期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2014
卷号：111
期号：46
页码：16343-16348
DOI：10.1073/pnas.1407524111
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceHow do large-brained primates maintain high rates of energy intake when times are lean? By analyzing early-morning departure times and sleeping nest positioning of female chimpanzees as a function of the ephemerality of next day's breakfast fruit and its location, we found evidence that wild chimpanzees flexibly plan when and where they will have breakfast after weighing multiple factors, such as the time of day, their egocentric distance to, and the type of food to be eaten. To our knowledge, our findings reveal the first clear example of a future-oriented cognitive mechanism by which hominoids, like great apes, can buffer the effect of seasonal declines in food availability and increased interspecific competition to facilitate first access to nutritious food. Not all tropical fruits are equally desired by rainforest foragers and some fruit trees get depleted more quickly and carry fruit for shorter periods than others. We investigated whether a ripe-fruit specialist, the chimpanzee (Pan troglodytes verus), arrived earlier at breakfast sites with very ephemeral and highly sought-after fruit, like figs, than sites with less ephemeral fruit that can be more predictably obtained throughout the entire day. We recorded when and where five adult female chimpanzees spent the night and acquired food for a total of 275 full days during three fruit-scarce periods in a West African tropical rainforest. We found that chimpanzees left their sleeping nests earlier (often before sunrise when the forest is still dark) when breakfasting on very ephemeral fruits, especially when they were farther away. Moreover, the females positioned their sleeping nests more in the direction of the next day's breakfast sites with ephemeral fruit compared with breakfast sites with other fruit. By analyzing departure times and nest positioning as a function of fruit type and location, while controlling for more parsimonious explanations, such as temperature, we found evidence that wild chimpanzees flexibly plan their breakfast time, type, and location after weighing multiple disparate pieces of information. Our study reveals a cognitive mechanism by which large-brained primates can buffer the effects of seasonal declines in food availability and increased interspecific competition to facilitate first access to nutritious food. We discuss the implications for theories on hominoid brain-size evolution.
