"If you're lost in the forest, follow the tamarin," she said. "They'll always find food."
The next step should be within reach: raising the golden lion tamarin's population to around a sustainable level of 2,000 or more.
The main obstacle, the sheer lack of habitat, is where the Olympics come in.
Brazil's coastal Atlantic forest is one of the world's biodiversity hotspots. About 2,200 different birds, mammals, reptiles and amphibians, including 60 percent of the country's threatened species, make their home in this jungle, one of the most diverse ecosystems on the planet and also one of the most threatened.
The monkey is an umbrella species whose protection ensures that dozens of other species in the region have a chance of survival, including the endangered maned three-toed sloth and the wooly spider monkey.
People depend on it as well. The Mata Atlantica forest, as it is known in Brazil, encompasses the nation's biggest cities, Rio de Janeiro and Sao Paulo, and about 70 percent of the country's population. Seven of Brazil's 10 biggest cities depend on its rivers and springs for water and electricity generation.
That kind of development has reduced the luxuriant jungle to 8 percent of its original 3.2 million acres (1.3 million hectares). About 80 percent of the land is privately owned, and it's expensive, much of it taken up with ranches and farms.
Conservationists say the monkeys need about 61,800 acres (25,000 hectares) of protected, interconnected forest for the species to thrive on their own. So far, they only have 40 percent of that required land to live on.
Expanding the forest comes with own challenges, first off finding quality seeds from the diversity of plants in the region and then sprouting those seeds into healthy shoots.
The rescuers have recruited people living in the forest, many of them former field workers who used to harvest vegetables, and trained them to recognize native trees, select seeds and monitor their growth, creating seven small-scale nurseries set up by locals.
For Marlene de Oliveira and her sister, the nursery business was a godsend. After decades of back-breaking work harvesting manioc root, they're now the proud owners of a sturdy wood-frame, mesh-walled nursery near the reserve for which their shoots are destined. In their first year, they produced 14,000 shoots of dozens of species.
The county where the de Olveiras work has become the nation's leader in private reserves, with 22. The landowner voluntarily grants the legal protection, but once a plot gets the designation, it's binding: The forest can never be cut down, even if the ground under it is sold.
"I used to think this was a funny idea, planting trees," said de Oliveira, through a wide, gummy grin from which most teeth were missing. "I used to wonder, why not plant food? What good is this to anyone? Now I see it's good for the monkeys, and good for everyone."
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