The vast majority of primates, including humans, possesses anatomical and behavioral adaptations for either a nocturnal (night-active) or diurnal (day-active) lifestyle. A group of prosimian primates in Madagascar, however, displays a distinctly different activity cycle where there is a potential for activity at any time of the day or night. Although such 24-hour activity is common among other mammalian species, it is extremely unusual in primates. Therefore, in this proposed dissertation study, fifteen months of data will be collected to examine the 24-hour activity in two lemur species, the mongoose lemur (Eulemur mongoz) and the common brown lemur (Eulemur fulvus fulvus). The research will be conducted in the tropical dry forest of Ankarafantsika Nature Reserve in northwest Madagascar. Specifically, this study will attempt to determine whether 24-hour activity in these primates is driven by such features of their natural environment as food availability, predator pressure, and climate. In addition, this study will examine whether any differences exist between the lemurs' daytime and nighttime behavior. The results of this research will be used to generate a model explaining why a 24-hour activity cycle is adaptive for these primates, and to also reach a better understanding of the importance of activity cycle in the evolutionary history of human and non-human primates.
