Her research is situated in the 2,365-acre federally protected Reserva Particular do Patrimônio Natural Feliciano Miguel Abdala, named after the coffee farmer who owned the land. After Abdala’s death in 2000, his heirs followed his wishes and put the forest into permanent trust as a reserve. More than four dozen Brazilian students have conducted research there under Strier, with pairs and trios rotating in and out every 14 months. Strier typically spends about a month each year at the reserve, conversing with the students and making quips in Portuguese, which she studied for one semester but largely picked up during her fieldwork. She spends the rest of her time in Madison, where she lives with her husband and their cats. She prefers dogs, but her travel schedule makes caring for them difficult.
Acting on her profound concern for the muriquis’ future, she has discussed in public lectures and scientific papers the need for national and international investment in wildlife preservation and for educational programs and employment opportunities that get the local community involved. She is a key member of the committee that advises the Brazilian government on its plans for muriqui conservation. Largely thanks to her efforts, the muriquis have become something of a cause célèbre of conservation in Brazil, featured on T-shirts and postage stamps. In June, the city of Caratinga, Brazil, not far from the reserve, made Strier an honorary citizen, and used her project’s 30th anniversary to announce a new long-term sustainability program.
Though northern muriquis are critically endangered, the population in Strier’s study site, which is protected from further deforestation and hunting, has increased. There are now 335 individuals in four groups, a sixfold increase since Strier started her study.
That’s a development worth celebrating, but it’s not without consequences. The monkeys appear to be outgrowing the reserve and, in response to this population pressure, altering millennia of arboreal behavior. These tree-dwellers, these born aerialists, are spending more and more time on the ground. At first the behavior was surprising. Over time, though, Strier made some sense of it. “They’re on an island, with no place to go but up or down. When humans didn’t have enough food, they invented intensive agriculture. Monkeys come to the ground. It makes me think of how hominids had to eke out an existence in a hostile environment. Our ancestors would have brought to that challenge the plasticity we’re seeing here.”
Initially the muriquis descended only briefly and only for necessities, Strier says. Now they’re staying down for up to four hours—playing, resting and even mating. One of Strier’s students shot a video of a big group of monkeys lounging on the ground, leaning against each other and casually hugging, as if they’re at a picnic. “Next they’ll lose their tails,” jokes Carla Possamai, a Brazilian postdoctoral researcher who’s been working with Strier at the reserve for a decade.
One day we watch muriquis eat white berries on low bushes. At first the monkeys hang from their tails above the bushes, but soon they drop to the ground and stand there like customers at a pick-your-own patch. Upright but awkward, they are out of their element. “You’re watching an animal whose body is adapted for something else, using it in new ways,” says Strier.
In another unexpected break with predictable behavior, five female muriquis emigrated to another forest on the far side of 200 yards of bare pasture. Two of these adventurers made the dangerous trip back into the reserve, where it’s suspected that one of them mated before again crossing the open ground to the new forest.
Eking out a living on the ground might sound like a radical departure with no real consequences, but it makes the muriquis more vulnerable to predators. Camera traps have captured images of ocelots and a family of cougars in the reserve, and feral dogs and other carnivores are known to roam the pastures.
“Basically they’re telling us they need more space,” Strier says. To give it to them, Preserve Muriqui, the Abdala family foundation that runs the reserve, is working with local ranchers and landowners to connect the forest to the archipelago of small forest fragments on the reserve’s periphery.
Strier wonders about the potential for other changes. What will peaceful, egalitarian primates do if crowding becomes more severe and resources run short? “I predict a cascade of effects and demographic changes,” she says. Will the monkeys become more aggressive and start to compete for food and other essentials the way chimps and baboons do? Will the clubby camaraderie between males fall apart? Will the social fabric tear, or will the muriquis find new ways to preserve it? Strier has learned that there is no fixed behavior; instead, it’s driven by circumstances and environmental conditions. Context matters.