Apparently chimpanzees, our closest primate relatives, are much smarter eaters than we are. That doesn’t come as a surprise, seeing as I have yet to hear reports of chimps crying in the corner with an entire bunch of bananas because the alpha male called him fat, or of teenage chimps running off with an entire horde of grapes to be consumed while mindlessly watching the people go by all day and night.
Modern economics, farming practices, and distribution networks have completely changed the way we eat. No longer are we forced to scavenger for food or run our prey down to exhaustion. No longer do we have to worry about certain plants spoiling or the seasons drying up a food source. Today we simply get fruits and vegetables from hydroponics bays or from tropical nations.
But these are still issues to chimps, and whether it’s engrained in their genetics or they’re making conscious decisions, they know what to eat and when to eat it.
Chimps in the African wild constrain their diets to fruit, leaves, plant stalks, roots, insects, and other vertebrate animals. The only difference between us and them in that last category is that they have absolutely no problem pounding prey to a pulp themselves before enjoying their tartare. You might even say that they follow the recently trendy Paleolithic diet – which I’m afraid to tell you makes absolutely zero sense evolutionarily speaking.
But I digress.
Humans aren’t the only animals that have Circadian cycles tuned into the sun and moon. If you look around a forest, you’ll quickly realize that breathing animals aren’t the only group of living organisms, either. Plans blooms with the changing of the day, take up nutrients depending on the sunlight, and even look more appetizing at certain times of the day.
And apparently chimps take notice, which is a good thing seeing as how when a plant looks it’s most delicious, it’s also at its nutritional height.
Researchers from Purdue University recently took careful observations of chimpanzees from Ngogo in Uganda’s Kibale National Park. They were specifically watching for when the inhabitants ate two species of saplings. After watching 41 adult males for nearly a decade and taking leaf samples during feeding periods, the scientists showed that the chimps ate their foliage at just the right times to get the most nutritional benefit from the leaves.
Pterygota mildbraedii is a very large tree, common throughout the Ngogo chimpanzee habitat. The chimpanzees, however, eat young leaves of the saplings found near the forest floor. This study found that the leaves’ hemicellulose – a more digestible fiber – and nonstructural carbohydrates – simple sugars and starch – increased 15 percent to 100 percent, respectively, from morning to evening. Cellulose and lignin, which make the leaves more difficult to digest, also decreased by day’s end. Celtis africana is a smaller tree than Pterygota, the saplings of which contain many thin branches and small leaves. The sugars in this plant’s leaves were found to double from morning to late afternoon.
As you might assume, the chimps chose to eat these two plants in the evenings rather than in the mornings.
“If these sugars or total non-structural carbohydrates are increasing, then the leaves are returning more calories late in the day,” said Bryce Carlson, an assistant professor of anthropology who studies primate ecology and nutrition in human evolution. “At this time, they may taste sweeter, and the chimpanzees may then learn and adjust their feeding behavior accordingly. We know they use vision, texture, taste and smell to gauge when to eat fruit, so it’s understandable to think they may do the same with leaves.”
No word yet on how the chimpanzee’s diet changes when Doritos are introduced in copious, continuous amounts.
The study, “Diurnal Variation in Nutrients and Chimpanzee Foraging Behavior,” was published in the American Journal of Primatology by Carlson, along with Jessica Rothman of Hunter College and John Mitani of the University of Michigan.