January 2009

Tracie See Monkey Do

They’re intelligent, inquisitive, and adaptable. Costa Rican monkeys are finding unexpected ways to live in an environment increasingly altered by human activity.
Tracie McKinney observes monkeys in Costa Rica's Curu Wildlife Reserve.

By providing fruits and leafy vegetables on tree platforms, McKinney's team can determine whether Howler monkeys accept (or shy away from) human-provided food.

Kira, a spider monkey at the rehabilitation facility, Curu Reserve, Costa Rica.

Kira was raised as a pet in a hotel where she was trained to hold the hands of tourists.

Photos by Jim Metzner.

Tracie McKinney is a doctoral candidate at Ohio State University’s department of anthropology. She leads teams of Earthwatch volunteers through Costa Rica’s Curu Wildlife Reserve, where they observe White-faced Capuchin and Mantled Howler monkeys. McKinney is investigating how human encroachment affects these animals by studying them in both disturbed and undisturbed habitats.

“Both of these species are responding fairly well to human change,” says McKinney, “but they are still declining in Costa Rica. What we want to see is how human disturbance is changing their behavior, how it impacts their diet, and if it has any major impacts that can really put these monkeys at risk. So for example, we look at the monkey’s diet. We compare the diet of monkey troupes living in farmland and monkeys who can steal things from garbage cans or get fed by tourists, with the diet of monkeys living in the forest, where monkeys normally used to live.”

She’s found, for example, that where forest has been replaced by mango plantations, Howler monkeys dig in. “These are not the types of trees monkeys would normally deal with in the wild,” she explains. “They’re all the same tree; there’s no real diversity here. But they’re making use of this for the few weeks of the year that mangos are in season. The monkeys are right here, and they forage as much as they can. So even though they’re mostly leaf eaters, howlers will take a lot of fruit, because it’s high in calories, high in sugar. It’s a good food for them if it’s available. And so they take advantage of it.”

Still, in a nation that’s reserved 25% of its land for wildlife, monkeys are at risk. Costa Rica has one of the world’s highest deforestation rates, and so the land that has been preserved is fragmented. “If [monkeys] can't travel between different areas and they're isolated,” McKinney says,” their populations are not going to be very viable. If there's more variation in your gene pool, then you are better able to adapt.” One solution is to provide intermediary habitats that link wildlife reserves. “If farmers are using their land in a way that allows animals to use it as a corridor, that provides connectivity between those two fragments.”

Wild monkeys are not lab rats, so although the research is paying off, the process can be slow. “We don’t have a lot of answers yet, but I’m beginning to see some trends,” McKinney explains. “This kind of project is going to be very, very long term. Monkeys have a long life span. It takes quite a while for one generation to breed and raise the next generation. So things that we’re doing now will be impacting monkeys 10 and 20 years down the road.”

To learn more about Earthwatch's tropical forest research click here.

Links to related stories:
Science Diary: Monkeys - Adaptability
Science Diary: Monkeys - Costa Rican Model
Science Diary: Monkeys - Howler Crop Raiders
Science Diary: Monkeys - Finding Howlers
Science Diary: Monkeys - Experiment
Science Diary: Monkeys - Capuchins
Science Diary: Monkeys - Habituate
Science Diary: Monkeys - Leaf Eaters
Science Diary: Monkeys - Capuchins Up Close and Personal
Science Diary: Monkeys - Social Dramas
Science Diary: Monkeys - Spider Rehab