eulemur mongoz) at Anjam ena are presented. The activity pattern is documented in detail for both we t and dry seasons based on observations conducted over the entire 24 h peri od. E, mongoz was found to be cathemeral throughout the year but exhibited shifts towards more diurnal activity in the wet season and more nocturnal a ctivity in the dry season. The cathemeral activity pattern in the mongoose lemur appears to be coordinated with sunrise, sunset, and day length and mo dulated by an inhibitory effect of low nocturnal light intensity in the for est during the wet season, resulting in mainly diurnal activity. Temperatur e and rainfall may also influence the activity pattern. Few advantages to f ood-related behavior appear to derive from this activity pattern, although resource accessibility may be enhanced by nocturnal behavior in the dry sea son, leading to reduction in interspecific competition, Cathemerality may a lso represent a behavioral thermoregulatory mechanism allowing the mongoose lemur to conserve energy by being active during the cool nights of the dry season. In addition, nocturnal behavior in the dry season probably allows avoidance of predation by raptors at the time of year when least protection is afforded by vegetation. Am. J, Primatol, 47:279-298, 1999. (C) 1999 Wil ey-Liss, Inc.