Golden-headed lion tamarins are an endangered species turned invasive, thriving in the suburbs of Rio. They are not as wild as they might be elsewhere, but not tame either. Are we okay with that?

By James Barilla

The highway that leads from the airport into the center of Rio is, according to Rob, known as the “Gaza Strip.” There are two favelas on either side of the road, and rival gangs are known to shoot at each other over the top of the streaming traffic.

Maybe Rob is just paranoid, and I’m just an anxious traveler. Maybe I’m just alert to the signs of heightened security that seem to be everywhere, like the guard in the booth who waves us up the steep, cobbled residential street to my bed and breakfast and the automatic metal gate we pull through to enter the drive.

The historic mansion is tucked beneath an ancient, bromeliad-studded mango tree. It was built to house the founder of the tramline that takes tourists on a winding tour through the Tijuca forests to the stone footing of the Christ statue. What I liked about it was that it backed onto the forest, with marmosets and monkeys and toucans visiting the grounds daily. The views from the veranda are spectacular, casting across a sweeping valley to the twinkling lights of a favela on the opposing ridge.

I lie awake, listening to the thumping bass of some tropicalia-inflected hip-hop, shouts of people having a good time, dogs barking in alarm: there’s a party going on in the favela next door. What’s brought me here? Not the dance parties or the tasty capirinhas or the beaches of Ipanema. I’m here to track down one of the black-tufted marmoset’s cousins, an endangered species that has been discovered on the exurban fringe of the city. An endangered species that also happens to be potentially invasive.

The contours of the story feel familiar. A veterinarian who kept a private zoo as a hobby passed away in Niteroi, leaving behind fifteen small primates with shaggy black fur and coppery manes. Only 6,500 golden-headed lion tamarins, or GHLTs, as biologists like to refer to them, still inhabit tiny fragments of the Atlantic rain forest in the northern Brazilian state of Bahia, which lies hundreds of miles and several impassable river drainages from Niteroi. The heirs, not knowing what to do with their charges and probably aware that there might be legal ramifications for possessing an endangered species, decided to do the animals a favor by releasing them into those jagged hills I saw from the airport road.

In 2002, residents of Niteroi observed them in just two or three groups, but a population explosion was already under way. By 2009, when a census was undertaken, there were fifteen groups with more than a hundred individuals, foraging in neighborhoods and roosting in the city’s protected forests.

One of the reasons these tamarins are doing so well here, scientists suspect, is because the local residents are feeding them. The benefits they receive in terms of calories outweigh the risks they take with roads and power lines, at least so far.

For an endangered species population to grow tenfold in less than a decade seems like a conservation success story. You might think anything you could do to boost their number in the wild would be a good thing. The bigger the metapopulation, the more tamarins you have in different locations, and the less chance you have of the species going extinct through some local catastrophe. Why not have tamarins free-ranging around the city’s green spaces? Why not have the local residents take a bigger role in caring for them? Wouldn’t that mean more habitat, more tamarins, more people with a stake in their survival . . . .

If only things were that simple. There’s another conservation success story to consider here, one of the greatest in conservation history, in fact: the golden lion tamarin. The golden lion tamarin, or GLT, is the only primate species whose fortunes have improved enough to be downlisted from Critically Endangered on the IUCN Red List of Threatened Species to Endangered. Amid a human population explosion, widespread deforestation, and urban sprawl along Brazil’s Atlantic coast, human beings have managed to turn things around for this tiny primate. It’s a relative triumph to be sure, since the fate of the species remains tenuous. But it’s good news in a time when we have too little to cheer about.

Look at a map of golden lion tamarin populations, and what you’ll see is a constellation of green dots spread in a rough semicircle northeast of Rio, most around an hour’s drive from the city. One of these dots is less than twenty miles from the burgeoning population of nonnatives.

For GHLTs, those twenty miles still constitute a formidable obstacle course. The greenery of Niteroi’s protected hills is misleading; beyond them, major highways thunder through cattle pastures and densely populated towns with nary a tree in sight, mile after mile of sprawl. Tamarins don’t do well under such circumstances—that’s why they’re endangered, because development has replaced their native forest with roads and fields and housing developments.

Nevertheless, biologists are worried that some resourceful individuals might thread the needle and arrive in the habitat already occupied by golden lion tamarins. And there’s always the chance some sympathetic homeowner will decide to deal with a nuisance tamarin by transporting it to the nearest forest in the back of their car, just as I did with the possum under our house.

Nobody really knows what might happen if the two species were to meet. Nobody anticipated that a creature with a tenuous hold on life would suddenly become an invasive species. The two species have been known to hybridize in captivity, but in the wild it’s also possible that they would compete for limited nest cavities and food. The nonnatives might also introduce diseases they picked up along the way.

