Her interest in monkeys directly relates to her roles as an anthropologist and biologist. "Anthropologists are interested in humans and the biology of humans," says Winkler. "We are primates - monkeys are primates, so we are also interested in animals."

Five years ago the University of Pittsburgh provided grant money for Winkler to develop her research project to begin studying the noisy, entertaining monkeys in Costa Rica. Then in 1998, Winkler began research on Ometepe and, at the request of the field station where she worked, created and began teaching a course on primate behavior and biology that correlated with the work she was doing.

Students who participate in the summer course assist with research, study the monkeys" behavior, absorb another culture, and earn six credits at the completion of the 30-day program. During the summer of 1998, Winkler, her students, and two veterinarians from Utah and Michigan tagged the monkeys, which weigh between 11 and 14 pounds.

Tagging, also known as collaring, involves darting the monkeys with anesthesia to sedate them and then placing a tag on them to allow for future identification and ease of study. "Without tags, you can not identify them from the ground," says Winkler.

Winkler said this procedure does not hurt the monkeys and, in fact, is used to provide medical care. While the monkeys are under sedation, Winkler and the veterinarians follow standard capture techniques that include giving physical and dental exams, removing ticks, and withdrawing blood.

The veterinarians try to correct any physical problems they may detect during the examinations. They look for evidence of disease exposure and check for giardia, malaria, yellow fever, dengue (also a mosquito-born disease), measles, and encephalitis.

The blood that is collected is used to study DNA as it relates to diseases and to determine the monkeys" resistance to particular diseases. The DNA also helps identify diversity. If the DNA is exactly alike, the monkeys may not have the capacity to respond to environmental change.

"When you see a large population, you want to see a breeding pool that is diverse," says Winkler. "If the breeding pool is exactly alike and a new disease is introduced or a drastic environmental change occurs, it can wipe out the entire group because they have no resistance.

"If you have variance in the population, then chances are that some of them will survive no matter what happens. This is a standard biological principle." A lack of diversity can be attributed to the isolation of the island and inbreeding. But so far only a small number of howling monkeys have been studied. Winkler says they do not know what they might find in other locations.

Although the monkeys roam freely throughout the jungle, they tend to stay within their own territory. When Winkler returned in 1999, she found all but two of the monkeys tagged the previous year had remained in the area. (One had died and one was missing.) It is important that the monkeys remain free because this allows Winkler and her students to study them in their natural habitat.

When Winkler and her class first arrive, they must give the monkeys time to acclimatize to human presence. "It takes a couple of weeks for them to adjust to us being there," says Winkler. "Once they get used to us, they continue with their usual routine. We habituate them to us being around.

The howling monkeys are one of the most common mammals on the island and offer the greatest potential for tourism on Ometepe because of their entertaining behavior, which includes their howling. In addition to the monkeys, the island boasts two volcanoes, breathtaking scenery, and dry, tropical, undeveloped forests perfect for hiking, biking, and kayaking.

Winkler's concern is that as the population, in the form of tourism, continues to grow on the island, the monkeys survival will be at risk since they showed no exposure to the diseases for which the veterinarians checked. The potential is that if the howling monkeys have never been exposed to a disease, exposure through human carriers could wipe them out. It's not the people, she says, it's the development. If people come and enjoy the island and leave it as they found it, then it's okay.

Winkler stresses that conservation steps are necessary for their survival. "The big thing is preserving the population (of monkeys)," says Winkler. "The other outcome of the project is by tagging the animals we can encourage the students we take plus the local Nicaraguan students to watch and monitor the behavior."

To that end, Winkler, with a new group of students, will resume her research this summer, as well as continue to write and present papers at symposiums to increase awareness.