Life should be a breeze in the tropical forest. The weather is warm, and there’s plenty of food for the asking. In theory, you need only reach out and luscious fruits and other tidbits will fall into your hands. Sadly, it’s not so, says Katharine Milton--particularly if you’re a monkey. Milton, a physical anthropologist at the University of California at Berkeley, has spent the last 20 years studying howler and spider monkeys in the forests of Panama. Life, she’s concluded, is tough in the forest-- animals need to devise all sorts of ingenious tactics just to get enough food to survive. Finding food is so tough, Milton thinks, that successful strategies have driven the evolution of the species. It is the solutions to the problems of diet that have made primates primates, she says. And what pertains to forest primates pertains as well to their city-slicker cousins--us. In other words, the food we eat has made us human.
Milton began her observations in 1974 on the island of Barro Colorado in Panama. For the fledgling anthropologist--Milton was then a New York University graduate student--it was an ideal spot. The island offered a protected forest inhabited by numerous species of wild animals, including howler monkeys--13- to 18-pound primates notorious for their terrifying, unearthly howls. It was also the site of a Smithsonian Institution research station, complete with an extensive herbarium for identifying indigenous plants.
Milton threw herself into her work. I’d get up every morning at 4:30, go to the dining hall, stuff as much food in my face as I could, make a bunch of peanut butter sandwiches, fill my water bottle, then walk into the forest to where I’d left the monkeys the night before, she recalls, in the twang of her native Montgomery, Alabama. I’d sit on a log in the dark, and as soon as they started to wake up at dawn, about 6, I’d start taking notes. She would then follow the monkeys as they meandered along the forest canopy some 80 feet above, note where they stopped to eat, and collect the scraps of food that dropped to the ground.
I’d follow them until 6 P.M., when it got dark, and watch them settle down for the night. Then I’d run back with a flashlight, jumping down the trail like a little goat. I’d get to the dining hall, nobody there, but the cook would have made a plate for me and covered it with tinfoil. I’d gobble down my dinner, run to the herbarium and identify my plant scraps, take a shower, and go to bed. And the next day the same thing.
Thus passed the bulk of three years. Milton found that most of the time the howlers ate leaves and fruit in almost equal measure, but when seasonal fruits were in short supply, the animals filled up on leaves. Howler monkeys were finicky, though. They ate only tender, young leaves, and only the tips at that.