Conservationists aren’t willing to take that chance. Led by the Brazilian primatologist Cecilia Kierulff, a team will soon undertake the delicate task of trapping and relocating an endangered species in the urban wild.

Luring the animals into a cage is a fairly straightforward process, particularly for animals that already associate humans with food. Bananas work well for attracting tamarins, according to Leonardo Oliveira, who studies GHLTs in their native habitat. And although there is always a risk of mortality, he told me, he’s never seen one injured.

But to trap in a residential area, you need the support, if not the permission, of the human inhabitants. Otherwise, traps tend to spring shut with nothing inside or disappear entirely. That support is far from certain here, which isn’t surprising. The conservation community has spent decades convincing people that wild tamarins are a blessing to have around. Now, however, the message is getting complicated. One species of tamarin belongs; the other is a charismatic interloper that must be removed. And to further confuse matters, the tamarin that belongs here isn’t actually here. You’re not replacing one tamarin with another, at least not yet.

“Some people call them ‘my monkeys,’” Kierulff told me from her home in São Paulo, describing the people she’d encountered while surveying for GHLTs in Rio’s exurbs.

“They don’t want us to take them.”

Her task will be to convince the locals that their “monkeys” will be better off elsewhere. The team plans to trap the tamarins in family groups, quarantine them to ensure that they are free of disease, and eventually transfer them to a ten-thousand-acre preserve within their native range. This forest currently has no resident tamarins, an indication of just how rare this species is in the wild. Kierulff expects the entire process to last three years, because the team will continue to monitor the trans-located population after their release. That post-release monitoring has proven crucial to success with golden lion tamarin reintroduction. In fact, one of the many ironies here is that the painstaking effort to figure out what reintroduced GLTs need to thrive now offers scientists a detailed model for how to translocate their invasive cousins.

Everybody knows where the golden lion tamarins are. The private preserves have become popular ecotourist destinations, and if you show up, the star attractions are usually quite obliging. But the nonnatives aren’t on any tourist map, and they aren’t easy for an outsider, especially an outsider whose command of Portuguese is basically limited to smiling inanely and muttering things like Sorry and Speak English? to find. The aerial photos in my possession show pale puzzles of dense urban development extending deep into the interior, the borders of one satellite city blurring into another. But right in the midst of this sprawl, two fingers of green forest seem to reach down the steep slopes of the mountains toward the coast. One is a state park. The other is a regional park. The tamarins are in between there . . . somewhere.

I’ve enlisted help to find them. The hotel owner’s son, Diogo Valença, grew up in one of the beachside communities of Niteroi and has agreed to be my guide. I like Diogo; he’s a brawny young guy who plays guitar in a rock band and speaks excellent English, having spent time in Miami and Los Angeles.

Our first foray into the hills above Niteroi ends with a pedestrian waving our little sedan off—the steep and winding road ahead is good only for all-terrain vehicles, especially during the rainy season. We’d just spent the better part of an hour searching for this very road in a busy commercial district. You see something on Google maps, tidy lines superimposed on a grainy satellite image, and you think, okay, no problem. Then you ground truth and discover that online topography doesn’t look nearly as rough and pitted as the real thing. Back down into the haphazardly marked city we go!

Eventually, we find our way up the other side of the ridge, where the walled compounds of the wealthy end in a rambling dirt road shaded with bamboo and jackfruit trees. Here, hard by the boundaries of the state park, residents live in exurban seclusion. We’ve finally reached that patch of green on the Google map.

It looks like a jungle version of the small town in Massa-chusetts where I grew up. A heavy black power cable stitches the sky over the washboard dirt road. Each house is set within a parcel of several tangled acres, the kind of development Brazilians refer to as a sítio, a weekend retreat, a hobby farm.

Several of these retreats are almost palatial, but the place on the corner is a humble collection of cottages and sheds terraced into a hillside above a trickling stream. Laundry hangs from a line. Young kids are playing under the watchful eye of their grandmothers and the family dogs.

Diogo asks the older women if they’ve seen the “micos,” not the mico estrelas, the nonnative black-tufted marmosets that have been introduced here, or the other introduced species, the mico comum, the common marmoset with the white tufts around its ears. What about the mico leão da cara dourada? The one with the golden face?

“Oh, yes, yes,” they say, which is about the extent of my understanding of the conversation. They gesture to the woods across the street, where there’s an elevated platform for garbage collection attached to the power line pole. Diogo translates.

“They come from there all the time. Every day they come. They travel on the power lines.”

