1Anthropology, Purdue University, 2Anthropology, University of Michigan
Friday All day, Plaza Level
Primatologists have long observed diurnal variation in the consumption behavior of wild chimpanzees, with young leaves most often consumed in the afternoon or early evening. Plant biologists have also recognized that the processes of photosynthesis and plant metabolism result in nutrient compositions that cycle over a 24-hour period. This project seeks to fuse these observations, asking whether those foods consumed most preferentially at one time of day likewise exhibit the highest nutrient content at that particular time.
Two species of sapling commonly consumed within the Ngogo chimpanzee dietary niche (Pterygota mildbraedii and Celtis africana) were selected as particularly representative of those consumed most frequently in the afternoon and early evening. Young leaves were collected from 5 individual trees of each species at dawn, midday, and dusk towards the end of the dry season in late-July and early-August. It was expected that concentrations of carbohydrate and protein should increase throughout the day as products of photosynthesis and resultant downstream anabolic processes.
Nutrient analyses revealed increasing sugar content among Celtis africana saplings and decreasing fiber fractions among Pterygota mildbraedii across the photoperiod. Both nutrient trends represent increasing nutritional value over the course of the day, which is consistent with increased consumption among the Ngogo chimpanzees. This study represents the first such evidence linking chimpanzee consumption with diurnal nutrient variability. These results suggest that future foraging studies should consider the impact of temporal variation on food quality and choice.
This study was funded by the National Science Foundation, grant number 0925785, and The Leakey Foundation.