But exposing the monkeys to tourism was linked to high death rates caused by aggressive behavior among adults and toward infants.
Although they didn't witness all the attacks, many of the infant corpses Berman's team found had bite wounds indicative of adult macaques.
The conflicts typically began with intense competition for food in the designated feeding areas.
As the animals became more aggressive, overall infant mortality rose from 14.8 percent to 54.6 percent.
The spread of disease from human to monkey and vice versa also became a persistent problem.
Most experts agree that ecotourism has helped many animals by generating funds for their protection, conserving habit, and giving local communities a stake in their survival.
Frans de Waal, a leading primatologist at the Yerkes National Primate Research Center in Atlanta, Georgia, agrees that ecotourism can backfire if it's not carefully managed.
"But I also feel that if done responsibly, everyone benefits," de Waal said.
"I think we need to teach tourists that if they want to see primates, they will have to go where the primates are. Provisioning with food should be done only to habituate the primates to humans, not to determine their movements."
The problem at Mount Huangshan may be in part a question of scale, the study authors note.
"This is a very popular tourist site in China. Millions of people come to see the mountains, and tens of thousands each year come to look at the monkeys," Berman said.
"They might have on a busy day three or four viewings of the monkeys, and there might be more than a hundred people watching them at once."
Many of these visitors, Berman noted, are not aware of how they should behave to lessen impact on the monkeys and may interact with them or even feed them.
In contrast, one of the best-known ecotourism success stories involves the endangered mountain gorillas in Rwanda and adjacent African countries.
The animals were likely saved from extinction—even during Rwanda's brutal civil war in the early 1990s—because of their economic value as an ecotourism attraction.
(Related: "Endangered Gorillas 'Held Hostage' by Rebels in Africa Park" [May 23, 2007].)
The gorillas are left in their natural habitat and become slowly acclimated to the presence of human researchers.
Only after a year or longer are they considered sufficiently ready for discreet visits by small groups of tourists who pay a permit fee.
"It's done in a very, very controlled fashion," said Craig Sholley, senior director of the African Wildlife Foundation and a former director of Rwanda's Mountain Gorilla Project.
"There is a protocol that dictates how many people go out on a regular basis and how close they can get to ensure that there is no interaction."
Studies of the gorillas over the past 15 to 20 years suggest that, from a reproductive standpoint, gorillas that are habituated to humans are doing at least as well as others if not significantly better, Sholley noted.
"But if the controls were taken away," he said, "it could very easily shift to a negative benefit."
M. A. Sanjayan, lead scientist for the Nature Conservancy, said that "no one will tell you that ecotourism for mountain gorillas didn't help to save them.
"But this only works when it's not mass tourism, not busloads or planeloads," he said.
"It's a few people paying a lot of money. Is that fair? I don't know," he added.
"There is an elitist feel to these specialized trips, but there's no doubt that it's better for the animals."
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