The woman with thick glasses and neatly fastened hair feeds them all the time. She likes them. But her sister doesn’t like them so much because they come into the house. In our neighborhood in Columbia, all houses have screens. But here, people seem to like their windows open. Despite the risk of contracting dengue fever from a mosquito species that prefers to lurk indoors, I haven’t seen a single screen. The breakfast room in my hotel has spacious open windows, and I can easily imagine a tamarin climbing in to sample the fruit bowl.

I ask the women if they’ve seen the tamarins today. In their native habitat, the group would probably travel over a mile in their daily foraging for food. But in a residential neighborhood, they might stick closer to their known food sources, as free-range tamarins do at the zoo. Could the wires above the road be their circuit from house to house?

We park near a sign that lays out lots for sale and set out on foot around the circle. There are primates in the vicinity: a group of black-tufted marmosets scrambling along the power line in front of somebody’s hobby farm. Just like the squirrels back home. The group considers us from the mossy boughs of an old tree, tilting their heads to examine us while a stocky, old dog stands guard at the end of the driveway below. I’m hoping for a flash of copper mane; like squirrel monkeys and capuchins, it’s not uncommon for the tamarins and this species of marmoset to form mixed groups in their native ranges. Even though they’re foraging for the same kinds of food, more eyes means more protection from predators, especially raptors like the caracara we saw perched on top of a telephone pole just down the road.

“They’d come down,” Diogo says, “if we gave them a banana.” That’s the international currency of human-primate relations, the banana, good for currying favor with macaques, marmosets, and, we hope, tamarins. Unfortunately, we’re rather poor in the banana department—I just ate mine, leaving us with one left over from lunch.

We pass a man raking leaves who says he just saw the tamarins. Yes, he’s sure they were tamarins, not mico estrela. Yes, they had the golden faces. They were just here. They like that big jackfruit tree across the street.

This affinity for jackfruit, according to Leonardo Oliveira, is a key distinction between GHLTs and their golden cousins. He studies GHLTs inhabiting what is known as cabruca, shade-grown cacao plantations along northern Brazil’s Cocoa Coast, in which farmers clear the understory for their crop but leave an overstory of native trees to provide shade. These are disturbed forests, often lacking complex layers of habitat, yet the tamarins have managed to adapt, thanks in part to the calories provided by this Asian import.

We pass a father and son trundling a washing machine down the road on a handcart. Yes, they, too, have seen the tamarins. Just down there, they say, there was a film crew shooting footage of them. Last week. Just down there in that bamboo.

They seem to be ambivalent about the animals’ presence. They understand they’re endangered, they say, but five years ago, before the first tamarins appeared, they regularly saw birds nesting in their yard that have since disappeared. Spectacular birds, like the seven-colored tanager, birds they miss. The tamarins find everything, the father says, pawing the air tamarin-style, as if he’s combing through thick vegetation for bugs and frogs and nestlings.

Down the hill, a banana plantation runs in a narrow strip along the road, with a steep, forested ridge above. Across the road is another house, half hidden by a massive clump of timber bamboo.

I’m about to say something to Diogo about the incongruity of parked cars and endangered primates when I see a figure scamper across the road into the brush. My first thought is just as before: a cat. A black cat. What’s that cat doing out here? Then I’m running with my binoculars slapping my chest. And Diogo is sprinting ahead and yelling, “It’s them! It’s them! The micos!” He’s gesturing wildly toward the banana trees, which are flapping their floppy leaves as the tamarins try to flee. Their alarm calls sound . . . alarming, like the piercing last cry of a rabbit squeezed in the jaws of a predator.

Caught on the wrong side of the road, the last member of the group perches high in the swaying culms of bamboo, searching frantically for a way to get around us. As it clambers higher, we spot the reason it’s traveling more slowly—two tiny infants cling to its back. They’re each about the size of a chipmunk, with the brushy stubble of a black-and-tan Yorkshire terrier pup. Tamarins usually give birth to twins, then share the responsibility for carting the youngsters around. This adult we’ve cornered could be their father or their older sibling or their mother.

To see these animals in the wild is rare. To see one scrambling along the edge of someone’s yard is disconcerting and heartening all at once, casting doubt on easy assumptions about the frailty of endangered species and their inability to tolerate human contact. One myth that is gradually giving way is that endangered species must be inherently unable to coexist with humans. In the case of tamarins, the assumption that these animals require pristine old-growth forest has shifted in response to research, which has shown that even relatively young forests can offer certain advantages for these animals. Some endangered species can apparently do just fine with people around, especially if those people are feeding them.

Diogo peels his banana and wades into the roadside brush. Behind the bamboo sits a tile-roofed garage shading what appear to be a rusty tractor and various piles of odds and ends. I’m not paying any attention to what’s in there and whether it might be valuable, but somebody is. I hear him shout. In Portuguese, so I have no idea what he’s saying. He’s further up the driveway, presumably inside the house.

