There are other reasons she works with howlers. “Howlers are good monkeys. They eat leaves, mostly, and so they stay together on a single group of trees to feed. That’s easier than having to find a lot of single monkeys. They are easier to find than other monkeys, too, because I know that I can follow the sounds of the howling when they wake up in the morning.”

To prepare for her experiments, Ellen collects seeds from the forest, and then painstakingly attaches long, thin strings to them. After rolling the seeds in dung— “it’s best if it’s fresh!”— she places the dung balls out in the forest for the dung beetles to find. The long strings will act as markers so she’ll be able to locate the seeds from wherever the dung beetles move them, and then watch to see if the seed successfully germinates. “By observing the dispersion of the seeds, and recording their fate, I can generate a picture of the role of the dung beetles in this system.” Having to deal with dung or not, Ellen loves her work in the forest. She explains, “When I’m not here, I just miss it. I miss the rainforest. To me it feels healthy, it’s fun.”

But even Ellen has her limits. “I don’t like the rain,” she says. “Howler monkeys are just like people— when it rains, they just hunker down miserably and don’t go anywhere. And then I have to be quicker, too, or else the rain will dissolve what dung there is. Some days I don’t get any dung, and that makes me frustrated, because I can’t do my work.” And she wouldn’t agree that the rain is necessarily refreshing. “No one knows better than I, that a lot of the dung doesn’t hit the ground on the first try. When it rains, and the rain washes down the leaves of the forest on you, well, then you get the rest of the dung.”

Editor’s Note: To learn more about the complex interrelationships between animals, plants, insects and the environment, see Activity 2.3, The Tropical Rainforest Food Web Game, in the Teacher’s Guide. Visit the EDUCATOR section online for information on the Teacher’s Guide