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Importance of Timing Activities:
The Adaptive Significance of Cathemerality in the Brown Lemurs in the Dry Forest of Northwestern Madagascar

Despite the contrasting niches during daytime and nighttime, primates known as cathemeral exhibit significant levels of activity throughout both the day and night. As cathemeral primates have some intermediary traits of diurnal and nocturnal primates, they are likely to enhance our understanding of the evolutionary direction of temporal niches and activity patterns in primate ancestors. The adaptive significance of cathemerality in Malagasy primates has been suggested as a thermoregulation strategy to avoid heat/cold stress, an antipredator strategy to avoid diurnal raptors, a dietary metabolic-related strategy to get energy using fibrous food during periods of fruit scarcity, and a dehydration-avoidance strategy with increasing water rich-food consumption and long midday resting to maintain water balance under high daytime temperatures and long dry season. Nocturnal activity has been interpreted as fulfilling energy requirements. Although these hypotheses are associated with seasonality of environmental factors in Madagascar, previous studies tested these hypotheses in rainforests but little investigation has been effectuated in dry forests. The dietary metabolic-related strategy was pointed out as the strongest variable determinant of cathemerality in brown lemurs in the eastern rainforests of Madagascar, but is that true for the brown lemurs in the northwestern dry forests? Diurnal and nocturnal behavioral observations of brown lemurs over 9 months, equally distributed in dry and wet seasons, were conducted in a dry forest in northwestern Madagascar. In this seminar, after a brief introduction to cathemerality, I will report the results of our research on cathemeral feeding ecology, and then, discuss the adaptive significance of cathemerality in brown lemurs.

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