Diogo pays him no heed. He’s turned into the tamarin whisperer, a chunk of banana held high, a stream of comforting nonsense pouring out of his mouth. The tamarin remains unconvinced by all this attention, poised to leap. But where? Its family is calling frantically from the ridge beyond the bananas now, but how can it reach them? It calls back; we can see its tiny lower jaw flicker like the needle on a sewing machine.

Whoever is in the house shouts something again, his husky baritone sounding more and more peevish. Diogo pushes deeper, urging the tamarin to trust him.

It seems interested. It follows every move of the banana, as if maybe, if it were high enough, it might . . .

Diogo takes another step, reaching, stretching, then crashing down into the ditch that’s hidden beneath the lush vegetation. Dead branches snap and crackle like gunfire beneath his feet.

The next thing I hear is footsteps; someone’s running down the driveway. With a bellowing roar, an old man charges into the road. He’s shirtless, his tanned skin collecting in loose folds above his shorts, his hair wild around his bald crown, a pair of thick, misty bifocals riding down his nose.

What rivets my attention instantly, however, is the machete. A hefty blade, dark with use, is cocked over the guy’s head, as if he’s about to chop our heads off.

I’m closest.

He gallops about three steps toward me, pigeon-toed in his flip-flops, before he really sees me. Binoculars. Mini cam, index finger still pressing the record button. Sun hat, the kind with the flattering nylon neck drape that no self-respecting Carioca would be caught dead in.

He skids to a halt. He’s panting, stiff with adrenaline, his glasses fogged so thick his eyes look like they’re floating in half-rinsed cups of skim milk.

The machete wavers, then slides to his waist.

I haven’t had time to move or even raise my hands in terror. With my rudimentary Portuguese failing me, I pivot and point emphatically at Diogo.

I hear Diogo say something reassuring about micos and Americans. It’s probably good that I don’t speak Portuguese at this point, because I imagine there’s probably a bit of sympathetic back-and-forth about the crazy things we crazy tourists insist on doing. Or maybe the old man is a friend of the tamarins. Maybe he feeds them under the roof of that garage—that’s why they keep showing up here.

I don’t get the sense he wants to be questioned by us. I’m beginning to suspect we woke him from a nap.

“Tudo bem,” he proclaims, and heads back to the house.

Our quarry has taken advantage of the incident to get beyond us, hastening along through the branches to a bough that reaches over the road. We watch it shimmy across, then spring into the vegetation beyond, working its way along a path that doesn’t touch the ground.

I have to keep reminding myself that these are endangered animals, that unlike the squirrels in my yard, these creatures aren’t abundant everywhere. We’ve seen how resourceful they are. We’ve seen them on the ground. Seen them cross a road. Not a busy four-lane highway filled with traffic, but still a road. Maybe they could indeed find a way to make it to the golden lion tamarin preserve. Maybe those fears are justified.

One day soon, the researchers will come with baited traps, and these tamarins will be on their way back to their native haunts. As I watch this one disappear with its precious cargo, I wonder what this place will feel like when they’re gone. Will this exurban habitat feel empty without them? There’s been some talk of reintroducing golden lion tamarins here after the current inhabitants are gone, but many of the biologists I spoke with doubt that would be worth the investment of time and money. Ultimately, this area is still just a small island of habitat, cut off from other populations, clearly affected by human habitation. Rio’s backyard, not endangered species habitat. Better to spend limited resources on improving existing preserves.

This view assumes that conservation costs a lot and has to be handled by professionals, especially when it comes to endangered species. What I see here, however, is conservation that costs nothing. Nobody’s paid to monitor this endangered species or provision them. Nobody’s paid to manage them. These endangered animals are as wild as the squirrels and cardinals on the bird feeder in my front yard, as wild as the rhesus in Delhi, as wild as the black bears rambling around the yards of Northampton. Not as wild as they might be elsewhere, but not tame either. The complications and contradictions are almost paralyzing, but I’ve come to appreciate the power of our affinity for wildlife, of our desire for an immediate, positive relationship. If you can harness that power, then you can make a real difference.

Excerpted from: My Backyard Jungle: The Adventures of an Urban Wildlife Lover Who Turned His Yard Into Habitat and Learned to Live With It by James Barilla. Published in April 2013 by Yale University Press. Reprinted with permission.

James Barilla is an assistant professor at the University of South Carolina in Columbia, where he teaches creative nonfiction in the MFA program. His environmental essays and stories have been featured in The Atlantic, National Geographic, Places, Ecological Restoration and elsewhere.